INDUSTRIAL PERSPECTIVES FOR BIOETHANOL DIRETORIA EXECUTIVA Mauricio Prates de Campos Filho Diretor Executivo Nelson Antonio Pereira Camacho Diretor para Assuntos Administrativos e Financeiros Saul Gonçalves d’Ávila Diretor para Assuntos Científicos e Tecnológicos INDUSTRIAL PERSPECTIVES FOR BIOETHANOL Eduardo P. Carvalho Isaias C. Macedo José Luiz Olivério Pedro Wongtschowski Francisco I. Pellegrini Flávio C. Cavalcanti Anderson F. Cunha Silvia K. Missawa Gonçalo A. G. Pereira Silvio R. Andrietta Maria da Graça Stupiello Andrietta Adrie J. J. Straathof Çagri Efe Luuk A. M. van der Wielen Peter M. M. Nossin Telma T. Franco Carlos Eduardo Vaz Rossell H. J. Veringa P. Alderliesten Edited by Telma Teixeira Franco Coleção UNI E M P Inovação INDUSTRIAL PERSPECTIVES FOR BIOETHANOL ISBN 85-98951-06-4 Av. Paulista, 2.200 - 16 o andar Tel. (11) 2178-0466 Fax. (11) 3283-3386 [email protected] www.uniemp.org.br 01310-300 São Paulo - SP Produzido no Brasil 2006 LIST OF CONTENTS Preface Telma T. Franco 9 Section 1 Industrial Perspectives for Bioethanol: a Brazilian approach 11 Chapter 1 Ethanol from Sugar Cane in Brazil: the Industrial Technology Perspectives Eduardo P. Carvalho and Isaias C. Macedo 13 Chapter 2 Technological evolution of the Brazilian sugar and alcohol sector: Dedini’s contribution José Luiz Olivério 19 Chapter 3 Insertion of bioethanol into a new paradigm for the Brazilian chemical industry Pedro Wongtschowski, Francisco I. Pellegrini and Flávio C. Cavalcanti 33 Section 2 BioTechnology and Engineering Science integration for Chemical and Fuel Industries 57 Chapter 4 Industrial Potential of Yeast Biotechnology in the Production of Bioethanol in Brazil: the Example of Conditional Flocculation Anderson F. Cunha, Silvia K. Missawa and Gonçalo A. G. Pereira 59 Chapter 5 Optimization and Limits of Ethanol Production Silvio R. Andrietta and Maria da Graça Stupiello Andrietta 77 Chapter 6 Innovation and sustainability through industrial biotechnology Adrie J. J. Straathof, Çagri Efe, Luuk A. M. van der Wielen, Peter M. M. Nossin and Telma T. Franco 91 Chapter 7 Advances of the Brazilian production of chemicals and other products from biomass Telma T. Franco 107 Section 3 Role of Bioethanol in the Energy Landscape 121 Chapter 8 Conversion of lignocellulose biomass (bagasse and straw) from the sugar-alcohol industry into bioethanol Carlos Eduardo Vaz Rossell 123 Chapter 9 Advanced techniques for generation of energy from biomass and waste H. J. Veringa and P. Alderliesten 143 Preface Telma T. Franco The sixth volume of Uniemp collection is dedicated to the Industrial perspectives of Bioethanol. It is organized in three sections, the Brazilian approach to the industrial perspectives for Bioethanol; the biotechnology and engineering science integration for chemical and fuel Industries and finally, the role of Bioethanol in the energy landscape. Each of these sections aims to cover different views of experts from academic, industrial and governmental areas. The Brazilian industrial perspectives for Bioethanol is covered in three chapters. Different views of the industrial sector are described, namely that of the sugar cane producers, of the equipment manufacture and the view of the chemical industry. The first chapter was written by the president of the São Paulo Sugarcane Association, Eduardo Pereira de Carvalho with a collaboration of Isaías Macedo; the second was written by the director of Oxiteno, Pedro Wongtschowski, with the collaboration of Francisco I. Pellegrini and Flávio C. Cavalcanti and the third chapter was written by the Senior Operational Vice President, Dedini S/A Indústrias de Base, José Luiz Olivério. Carvalho and collaborator address the current perspectives of the sugarcane producers. The text describes their current context, some technological achievements and evolution, discusses medium and longterm future technologies and points out the potential and feasible new products from Bioethanol and sugarcane. Pedro Wongtschowski and collaborators, from Oxiteno, discuss the insertion of Bioethanol for the Brazilian chemical industry, the competitiveness of Bioethanol as fuel and raw material for the chemical industry. 10 INDUSTRIAL PERSPECTIVES FOR BIOETHANOL Jose Luis Olivério discusses a model to explain the development of the sugar cane industry. The model is divided in five stages that refer to five different aspects: the capacity of equipment, the overall yield, the sugar cane energy, the improvement of the use of sugarcane products and byproducts and the view of a sugar and alcohol mill as energy-andfood- producing unit. The integration of biotechnology and engineering sciences for changes in chemical and fuel industries is addressed by four experts. Fundamental aspects of molecular biology and an application case are outlined by Gonçalo Amarante Guimaraes Pereira & collaborators, from Unicamp. A simple case describes how a microorganism can be modified to satisfy the needs of an industrial technological process. Engineering aspects of fermentation are discussed by Silvio Andrietta and Maria da Graça Stupiello Andrieta, from Unicamp. The possibilities for optimizing ethanol production, the limiting factors for ethanol productivity and yields and the environmental impact and restrictions are discussed. Future possibilities for industrial plant are addressed by Adrie J.J. Straathof, Çaðri Efe and Luuk A.M. van der Wielen (Delft University of Technology) Peter M.M. Nossin (DSM Corporate Technology) and Telma T. Franco (Unicamp), with emphasis on the integration of hydrolysis and fermentation to Bioethanol. The seventh chapter and the last of this section is written by Telma T. Franco (Unicamp), who reviews the advances of the Brazilian production of chemicals and other products from biomass. The role of Bioethanol in the energy landscape is covered by two chapters. Carlos Eduardo Vaz Rossell, from the Energy group of NIPE, explores the complexity of the sugarcane bagasse and of straw. Their chemical composition and morphological aspects are discussed. H. J. Veringa and P. Alderliesten, from the Energy research Centre of the Netherlands, emphasize the conversion process and equipments for the generation of energy from biomass and waste. Section 1 Industrial Perspectives for Bioethanol: a Brazilian approach Ethanol from Sugar Cane in Brazil: the Industrial Technology Perspectives Eduardo Pereira de Carvalho Isaias C. Macedo Introduction The establishment of the ethanol program in Brazil has required extensive technology development in production, logistics and end utilization in the last 30 years. It is expected that in the next 10 – 20 years a much more efficient use of the sugar cane biomass will increase significantly the range of products and their value. Energy (both power and liquid fuels) may become the most important fraction of the sales. Technologies in development (worldwide) may be the key for this transformation: the hydrolysis of biomass (bagasse and trash), as well as many different fermentation technologies; and the biomass gasification, leading to power or fuel synthesis. Sugar cane appears as an ideal feedstock for the future “bio-refineries”, for its relatively low cost, large availability and an interesting mix of 1/3 sucrose, 2/3 pre-processed ligno-cellulosic material. The context today In 2005, 380 M t sugar cane were processed in 310 sugar mills in Brazil (41 new are being built), yielding 26 M t sugar and 15.7 M m3 ethanol. Brazil is the world’s largest producer of sugar cane (33.9%), sugar (18.5%) and ethanol (36.4%). It is also the largest exporter of sugar and ethanol. 14 INDUSTRIAL PERSPECTIVES FOR BIOETHANOL Ethanol corresponds to 40.6% of the fuel for light vehicles (total fleet: 19.2 M vehicles). Flex-fuel cars correspond to more than 70% of the sales of new units (end of 2005), and all the gasoline is blended with 20% ethanol. Ethanol production and use in Brazil has been considered an important example of the introduction of renewable energy sources, with a large scale of production. Complete process integration was obtained, at the sugar mills: flexibility, better sugar quality and reduced losses. It required extensive technology development in production, logistics and end utilization in the last 30 years. It also required specific legislation, initial subsidies and a great deal of negotiation among producers, automakers, government officials and the “competition”: the oil industry. Highlights in technology evolution From 1980 to 1990 some achievements were important: · · · ·· · · Introduction of cane varieties developed for Brazil; stillage use in ferti-irrigation; biological controls in cane production and improvement in agricultural operations (cultivation, harvesting) Development of the “4 roll” milling system; microbiology for large scale “open” fermentations; production flexibility: synergy ethanol/ sugar; and increased energy production (self-sufficiency) Ethanol specifications; engine (E-100) developments; blending, storage and transportation systems From 1990 to 2000 the developments included: Optimization of cane harvesting, loading and transportation; mapping of the sugar cane genome; plant transformations; harvesting mechanization Selling of surplus power; advances in industrial automation; better technical management systems (agriculture and industry) The Flex-fuel engines Net results for the 1975-2000 period, in S. Paulo, indicate increases of 33% (t cane/ha); 8% (sugar % cane); 14% conversion: (sugars in cane) ETHANOL FROM SUGAR CANE IN BRAZIL: THE INDUSTRIAL TECHNOLOGY... 15 to (ethanol); and also 130% in fermentation productivity, m3 ethanol / (m3 reactor . day) For the Brazilian Center South, averages in 2003/4 were ·· · Sugar cane productivity: 84.3 t / ha Sugar % cane: 14.6 Industrial conversion: 86% A frequently asked question relates to the possibilities of yet large advances for the next years. Can we say that the sugar cane agro-industry in Brazil has a “mature technology” status, with worldwide lowest costs and high product quality? Are we looking for continuous, small improvements, from now on? Technologies for the future Some of the most promising advances for the next years may be: · · ·· · Technology evolution: (precision agriculture, separation processes, integrated harvesting / loading / transportation systems, industrial automation) By- products: surplus electricity (already started); ethanol from bagasse and trash (5 – 10 years?) Sucrose derived products (being implemented) Medium – long term perspectives for sugar cane genetically modified varieties Medium-long term: the “bio-refineries” with full utilization of sucrose and wastes (bagasse and trash) The full utilization of biomass wastes is being considered for its very large potential, for energy or materials production. As an example, sugar cane in Brazil (2005: 60 M t sucrose; 120 M t ligno-cellulosic material) could yield (using 30% surplus bagasse + 50% trash could) 48 M dry t of biomass wastes, with a very low recovery cost (~1 €/GJ). Average (world) costs for biomass today (wastes, energy farms) are 2 - 3 • /GJ; plans for 1.5 • /GJ, future. 16 INDUSTRIAL PERSPECTIVES FOR BIOETHANOL It is clear that the sugar cane industry can invest in the full utilization of 2/3 of its raw material (the “wastes”, today) to promote a large diversification, in the same scale as ethanol is a diversification (in Brazil). Two processes (with many variations) may be the key to the “bio-refineries” in the future; both are in development today: · · Biomass (hydrolysis) —— > sugars, (ethanol, other): commercial ~ 2010 to 2020 Biomass (gasification) —— > power or synthesis fuels (ethanol, DME, gasoline, diesel); commercial ~ 2015 to 2025. Both need more efficient, cheaper technologies and cheaper biomass. Biomass gasification brings two important concepts: power generation with BIG-CC cycles; and more recently fuel synthesis. Both need significant cost reduction to compete with oil at $30. /bbl, or with “conventional” electric energy. Needed R&D includes: biomass feeding systems; gasification for medium Heating Value gas, using air; gas cleaning; turbines for low HV gas; synthesis reactors (example, liquid phase reactors for DME synthesis). Biomass hydrolysis, yielding sugars from ligno-cellulosic materials, has strong R&D efforts in pilot plant phase (some pre-commercial) aiming at cost reduction; it could lead to a wide range (and large scale) applications worldwide. Future pre-treatments would be mostly physical (steam explosion, Liquid Hot Water); hydrolysis/fermentation processes could be coupled, and use the 5 and 6 Carbon sugars (for ethanol). Future processes could reach 52% of energy recovery from biomass (in ethanol) against 35% today. The research programs include demonstration of pretreatment physical processes; biomass feeding; microorganisms and enzymes for CBP (and simpler) processes. Other uses of sucrose (or sugars from hydrolysis) There has been significant expansion in the last 15 years, worldwide, with some products reaching 1 M t / year. ETHANOL FROM SUGAR CANE IN BRAZIL: THE INDUSTRIAL TECHNOLOGY... 17 · · ·· · · They represented 23% of the global sweetener market (2002): fructose, glucose, and polyols. Organic acids (citric, gluconic, lactic, ascorbic): 0.7 M t / year (1998) Amino-acids (MSG, lysine, threonine): ~1.5 M t / year Polyols: 1.4 M t / year (48% sorbitol, 2001); glycerol (from all sources) was 0.8 M t / year (2000). Enzymes: smaller volumes, high added value; from all sources, US$ 1500. M / year, expected to double till 2008. Plastics: still as a promise: PLA, PHAs, 3-GT; 10 M t / year could be used only for packaging, substituting for oil derived plastics. The sugar industry in Brazil has some commercial production: Llysine; MSG; yeast extracts; citric acid; and sorbitol. Plastics (PHB) are in pre-commercial stage. Possibilities for “larger scale” products (~1 M t/year) and specialties (10 – 50k t/year) are being evaluated in many sugar mills. Ethanol based products have been established in Brazil; they were discontinued in the 90’s, and are being re-evaluated. From 1980 to 1990 more than 30 products used up to 0.5 M m3 ethanol / year; in 1993 the installed capacity for 14 products was larger than 100000 t / year. The analyses for the development of sucrose derived products in Brazil consider: · · Materials and auxiliary systems have relatively low cost (sugar, energy, effluent treatment and disposal) An “average size” sugar mill, with 1/3 of its cane, could produce ~ 70,000. t / year of a new sucrose derived product; it would probably be self-sufficient in energy, and in many cases the mill’s effluent / disposal systems would be used Technologies for “new” products are in many cases available (though not always the “best”) for licensing or buying. Commercializing the product is a difficult point for most sugar mills; adequate partnerships and associations may be necessary in some cases, especially if exportation is considered (the most usual situation). · · 18 INDUSTRIAL PERSPECTIVES FOR BIOETHANOL Comments It is expected that in the next 10 – 20 years a much more efficient use of the sugar cane biomass will increase significantly the range of products and their value. Energy (both power and liquid fuels) will become the most important fraction of the sales. Some technologies in advanced development stage (worldwide) may be the key for this transformation: the hydrolysis of biomass (bagasse and trash), as well as many different fermentation technologies; and the biomass gasification, leading to power or fuel synthesis. Sugar cane appears as an ideal feedstock for the future “biorefineries”, for its relatively low cost, large availability and an interesting mix of 1/3 sucrose, 2/3 pre-processed ligno-cellulosic material. Eduardo Pereira de Carvalho UNICA Isaias C. Macedo NIPE, UNICAMP Technological evolution of the Brazilian sugar and alcohol sector: Dedini’s contribution José Luiz Olivério Abstract During the past 30 years, the sugarcane production in Brazil, increased from less than 100 million metric tonnes to more than 400 million tonnes today. This expansion was necessitated by the expansion in the bioethanol and cane sugar demand, both locally and globally. This paper describes and discusses the various stages of the evolution of the industry, as well as the next trends, supported by technological advances, in particular those emanating from Dedini’s significant expertise. La evolución tecnología en la industria del azúcar y del alcohol en Brasil: la contribución de Dedini Durante los últimos 30 años la producción de caña de azúcar en Brasil aumentó de una cifra por debajo de 100 millones de toneladas métricas a más de 400 millones de toneladas en la actualidad. Dicha incremento fue el resultado del aumento en la demanda por bioetanol y caña de azúcar, tanto local como global. En este trabajo se describen y analizan las varias etapas de la evolución en la industria, así como también las tendencias futuras respaldadas por los avances tecnológicos, en particular aquellos procedentes de la valiosa experiencia de Dedini. Die technologische Evolution des brasilianischen Zucker- und Alkoholsektors: Dedinis Beitrag In den letzten 30 Jahren hat sich die Zuckerrohrproduktion in Brasilien von unter 100 Millionen Tonnen auf heutige über 400 Millionen Tonnen erhöht. Diese Expansion wurde durch die lokale und globale Steigerung der Bioethanol- und Rohrzuckernach- 20 INDUSTRIAL PERSPECTIVES FOR BIOETHANOL frage notwendig. Dieses Referat beschreibt und diskutiert die verschiedenen Stadien der Evolution dieses Industriezweigs sowie die nächsten Trends, die, von technologischen Fortschritten unterstützt, insbesondere aus dem beträchtlichen Wissensschatz von Dedini entspringen. Introduction The Brazilian sugar and alcohol industry is the most competitive in the world, matched by high productivity, better yields and low costs. The industry well demonstrates how Brazilian technological capabilities can respond quickly and effectively to the most diverse market stimuli and demands, by offering quality products, that have been developed with its own technology or, when acquired abroad, is well capable of embracing new technology, as well as expanding the know-how to produce the technology locally and thereby minimize imports. The catalyst responsible for such development has been the expansion that the industry has experienced over the last 30 years, spurred on by increase in ethanol production, followed later by sugar production and, more recently, focus on maximizing the use of sugarcane. Over this period, combination of experience and accumulation of new knowledge has been successfully applied to improving not only productivity on, but also innovations in the development of new equipment and processes or systems as well as the establishment of optimized plants. We believe that such evolution is due to the integration and interaction of four stakeholders in the process: namely the equipment manufacturers, the technology institutes and R&D centers, industry consultants and the mills/distilleries. Dedini, as a leading company in the supply of parts, components, equipment, systems and complete plants, throughout its history and nowadays, has contributed significantly to the advances in the industry through the introduction of pioneering solutions and products. Model of technological evolution – the 5 big stages It is our understanding that such development in the industrial area may be explained by Figure 1, where the 5 big stages of the technological TECHNOLOGICAL EVOLUTION OF THE BAZILIAN SUGAR AND ALCOHOL SECTOR... 21 evolution in the past few decades are highlighted: 1) increase of equipment capacities; 2) increase of overall yields; 3) greater use of sugarcane energy: 4) greater use of sugarcane products and byproducts; 5) sugar and alcohol mill defined as an energy-and-food producing unit. Figure 1. Sugar and alcohol sector - model of industrial technological evolution - 5 big stages Figure 2. The sugar and alcohol mill defined as an energy-and-food producing unit 22 INDUSTRIAL PERSPECTIVES FOR BIOETHANOL Increase of equipment capacities With the implementation of PROALCOHOL programme, priority was first given to the development of capacity increase. Such priority was justified by the need to raise sugarcane processing to obtain bigger production volumes (a PROALCOHOL requirement), allied to the lack of resources for investment in plants expansion. As a consequence, the existing equipment were used to their limits and upgraded by means of the development of the materials used, fittings, components and design modifications to achieve better performances. Item 1 of Figure 3 shows this first stage. Figure 3. Results obtained by the technological evolution with emphasis on Dedini products Increase of overall yields Both at individual process level and overall plant efficiency, there have been significant advances in productivity. This has been made possi- TECHNOLOGICAL EVOLUTION OF THE BAZILIAN SUGAR AND ALCOHOL SECTOR... 23 ble with an important contribution of the technology developed by the equipment manufacturers, who can offer solutions for maximizing alcohol and sugar production. The examples are presented in items 2 and 4 of Figure 3. Greater use of sugarcane energy The concept of sugarcane use has evolved during this period of time, from exclusive juice supplier to juice and energy supplier, by using the byproducts bagasse and stillage (effluent from alcohol production) as energy inputs. Regarding energy optimization, besides improvements in maximizing the production of energy at the mill, there has also been a concerted effort to minimize its consumption during sugar and alcohol production. This has resulted in energy surplus available to be sold to the grid for profit. A whole set of equipment and engineering solutions has been developed to allow such better use of the cane energy, as can be seen in items 3 and 4 of Figure 3. Greater use of sugarcane products and by-products At the early stages of PROALCOHOL programme, sugarcane was only used as feedstock for sugar and alcohol production. But significant advances in technology and process conversion has made it possible today for a modern mill to produce different types of sugar and alcohol, yeasts for cattle feed, huge energy surplus in the form of bagasse, electricity or heat supplied to third parties, stillage as fertilizer and feedstock for the production of biogas/biomethane, and biodegradable plastics, among others. Those technologies are available from the equipment manufacturers. The sugar and alcohol mill defined as an energy- and- food producing unit Some entrepreneurs of the industry conceive the agricultural (+) industrial integrated unit not only as a sugar and alcohol producing unit but as energy and food too. Figure 2 is self-explanatory and shows this 5th 24 INDUSTRIAL PERSPECTIVES FOR BIOETHANOL stage of technological evolution. It should be emphasized that the representation is simplified, since the number of by- and co-products from agricultural and industrial activities are much higher. The equipment industry meets the requirements of the mills by supplying the plants and machinery required for such diversified production with Brazilian technology. Results of the technological evolution The advances in technological developments, from the beginning of PROALCOHOL up to now, has served to improve industry performance while at the same time reduced costs. Figure 3 highlights this evolution and presents the respective state of-the-art of the technology that is available in the marketplace for sugarcane processing, as well as Dedini’s technologies and equipment that make possible such performance. The contribution of this development is also reflected in costs reduction, as shown in Figure 4, making Brazilian ethanol industry very competitive, particularly in light of the current high price of crude oil. With these results, Brazilian bioethanol is already competitive with fossil fuels. The next great leap In addition to the environmental benefit for the use of ethanol or ethanol-gasoline blends, the comparatively low current Brazilian bioethanol production cost of around US$ 30 per barrel compared with over U$60/barrel for crude oil currently, has not only increased local demand but globally too. These developments in paralel with the growing demand of bioenergy has clearly set up opportunities for equipment manufacturers involved in this sector, to penetrate the market. With this in mind, we will present the new technologies that we understand have the higher potential to contribute to this new stage of accelerated development. New technologies - the 3 BIOs revolution Dedini’s vision is that the technological evolution will be focused on the optimum use of the resources that are available in sugarcane agribusiness, and new technologies will be developed with this purpose. TECHNOLOGICAL EVOLUTION OF THE BAZILIAN SUGAR AND ALCOHOL SECTOR... 25 Currently, a number of new developments are underway. We highlight 3 new technologies - the 3 BIOs - due to the revolutionary impact that they will have on the sugarcane industry: (a) production of bioelectricity from the use of bagasse, straw, and co-products, such as stillage; (b) bioethanol production from bagasse and straw; (c) biodiesel production integrated to the sugar and alcohol mill. Emphasis is given to the use of straw (i.e., tops, leaves and straw), since it contains about 1/3 of the cane energy (in rough numbers, the remaining 1/3 is found in juice, and the other 1/3 in bagasse). Figure 4. Technological evolution: anhydrous bioethanol cost reduction - Brazil Bioelectricity production - the 1st BIO The energy content of the sugarcane produced in Brazil annually is quite significant, in the same order of magnitude of the Brazilian yearly production of oil, as shown in Figure 5. It was based on the annual volume of cane processed for sugar and alcohol production (produced during the milling season, 6 – 8 months), measured in kcal and compared to the annual production of oil (12 months), also expressed in kcal. By way of information, 386.2 million metric tons of sugarcane were processed by the sugar and alcohol industry during the 2004/05 season. Figure 26 INDUSTRIAL PERSPECTIVES FOR BIOETHANOL 5 shows the average daily production of oil (barrels/day), but the energy calculation was based on the total oil produced in the respective year. Bagasse is extensively used today in mills as a source of energy for the industrial process. The efficiency however has been low, but this can be improved significantly with available technology. Further, biogas, which is produced from the anaerobic biodigestion of stillage can be used for energy purposes too. The new development is to exploit energy contained in cane crop residues. Technical hurdles and economic rationale for its exploitation has already begun, but the issue of collecting and transporting these residues to the factories, and the underlying costs associated withal those operations has yet to be fully developed. Today, several Brazilian mills, mainly in the State of São Paulo, have already been using crop residues as fuel. Technology is now available to make use of these residues in boilers. We confidently feel that the transference costs will be recovered several fold from the subsequent energy produced. Surplus cogeneration of power from these residues (as well as bagasse and biogas) adds to the overall profitability of the enterprise (see figure 6). It should be emphasized that the technology is already available to the industrial sector, and that the solutions and equipment for energy optimization that are shown in the “mill features” are part of Dedini’s products line. Figure 5. Comparative total yearly energy content: sugarcane x oil - Brazil TECHNOLOGICAL EVOLUTION OF THE BAZILIAN SUGAR AND ALCOHOL SECTOR... 27 Figure 6. Sugar and alcohol mill for maximum production of bioelectricity. Bioethanol production from bagasse and straw - the 2nd BIO Bioethanol production from lignocellulosic materials is increasingly receiving research interest worldwide. In this direction, Dedini has developed the DHR-Dedini Hidrólise Rápida (Dedini Rapid Hydrolysis) - a hydrolysis process that converts the cellulosic matter of bagasse into sugars that, when fermented and distilled, result in bioethanol production. DHR revolutionary continuous process reduces hydrolysis reaction time, enabling high yields, few unit operations, minimum investment, reduced energy consumption and low operating costs. The process was developed in the late 80s in laboratory and in pilot scale, and its technicaleconomic feasibility has since been confirmed quite satisfactorily. In 2003, a Semi-Industrial Plant of 5,000 liters of ethanol/day started operations in São Luiz Mill, Pirassununga, Brazil, of Dedini Agro Group, through a joint venture between Dedini, COPERSUCAR and FAPESP (Research Support Foundation of the State of São Paulo). The Unit is currently in the stage of continuous operation, with the purpose of completing the engineering parameters for production on industrial scale. Figure 7 presents two pictures of the Semi-Industrial Plant. When its full potential is attained, 28 INDUSTRIAL PERSPECTIVES FOR BIOETHANOL DHR will have a huge impact to the industry. We confidently feel that , it will: • almost double the current production of bioethanol per hectare of harvested cane, with the use of the surplus bagasse and straw; and • bring down the costs of bioethanol production. Figure 8 shows the impact of the DHR process on the overall productivity of the bioethanol mill. Figure 7. The semi-industrial plant - 5,000 I/day - DHR process Figure 8. DHR - impact on production and productivity. TECHNOLOGICAL EVOLUTION OF THE BAZILIAN SUGAR AND ALCOHOL SECTOR... 29 Biodiesel production integrated to the sugar and alcohol mill – the 3rd BIO As noted earlier in the 5th stage of the technological evolution, the mill is conceived not only as a sugar-and-alcohol producing unit but of energy and food too. More recently, this 5th stage of technological evolution embraced the integration of biodiesel production in sugar and alcohol plants. This integration makes it possible to maximize the use of available resources while helping to keep biodiesel production cost to a minimum. It is important to note that the Brazilian Biodiesel Program was approved by the Government and entered into force in 2004/2005. Biodiesel is a natural substitute for diesel oil, using renewable feedstocks like vegetable oils, animal fats and re-used cooking oil reacting with ethanol or methanol in the presence of acid or basic catalyst. If the ethyl route with bioethanol is used, the biodiesel produced will be 100% renewable. The biodiesel/sugar and alcohol mill integration concept was introduced by Dedini into the market in 2004, and has become reality, with Dedini closing the first pioneering sale in the world of an integrated biodiesel plant for Barralcool Mill in Barra do Bugres, Mato Grosso, Brazil, in November/2005. The plant has capacity for 50,000 tons/year of biodiesel, and a series of advanced and innovative features, such as, the use of a number of different types of vegetable oils (such as oils from soya, sunflower, peanuts, cotton seed, etc.) and animal fats as feedstock in the same plant, which operates with flexibility in the ethyl or methyl route. As Barralcool Mill has already pioneered the bioelectricity production in Mato Grosso State, this mill will be the first in the world to produce bioethanol, bioelectricity and biodiesel. The stages of full integration of biodiesel production in a sugar and alcohol mill are shown in Figure 9. The Barralcool Mill is already in the first stage, that means, partial industrial integration. The 2nd and 3rd stages are the next implementation phases of this new concept. The 2nd stage already has supporting technology for successful implementation. The 3rd one is in the initial stage of development and will have a great impact in additional cost reduction of biodiesel, as well as bioethanol. Figure 9 shows the 3 BIOs as products of the same sugar and alcohol mill: bioelectricity, bioethanol and biodiesel. 30 INDUSTRIAL PERSPECTIVES FOR BIOETHANOL Figure 9. Biodiesel production integrated to the sugar and alcohol mill the 3 evolution stages Conclusions Figure 3 well demonstrates the significant technological advances in the sugar and alcohol sector in Brazil which has informed its development and made it the key player in the global industry. The advances TECHNOLOGICAL EVOLUTION OF THE BAZILIAN SUGAR AND ALCOHOL SECTOR... 31 have not been restricted just to the processing sector. Sugarcane production has expanded from less than 100 million of tons at the beginning of PROALCOHOL programme, to around 400 million tonnes today. Arguably, Dedini has been and continues to be one of the leading players contributing to the success of the industry. Figure 10 presents Dedini’s contribution to the sugar and alcohol mills, with reference to the supplies made, which represent the biggest sales volume in the world. Among other facts, the following must be pointed out: • Dedini’s market share in equipment already installed in Brazilian mills (Historical Market Share) is higher than 80%; • more than 80% of all bioethanol produced in Brazil - which numerically correspond to around 30% of the world ethanol – use Dedini distilleries and equipment. Finally, it must be pointed out that Dedini accepts the challenge to contribute even further to the competitiveness of the sugarcane industry, by fully meeting the demand for technology, equipment and complete plants, and making it possible to raise even more the high performance of yields, productivity and costs. Figure 10. Dedini’s contribution to the sugarcane industry José Luiz Olivério Senior Operational Vice President, Dedini S/A Indústrias de Base. Tel: +55 19 3403 3006 Fax: +55 19 3421 3642 E-mail: [email protected] Web: www.dedini.com. 32 INDUSTRIAL PERSPECTIVES FOR BIOETHANOL References COPERSUCAR, Área Central de Planejamento e Economia. PROÁLCOOL – Fundamentos e Perspectivas, São Paulo; ed. COPERSUCAR, 2nd edition 1989, 122 p., Brasil. Goldenberg, J., Coelho, S.T. and Lucon, O.(2002) – Ethanol Learning Curve – The Brazilian Experience, Elsevier, Biomass and Energy, 26, pg 301-304. Olivério, J. L. – “Desenvolvendo Integralmente o Potencial de Geração com as Tecnologias Existentes”, In: 2nd Sugarcane and Energy International Seminar, 2002, Ribeirão Preto, INEE-Instituto Nacional de Eficiência Energética, Brazil. Olivério, J. L. – “Produção de Álcool a Partir do Bagaço: o Processo DHR”. In: II International Conference – Fuel Ethanol Internationalization, 2002, São Paulo, DATAGRO, Brazil. Olivério, J. L. – “Evolução Tecnológica do Setor Sucroalcooleiro: a Visão da Indústria de Equipamentos”, In: 8th STAB National Congress, November 2002, Recife, PE, Brazil. Olivério, J. L. and Hilst, A.P. – “DHR-Dedini Hidrólise Rápida (Dedini Rapid Hydrolysis) – Revolutionary Process for Producing Alcohol from Sugar Cane Bagasse”, Proceedings XXV ISSCT Congress, 2005, Guatemala, pg. 320-327. Olivério, J. L. and Hilst, A.P. – “DHR-Dedini Hidrólise Rápida (Dedini Rapid Hydrolysis) – Revolutionary Process for Producing Alcohol from Sugar Cane Bagasse”, International Sugar Journal, March 2004, ner 1263, pg. 168-172. Olivério, J.L. – “A Indústria Brasileira das Produtoras de Biocombustíveis:, Bioetanol e Biodiesel”, 1st Brazil-Germany Biofuels Fórum, November 2004, São Paulo, Brazil. Acknowledgments: This article was firstly published in the International Sugar Journal 2006, vol. 108 (1287): 120-129, and it is now here published with their authorization. Insertion of Bioethanol into a new paradigm for the Brazilian Chemical Industry Pedro Wongtschowski Francisco I. Pellegrini Flávio do Couto Bezerra Cavalcanti CONTENTS INTRODUCTION General Bioethanol as Fuel Commercial Bioethanol as raw material Integrated production of chemicals ·· ·· · COMPETITIVENESS OF BIOETHANOL AS FUEL Competitiveness of conventional production Production cost of bioethanol Price composition of bioethanol producer price The economic attractiveness of conventional bioethanol · · · · Competitiveness with full utilization of sugarcane Hydrolysis of lignocellulosic materials · Production cost of bioethanol – Full utilization · Economic attractiveness of Bioethanol – Full utilization · ETHANOL AS RAW MATERIAL FOR THE CHEMICAL INDUSTRY Non-Integrated Production of Ethylene Integrated Production of Ethylene ·· 34 INDUSTRIAL PERSPECTIVES FOR BIOETHANOL Conventional ethanol · Full utilization of sugarcane · Conclusions · The Tree of Bioethanol Derivatives · · Ethylene Traditional Derivatives – Acetic Acid and Ethyl · AcetatePotential Derivatives – n-Butanol, Methyl Ethyl · · Ketone, Ethylene Oxide, Monoethylene Glycol Bioethanol as coadjuvant raw material The Tree of Bioethanol Derivatives revisited INTRODUCTION General All of the ethanol produced in Brazil is bioethanol, in the sense that it is produced by aerobic fermentation (with Saccharomyces cerevisiae) of musts containing mainly sugars with six carbon atoms, such as glucose and fructose obtained after inversion (hydrolysis) of sucrose in slightly acid medium at low temperatures, the sucrose being obtained from milled cane stalks. The use of bioethanol as a renewable raw material as required for its insertion into a new paradigm for the chemical industry, depends fundamentally on three aspects: producer price (identified here as the price paid to sugar mills and/or distilleries); availability and reliability, in that order. Whenever the producer price is higher than production cost, the production becomes feasible and ensures product availability in amounts that can be considered unlimited in the short and medium terms, given the availability of agriculturable land with appropriate climate, in Brazil. In other words, it is possible to say that bioethanol is an abundant raw material or that it can at least be produced in relative abundance, provided its production is required and remunerated by the market. INSERTION OF BIOETHANOL INTO A NEW PARADIGM FOR THE BRAZILIAN... 35 The reliability of bioethanol supply, on its turn, is connected to the reliability of the economic appeal of its production that, as seen below, is also influenced by agribusiness exogenous factors such as the international price of crude oil and the tax burden. Although these factors are decisive, they will interfere only indirectly on the economic appeal of bioethanol production, whose technical reliability can be undoubtedly ensured. For now, it is enough to mention that there is great hope that the bioethanol production will maintain its economical appeal for a long time, ensuring its supply at least in the fuel market context. As mentioned before, the use of bioethanol as raw material will depend on other factors. Let us analyze the status of bioethanol in two different scenarios, one based on the conventional production of bioethanol and the other based on full utilization of sugarcane. Also, let us state from the beginning that the lower its production cost, the higher the probability of its availability to the fuel market. The use of bioethanol as raw material for the chemical industry, in non-integrated plants, will naturally depend on the price paid to the bioethanol producers, by the market, and on the economical feasibility of this operation at market prices of the end products, many of which are also influenced by the international price of crude oil. Finally, we will also analyze the competitiveness of integrated production of chemicals where, instead of purchasing bioethanol at the market, the producer of chemicals buys sugarcane from a supplier and bioethanol remains as an intermediate link in the process chain. Concerning integrated production of bioethanol, two different scenarios are possible, one conventional and the other with full utilization of the sugarcane, with expectation of advantages for the latter. Bioethanol as Fuel The market price of bioethanol, which is directly correlated to the bioethanol producer price, is defined by mechanisms intrinsic to the domestic fuel market that, on its turn, is influenced by the global fuel market and, to a lesser extent, by the price of sugar on the global markets. The key parameter in the fuel market is the international price of crude 36 INDUSTRIAL PERSPECTIVES FOR BIOETHANOL oil; therefore, to a great extent, the price of commercial bioethanol and the bioethanol producer price become directly influenced by the international price of crude oil. Whenever international prices are high, the domestic market pays more for automotive fuels, including bioethanol, either used alone or mixed with gasoline, and the producer gets higher prices for the bioethanol that is made available in distilleries. Conversely, when international prices of crude oil are low, producers will pay less for the bioethanol in the distillery. A progressive decrease in international prices of crude oil might make the production of bioethanol unfeasible, for the fuel market, if the price of bioethanol received by the producer were lower than its production cost. This is what really happens, although the current mechanism of price fixation for sugarcane (the raw material for bioethanol production) is connected to the prices of sugar and alcohol, which to a certain extent are related to the international price of crude oil. Thus, a reduction in price of crude oil promotes a reduction in price of sugarcane, although not in the same proportion, somehow protecting bioethanol producers and strengthening their business. As expected, the crucial questions posed refer to the future performance of the international price of crude oil. Given that, since the crises occurred in the 1970s, the international prices of crude oil do not show any direct correlation with its production costs and often are multiples of them, a climate of total uncertainty concerning the future performance of these prices will always prevail. Speculations concerning the occurrence, on the medium term, of the so-called production peak of crude oil suggest that, as a function of a tendency toward relative scarcity, the international price of crude oil will never return to the levels shown in the 1990s and in the beginning of this century, around $ 25 per barrel, unless technological breakthroughs were to occur concerning either exploitation and production of crude oil or consumption of automotive fuels. Even in such case, crude oil suppliers would, as they are today, be in the comfortable position of, at the least menacing signs, being able to reduce considerably the prices of crude oil by merely reducing their profits, without necessarily incurring in losses. INSERTION OF BIOETHANOL INTO A NEW PARADIGM FOR THE BRAZILIAN... 37 Currently, for a crude oil production cost in the order of $10 per barrel, which is considered reasonable as an indication of the average global cost, the production cost is in the order of $ 75 per ton or approximately $ 2.0 per million Btu, indicating the extreme competitiveness of the crude oil and fuel derivatives industry, besides establishing the parameter which industries using alternative fuels will have to compete with. If we consider a minimum sales price of crude oil that ensures remuneration for investments and payment of royalties on production, the minimum global average price of crude oil would be in the order of $ 3.0 per million Btu, requiring fuel derivatives to be sold for approximately $ 3.5 per million Btu. Therefore, any producer of an alternative fuel whose production cost is higher than $3.5 per million Btu is really in an uncomfortable position. An international price of crude oil of $ 60 per barrel, such as the current one, increases sales prices of fuel derivatives to approximately $ 15.2 per million Btu, placing alternative fuel producers in a circumstantially more comfortable position. Commercial bioethanol as raw material for the chemical industry Since most bioethanol goes to the automotive fuel market, both in its pure form and mixed with gasoline, its use as raw material in the chemical industry depends, as mentioned above, on its market price as established by a mechanism of direct competition with gasoline, based on their respective heat powers and combustion efficiencies in Ottocycle engines. On the other hand, the price of gasoline at fuel stations is directly correlated with the international price of crude oil, although through variable correlation coefficients, since the factors intervening in the establishment of these coefficients (such as the corresponding tax burden) vary as a function of the balance established in the Brazilian social and political scenarios and of the use of administered prices as parameters of macroeconomic adjustments. This shows that the international price of crude oil is the parameter fixing the limits of competitiveness of the commercial bioethanol, as 38 INDUSTRIAL PERSPECTIVES FOR BIOETHANOL raw material for the chemical industry since, on one hand, it establishes a floor price for commercial bioethanol due to its energetic equivalence to gasoline and, on the other hand, establishes a ceiling price for chemicals that can be produced both from bioethanol and crude oil derivatives. Establishing the floor price of commercial bioethanol and the ceiling price of each chemical that can be produced both from bioethanol and from crude oil derivatives, as a function of the international price of crude oil, becomes then the main objective of any technical and economical analysis intended to determine the feasibility of bioethanol use as raw material for the chemical industry. For each specific application of bioethanol as raw material it is possible to identify an alternative standard process where the raw materials are crude oil derivatives and/or natural gas derivatives and compare it with the alcohol-chemistry process, and also determine a critical price for crude oil, above which the alcohol-chemistry process, besides being competitive with the alternative standard process, shows to be economically attractive according to a specific profitability criterion. Integrated production of chemicals As an alternative to commercial bioethanol, integrated production of chemicals from sugarcane has been suggested, where bioethanol appears only as an intermediate product. In this case, if we disregard the opportunity cost represented by the simple sale of bioethanol to the fuel market, it would be possible to expect that one of the restrictions imposed by crude oil price, that is, the price floor of the raw material, would be eliminated. However, even when we consider integrated production of chemicals from sugarcane, the price of bioethanol in the fuel market, together with the price of sugar in the international market, continue to affect the feasibility of using bioethanol, now an intermediate, as raw material for the production of chemicals. This is due to the fact that sugarcane price is directly correlated to bioethanol producer price through the bioethanol market price, as well as to sugar producer price through the international market price of sugar. INSERTION OF BIOETHANOL INTO A NEW PARADIGM FOR THE BRAZILIAN... 39 Therefore, the integrated production of chemicals that use sugarcane as a raw material experiences (i) a direct restriction by the international price of crude oil, that continues to fix the ceiling price of chemicals that can be produced both from bioethanol and crude oil derivatives; (ii) an indirect restriction by the international price of crude oil that affects the market price of bioethanol and, as a consequence, the price of sugarcane and (iii) a direct restriction by the international market price of sugar, which also affects the price of sugarcane. Moreover, the prevailing pricing rule to establish the price of sugarcane, whose parameters necessarily reflect conjunctural aspects, can be changed unpredictably. Under certain circumstances, a substantial change in price of sugarcane can render an operation to be implemented, or even an ongoing operation of integrated production of a given chemical, unfeasible. When purchasing sugarcane or, more specifically, when buying cane stalks from the supplier, the integrated producer of chemicals is acquiring not only the sucrose paid for, according to the rule that established the price of sugarcane, but also the whole amount of lignocellulosic material associated with the stalk, that is, the bagasse, which, in principle, the supplier will provide at no cost. Therefore, if the integrated producer has access to appropriate technologies for bagasse processing aimed to its conversion into additional sugars, even if the parameters of fixation of sugarcane price are kept unchanged, the integrated producer will notice that the effective price of the raw material is lower than the price of cane stalk. The more additional sugars can be produced from bagasse, the higher the cost reduction of raw material. The feasibility of bagasse conversion into additional sugars directly induces us to the feasibility of using also the tops and straw remaining on the sugarcane plantation after mechanized harvesting. Of course a substantial fraction of the tops and straw produced during the harvest can be conveyed to the industrial unit, as an additional raw material for the conversion unit that converts bagasse into additional sugars, further reducing the apparent price of the raw material. For estimate purposes, it is worth mentioning that the amount of biomass pre- 40 INDUSTRIAL PERSPECTIVES FOR BIOETHANOL sent in integral sugarcane (stalk + tops and straw) is, on the Brazilian average, equally distributed among sucrose, dry fibers from bagasse and dry fibers from tops and straw. This means that the total biomass produced by a given sugarcane plantation in one crop equals three times the total amount of sucrose used to produce sugar and alcohol by conventional operations. Therefore, full utilization of sugarcane using any technique for conversion of lignocellulosic materials is the means integrated producers can use to reduce the apparent price of his raw material and become more competitive vis-à-vis producers who use crude oil derivatives as raw material. COMPETITIVENESS OF BIOETHANOL AS FUEL Competitiveness of conventional production · Production cost of bioethanol Given the technical and economical parameters currently prevailing in the sugar and alcohol sector, Brazil is the region with the lowest production cost of ethanol in the world, even when using the conventional technology, since – Both in Southeastern and Northeastern Brazil, the crop season is long (about 8 months); – The average agricultural productivity, in the five-cut schedule is high, in the order of 80 ton/ha per year; – The dry biomass content in the plant itself is high, in the order of 36% (w/w); – Finally, the species used are highly resistant to pests, so no incidents of this kind were noticed in the recent past. If we consider that (a) cane stalk has an average sucrose content of 14.6% (w/w); (b) approximately 98% (w/w) of sucrose are recovered in the milling process; (c) the yield of bioethanol equals 45% the sucrose INSERTION OF BIOETHANOL INTO A NEW PARADIGM FOR THE BRAZILIAN... 41 yield in the fermentation and distillation processes, the conclusion is that, according to the conventional process, 64.2 kg of bioethanol are produced per ton of cane stalk fed to the distillery; this means that 15.6 tons of cane stalk are required to produce one ton of bioethanol. Knowing that, besides the cane stalk, there is a $ 43 cost to produce one ton of bioethanol, its total production cost can be easily estimated using the equation below. Production cost of bioethanol = 15.6 x price of cane stalk + 43.0 (I) Where the price of cane stalks and the production costs of bioethanol are expressed as $ per ton. This equation is generally valid regardless the price of crude oil, since its angular coefficient (15.6) is not affected by the price of crude oil and its already small linear coefficient (43.0) almost does not change with the price of crude oil. In other words, equation (I) above provides a fair estimate of bioethanol production costs. For example, in the current scenario – beginning of 2006 –, with the cane stalk supply price equal to $ 15 per ton, which still does not mirror the unexpected increases both in the bioethanol producer price and the international price of sugar, which in the last 3 years rose from an average $ 200 per ton to $ 400 per ton, using equation (I) above, we have a total production cost for bioethanol in the order of $ 277 per ton. This corresponds to a production cost of approximately $ 10.3 per million Btu, an intermediate situation between the minimum sales price and the current average price of fuel derivatives, respectively $ 3.5 per million Btu and $ 15.2 per million Btu. Since the current bioethanol producer price is approximately $ 620 per ton, which is incompatible with the international price of crude oil, it can be seen that the production of bioethanol is today an abnormally appealing operation, given the current price of cane stalk, with a unit gross profit in the order of $ 340 per ton for a unit investment of $ 300 per ton bioethanol/year and a gross profit/investment ratio in the order of 1:1. However, the adjustment of the cane stalk price to the current international market sugar price, that reflects directly on the domestic market 42 INDUSTRIAL PERSPECTIVES FOR BIOETHANOL sugar price, could be concerning both for bioethanol producers and integrated producers in terms of the price of sugarcane, that is fixed as a function of the bioethanol producer price and sugar producer price. Supposing we applied the correlation to estimate the price of sugarcane as a function of the bioethanol producer price ($ 620 per ton) and sugar producer price ($ 400 per ton), the price obtained for sugarcane would be approximately $ 26 per ton and the production costs of bioethanol would rise to approximately $ 440 per ton. Bioethanol producers would face a reduction in the unit gross profit from approximately $ 340 per ton to approximately $ 180 per ton, as well as a reduction in the gross profit/investment ratio to something around 0.6:1, which is closer to the historic average of the sector. This sharp increase in the international price of sugar, a phenomenon that has occurred before, is supposedly a reflex of a slight transient reduction in the global stocks of this product, associated with a perception of the increase in bioethanol demand and production. Since both products come from the same raw material (sugarcane), it would be possible to infer that a fraction of sugarcane larger than the currently used would be diverted to bioethanol production, causing a relative scarcity of sugar. In reality, the global demand for sugar grows vegetatively and the growth of this demand is easily met by major producers through gradual increases in the production capacity, either by using idle capacity or diverting less sucrose to produce ethanol, since most industrial units are designed to simultaneously produce sugar and bioethanol and, in some cases, present flexibility beyond the 50-50 ratio in the distribution of sucrose between sugar production and bioethanol production. It is also possible to interpret this increase in the international price of sugar as an attempt from producers to keep it aligned with the so called parity criterion that correlates the bioethanol and sugar producer prices, taking into account that to produce and sell one ton of bioethanol, the producer will not produce and sell 2.2 tons of sugar. Historically, in the last few years, the price of sugar has been equivalent to 150% the parity price of sugar in relation to bioethanol; so, it would be possible to express the price of sugar by the following equation: INSERTION OF BIOETHANOL INTO A NEW PARADIGM FOR THE BRAZILIAN... 43 Sugar producer price = 1.5 x bioethanol producer price / 2.2 (II) Where the sugar producer price and the bioethanol producer price are expressed as $ per ton. Coincidentally or not, for a bioethanol producer price equal to $ 620 per ton we can estimate a sugar producer price, according to the correlation with the parity price, in the order of $ 420 per ton, for a current price in the order of $ 400 per ton. Based on this, the conclusion is that the abnormality does not lie in the international price of sugar, but in the bioethanol producer price, that is abnormally high compared with its historical correlation with international prices of crude oil. A return to normality is expected for the near future, with a decrease in bioethanol and sugar producer prices, without unexpected rises that could cause temporary or permanent increases in cane stalk prices. · Formation of bioethanol producer price The possibility of using bioethanol directly as an automotive fuel in “dual fuel” engines, as well as in engines adapted to use a mixture of gasoline and ethanol provides a mechanism to form the bioethanol producer price based on its market price at fuel stations, connected to the price of gasoline at these same fuel stations. Based on the ratio between the combustion heats of bioethanol and gasoline, as well as on the ratio between the efficiencies of Otto cycle engines, when using bioethanol and gasoline, an equilibrium point is established, to form the price of bioethanol at fuel stations, equal to 70% the price of gasoline in these same stations, with both prices expressed as volume or mass units. Maximum price of bioethanol at fuel stations = 0.700 x price of gasoline at fuel stations (III) In other words, whenever the price of bioethanol is higher than 70% the price of gasoline at the fuel station, if there is a supply of gasoline 44 INDUSTRIAL PERSPECTIVES FOR BIOETHANOL in the same sales point, consumers who own dual-fuel vehicles will immediately suspend the purchase of bioethanol and shift toward gasoline. This is an effective mechanism to control the price of bioethanol. On the other hand, the net bioethanol producer price delivered to the door of the distillery keeps historically a variable proportion within a narrow range in relation to the price of bioethanol at fuel stations, 51.5% being a good estimate of this proportion. This means that the producer receives a net price for bioethanol in the distillery in the order of 36% the price of gasoline at fuel stations. Net bioethanol producer price = 0.361 x price of gasoline at fuel stations (IV) Taking into account that the price of gasoline at Brazilian fuel stations expressed as dollar per ton keeps historically an average ratio of 24.1 with the international price of crude oil expressed as dollar per barrel, it can be seen that the bioethanol producer price correlates with the international price of crude oil according to equation (V) below. Net bioethanol producer price = 8.717 x international price of crude oil (V) Where the price of bioethanol is expressed as $ per ton and the international price of crude oil is expressed as $ per barrel. This correlation expresses approximately what was observed in the recent past and is expected to occur in the short and medium terms, in the Brazilian scenario of automotive fuels. It is not expected that realization prices, equivalent to net sales prices, for gasoline received by Brazilian refineries will be different from international prices of this product; also not expected is a major reduction in the tax burden charged on the price of gasoline; no significant structural change is foreseen in the automotive fuel sector; as a consequence, it is possible to admit a high probability of validity of the correlation expressed by equation (V) at least in the short- and medium terms. It is exactly from equation (V) above that we infer that the bioethanol INSERTION OF BIOETHANOL INTO A NEW PARADIGM FOR THE BRAZILIAN... 45 producer price is at least approximately 18% higher than the price this product should present as a function of the international price of crude oil. · The economic attractiveness of conventional bioethanol Based on the correlations shown above, the conclusion is that exclusive production of bioethanol by the conventional process has great economical attractiveness, characterized by a less than 4-year simple payout period, when the price of crude oil is higher than $ 43 per barrel, as can be seen from the following estimates: – International price of crude oil: – Bioethanol producer price: – Sugar producer price: – Cane stalk supplier price: – Production cost of bioethanol: – Unit gross profit: – Unit total investment: – Gross Profit / Investment Ratio: $ 43 per barrel $ 375 per ton $ 256 per ton $ 15.9 per ton $ 291 per ton $ 84 per ton $ 300 per ton 28.0 % per year It is worth emphasizing that the attractiveness of conventional production of bioethanol, as shown above, lies on the premise that the price of gasoline at Brazilian fuel stations will keep, with the international price of crude oil, a relationship higher than the relation prevailing among international prices of gasoline, in different consumer markets, and the international price of crude oil. This means that Brazilian gasoline is proportionally more expensive than gasoline sold in the different global markets. In summary, supposing the validity of the premises on international price of crude oil and the relationship between the price of gasoline at fuel stations and the price of crude oil, the production of bioethanol, based on extraction of sucrose from cane stalks and on the use of bagasse fibers as fuel, is reliable and highly profitable. Moreover, given the high probability that international prices of crude oil will keep over the $ 43 per barrel and that the structure of the price of Brazilian gasoline will be maintained, the probability of the 46 INDUSTRIAL PERSPECTIVES FOR BIOETHANOL attractiveness of bioethanol production, even using the conventional process, will be also maintained high. However, it is worth emphasizing that the attractiveness of the conventional production of bioethanol, for the fuel market, lies currently on premises for which there are no guarantees of permanence in the medium and long terms, except for the guarantee connected to the perception of relative scarcity of crude oil, the global demand for biofuels, and the Brazilian government avidity for taxes. Competitiveness through full utilization of sugarcane · Hydrolysis of lignocellulosic materials Recently, emphasis has been given to the possibility, published since a long time in the technical and patent literature, of full utilization of sugarcane by applying the lignocellulosic hydrolysis technology to the dry fibers contained in the bagasse and also in tops and straw, or more precisely, to be applied to the hemicellulose and cellulose contained in fibers of bagasse and tops + straw, respectively around 35% and 40% (w/w). In one of its most popular versions – the diluted acidic hydrolysis – the lignocellulosic materials hydrolysis process can be performed in stages. The first stage, known as pre-hydrolysis, is milder and aims to convert hemicellulose into a solution of pentoses (sugars with 5 carbon atoms). Subsequently, the remaining fiber, now containing essentially lignin and cellulose, can be subjected to a second, more energetic stage, also known as hydrolysis, that aims to convert cellulose into a solution of hexoses (sugars with 6 carbon atoms). Another version of the process is enzymatic hydrolysis that is very encouraged by enzyme producers; similar to the starch enzyme hydrolysis that is applied mainly in the US to produce ethanol from corn, it could be applied to sugarcane lignocellulosic materials. However, due to the characteristics of these lignocellulosic materials, the specific consumption of enzymes – a costly insum – is still very high, making the process apparently unattractive from an economic perspective. INSERTION OF BIOETHANOL INTO A NEW PARADIGM FOR THE BRAZILIAN... 47 A third way that is also being developed is the so-called SSF (Simultaneous Saccharification and Fermentation) where genetically modified microorganisms are used to simultaneously hydrolyze hemicellulose and cellulose, converting them into their respective C5 and C6 sugars which would then be converted into bioethanol by fermentation in the reaction medium itself. The tops and straws are burnt prior to manual harvesting; or, they are left on the field during mechanical harvesting. Bagasse is entirely burnt in sugar mills (to produce exclusively sugar) or in distilleries (to produce exclusively ethanol) for steam and electric power generation. As for distilleries, 25% of the amount of bagasse produced in sugar mills would be more than enough to meet the demand of the distillery for steam and electric power; this means that with a properly designed distillery there would be a surplus of bagasse equal to 75% the total amount of bagasse that was produced in the sugar mills, which reached the distillery incorporated to the cane stalks. In reality, since lignin represents about 25% (w/w) of fibers both from bagasse and tops + straws, the potential increase in production of sugars by hydrolysis of hemicellulose and cellulose, that represent together 75% of fibers, equals 150% the production of sucrose; this means that, ideally, for the same planted area, the production of bioethanol could be multiplied by a factor of 2.5. However, supposing that hydrolysis yields are lower than theoretical yields, we can achieve twice the production of bioethanol for the same plantation area. · Production cost of bioethanol – Full utilization With full utilization of sugarcane, only 9.4 tons of integral sugarcane are required to produce one ton of bioethanol. Moreover, a reduction in the other production costs from $ 43 to about $ 32 per ton of bioethanol is noticed. Therefore, equation (V) is converted Production cost of bioethanol = 9.4 x Price of integral sugarcane + 32.0 (VI) 48 INDUSTRIAL PERSPECTIVES FOR BIOETHANOL For a price of integral sugarcane equal to that of cane stalk ($ 15 per ton), a new total production cost of bioethanol, in the order of $ 175 per ton of bioethanol is obtained. This means a reduction in the production cost in the order of $ 102 per ton of bioethanol, corresponding to approximately 37%. · Economic attractiveness of bioethanol - Full utilization From the correlations developed above, the conclusion is that exclusive production of bioethanol by the process of full utilization of sugarcane has great economical attractiveness, characterized by a less than 4-year simple payout period, when the price of crude oil is higher than $ 21 per barrel, as shown by the estimates below. – International price of crude oil: – Bioethanol producer price: – Sugar producer price: – Cane stalk supplier price: – Production cost of bioethanol: – Unit gross profit: – Unit total investment: – Gross Profit / Investment ratio: $ 21 per barrel $ 183 per ton $ 125 per ton $ 7.8 per ton $ 105 per ton $ 84 per ton $ 300 per ton 28.0 % per year In short, assuming the same premises concerning the conventional production of bioethanol are valid, we note that an improved production using the lignocellulosic materials hydrolysis process remains as reliable as the conventional production, although more competitive, as indicated by the international price of crude oil, that ensures the simple 4-year payout period, which is shorter for production with full utilization of sugarcane than for conventional production. Moreover, the improved process shows to be more robust in face of a low probability tendency of alignment of the relationship between the price of Brazilian gasoline and the international price of crude oil, with the prevailing relationship among the prices of gasoline in different markets, and the international price of crude oil. Similarly, the improved process INSERTION OF BIOETHANOL INTO A NEW PARADIGM FOR THE BRAZILIAN... 49 shows to be more robust than the conventional process in face of casual drops in the international price of crude oil, which is also not probable. ETHANOL AS RAW MATERIAL FOR THE CHEMICAL INDUSTRY Non-integrated production of Ethylene Concerning the possible use of ethanol as raw material for the chemical industry, it is enough to examine the economical feasibility of Ethylene production, for Ethylene market prices, as defined by conventional production from naphtha produced from crude oil, since Ethylene production is the most onerous operation in terms of bioethanol mass yield, requiring the consumption of almost 1.7 tons of bioethanol per ton of Ethylene to be produced. In short, it is known that, usually, the international price of Ethylene related to the international price of crude oil, through the price of naphtha, can be expressed, as $ per ton, with a factor that ranges from 17.0 and 19.0 multiplied by the international price of crude oil, expressed as $ per barrel. Assuming the range average value: International price of Ethylene = 18.0 x international price of crude oil (VII) On the other hand, it is possible to estimate the total production cost of Ethylene from bioethanol purchased at the market, using a simple linear correlation with bioethanol and multiplying the price of bioethanol by a factor of 1.676 and adding a factor of 60, the result being expressed as $ per ton of Ethylene. Production cost of Ethylene = 1.676 x price of bioethanol + 60 (VIII) To simplify the comparison we can express the total production cost of Ethylene from bioethanol as a direct linear function of the international 50 INDUSTRIAL PERSPECTIVES FOR BIOETHANOL price of crude oil, taking into account the existing correlation between the price of bioethanol (in $ per ton) and the international price of crude oil (in $ per barrel): Production cost of Ethylene = 14.612 x international price of crude oil + 60 (IX) Direct comparison between the production cost of Ethylene from bioethanol purchased at the market, and the international price of Ethylene, both prices varying as a function of the international price of crude oil, shows that for an investment index of $ 300 per ton of Ethylene per year, one obtains a less than 4-year simple payout period if the price of crude oil is higher than $ 42.5 per barrel. Under these conditions we have: – International price of crude oil: – Bioethanol producer price: – Production cost of Ethylene: – International price of Ethylene: – Unit gross profit: – Unit total investment: – Gross Profit / Investment ratio: $ 42.5 per barrel $ 370 per ton $ 681 per ton $ 765 per ton $ 84 per ton $ 300 per ton 28.0 % per year This means that if the correlations among prices of bioethanol, crude oil and Ethylene are maintained, the non-integrated production of Ethylene from commercial bioethanol becomes feasible and economically attractive with global crude oil prices over $ 42.5 per barrel. It is worth noting that even if the conventional process is used, this price already makes bioethanol production for the fuel market feasible, thus ensuring its availability. The risks assumed in the production of Ethylene from bioethanol are the same incurred when the production of bioethanol itself is established, that is, tendency to align the price of Brazilian gasoline to the price of gasoline in different markets, in terms of its relation with the international price of crude oil, and drop in the international price of crude oil INSERTION OF BIOETHANOL INTO A NEW PARADIGM FOR THE BRAZILIAN... 51 itself, to values below $ 42.5 per barrel, although these are unlikely events, at least on the short term. Integrated production of Ethylene · Conventional ethanol In the integrated production of Ethylene from sugarcane by means of the conventional process to produce ethanol, a less than 4-year simple payout period is obtained for an international price of crude oil over $ 52.2 per barrel. Under these conditions we have: – International price of crude oil: – Sugarcane supplier price: – Production cost of Ethylene: – International price of Ethylene: – Unit gross profit: – Unit total investment: – Gross Profit / Investment ratio: $ 52.2 per barrel $ 15.3 per ton $ 713 per ton $ 939 per ton $ 226 per ton $ 800 per ton 28.0 % per year The requirement of an international price for crude oil, in this case, higher than the one required in the case of non-integrated production of Ethylene, reflects the need for a higher unit gross profit to ensure the same profitability, at a higher investment index that includes, not only the production of bioethanol but, also the production of Ethylene. It can be seen that the requirement of a higher international price for crude oil reduces the probability of maintaining the economic attractiveness of conventional integrated production of bioethanol because it is lower the probability of maintaining the international price of crude oil above $ 52.2 per barrel. · Full utilization of sugarcane In the case of integrated production of Ethylene from sugarcane, with full utilization, a less than 4-year simple payout period is obtained with an international price of crude oil over $ 25.3 per barrel. Under these conditions we have: 52 INDUSTRIAL PERSPECTIVES FOR BIOETHANOL – International price of crude oil: – Sugar supplier price: – Production cost of Ethylene: – International price of Ethylene: – Unit gross profit: – Unit total investment: – Gross Profit / Investment ratio: $ 25.3 per barrel $ 7.4 per ton $ 230 per ton $ 455 per ton $ 226 per ton $ 800 per ton 28.0 % per year The need for an international price of crude oil, in this case, lower than the international price of crude oil using integrated production without full utilization of sugarcane, reflects the reduction of the ratio between the production cost of Ethylene and the crude oil price from 16.4 to 9.1 (with crude oil at $ 25.3 per barrel) and from 13.7 to 6.8 (with crude oil at $ 52.2 per barrel). Most important, however, is to note that being higher the probability of crude oil prices exceeding $ 25.3 per barrel, higher is the probability of maintaining the economic attractiveness of integrated production of Ethylene with full utilization of sugarcane. Conclusions Therefore, we reach the conclusion that both versions of Ethylene production from sugarcane, namely the conventional processing and the process based on full utilization, currently have an economic appeal. However, as expected, the alternative more likely to maintain its economic attractiveness is the integrated production with full utilization of sugarcane. This led to the ongoing effort, in Brazil and abroad, to make the industrial technology required for such full utilization commercially available. The Tree of Bioethanol Derivatives · Ethylene The previous section showed the high probability of the economic attractiveness of Ethylene production from bioethanol, both in nonintegrated and integrated models and in the latter case, in its two versions, namely the conventional bioethanol production process and INSERTION OF BIOETHANOL INTO A NEW PARADIGM FOR THE BRAZILIAN... 53 the process that adopts full utilization of sugarcane. As expected, integrated production with full utilization of sugarcane is the most attractive among all cases studied. · Traditional derivatives: acetic acid, ethyl acetate and others The same can be said about the production of other first generation derivatives of bioethanol, such as acetic acid and ethyl acetate that can be obtained by the so-called direct routes; acetic acid, via an old, well known route with new clothing, that is, aerobic fermentation using Acetobacter, and ethyl acetate by catalytic dimerization of ethanol. Moreover, considering that in Brazil the alcohol-based chemical industry preceded the petrochemical industry by approximately 40 years, it is worth mentioning, at least en passant, some products that have been produced from bioethanol along the time. The Brazilian chemical production of alcohol started its activities in the 1920s1 with the production, by Rhodia, of ethyl chloride, diethyl ether and acetic acid, and grew due to the implementation, fomented by a fiscal incentive policy, of several industrial units, some of which operate to this day. During the 1960s, Rhodia and Fongra started to produce acetic acid derivatives from bioethanol in Brazil (currently Rhodia imports acetic acid); later, Fongra was purchased by Hoechst to be deactivated in 1980; Victor Sense (also deactivated in 1980) produced butanol and acetone; Eletroteno (Solvay) and Union Carbide produced Ethylene. Today, the units of Solvay and Union Carbide (currently DOW) operate with petrochemical Ethylene whose production started in Brazil in 1972, when Petroquímica União started operating, followed in 1978 by COPENE (Companhia Petroquímica do Nordeste), starting the competition between bioethanol and naphtha for the production of Ethylene. Between 1965 and 1971, Coperbo – Companhia Pernambucana de Borrachas – located in Cabo city, produced polybutadiene by polymerization of butadiene obtained from bioethanol. The Butadiene Unit remai1 For more information on this matter refer to Chemical industry – Risks and Opportunities (in Portuguese) by P. Wongtschowski, Edgard Blücher Ltda Publishers, 2nd ed., 2002. 54 INDUSTRIAL PERSPECTIVES FOR BIOETHANOL ned deactivated from 1972 through the beginning of the 1980s and was modified to produce Ethylene and acetic aldehyde from bioethanol; these products were used by CAN – Companhia Alcoolquímica Nacional – a company located next to Coperbo, to produce vinyl acetate monomer. In 1969, in Igarassu city, also in Pernambuco state, Elekeiroz do Nordeste started the production of 2-ethyl-hexanol from bioethanol via a route that begins with the dehydrogenation of bioethanol to give acetic aldehyde (that is also a precursor of acetic acid); acetic aldehyde is dimerized to give acetaldol which, on its turn, is dehydrated to give crotonaldehyde. Crotonaldehyde is then hydrogenated to give butyric aldehyde, a precursor of both n-butanol and 2-ethyl-hexanol. This was the base for the extension of Elekeiroz’s product range that in 1977 already produced, besides 2-ethyl-hexanol (also called octanol), butanol and ethyl acetate; in 1986 the line was extended to include acetic aldehyde, acetic acid and 2-ethyl-hexanoic acid. With the change in the incentive policy, competition with Petroquímica became unfair and the Igarassu Unit was closed in 1993. Salgema was incorporated into Trikem in 1996 (today Braskem) and for some time produced Ethylene from bioethanol as a permanent raw material for its dichloroethane unit that is currently supplied with Ethylene from Braskem; CBE – The Brazilian Styrene Company – began to make ethylbenzene from Ethylene produced from bioethanol, replaced later by petrochemical Ethylene; CBE produced also ethyl chloride until 1996. · Bioethanol as a coadjuvant raw material Besides the derivatives produced by using exclusively bioethanol as raw material, there are other important derivatives that use bioethanol as a coadjuvant raw material. These derivatives will benefit directly from any possible reduction in the market price of bioethanol; such derivatives include the ethyl ethers of MEG/DEG/TEG (mono/di/tri ethylene glycol) produced by reacting ethanol with Ethylene oxide; ethyl ethers of MPG/DPG/TPG (mono/di/tri propylene glycol) produced by reacting ethanol with propene oxide, and ethyl acetate produced by reacting acetic acid (in this case derived from methanol) with bioethanol. INSERTION OF BIOETHANOL INTO A NEW PARADIGM FOR THE BRAZILIAN... 55 The Tree of Bioethanol Derivatives revisited Based on the above, we can redraw the Chemical Alcohol Tree based on a criterion of competitiveness and profitability in order to contain: – Ethylene and derivatives (openly competing with Ethylene from naphtha): (P-001) · Ethylene Ethylene oxide (P-002) and derivatives · Polyethylenes · PVC (P-004) (P-003) · Styrene and Polystyrene (P-005 and P-006) · – Acetic acid and Acetates Acetic acid (P-007) · Ethyl (P-008) · Butyl acetate acetate (P-009) · – Ethyl acetate (via direct route – P-008) – Ethylene oxide (P-002 via direct route) and derivatives – Methyl ethyl ketone (P-009) – Propylene oxide ethers (P-010) It can be seen that at least 10 important products and/or families in the Brazilian chemical sector can be competitively produced from bioethanol, provided that the ongoing development efforts are completed and the results obtained with the completion of these efforts correspond to expectations. Pedro Wongtschowski, Francisco I. Pellegrini and Flávio do Couto Bezerra Cavalcanti OXITENO, São Paulo Section 2 BioTechnology and Engineering Science integration for Chemical and Fuel Industries Industrial Potential of Yeast Biotechnology in the Production of Bioethanol in Brazil: the Example of Conditional Flocculation Anderson Ferreira da Cunha Silvia Kazue Missawa Gonçalo Amarante Guimarães Pereira Introduction The existence of life on earth as we know it is due fundamentally to the reduction of CO2 levels primarily existing in the atmosphere, mainly through the fixation of this compound into carbon chains. These longterm processes combine with geologic events, although they are basically biological activities. Man as a species has developed in this rather milder atmosphere, although his social and economic progress, in the last hundred years, has reversed the direction of carbon fixation and is now jeopardizing biological maintenance of the atmosphere. Since the introduction of fossil fuels (gasoline, diesel, etc.) utilization, we have systematically released gigantic amounts of carbonic gas back to the atmosphere effectively reversing millions of years of carbon fixation. This means that our social progress is taking us back to our biological environmental starting point, which will certainly have major consequences. In recent years a number of research studies, as well as scientific and social organizations, have pointed to this problem, although without much success. The largest producers of CO2 even admit that this process is occurring, but up to now, they have only considered it as something that will occur in the remote future. Within this context, weather changes 60 INDUSTRIAL PERSPECTIVES FOR BIOETHANOL that have occurred in the past few years, particularly floods and the record number of hurricanes, have brought to light an unmistakable demonstration that the consequences of fossil fuels are already here. Therefore, there is no more time to wait, alternative and renewable energy sources must be found. The history of economic events show that during great crises, great opportunities arise and the ability to capitalize during these times is key to economic success. In the specific scenario of the fuel crisis a huge opportunity has been created for countries that have ample land, sun and water. This is undoubtedly the case of Brazil. Although most of the developed world has reached a situation that is considered critical, with dependence on imported petroleum and alarming and overwhelming natural phenomena linked to climate changes, Brazil started take positive step to reduce this situation about 30 years ago, for economical reasons. With the oil shortage that occurred in 1973 and 1979, oil prices rose from US$ 4.00 to US$ 40.00 per barrel. Between 1973 and 1974, fuel costs jumped from US$ 600 million to over US$ 2 billion. This gigantic impact on the balance of payments showed the strategic vulnerability of Brazil, which at the time was importing nearly 80% of the oil consumed by the Country, and therefore was highly susceptible to an energy collapse. In 1975, Brazil launched Proalcool, the Brazilian Program for Alcohol Fuel. Sugarcane alcohol soon provided an ideal alternative fuel for gasoline. In order to make this program feasible, the Brazilian government offered a financial plan that was supported by the World Bank, which made it possible to increase the areas planted to sugarcane, build new plants and develop and enlarge boiler shop industries (source: UNICA, the Sao Paulo State Sugarcane Agribusiness Union – www.unica.com.br). Once available, this so-called green fuel was harnessed in two forms. Initially, it was mixed with gasoline as anhydrous alcohol. This process has increased the amount of alcohol in gasoline over time, i.e. the gasoline distributed in Sao Paulo city changed from a 20% v/v mixture in 1977 to 22% in 1980, which has been adopted all over the country (Demetrius 1990). Also during this period the first cars that exclusively INDUSTRIAL POTENTIAL OF YEAST BIOTECHNOLOGY IN THE PRODUCTION... 61 utilized hydrated alcohol were introduced, unfortunately, these vehicles used poorly adapted gasoline motors and were not well received. Only during the 1980s, after the second oil shortage did automobile manufacturers launched new models that were especially manufactured to work with alcohol. Also during this time alcohol prices were kept favorable to gasoline, through governmental subsidies. The success of these automobiles exceeded all predictions. In 1984, alcohol-powered cars represented 94.4% of the assembly line production in Brazil, which accounted for 19 out of 20 cars. However, this huge increase in demand was not maintained and combined with increases in the Brazilian production of crude oil and the reduction in the world price of this commodity, there was limited interest in maintaining the alcohol subsidies. Moreover, ethanol producers started an irrational process of increasing prices, which led to a shortage of the product, resulting in a lack of confidence in the consumer market. As a combined consequence, the production of alcohol-powered cars fell from 88.4% in 1988 to 61% in 1989, to 19.9% in 1990 and finally to 0.3% in 1996. However, in spite of the program’s limit adoption, the government viewed this as strategically important to the country and kept alcohol production at high levels. In 1991 a new federal law mandated the addition of 22% anhydrous alcohol to gasoline, which helped to promote the production of ethanol for fuel purposes. Associated with this strategy, environmental factors in cities like Sao Paulo, where air pollution had reached alarming levels, could also be improved by the addition of alcohol to gasoline. More recently, the alcohol program has once again returned to the spotlight, at first because a consistent and apparently irreversible increase in the international crude oil prices and due to the development of the so-called FLEX engines that are capable of burning hydrated alcohol/gasoline mixture at any proportion. Cars with these new motors have given Brazilian consumers a choice in which fuel to use and thus a relevant power to resist increases in gasoline prices. Thus, given the global demand for alternative fuels, Brazil now presents itself as the country capable of leading the world. Brazil has a huge production capacity and has developed new technologies for production, 62 INDUSTRIAL PERSPECTIVES FOR BIOETHANOL distribution and utilization of ethanol, as well as demonstrating increased implementation of these technologies. For example, the sugar mill extract process has increased the amount of sugar that can be processed from sugarcane. The sugar extraction index, that was 89%, at the beginning of the Proalcool program, has reached 97% today. In parallel, the sugarcane residues (bagasse) burning technology to produce energy has been widely adopted, thus making approximately 95% of the sugar mills self-sufficient in terms of electricity (van Haandel 2005), and in some case providing excess electric that is redirected into the national electrical networks. However, there are still technological advances that remain to be developed in order to maximize the inherently biological processes. In the case of sugarcane, over the last few years an intensive research effort has been developed to improve the plant. Genomics have been used to in an attempt to understand the biochemical processes connected to the plant’s physiology, and these have lead to potential features of agronomic importance (Vettore et al. 2003; Vincentz et al. 2004). This advancement has led to the recent creation of companies focused on the use of biotechnology in the development of new cultivated varieties, as in the case of Canavialis (www.canavialis.com.br). Curiously, this has not happened in the case of Saccharomyces cerevisiea. Even though this yeast is an essential part in fermentation, very little research has been done to improve its efficiency and specificity. This lack of research presents huge opportunities for biotechnological improves. This issue will be discussed in detail in the following items. The Biochemistry of Ethanol Production The ethanol production process in Brazil occurs almost exclusively by fermentation of sugarcane juice by yeasts, mainly the Saccharomyces cerevisiae species, an organism that, given its technological importance, is widely used as an experimental model to understand eukaryotic cells (Goffeau et al. 1996). Biochemically, alcohol fermentation is the degradation of hexoses into ethanol with the production of 2 ATP molecules in the process. In INDUSTRIAL POTENTIAL OF YEAST BIOTECHNOLOGY IN THE PRODUCTION... 63 the case of sugarcane juice, the fermentation process metabolizes the disaccharide sucrose that is formed by one molecule of fructose and one molecule of glucose. The first step is the hydrolysis of sucrose by invertase enzyme that is encoded by the SUC2 gene. Both glucose and fructose enter the glycolytic pathway and are converted into pyruvate via a sequence of reactions (Figure 1). Pyruvate is then decarboxylated to form acetaldehyde and this releases CO2 and causes intense bubbling when the cells are grown in liquid medium. Later, the acetaldehyde molecule is reduced to ethanol, and this reaction is catalyzed by the enzyme alcohol dehydrogenase 1 (ADH1). The glucose depletion results in the end of the fermentation phase. During this period the yeast cells vigorously multiply, which is characterized by an exponential growth phase. From the depletion point on the yeasts seem to enter a stationary phase, but they actually continue to grow for a long period, and actually consume the ethanol previously produced through respiration. This change from fermentation metabolism into respiratory metabolism is called diauxic shift, which involves intense genetic reprogramming (De Risi et al. 1997; Lashkari et al. 1997), and is based on an increase in the transcription of certain genes and repression of others. To better understand these processes it is important to briefly mention how these genes are organized and how they work. Basically, the genes that encode proteins are organized into two independent regions, namely, a promoter region and a coding region. The promoter region is responsible for the transcription regulation that defines when a gene should be switched on or off. When the gene is switched on, in a portion close to the coding region, a messenger RNA (mRNA) starts to form and copies the information from the coding region, which will be translated later into a protein by ribosomes. It is fundamental to note that these regions of the gene act independently and may be interchangeable through genetic engineering, for example, leading to the formation of new genes with unique expression patterns (Lewin 1990). In particular, the growth in a medium containing glucose leads to the repression of a series of genes involved with respiration and the use of alternative sources of carbon. The SUC2 gene is repressed under these conditions, thus preventing the release of further amounts of glucose 64 INDUSTRIAL PERSPECTIVES FOR BIOETHANOL and fructose stored in the sucrose molecule (Gancedo 1998). The ADH1 gene, on the other hand, is induced by this sugar. The end of fermentation activates a set of genes required for respiration and leads to intense multiplication of mitochondria (Mahler et al. 1975; Ulery et al. 1994). In particular, the absence of glucose in the medium activates the transcription of ADH2 (alcohol dehydrogenase 2) gene (Ciriacy 1979). The enzyme produced by the expression of this gene oxidizes ethanol to acetaldehyde via the reverse of the ADH1 pathway; acetaldehyde is then converted into acetate, which participates in the later stages of the Krebs cycle that is the major aerobic respiration cycle (Devlin 1997) (Figure 1). Figure 1. Schematic diagram of the fermentation and respiration reactions. The dotted arrows indicate the pathway that is activated after glucose depletion (ethanol oxidation). PDC1, 5, 6: pyruvate decarboxylase; PDA1, PDB1, PDX1, LPD1, LAT1: enzymes form the pyruvate dehydrogenase complex; ALD6: aldehyde dehydrogenase; ACS1: acetylCoA synthetase; ADH1: alcohol dehydrogenase 1; ADH2: alcohol dehydrogenase 2. INDUSTRIAL POTENTIAL OF YEAST BIOTECHNOLOGY IN THE PRODUCTION... 65 Industrial Production of Ethanol An interesting question is: why do yeasts produce ethanol? This would seem to be a waste if we consider it from the energetic perspective; respiration produces a much higher amount of energy compared to fermentation. However, from the strategic perspective, this seems to have been an effective evolutionary pathway. After all, only a few organisms are able to live in high concentrations of ethanol, a compound that is largely used as an antisepsis. While the yeast developed the ability to produce high concentrations of ethanol, the species also developed a system to resist this compound. Therefore, during theproduction of ethanol, the yeast can reduce significantly the competition from other organisms for the existing substrates and afterwards can consume the ethanol that was produced; while waiting for new stocks of sugar to be made available. If we look at the natural environments, this seems to be the logical strategy used by yeasts in fruits like grapes. As fruits fall from the vine, an environment is created that is similar to a fermentation vat, where ethanol is rapidly produced in large amounts. When new fruits fall from the vine this provides new stocks of sugar, and the entire cycle begins again. This parallel shows that the industrial fermentation of alcohol is just a scaled increase of a natural phenomenon. This process is not a human invention, but rather a human discovery. Industrially, the production of alcohol follows basically two processes: fed-batch and continuous fermentation, with the first being the most used. In the fed-batch process, fermentation occurs in independent vats, beginning with low concentrations of yeast cells and high concentrations of substrate. The whole mixture of must (mixture of sugarcane juice and molasses), nutrients and yeast is added to the vat and after approximately 8 hours, once the fermentation has ended, the entire contents are removed and centrifuged. The “wine” – a name used in the sugar mills industry to indicate the fermented sugarcane juice without the yeast – is conveyed to the distillation towers, while the yeast milk, that is, the yeast broth obtained by centrifugation, is subjected to a decontamination treatment in the treatment vat consisting of a lowering of the pH with concentrated sulfuric acid. The yeast is then returned to 66 INDUSTRIAL PERSPECTIVES FOR BIOETHANOL the vat and a new load of must is added, to start a new fermentation cycle (Wheals et al. 1999) (Figure 2). Figure 2. The fed-batch process of ethanol production. The whole mixture of must, nutrients and yeast is added to the vat and, once the fermentation has ended, the whole contents are removed and centrifuged. The wine is distilled and the yeast milk is returned to the vat, where a new load of must is added, starting a new fermentation cycle. To start the fermentation, the original yeast used by sugar mills is usually multiplied under sterile conditions up to 50 liters and sent to a pilot stage until it reaches the volume required to start the production. This volume varies according to the size of the mill and can reach a value of up to 600,000 liters (Zarpelon and Andrietta 1992, Wheals et al. 1999). An important observation that was only recently ascertained was that, although the yeast is inoculated at high levels, in some sugar mills it is rapidly replaced with wild yeast strains within a few fermen- INDUSTRIAL POTENTIAL OF YEAST BIOTECHNOLOGY IN THE PRODUCTION... 67 tation cycles and is then maintained until the end of the cropping season (da Silva Filho et al. 2005). In many cases this replacement is not even noted and there is no decrease in the productivity of the mill, possibly because the invading yeasts are better adapted to the conditions of the mill. Recently we have detected this fact in a large sugar mill in the Campinas region that for many years had been inoculating a strain to start the crop, and after a few weeks this strain was replaced with a wild strain that increased the process. This fact demonstrates clearly the low importance given to the fermentation agent, which is considered an abiotic factor. These factors may actually open up new opportunities for the development of new technological advances for improving the yeast strains used. The Yeast This microorganism has been used in the production of bread and beverages for centuries. Since the nineteenth century it became an important experimental model, to the extent that it was the first eukaryotic organism to have its genome fully sequenced (Goffeau et al. 1996; Goffeau 1998), which tremendously simplified investigations to understand its metabolism. Moreover, Saccharomyces cerevisiae is an organism that can be easily genetically manipulated, which has led to a systematic deletion of all of its genes, either individually or in combination, in order to analyze their functions and determine how their products interact (Dujon 1998; Hauser et al. 1998). Full information is available for real time searches at the site www.yeastgenome.org. The effective production of ethanol requires that yeasts included in the process have some essential characteristics such as: (1) ability to ferment rapidly and, effectively produce ethanol; (2) a high tolerance to ethanol; (3) a high osmotolerance (ability to ferment concentrated solutions of carbohydrates such as, for example, sugar molasses used in many sugar mills to produce ethanol); (4) genetic stability; (5) cellular viability and tolerance toward repeated fermentation cycles; (6) tolerance to temperature variations; (7) a high competitive capacity. There are several yeast species capable of producing ethanol on a large scale; 68 INDUSTRIAL PERSPECTIVES FOR BIOETHANOL however, over 97% of processes involve the use of the species Saccharomyces cerevisiae (Stewart et al. 1987). Therefore based on the knowledge we have of this organism, it is possible to manipulate it genetically to adequate it even further to the fermentation process. Several methods that have been used in the past have been to employed classical methods such as: cross hybridizations, selection and isolation of new strains. The advent of molecular biology and the development of genetic engineering techniques made it possible to manipulate genes to increase the possibility of changing undesired characteristics or adding new desirable ones. Through transformation of an organism with modified genes, it is now possible to make the organism express certain characteristics that are not identified in natural populations. This means that it could be possible to build strains with specific functions, for industrial uses. Yeast flocculation and its use in alcohol fermentation processes A phenomenon that plays an important role in industrial production is yeast flocculation, that can be defined as the ability of certain strains to aggregate and form multicell masses that will separate by sedimentation or flotation (Stratford 1996; Stan and Despa 2000). This feature has been employed successfully in the beer industry to facilitate the removal of cells once the fermentation has ended (Stratford 1996). This precedent makes us think about it could possibly be used in a similar fashion in the ethanol production industry, since it would eliminate the need for centrifugation, an expensive and complicated step in the process. In fact, this idea has led to the development of industrial procedures of alcohol production based on flocculating yeasts (Domingues et al. 2000, Domingues et al. 2001, Kondo et al. 2002). However, it was shown that continuous flocculation has a series of disadvantages and can lead to a reduction in the overall production of ethanol, as well as to in-process problems such as duct clogging (Stratford 1992, Verstrepen et al. 2003). The physical and genetic mechanism of flocculation has been widely studied in recent years (Verstrepen et al. 2003). It involves primarily the interaction of surface proteins of a certain lecithin-like, sugar-binding INDUSTRIAL POTENTIAL OF YEAST BIOTECHNOLOGY IN THE PRODUCTION... 69 cell, with exposed sugar residues on surrounding cells. Thus, a cell producing a flocculation protein is capable of interacting with cells that do not produce the protein, and interact with the exposed sugars of those cells (Stratford and Carter 1993) (Figure 3). Figure 3. Schematic diagram of flocculation mechanism showing that all cells have sugar residues on their cell walls and that, after glucose (C6H12O6) depletion, flocculin – the flocculation-related protein – is formed. Several genes have been genetically identified as being responsible for flocculation. Such genes express proteins called flocculins. The control mechanism for flocculins and proteins encoded them is different and has been intensely studied (Cormack 2004; Halme et al. 2004). The option used by industry has been to control flocculation by using engineering solutions. However, it seems that there is a huge potential for using biotechnological techniques to develop strains more adequate to the industrial process. Based on this, we developed the following scenario: the ideal yeast should be perfectly soluble in the medium while this medium would include a fermentation substrate, i.e. sugar. The cells would be able to efficiently exploit this substrate because they would multiply and reach the maximum total contact surface. However, once the sugar was depleted, ideally we should have the opposite response, that is, the cells would aggregate and be deposited on the bottom of the vat. This would prevent ethanol consumption and the cells could be separate naturally, thus eliminating the need for centrifugation. To determine if this idea was viable we used laboratory strains of S. cerevisiae, which are easily manipulated. At the same time we created a hybrid gene containing the promoter region of the ADH2 gene asso- 70 INDUSTRIAL PERSPECTIVES FOR BIOETHANOL ciated with the coding region of the FLO5 flocculation gene. From this point on we had a desired effect. As mentioned before, the ADH2 gene promoter is repressed by glucose, and induced when this sugar is depleted from the medium. This mechanism selectively insures that the cells will continue to produce ethanol while preventing its oxidization to acetaldehyde when there is a flow in the opposite direction (Figure 1). At this point the flocculin encoded by the FLO5 gene is produced, and mobilized to the cell surface thus leading to a synchronized sedimentation (Figure 4). Starting with this simple system we were able to achieve a situation where we could sense the sugar levels in the medium, quench the fermentation at the appropriate moment and removing the yeast cells at that point. In a broader sense, we developed intelligent yeast – or, at least, smart yeast. Figure 4. Expression of FLO5 gene under the control of the ADH2 gene promoter regulatory region. 1- Wild strain; 2- Wild strain with the flocculation gene controlled by glucose levels; 3Wild strain with constitutively activated flocculation gene. A. Culture medium with glucose; B. Culture medium after glucose depletion. As shown in the figure, the strain whose flocculation gene is controlled by glucose levels is deposited after carbohydrate depletion. INDUSTRIAL POTENTIAL OF YEAST BIOTECHNOLOGY IN THE PRODUCTION... 71 This prototype worked perfectly in the laboratory, was patented (INPI # 0001122), and was awarded a Honorable Mention in the 2000 issue of the National Contest of Brazilian Inventions. It was the only laureate invention in the biotechnology area. However, we know that a huge challenge is in front of us. As mentioned before, in the fermentation vats there is strong competition among microorganisms, and only the best-adapted strains reside in the process. Thus, our invention has no potential to produce a default strain that could be largely employed. On the contrary, we must be capable of identifying specific strains from the different sugar mills and modify them genetically so that they acquire the ability to flocculate according to the schematic diagram shown above. Recently we achieved this in the first industrial strains (Cunha et al. 2006) by integrating the flocculation cassette into the arginine permease gene present in all isolates of the species. This makes cells resistant to a drug called canavanine, allowing the selection of the transforming agents. However, the production of alcohol using these transforming agents is still unsatisfactory, and is the object of intense investigation. Additionally, our laboratory team is committed to developing strains that are more resistant to ethanol and less capable of consume this compound. Theoretically, this can be achieved by deleting a few alreadyidentified genes. This is an ongoing study and preliminary results are not yet ready to be disclosed at this time. With these first steps accomplished we are hopeful that it is possible to achieve higher concentrations of ethanol in the fermentation stage. Conclusion Based on all current information, it appears that the demand for ethanol is no longer a national issue, but a global concern. This change in scale suggests that future ethanol programs will need to have a lot more stability than previous programs in order to meet future requirements. Thus, the search for an increase in ethanol production and in the efficacy of the process will dramatically increase and will be an opportunity for Brazil to develop high tech solutions on its own. Innovative improve- 72 INDUSTRIAL PERSPECTIVES FOR BIOETHANOL ments have already been made to fermentation engineering and the automotive industry, particularly with the launching of FLEX fuel cars. However, major advances in the biological process of fermentation, or more specifically in the genetics of the yeast S. cerevisiae have yet to be accomplished. This report presents the development of conditional flocculating yeasts that have the potential of eliminating the need for centrifugation from the industrial fermentation process. When this system is available on the industrial scale, the possibility of having small alcohol/ sugar mills spread all over the country using the fed-batch production process, will be feasible since the costly centrifugation step will be replaced with genetically modified “smart yeast”. Anderson Ferreira da Cunha, Silvia Kazue Missawa and Gonçalo Amarante Guimarães Pereira Institute of Biology, Department of Genetics and Evolution State University of Campinas - UNICAMP Campinas, SP – Brazil INDUSTRIAL POTENTIAL OF YEAST BIOTECHNOLOGY IN THE PRODUCTION... 73 References Ciriacy M (1979). Isolation and characterization of further cis- and trans-acting regulatory elements involved in the synthesis of glucoserepressible alcohol dehydrogenase (ADHII) in Saccharomyces cerevisiae. Mol Gen Genet 176(3): 427-31. Cormack B (2004). Can you adhere me now? Good. Cell 116(3): 353-4. Cunha AF, Missawa SK, Gomes LH, Reis SF, Pereira GA (2006). Control by sugar of Saccharomyces cerevisiae flocculation for industrial ethanol production. FEMS Yeast Res 6(2): 280-7. da Silva-Filho EA, Brito dos Santos SK, Resende Ado M, de Morais JO, de Morais MA, Jr., Ardaillon Simoes D (2005). Yeast population dynamics of industrial fuel-ethanol fermentation process assessed by PCR-fingerprinting. 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Vincentz M, Cara FA, Okura VK, da Silva FR, Pedrosa GL, Hemerly AS, Capella AN, Marins M, Ferreira PC, Franca SC, Grivet L, Vettore AL, Kemper EL, Burnquist WL, Targon ML, Siqueira WJ, Kuramae EE, Marino CL, Camargo LE, Carrer H, Coutinho LL, Furlan LR, Lemos MV, Nunes LR, Gomes SL, Santelli RV, Goldman MH, Bacci M, Jr., Giglioti EA, Thiemann OH, Silva FH, Van Sluys MA, Nobrega FG, Arruda P, Menck CF (2004). Evaluation of monocot and eudicot divergence using the sugarcane transcriptome. Plant Physiol 134(3): 951-9. Wheals AE, Basso LC, Alves DM, Amorim HV (1999). Fuel ethanol after 25 years. Trends Biotechnol 17(12): 482-7. Zarpelon F, Andrietta SR (1992). Fermentação contínua para obtenção de álcool. STAB (March-April): 23-28. Optimization and Limits of Ethanol Production Silvio Roberto Andrietta Maria da Graça Stupiello Andrietta 1. Introduction The use of alcohol to replace gasoline, once more a Brazilian reality, is now a global reality. This biofuel is gaining importance in the world market as a renewable fuel. This fact has multiple reasons, the main one being the need for developed countries to reduce their dependence on crude oil, given that the world’s largest reserves of this fossil fuel are located in politically unstable regions. Climate changes observed in recent years have called the attention of the global population to the effects of global heating caused by burning fossil fuels. Within this scenario, Brazil is in a privileged position since it started a program to produce alcohol (Proálcool) in 1970. In addition, the country has production growth potential, thanks to the availability of land for growing sugarcane, the raw material used for alcohol production in Brazil. However, this scenario was not always favorable. Once Proalcool – the program developed to boost alcohol production – was created, a production peak occurred as a function of the installation of a large number of industrial units. At that time there were signs that the price of crude oil would progressively increase in the years to follow, a fact that was not confirmed. With the price of crude oil falling to a level of 15 American dollars per barrel in the 1980s, the price of alcohol could not compete with the price of gasoline, not even with all the existing productivity improvements. So, the government had to subsidize its production, making it 78 INDUSTRIAL PERSPECTIVES FOR BIOETHANOL less commercially appealing, since its price depended on state positive intervention. At the end of the 1980s and beginning of the 1990s a problem of alcohol fuel shortage occurred in fuel stations, creating consumer distrust. This brought the sales of alcohol-powered cars to near extinction. Eventually, alcohol consumption was dramatically reduced and the supply became greater than demand. As a function of this new reality, in the following years the production units invested in sugar mills, increasing the production of sugar to the detriment of alcohol production. With the increase in sugar supply, the price of this product in the global market dropped significantly, having reached its minimum value in 2001, which caused one of the greatest crises in the production sector. At the beginning of the present century the marketing of ethanol has benefited once more from the situation. The introduction of the dual-fuel motor car by the main assembly plants plus the crude oil price increase in the global market, associated with environmental appeals, made alcohol viable again as a price-competitive fuel when compared to gasoline, bringing investments back into the sector. However, the 1980 and 1990 decades were marked by a lack of investment in fermentation processes. Without investments, ethanol production stabilized around 15 million liters per year. The sector reacted to this new reality, and 75 new production units are predicted to be installed until 2015, with an expected production of over 30,000,000 billion liters of alcohol. 2. Production Limits Ethanol production in Brazil is not limited by lack of cultivable land and labor for sugarcane production, but by market oscillations and lack of definition, by the government, of an energy matrix for the Country. The price of alcohol depends on different factors such as product demand and price in the internal and external markets, and price of crude oil. Because alcohol consumption by dual-fuel motor cars is 30% higher than gasoline consumption, the price of alcohol should be at most 70% the price of gasoline for the use of alcohol to become advantageous to consumers. With a strong Brazilian currency, the price of gasoline has been kept stable in spite of its price increase in the global OPTIMIZATION AND LIMITS OF ETHANOL PRODUCTION 79 market. This fact limits the price of alcohol in the internal market. On the other hand, the demand for alcohol in the international market has been increasing, levering its price upwards. Moreover, the possibility for Brazil to produce more alcohol – and consequently, less sugar – to supply the internal market increases the price of sugar in the global market, making sugar more profitable than alcohol. Should this trend be maintained, the amount of ethanol produced in the 2006 crop should be smaller than planned, with likelihood of shortage to the extent that sales of dual-fuel motor cars would be affected. With the current installed capacity, ethanol could achieve an annual production of over 20 million liters, diverting a larger amount of sugar from sugarcane to ethanol production. However, this may not happen because when sugar production is reduced, its price tends to increase and the production becomes economically more interesting. The combination of these factors will affect the production of alcohol fuel by limiting it to profits linked to the sale of this product. To solve this problem a progressive increase in sugarcane production will be required in order to meet the demand, regulating the price of sugar in the global market and allowing the alcohol production to increase by using the excess amount of sugarcane. In addition, policies are required that favor alcohol production by minimizing the period between the old and a the news season crop and making it possible for small producers with small working capital to obtain better prices with the sale of this product, since they are forced to quickly sell their production in order to meet their expenses. The increasing demand for alcohol in the external market is another factor that can cause a shortage in the internal market in case the price of gasoline is not significantly readjusted in the coming years. If alcohol prices in the internal market are kept at a high level such that the use of alcohol for dual-fuel motor cars becomes unfeasible, a shrinkage in the market of these cars might occur, affecting their commercialization in the future. The market of crude oil and sugar is now and will continue to be the limitation of alcohol production in the next years since the trend is that the demand for this product will grow faster than supply in the next few years. 80 INDUSTRIAL PERSPECTIVES FOR BIOETHANOL 3. Production Optimization The productivity increase in sugar-alcohol industry is based on two main items, namely, gains in agricultural production and gains in the fermentation unit. Gains in agricultural production have occurred since the implementation of the Alcohol Program in the 1970s. New varieties of sugarcane produced by different research centers have improved agricultural productivity, increasing significantly the production of total reducing sugars (TS) per acre. This is made possible thanks to studies that were aimed at finding sugarcane varieties more resistant to different diseases, have maturation cycles appropriate for early- and late season crops, adapt themselves better to more rigorous environmental conditions, and reach higher TS levels. Besides increasing the productivity and profitability for production units, this improvement and selection task can promote a 70% reduction in the cost of raw material in relation to the total production cost. Another strength is that these new varieties of sugarcane can be cultivated in regions that were not indicated before for this type of culture, such as Center Western Brazil. On the other hand, although technological innovations were introduced in industry along the years in the extraction, juice treatment, evaporation and distillation processes, efficacy and productivity gains are low compared with those obtained by optimization of bioconversion units. This is due to the fact that these units employ microorganisms to convert fermentable sugars into ethanol in a totally no sterility environment from the microbiological perspective, without proper control of the raw material employed, and often using rudimentary processes. The evolution of alcohol fermentation in Brazil went through various stages worth describing. Already in the 1960s, the fed-batch process started being used in Brazil to produce aguardente (a spirit distilled from sugarcane) and ethanol. Due to its satisfactory performance, this process was chosen to equip the industrial units that were introduced when the Alcohol Program was launched, totally replacing less productive methods such as the cutting process and classical processes traditionally used to ferment depleted molasses from sugar mills in the early 1960s. Even though OPTIMIZATION AND LIMITS OF ETHANOL PRODUCTION 81 the operating process was not suitable, given that it tried to maintain the substrate in the medium at relatively low constant levels throughout the filling, and since it aimed to prevent the supposed substrate inhibition of the bioconversion agent (in this case, Saccharomyces cerevisiae yeast), it was possible to achieve great productivity increase in the processes thanks to the use of an effective system of cell separation and recirculation that increased the yeast concentration inside the bioreactors. In the following years, the fed-batch process operation gradually improved with the implementation of microbiological control laboratories and became less susceptible to fermentation accidents. However, a more adequate evaluation of its theoretical fundaments and changes in the conduction of this process did not occur. Parallel studies on continuous fermentation processes were started whose primary objective was to increase the productivity of bioconversion processes, allowing the full use of the installed equipment, which is impossible in the fed-batch process. The first continuous fermentation processes were adaptations of the already existing fed-batch process in the unit. These so-called first generation processes presented serious operating problems, since they did not take into account any engineering principle concerning the in-process flow of material. Both the interconnections between bioreactors and their design were inappropriate, since they allowed in-process material accumulation due to cell sedimentation inside the bioreactors. These conception errors in the first processes led to a series of operating problems that, on their turn, delayed the implementation of new continuous fermentation processes, providing them with undesirable features such as low stability. During the second half of the 1980s the second generation of continuous fermentation processes was introduced. These processes were based on engineering principles that emphasized the bioreactor design and how bioreactors were interconnected, but the advances were limited to this. Although operating problems were significantly reduced, the processes continued to present problems, since they had been intuitively conceived with no previous kinetic studies, which led to errors that impaired the performance of these processes. In the beginning of the 1990s the first continuous alcohol fermentation processes based on kinetic studies and greatly concerned with bioreactors 82 INDUSTRIAL PERSPECTIVES FOR BIOETHANOL design and their interconnections were introduced. These so-called third generation processes require good agitation in the bioreactors and a design that allows proper cleansing of the parts that are not immersed in the wine during the processing, besides preventing in-process accumulation of material inside the bioreactors. These new processes have been used successfully in many distillation plants built from 1990 on, without any relevant problems and with good stability. Such evolution in the fermentation processes was responsible for an approximately 60% increase in the bioconversion process productivity, from 6.0 g ethanol / unit volume (liter) of bioreactor x h to values close to 10 g ethanol / unit volume (liter) of bioreactor x h. In spite of the advancement occurred during the last years, studies aiming to improve bioconversion unit productivity have been performed and several ways have been analyzed and evaluated with the clear purpose of achieving productivity increase without negatively affecting the process yield. The main studies include the selection of more productive yeast strains, effective application of kinetic concepts to fermentation processes, and development of new processes. In an attempt to find more productive yeast strains, natural selection was the adopted way, since the use of genetically modified strains showed limitations due to the characteristic of the process that operates in a non-sterile manner, therefore with a mixed population of yeasts and bacteria. Under these conditions, the genetically modified lineages introduced into the process were not capable of competing with native microorganisms present in the process, being quickly replaced. Desirable features of lineages of industrial use are the following: high yield of ethanol and cells, high conversion speed, high tolerance toward ethanol, and resistance toward temperatures around 35°C. Based on these features, several research groups have been working with the purpose of selecting new strains for industrial use from the fermentation processes themselves, since yeasts isolated from the sugarcane juice / fermentation vat itself “ecosystem” have great chances of success in vat environments. Currently, four strains isolated from industrial units are widely employed with success in industrial processes. With regard to conception and operation of fermentation processes, OPTIMIZATION AND LIMITS OF ETHANOL PRODUCTION 83 an important tool for optimizing the operation and achieving maximum productivity is the use of kinetic models to better understand the behavior of the yeast lineages employed in the process. Although the fed-batch process has been used for years, its operation was not optimized according to kinetic performance. Operations of this process in Brazilian distillation plants are a function of the amount of juice available. In such distillation plants, the juice from the mill is sent to bioreactors under the same flow conditions as it was generated, which implies poor flexibility to control the feeding flow. Under these conditions the substrate concentration changes continuously inside the bioreactors, reaching up to 120 g/liter. Recent studies showed that the filling speed is in direct proportion to productivity, meaning that the faster bioreactors are fed, the faster the fermentation. This fact shows that yeast cell inhibition caused by high cell concentration in the beginning of the process – where it can reach 90 g dry mass per liter – is much more significant than substrate inhibition. In fact, substrate inhibition is not observed with levels of up to 150 g/liter when treated sugarcane juice is used as raw material. This fact allows us to state that it would be possible to use a simple batch process without impairing the process productivity and that the fed-batch process was adopted only due to the physical limitation of having to instantly fill the bioreactors. In addition, other factors such as foam formation and availability of heat exchangers to remove the heat that was generated are important when making the decision to adopt the process operation strategy. By using the knowledge of the kinetics of the process, it is possible to simulate and optimize the operating conditions of these processes and increase their productivity without affecting the production cost because of an increase in consumption of inputs or due to yield decrease. Similarly, we found that continuous processes operating with multiple bioreactors in series show much higher productivity compared to single-bioreactor fermentation systems. This occurs because product inhibition and substrate limitation are the factors that interfere most in the fermentation speed. Thus, processes allowing the formation of increasing gradients of product and decreasing gradients of the substrate will favor this bioconversion. Tubular bioreactors would be the most indicated in this case, but this does not occur because it is 84 INDUSTRIAL PERSPECTIVES FOR BIOETHANOL physically impossible to maintain a pumped flow for this application, since during ethanol production a large amount of carbon dioxide is formed which, when released, would promote the mixture of reactants materials. However, multiple perfect-mixture bioreactors in series behave approximately like a tubular bioreactor, being therefore the most appropriate configuration for this application. Technical and economical viability studies performed in the beginning of the 1990s showed that the most appropriate configuration would include four bioreactors in series. Moreover, the conversion level, particularly in the first bioreactor, is fundamentally important for the good performance of the system. In the first bioreactor, conversion levels above 60% are not desirable since they decrease the fermentation speed during the process, which becomes less productive and may damage the yeast cells. To achieve significant productivity increases in alcohol production in installed plants that use all currently available technological resources, it is necessary to develop new processes that consider totally revolutionary operating conditions. Within this context and based on fermentation kinetics, different processes using strategies that favor the increase of productivity of the bioconversion process have been studied. Such processes follow basically two lines, namely the decrease of product inhibition by extracting it from the fermentation medium, and the increase of cell concentration inside the bioreactor with no need for recycling. Extractive fermentation, that attempts in-process extraction of the alcohol produced from the fermentation medium, aims to increase the bioconversion speed by reducing the inhibiting effect of alcohol on the yeast cells. The extraction can be performed in different ways, the most studied being alcohol evaporation in a flash tank coupled to the bioreactor. On the other hand, the aim is to increase the system’s conversion speed by increasing the in-process cell concentration without need for recycling. For this it is necessary that yeast cells be retained in the bioreactor, which is possible by means of immobilization processes, with or without support. Immobilization with support, besides implying higher costs, eventually brings operating problems, since it requires changing the bed due to the sizes of bioreactors. A simpler solution would be to use OPTIMIZATION AND LIMITS OF ETHANOL PRODUCTION 85 self-immobilizing cells that would not require the use of a support. These yeast strains have flocculating features and can be used in bioreactors, forming stable beds through which the fermenting medium percolates. These processes can reach productivities of over 25 g ethanol per unit volume (liter) of bioreactor x h and may be considered fourth generation processes. Currently, the great challenge is to stabilize these processes so that they become competitive and safe to the extent of being installed in industrial units. Based on the performance level currently achieved by either fed-batch or continuous fermentation processes, fourth generation processes will have to show that they are really interesting from the economic perspective in order to be implemented. This will require many laboratory and pilot scale studies until any one of those processes deserves the necessary trust. 4. Impact of environmental restrictions on the fermentation process Studies performed before 2000 aimed only at productivity increase and efficacy of bioconversion units. However, particularly in Sao Paulo state, the new environmental rules – that should reach other Brazilian states in a near future – have important limitations to operating conditions in ethanol production units. The first rule concerns the amount of water impounded directly from rivers for use in industrial processes. Before that, the cooling water used in bioreactors was collected directly from rivers at a mean temperature of 26°C. Since direct water collection from water springs is being limited by environmental agencies and will be charged for in a very near future, alcohol production units are adapting themselves to the new reality and closing the cooling water circuit. Water cooling towers are installed in these systems and, depending on the region, the water is supplied at 30°C. Since the desirable operating temperature in a bioreactor is 34°C, the heat exchanger areas increase, as well as the flows of water and fermenting wine through the heat exchangers, requiring higher initial investment and higher energy consumption to displace the reagent fluid and the cooling fluid. The increase in the cooling water temperature makes operations at temperatures lower than 86 INDUSTRIAL PERSPECTIVES FOR BIOETHANOL 33°C economically impossible; therefore, it is necessary to work with yeast strains that can resist operating temperatures close to 35°C. In continuous processes the aim is to achieve decreasing temperature gradients during the fermentation stages. This type of operation becomes interesting, since temperature becomes more prejudicial to the yeast cell when associated with high concentration of ethanol. Since the ethanol concentration in the first bioreactor is relatively low, its temperature can be a little higher. In the case of the last bioreactor, where the ethanol concentration is higher, temperatures lower that 33°C are recommended. The second restriction that has been applied to alcohol producers is the amount of the acidic residue from distillation (vinhoto in Portuguese) that can be applied into the soil according to the potassium concentration existing in it. Such residue is a suitable fertilizer and in some regions where rains concentrate during a few months of the year, as is the case in Goias state, this is an important source of irrigation water for sugarcane cultivation during the draught months. In regions where rains are better distributed, this acidic residue is less important as source of irrigation water and becomes a required fertilizer. However, since it is not too concentrated, its transportation to remote regions makes its use unfeasible, so a situation is generated where half of the cultivated area of the production unit receives twice the required amount of potassium from the acidic residue, while the other half is fertilized with commercial potassium chloride. This situation should change in the next years since the addition of potassium to soil will be restricted by the new environmental laws and the production units will have to adapt themselves to the new rules. The first steps are already being taken and consist of modifying the operating conditions in bioconversion units in order to generate more concentrated acidic residue. For this, the units must work with the highest possible levels of ethanol in the fermented wine, which implies multiple changes in the raw material preparation process, which must be capable to generate a feeding medium with concentrations of substrates high enough to reach desirable ethanol concentrations. This requires the installation of juice concentrators and brings the end of the practice that is so common in production units, where the juice from the first set of rollers is diverted to the sugar mill and the juice from the OPTIMIZATION AND LIMITS OF ETHANOL PRODUCTION 87 second set of rollers, which is the result of combined soaking and is much more diluted, is conveyed to the fermentation unit. The potassium concentration in the acidic residue depends also on the raw material used in fermentation. When sugarcane juice only is used, where the ratio between fermentable sugars and total soluble solids reaches values above 85%, the amount of potassium in the acidic residue is lower than when molasses are used, when this ratio can reach up to 60% for the same ethanol concentration in the fermented wine. Concerning the acidic residue of distillation, working with spent molasses as raw material from the fermentation unit seems more interesting. However, the increase in osmotic pressure and the presence of other inhibiting substances from molasses in the fermentation medium will eventually reduce the conversion speed and impair the process productivity. One reasonable solution for this problem can be the use of acidic residue concentrators that would solve the problem of potassium concentration in the residue without great changes in the fermentation process; however, to have this, a higher amount of energy would be consumed. A definite solution should allow to the microorganisms work under the limit conditions without a decrease in the yield of bioconversion and from then on the acidic residue from distillation should be concentrated up to the potassium amount required to make the cost of its distribution competitive with the cost of the fertilizer to be acquired in the market. 5. Final Comments Since multiple factors point out to an increasing global demand for alcohol, an increase in alcohol production is interesting. Brazil is one of the countries with highest potential to increase this production. However, the volume of investments directed to ethanol production is linked to market factors, particularly the sugar and crude oil markets. Productivity increases in production units lead necessarily to agricultural productivity increases; and, for the industry, to optimization of the bioconversion unit. The great majority of installed industrial units is outdated and could benefit from the existing technologies already 88 INDUSTRIAL PERSPECTIVES FOR BIOETHANOL implemented in some industrial units. However, in order to achieve significant gains in productivity, it will be necessary to apply new technologies that are being studied. The environmental restrictions imposed on production units require changes in the operating conditions of the bioconversion units, and the use of new technologies to handle effluents of these units, as well as the adjustment of fermentation processes to the new reality will be indispensable. Silvio Roberto Andrietta Maria da Graça Stupiello Andrietta Biotechnology and Process Division, Biological and Agricultural Research Center, University of Campinas (CPQBA/UNICAMP) OPTIMIZATION AND LIMITS OF ETHANOL PRODUCTION 89 References ANDRIETTA, S.R. Otimização de processos de fermentação alcoólica em múltiplos estágios. STAB Açúcar, Álcool e Subprodutos, 1991; 10(2):32-37. ANDRIETTA, S.R. Modelagem, simulação e controle de fermentação alcoólica contínua em escala industrial. Campinas, SP, Brazil 1994, 178 pages. Thesis (Doctor’s Degree in Food Engineering) – Faculdade de Engenharia de Alimentos, Universidade Estadual de Campinas. ANDRIETTA SR, MAUGERI FILHO F. Optimum design of continuous fermentation unit of an industrial plant alcohol production. Advances in Bioprocess Engineering 1994;1:47-52. FERREIRA E. Otimização de processos de fermentação alcoólica operando em batelada-alimentada. Campinas, SP, Brazil 2005, 128 pages. Thesis (Master’s Degree in Chemical Engineering). Faculdade de Engenharia Química, Universidade Estadual de Campinas. MOURA AG, MODL J. Concentração de vinhaça. Tecnologia, equipamentos e sua integração energética numa destilaria. Presented at the STAB International Symposium. Águas de São Pedro, SP, Brazil 2005. SILVA FLH. Modelagem, Simulação e Controle de fermentação alcoólica contínua extrativa. Campinas, SP, Brazil 1997, 162 pages. Thesis (Doctor’s Degree in Food Engineering). Faculdade de Engenharia de Alimentos, Universidade Estadual de Campinas. TOSETTO GM, ANDRIETTA SR. Influência da matéria-prima no comportamento cinético de levedura na produção de etanol. Presented at the VII Seminar on Enzymatic Hidrolysis of Biomass – SHEB, Maringa, PR, Brazil 2002. VIEGAS MC, ANDRIETTA MGS, ANDRIETTA SR. Use of tower reactors for continuous ethanol production. Brazilian Journal of Chemical Engineering 2002;19(2):167-173. Innovation and sustainability through industrial biotechnology Adrie J. J. Straathof Çagri Efe Peter M. M. Nossin Telma T. Franco Luuk A. M. van der Wielen Abstract Industrial biotechnology is expected to be a large contributor in the transition from a fossil-resource based energy landscape towards a more sustainable situation where biobased alternatives should have a substantial role. Two scenarios are presented here that show that on the basis of current levels of technology, economic feasibility can be expected. Moreover, it is envisioned that complete redesign of the biobased production of biofuels and chemicals can result in substantial innovation and a further improved economic opportunities in this inevitable transition. Introduction Increasing wealth and a rapidly expanding human population create an increasing demand on energy and raw materials. Fossils reserves are steadily drained and environmental (e.g. “Katrina”) and political (e.g. Iraque) disturbances impact price and security of delivery substantially. Furthermore, emission of CO2 from fossil resources has a substantial impact on climate change. Availability of sustainable, renewable resources for energy and chemistry are of tremendous societal urgency. 92 INDUSTRIAL PERSPECTIVES FOR BIOETHANOL Possible solutions may be offered by biobased, renewable resources, in Dutch “Groene Grondstoffen”, which are essentially created from solar energy and CO2. Aiming at lowering (towards zero) CO2 emissions and a reduced dependency on fossil resources, such as crude oil, while meeting the major technical challenges, new biobased, economic opportunities will also be created, for the Dutch agro, energy and chemicals industries as well as for the trade and transport sectors. The Platform for Renewable Resources (in Dutch: Platform Groene Grondstoffen PGG) is an advisory committee to the Dutch government on biobased solutions for the energy and fuels sectors, directed at all relevant economic sectors. For the Netherlands and under several constraints, a 30% replacement of fossil resources by biobased alternatives in the year 2030 seems feasible. An important constraint is zero growth in energy consumption relative to the level of 3000 PJ by the year 2000. To achieve these goals, a combined package of measures to increase energy efficiency and reduce consumption as well as to enable a largescale transfer towards biobased (and other) resources is necessary. This includes issues such as biomass (or its derivatives) and improved use of available agro-resources and residue streams. The following four main application areas for biobased resources are distinguished, and estimates of fossil replacement are given in brackets: transport fuels (60% or 324 PJ/a), chemicals and materials (25% or 140 PJ/a), electricity (25% or 203 PJ/a) and heat (17% or 65 Pj/a). PGG has identified groups of measures (in Dutch: “transitiepaden”) to achieve this situation by 2030: (1) import; (2) production of renewable resources; (3) coproduction of chemicals, fuels and energy; (4) production of synthetic natural gas and (5) innovative use of renewable resources. Within the third theme, coproduction of chemicals, transport fuels and energy, a wide range of conversion and fractionation (bioraffinage) options are considered. These include bio and thermochemical conversion towards fuels and chemicals, with the combined production of other energy forms; i.e. electricity and heat. Not all underlying technologies are mature, and particular their integration is not yet well established. This is clearly a field which is seeing and will see major technological development, and has substantial economic opportunities. A simplified INNOVATION AND SUSTAINABILITY THROUGH INDUSTRIAL BIOTECHNOLOGY 93 and schematic version of the network of potential conversions towards desired products is shown (Figure 1). Figure 1: Schematical and condensed overview of fractionation and conversion of biomass in desired industrial and consumer products. Based on these numbers, the biofuels and the chemical sector are expected to be key players in the transition to a sustainable future. The scale of the global tendency to embrace biobased solutions in these sectors will require (also) the large scale use lignocellulosic and other residual agro streams. Therefore, the inventory of technological and other innovation opportunities on the basis of specific case scenarios seems timely and relevant, and is the purpose of this contribution. Two scenario studies are presented. In the first one, ethanol production from lignocellulosic feedstock is described. In the second one, the potential to produce acrylic acid from sugars is discussed. Ethanol production from lignocellulosic feedstock In recent years, there has been an increasing interest in utilizing lignocellulosic biomass, which is the most abundant natural feedstock 94 INDUSTRIAL PERSPECTIVES FOR BIOETHANOL for ethanol production. Almost 70% of cellulose biomass can be hydrolyzed into pentose and hexose sugars, which can later on be fermented into ethanol. This section summarizes a desk study on the application of the current knowledge in the sugar-ethanol industry to investigate the feasibility of sugar and ethanol production from sugar cane in order to search for alternative usages for the side products of the sugar production and to improve the existing technology to get more sustainable and environmentally friendly processes. Therefore a conventional sugar/ethanol plant with current technology (year 2005) was compared to a future plant (year 2015). In the conventional plant (2005), 52% of the sucrose extracted from sugar cane is crystallized into sugar and the remainder is fermented into ethanol. Bagasse, the fiber remaining after extraction, is burnt to generate electricity. The vinasse, which is the organic and salt-rich stillage from distillation; the filter cake, which is rich in coagulated proteins, gums, organics, sulphate and phosphate salts; and the cogenerator ash, which is mainly composed of the mineral portion of the bagasse, are sent back to the fields to be used as fertilizer for the cane plantations. The proposed 2015 plant is generated based on the current technology. However, in this future case, the cellulose and hemicellulose fractions of lignocellulose are hydrolyzed into hexose and pentose sugars to be used as substrate for ethanol production. In addition, vinasse, filter cake and the genetically modified yeast are combusted and streams rich in organic materials are treated in a wastewater treatment plant. The proposed plant location is Sao Paulo, a state of Brazil. The proposed plants have a sugar cane processing capacity of 5 million tons/ year, which is within the range of the top ten largest existing plants. The ethanol processing plants yield yeast, carbon dioxide, vinasse, filter cake and bagasse as side products. Using the existing technologies, the yeast output of the plants is minimized and the yeast produced is combusted. The conventional plant utilizes bagasse as fuel for electricity and steam generation for the process. In the conventional plant, the main input streams to the plant are sugar cane and recycled water. Minor raw materials are limestone, sul- INNOVATION AND SUSTAINABILITY THROUGH INDUSTRIAL BIOTECHNOLOGY 95 phur and sulphuric acid. In the future case, in addition to the inputs listed for conventional plants, acidifying agents for pretreatment and cellulase for cellulose hydrolysis are inputs of the process. The design contains the following items, which are partly summarized in this text: Basic assumptions, plant capacity and location, composition of streams entering and leaving the process, block schemes and pure component properties. Thermodynamic properties relating to the components in the system. Process and the flow scheme of the plants. Process controls required. Mass and energy balances. Equipment designs. Safety and HAZOP analysis. Wastes generated. Economical evaluation. · · ·· ·· ·· · Description of the 2005 Plant The streams entering and leaving the designed 2005 plant are given in Figure 2. Figure 2. Process yields calculated for the 2005 plant (flows are given per ton of sugar cane) 96 INDUSTRIAL PERSPECTIVES FOR BIOETHANOL The sugar cane from fields is fed into a milling unit. Five roller mills are used in series that contain three rollers and another pressure roller. Bagasse from the mills is sent to a bagasse handling unit where the moisture content is reduced from 50 to 12 % and then it is sent to cogeneration and boiler units where it is combusted as fuel for the generation of steam and electricity for plant use. Since water evaporates during the combustion, its contribution to the heating value is negative. The airflow into the cogenerator is preheated by flue gases and then the flue gases are passed through the dewatering section to reduce the moisture content of the bagasse. The dark green juice from the mills is acid and turbid with a pH of approximately 5.5; 35% of the juice is destined for ethanol production and the remainder goes for sugar production. These proportions are determined based on the assumption that 48% of the sucrose in the juice is converted into ethanol and the rest into sugar crystals. A sulphitation unit operation is used to bleach the juice. The required sulphur dioxide is produced by burning elemental sulphur in sulphur burners and absorbed by juice in a sulphitation tower. Following sulphitation, overliming takes place to neutralize the juice to pH 6-8. Lime milk, about 0.5 kg CaO per ton of cane, neutralizes the natural acidity of the juice, forming insoluble lime salts. Heating the limed juice (95°C or above) coagulates the albumin and some of the fats, waxes and gums and the precipitate formed entraps the suspended solids as well as finer particles. The Ca(OH)2 is produced from CaCO3. The limestone is burned in a calciner to produce CaO, which is later on blended with the juice from the filters to prepare the lime milk. After sulphitation, during liming and juice heating, polymeric flocculant is added to the juice in clarification units. Sedimentation is carried out in tray type clarifiers and a rotary filter unit is used to recover the juice. The filter cake is sent back to the fields as fertilizer. The clarified juice is sent to a six-staged multi-effect evaporation section to increase the sugar content of the juice to 68 % w/w. The condensates from the evaporators are sent to a cooling tower and recycled INNOVATION AND SUSTAINABILITY THROUGH INDUSTRIAL BIOTECHNOLOGY 97 as process water. The last vapor is condensed in vacuum generators and removed as condensed water. In the next step, the concentrated sugar solution is sent to vacuum boiling pans. The crystallizer is fed with the crude sugar from the second stage crystallizer to supply the seed for the crystallization of the sugar. The molasses from the first pan is fed into the second pan and the molasses from the second pan is fed to the fermentors. The solid contents of the molasses from the centrifuge vary between w/w 60-70%. The moisture content of the crystal sugar from the centrifuge is less than w/w 1%. The sugar recovery in each crystallizer is 60% and the total sugar recovery is 84%. Crystalline sugar from the centrifuge is sent to driers. Rotary granulators are used for drying. The clarified juice is mixed with filtered juice from filters and molasses from crystallization. During the fermentation, sugar is converted to ethanol with 92% of the theoretical yield, which corresponds to 0.460.47 g ethanol/g sugar. Fermentation is carried out in six vessels to maintain a continuous operation and to prevent the need for extra storage tanks for broth and recycle biomass. The biomass is recycled to maintain high cell concentrations in the fermentors. The biomass is separated from the broth using continuous disc type centrifuges and sent to a biomass sterilization vessel, which is a stirred vessel for blending the biomass with a pH 2 acid solution. The carbon dioxide-rich gas from the fermentors is passed through an ethanol scrubber column to prevent volatile organic emissions to the atmosphere and to recover lost ethanol. This column is not only fed with the gas from the fermenter, but, also with the carbon dioxide rich vapor distillate from the beer column. The absorption water is recycled from the evaporators and boiling pans. Carbon dioxide is released to atmosphere. The medium from the fermenter is mixed with the ethanol solution from the ethanol scrubbers and sent downstream. In a beer column, ethanol is separated from the wine (initially at ~8%) as a vapor (~40%). The product is removed as a vapor stream from the sixth stage of the column. The carbon-dioxide rich distillate is removed out the tower at a temperature of 20ºC to reduce the amount of 98 INDUSTRIAL PERSPECTIVES FOR BIOETHANOL ethanol in the vapor. The bottoms, stillage, has most of the salts and suspension solids, but most important of all is the significant amount of glycerol, acetic acid and fusel oils in the bottoms. To recover the fusel oil and glycerol, another side draw is installed on the column, one stage above the reboiler, to separate most of the fusel oil and glycerol from the vinasse. All of the vinasse (the stillage) used as fertilizer. In a rectification column, the product from the beer column is concentrated to 92.5 % and some impurities are removed. Bottoms are removed with the side draw of the beer column outside the battery limit to be further purified. The final dehydration of ethanol is carried out in molecular sieve absorption columns. These work in tandem. The columns are regenerated by using hot nitrogen at 200ºC. The nitrogen is circulated in the system. Description of the 2015 Plant The streams entering and leaving the designed 2015 plant are given in Figure 3. Figure 3. Process yields calculated for the 2015 plant (flows are given per ton of sugar cane) INNOVATION AND SUSTAINABILITY THROUGH INDUSTRIAL BIOTECHNOLOGY 99 The 2015 case process is conceptually designed based on current 2005 technology. Like in the 2005 case, 48 % of the sucrose will be utilized for ethanol production and 52% will be isolated as sugar crystals. On the other hand, in the future case, the bagasse, the lignocellulosic portion of sugar cane, will be hydrolyzed to pentose and hexose sugars and lignin. In addition, the organic waste generated in the process (i.e. vinasse, filter cake, and microorganisms) will also be combusted in cogeneration units instead of sent to the fields untreated. The milling unit, sugar section and ethanol recovery section have the same structure as in the 2005 plant with some variations in equipment sizes. The first step in bagasse hydrolysis is pretreatment. Acid-catalyzed steam explosion is used. The liquid portion is removed from the fibers via screw presses. Before detoxification, some of the hydrolysate is bypassed to readjust its pH from 10 to 4.5. The fiber portion is transferred to cellulose hydrolysis vessels. The wash water for the screw presses is a portion of conditioned hydrolysates. The reason for this is to prevent dilution of the hydrolysate and to avoid large reactor sizes due to the dilution. The acetic acid concentrations are 2-3 g/l and do not inhibit fermentation. By diluting the hydrolysate with molasses clarified juice and filtrate from the filters, the concentration of all the inhibitory compounds will be halved. The final concentration of lignin degradation products going to fermentors after overliming is 1.4 g/l. Considering the high cell concentrations, this will not inhibit fermentation thus, detoxification is considered only during the overliming. Detoxification is carried out by overliming to pH 10. The suspension from the clarifiers is sent to a rotary filter and dehydrated to 55% water. The filter cake is sent to the cogenerator due to the presence of the organic material inside the cake. The filtrate is remixed with hydrolysate. As previously mentioned some portion of the hydrolysate is utilized as wash water for the screw presses. The remaining portion is sent to hydrolysis vessels. After pre-treatment the detoxified liquid fraction contains the pentose sugars and this stream is used to dilute the fibers to 20% solids. The solid fraction from pretreatment contains the cellulase and the lignin 100 INDUSTRIAL PERSPECTIVES FOR BIOETHANOL fraction. This solid fraction is exposed to cellulase to hydrolyze the cellulose in the hexose sugars. The cellulose hydrolysis vessels are composed of two parallel vessel sets of four vessels in order to mimic plug flow behavior and to prevent from being vessel volumes too large. After cellulose hydrolysis, lignin residue is separated from the mixed sugar solution and sent to the cogenerator as fuel. The liquid fraction which contains sugars is sent to the fermentors to produce ethanol. Similar to the 2005 plant, seven fermentors are utilized for fermentation. The downstream processes have the same structure as in the conventional plant. The waste streams generated in the process are the filter mud containing sugar cane organic ingredients, vinasse and water. The wastewater (condensates and vapors from evaporators, boiling pans, detoxification and dehydration) undergoes water treatment outside the battery limit, but the costs are included. The vinasse is concentrated and sent to the cogenerator as fuel. The lignin residue, yeast and the filter mud are dehydrated using the flue gasses from the cogenerator before being sent to furnace. Since the generation of steam and electricity is not sufficient to meet the demands of the plant, the generation of electricity is lowered and the generation of steam is increased to meet the demands. The excess of demand for electricity is supplied by purchasing from the grid. The solids from the furnace (ash, gypsum and dirt) are sent to land fills. The acid solution from the yeast sterilization unit is neutralized using lime and precipitated to be treated as land fill. The unit is outside the battery limit, but the costs are included in the cash flows. Economy of 2005 Plant The results of an economical analysis of the 2005 plant reveal that the required total capital investment is $102 million. The investment is determined using the location factor of 0.4 for Brazil. This factor is determined based on the social and economical comparison of Brazil with the US and European countries. Based on this investment value, INNOVATION AND SUSTAINABILITY THROUGH INDUSTRIAL BIOTECHNOLOGY 101 the net present value of the investment is $166 million using a discount rate of 4%. The sensitivity analysis shows that plant operation is profitable for a location factor of up to 0.7. The pay out periods is below 3.5 years up to a location factor of 0.7. This time period is acceptable for chemical plants. The same analysis reveals that the maximum interest rate for which investment can remain economical throughout the investment period is 26.5% for the location factor of 0.4. This value falls to 3.7% when the location factor is increased to 0.7. When compared to the current US inflation rate (~3.2%), the plant still remains compatible with the market. A cash flow analysis reveals that the price of sugar cane is the main yearly operational cost (87%). Therefore, the economic parameters are highly sensitive to the price of sugar cane. The other cost factors do not have major economic effects. The sensitivity analysis is carried out on the net present value, pay out period, discounted cash flow rate of return and rate of return values. Although the parameters are highly sensitive to the price of sugar cane, the net present value of the investment is $106 million even when the price of sugar cane is 20% higher than current prices. The parameters also are highly sensitive to revenues (ethanol and sugar). The sensitivity to electricity is lower, but still higher than the sensitivities to minor operating costs like utilities, labor etc. The production costs of ethanol are higher than the current reported production costs ($190/ton). However, the minimum production costs, excluding everything except the sugar cane, are approximately $140/ ton. Therefore, more insight into details of the plant should be obtained. The overall conclusion is that the 2005 plant is economical and favorable for investment even for investment costs of up to $170 million. Economy of 2015 Plant The calculated investment requirement for the 2015 plant is $133 million after including the location factor of 0.4 for Brazil. The net present value of the 2015 plant is $370 million, which is more than double the present value of the 2005 plant. The reason for this is that when ligno- 102 INDUSTRIAL PERSPECTIVES FOR BIOETHANOL cellulose hydrolysis is included in the design the investments do not change significantly, while the revenues are almost doubled. The payout period for the 2015 plant is 1.4, which means the plant recovers the investment in less then 2 years. The analysis shows that the plant remains profitable as long as the location factor is increased up to 1. The discounted cash flow analysis reveals that the plant investment can stand interest rates of up to 38% and 7.3% for location factors of 0.4 and 0.9, respectively. Like in the 2005 plant, the costs of sugar cane and the selling prices of ethanol and sugar are the major factors that can negatively affect the economic parameters. However, even a negative deviation of 30% in the price of sugar cane from the current prices yields a net present value of $150 million, which proves to be a profitable investment. In the 2015 plant, the economic parameters are not as sensitive to sugar cane and sugar prices as to ethanol prices. Still there are major effects. The variations of ±30% in ethanol and sugar prices yielded ±60% variations in the net present value of the investments. The sensitivity to cellulase prices is not as high as the sensitivity to sugar cane and product prices. Variations of ±30% in cellulase price yielded ±6% in net present value of the investment. None of the cost factors (i.e. labor, fixed cost etc.) have major effects on the economic parameters. Variations in fixed costs affected the parameters most, but still the sensitivity is ±6% for variations of ±30%. The costs of ethanol production (~$167/ton) are significantly lower than the production costs in the 2005 plant. In conclusion, this analysis shows that it is highly attractive to focus on ethanol production from lignocellulosic feedstocks. Feasibility of fermentative acrylic acid production from sugars As mentioned above, renewable materials such as sugars are interesting alternative carbon sources for the production of fuels and chemicals, in particular considering the potential of modern biotechnological methods. Acrylic acid is one of the target chemical products that is occasionally discussed in this context (Danner and Braun, 1999; Carole et INNOVATION AND SUSTAINABILITY THROUGH INDUSTRIAL BIOTECHNOLOGY 103 al., 2004; Willke and Vorlop, 2004). The potential of biotechnological routes to produce acrylic acid were recently reviewed (Straathof et al., 2005) and this study is summarized here. Acrylic acid (also known as 2-propenoic acid) is a commodity chemical with an estimated annual production capacity of 4.2 million metric ton, which ranks it about 25th in the list of organic chemical products. The major utilization of acrylic acid, its salt and esters, is in polymeric flocculants, dispersants, coatings, paints, adhesives and binders for leather, paper and textile. Acrylic acid is conventionally produced from petrochemicals. Currently most of the commercial acrylic acid is produced by partial oxidation of propene. In the so-called single-step process, the yield is at most 50-60%, resulting in large amounts of waste. A two-step process via acrolein is preferred, achieving about 90% yield overall. There is a requirement for efficient one-step processes starting from cheap carbon sources. Unfortunately, petrochemical carbon sources are not renewable. This implies that their use adds to global CO2 emissions and that they should become scarcer and more expensive in the future. Fermentative production of acrylic acid from sugars might be an interesting alternative. A major hurdle for the development of an industrial fermentative process for production of acrylic acid from sugars is the toxicity of acrylic acid to potential host organisms. However, by analogy to other fermentative carboxylic acids, it may be assumed that microorganisms after adaptation might survive at concentrations up to 50 g/L acrylic acid. The current literature reports only very low yields of acrylate on sugars (Straathof et al., 2005). Still, several attractive candidate metabolic pathways for converting sugars to acrylate have been identified (see Figure 4). The efficient expression of any of the candidate pathways in a host organism will require extensive genetic engineering and might even require some as yet unknown enzyme activities and export proteins. Some pathways might result invery high yields of acrylate on sugar, without aeration. However, these pathways, including export of acrylic acid out of the cell, still need to be evaluated in more detail to show that a microorganism could generate ATP from them. If not, pathways that will lead to economically less attractive routes might be required instead. 104 INDUSTRIAL PERSPECTIVES FOR BIOETHANOL Figure 4. Potential metabolic pathways to acrylic acid. 3-HP = 3-hydroxypropanoate. Assuming that a host organism can be constructed for the effective production of acrylate, a fermentation process including removal of pure acrylic acid was conceptually designed and economically evaluated. This process (Figure 5) uses known technology. Figure 5. Flow sheet of the hypothetical process designed for the production of acrylic acid from sucrose. Only major equipment and steams are shown. INNOVATION AND SUSTAINABILITY THROUGH INDUSTRIAL BIOTECHNOLOGY 105 An economic evaluation shows that the designed process will be feasible. The cumulative net present value and internal rate of return were found to be 220 million euros and 34%, respectively. This indicates that there is a clear incentive for development of the required microbial host and the process, in particular considering the environmental sustainability of the designed process (Straathof et al., 2005). Conclusions The case studies presented here clearly indicate positive opportunities for biobased processes using industrial biotechnology for chemical alternatives. In both scenarios, relatively conventional technology was employed to strengthen the view that these opportunities are within reach. The case studies also underline the need to develop second generation processes on the basis of lignocellulosic and other residual flows. In part the need originates from indications of limited availability of conventional sugar-based fermentation feedstocks (see other contributions in this work). But moreover, a straightforward and not fundamentally reconsidered approach will not fully utilize the innovation potential of the biobased opportunities that the near future forces humanity to embrace. Acknowledgements These investigations were supported (in part) by the Netherlands Ministry of Economic Affairs through the Netherlands Organisation for Scientific Research (NWO) in the NWO-ACTS research programme BBasic and in part by Fundação de Amparo à Pesquisa do Estado de São Paulo, Brazil FAPESP). 106 INDUSTRIAL PERSPECTIVES FOR BIOETHANOL Adrie J. J. Straathof a, Çagri Efe a, Peter M.M. Nossin b Telma T. Francoc and Luuk A. M. van der Wielen a a* Department of Biotechnology, Delft University of Technology, Julianalaan 67, 2628 BC Delft, The Netherlands b DSM, Corporate Technology, P.O. Box 18, 6160 MD Geleen, The Netherlands c Chemical Engineering School, State University of Campinas (Unicamp), P.O. box 6066, Campinas, São Paulo, 13081-970 Brazil * Corresponding author. Tel.: +31-15-2782361. Fax +31-15-2782355. E-mail: [email protected] References Carole TM, Pellegrino J, Paster MD (2004) Opportunities in the industrial biobased products industry. Appl Biochem Biotechnol 113-16: 871-885. Danner H, Braun R (1999) Biotechnology for the production of commodity chemicals from biomass. Chemical Society Reviews 28: 395-405. Straathof AJJ, Sie S, Franco TT, van der Wielen LAM (2005) Feasibility of acrylic acid production by fermentation. Appl. Microbiol. Biotechnol. 67: 727-734. Willke T, Vorlop KD (2004) Industrial bioconversion of renewable resources as an alternative to conventional chemistry. Appl Microbiol Biotechnol 66: 131-142. Rabou, L.P.L.M., Deurwaarder E.P., Elbersen, H.W., and Scott, E.L. (2006), Biomass in the Netherlands Energy Household in 2030. Platform Groene Grondstoffen , jan 2006. Advances of the Brazilian production of chemicals and other products from biomass Telma Teixeira Franco Introduction Brazil is fortunate for the abundant and diverse agricultural and forest resources. Occupying a total area of 8,511,996 km2 between 5°16’N and 33°44’S, Brazil has a broad climatic and geomorphologic variety, which is responsible for the presence of several important biomes and ecosystems, which lodge about 10% to 20% of the world’s known living species [1]. In the last 50 years, Brazilian agribusiness is developing into a more modern, more efficient and much more competitive sector. The Brazilian climate, the reasonable rain distribution, the solar energy, the abundance of water resources and the size of the available land are factors which make 390 million hectares suitable for agriculture. However, not all this land is used so far for this purpose. In the year 2005, thirty and three percent of the GNP (gross national product) resulted from agribusiness, which provided 37% of the jobs in Brazil and was responsible for 42% of the national exports. The main products of Brazilian agribusiness are coffee, sugar cane, ethanol, fruits and processed fruit juices, soybean, cattle and beef, chicken products, tobacco, leather, cotton [[2]. Besides of nature, there were target directed efforts to improve Brazilian agriculture as the creation of Embrapa, Brazilian Agricultural Research Corporation’s, in 1973 by the Ministry of Agriculture in order to speed the development of agriculture technologies & innovation. It helped 108 INDUSTRIAL PERSPECTIVES FOR BIOETHANOL Brazil to increase the offer of food while, at the same time, conserving natural resources and the environment and diminishing external dependence on technologies, basic products and genetic materials. Networking of research centers, service centers and central divisions of Embrapa make that almost all the states of the Union have an Embrapa local agency. For each Brazilian main agribusiness there is usually at least one Embrapa local agency close to the producers [3]. Another important and direct effort was targeted towards the study of the biodiversity. The first program was designed in 1999 in Sao Paulo state supported by Fapesp, which is the Biota program (Fapesp is the The State of São Paulo Research Foundation). Biota, in less than 5 years, managed to aggregate more than 500 researchers from different 50 projects in a virtual network and described more than 4 thousand species of plants, animals and microorganisms of Sao Paulo State. The success of the program is registered by the online journal Biota neotropica [4]. A similar program was created later by the Science and Technology Ministry (CNPq) aiming to identify the national biodiversity. A very important action was taken in order to improve the in depth knowledge of the main Brazilian crops. Several projects on plant genomics have been developed in the last five years, also with the support of Fapesp and CNPq (orange, sugar cane, coffee, eucalyptus, banana, etc.). Therefore, the discussed maturity of the Brazilian sugar cane agribusiness is not a result of random causes, but of several organized initiatives developed by national and local administrations and by the associations of the producers (i.e: Copersucar earlier, CTC more recently) with research centers. 1. Recent advances of genetic engineering of the Brazilian sugar cane In 2003, it was announced that a team of Brazilian scientists had sequenced the genome of sugarcane. Their findings, published in a forthcoming issue of Genome Research, suggest that 2,000 of the more than 33,000 genes in the sugarcane genome are associated with sugar production in the plant. The sequencing of the genome was co-ordinated by Paulo ADVANCES OF THE BRAZILIAN PRODUCTION OF CHEMICALS... 109 Arruda of the State University of Campinas (Unicamp). More than 200 scientists from 22 Brazilian research groups were involved in the study, which started in 1999 [5]. Earlier, these Brazilian laboratories participated in the Sugarcane Expressed Sequence Tag Project (SUCEST), which was launched in September 1998. The project was supported by CTC (a private company) and the Fapesp. Different aspects were mainly targeted, as pathogen response, photoreceptors, cell cycle, and aluminum tolerance [6]. Genetic engineering has given to Canavialis, a Brazilian company targeted to sugar cane development, a new tool for development of novel varieties. With this tool, one is able to identify the DNA sequences that confer a desired trait and transfer that trait from one plant to another without having to perform crosses, and without altering the other traits of that variety. The gene marked for insertion can come from a plant of the same species, or from other plants of different species, or even from other organisms and animals. Thus, the possibilities for advancement through the use of this technology are broad. In this scenario, classic or conventional genetic improvement breeding is fundamental since the traits introduced through genetic engineering should be added to elite varieties adapted to the soil and climate conditions of the sugarcanegrowing regions. Therefore, transgenic sugar cane plants have also been studied by Brazilian laboratories in cooperation with local industries [7]. 2. Top value added chemicals from biomass A study developed by the Pacific Northwest National Laboratory (PNNL) and the National Renewable Energy Laboratory (NREL) of USA in 2004 described a series of top value products from all biomass components, identified a group of promising sugar-derived chemicals and materials that could serve as an economic driver for a biorefinery. Top value added chemicals from biomass, 2004). [8] Initially a group of 300 possible building blocks was identified from a variety of resources, however after the development of a more critical screening criteria, this number was reduced to 30 and later to 12. These building block chemicals which can be produced from sugars via biological or chemical conversions were identified and selected and the subsequent conversions into a number 110 INDUSTRIAL PERSPECTIVES FOR BIOETHANOL of high-value bio-based chemicals or materials were studied. The final list of the American study is the following: 1,4-diacids (succinic, fumaric and malic), 2,5-furan dicarboxylic acid, 3-hydroxy propionic acid, aspartic acid, glucaric acid, glutamic acid, itaconic acid, levulinic acid, 3-hydroxybutyrolactone, glycerol, sorbitol, and xylitol/arabinitol. Building blocks are molecules with multiple functional groups, which can be later transformed into other group of molecules, by chemical or biological conversion. As, potentially, a group of desirable chemical building blocks can be obtained from biomass, the current literature already describes the efforts to establish technologies to develop flow-chart models for products derived from biomass feedstock, similarly to the flow-charts previously developed for the petrochemical industry. The idea of flow charts is based on chemical data, known market data, properties, performance of the potential candidates and the prior industry experience. The current literature already describes the achievements and the planning of some large industries on the development of products based on biorenewables, like the 1,3 propanediol (DuPont, USA), polylactic acid (Cargil, USA), PHB (joint 50 ton plant: Metabolix + ADM, USA and another plant by PHB, Brazil), fermentative route for caprolactam (DSM, Netherlands), the development of L-methionine, L-lysine and L-threonine routes (plans of Degussa) [9]. Brazilian situation towards top value added chemicals from biomass This present work aims to review the main Brazilian results on the use of sugar cane as a biomass to produce chemicals or chemical products, besides of the bioethanol. Four hundred million tons of sugar cane is currently employed in Brazil for the production of 20 million tons of raw sugar-cane and 15 billion liters of bioethanol yearly. The potential of the sugar cane is not new, since it played a central role in Brazil’s culture and economy since the beginning of the colonial period, when a significant amount of sugar was exported to Europe. ADVANCES OF THE BRAZILIAN PRODUCTION OF CHEMICALS... 111 Research on the fermentation of sugar cane has extensively been investigated in Brazil, mainly towards the bioethanol and yeast production. Therefore, initially this present work focused on a survey to identify the work done in Brazil on the production of these twelve building blocks, described by the American screening. However, very little information was found on those building blocks production, most of the information found was related to organic acids, aminoacids and biopolymers. The most often produced chemicals in Brazil by fermentation of sugar cane as feedstock, as also other products obtained from biomass were identified (Figure 1 and Table 1) and will be described. Figure 1: Chemicals and products produced from sugar cane as biomass, in Brazil. 112 INDUSTRIAL PERSPECTIVES FOR BIOETHANOL Table 1: Chemicals and products produced from sugar cane as biomass, in Brazil. ADVANCES OF THE BRAZILIAN PRODUCTION OF CHEMICALS... 113 3. Organic acids produced by fermentation of biomasses Besides the two industries which produce and commercialize citric acid and lactic acid in Brazil, several processes were developed in universities and research centers on this topic, where submerged and solid state fermentation were mainly employed. Soccol and collaborators have extensively studied the possibility of producing reasonable concentrations of lactic and fumaric acid in culture media using agricultural wastes as a solid substrate. They also studied the optimization of processes to achieve twenty grams per liter of fumaric acid by fermentation of Rhizopus strains in culture media containing cassava hydrolysates and for bioconversions to produce organic acids, flavours, aromas and mushrooms [10-12]. Submerse aerobic fermentation also leads to fumaric acid production by Rhizoups, then it was purified by precipitation with CaOH in H2SO4, when the achieved yield is 0.6 kg/ reducing sugars. The chemical route for fumaric acid can be cheaper, but the fermented route is nowadays preferred due to the clients preference for natural products. Acetic acid is mainly produced in Brazil by chemical route; however there is some production by fermentation with Acetobacter at 30 to 35 C and initial pH 4.5. The acid is further recovered by liquid extraction or by distillation. Fermentation yields of acetic acid can reach 115 g/l [13]. Lactic acid and lactates are produced by PURAC Sínteses in Campos, Rio de Janeiro state, in plants located next to sugar mills. [14] Sucrose is used as main substrate in a relatively simple fermentation route and the produced lactic acid is then recovered by ion exchangers. Despite of the lactic acid production in Brazil, there is currently no production of polylactates there. Citric acid is also produced by submerse fermentation of Aspergillus niger in the Mercocítrico Fermentações S.A., in Ribeirão Preto, São Paulo state, and is further recovered. [15] Currently there is no chemical process for citric acid production. 4. Production of biodegradable plastic in Brazil PHB Industrial S.A. is a Brazilian company created by Biagi and 114 INDUSTRIAL PERSPECTIVES FOR BIOETHANOL Balbo groups, two large producers of the sugar & bioethanol sector, located in Serrana, São Paulo state (Figure 2). Their joint area of land for sugar cane crop is approximately 100,000 hectares, from where 20 million pack of sugar (50 kg/pack) and 500 million litres of bioethanol are obtained. This year, this company announced an investment of U$ 50 million to scale up the production of 2,000 tons/ year of polyhidroxybutyrate, which would allow the preparation of 4,000 tons of composites/ year [16]. Figure 2: PHB Industrial S.A. plant located in Serrana, São Paulo state. According to Rossell [17] PHB is an environmentally degradable material belonging to the polyhydroxyalkanoates (PHA) family, polyesters which were first described in 1926. It has some unique characteristic among thermoplastics because it presents a complete cycle starting from sugar cane and bacterial fermentative synthesis. In the absence of microorganisms biodegradability the hydrolysis of PHB in aqueous environments is slow, because of its hydrophobicity. Thus, in principle, the ADVANCES OF THE BRAZILIAN PRODUCTION OF CHEMICALS... 115 lifetime of a stored PHB product is unlimited; after its disposal, however, PHB becomes clearly biodegradable in domestic effluent-treatment systems. PHB is a biocompatible, biodegradable, thermoplastic, hydrophobic, and stereospecific material. It has a high molecular mass, high crystallinity (55 to 75%), good chemical resistance, and its barrier properties enable practical packaging applications. Polyhydroxybutyrate can be processed as a conventional thermoplastic in most industrial transformation processes, including extrusion, injection, and thermopressing and can be transformed into rigid shapes (for example pipes) and films for packaging. PHB can also be modified by extrusion by incorporation of additives (stabilizers, plasticizers, and pigments), immiscible additives (e.g. wood and starch powder), or by mixing with other plastics. The investigation on the feasibility of the production of PHB in Brazil was developed during the 90’s, with a partnership between Centro de Tecnologia Canavieira (ex-Copersucar, nowadays CTC), the Institute of Technological Research (IPT) of the State of São Paulo and the Institute of Biomedical Sciences of the University of Sao Paulo. In the year 2000, the rights for the production of PHB were sold from Copersucar to the PHB Industrial S.A. The production capacity was at that time about 1.5–2.0 t/ year and currently, it operates a capacity of 60 t/yr, by fermentation of the sucrose from sugarcane by Ralstonia eutropha (Alcaligenes eutrophus) [16]. According to this industry, there is a technical limitation to scale up the PHB production, which is the size of the anaerobic fermenters. The largest feasible anaerobic tanks have capacities of 500 m3, but the most often used ones have 200 m3. The cells of the microorganisms in the PHB Industrial SA can produce up to 100g PHB/ /L, with cell concentrations up to 180 g /L (60 to 70% of cell mass is PHB); being the biopolymer extracted from the cell with alcohol at high temperatures. The achieved quality, properties and resistance of their purified polymer are similar to non-biodegrable polymers. Besides the Brazilian PHB Industrial S.A., there is only one company which also produces PHB, Metabolics (created in 1996 in the USA). This company has announced the scaling up of their PHB production to 50,000 tonn/year. 116 INDUSTRIAL PERSPECTIVES FOR BIOETHANOL 6. Xylitol Different techniques have been used by Faenquil’s group to produce xylitol by fermentation, always employing hemicellulose hydrolysates. The most used substrates described by the group were the hydrolysates of rice straw, sugar cane bagasse and the most described microorganism was Candida guilliermondii.. Xylitol concentrations as high as 36 g/L were achieved, corresponding to a xylose-to-xylitol yield factor (YP/S) up to 0.79 g/g. Different processes to produce xylitol were compared and Table 2 shows that the conversion factors of xylose into xylitol and the volumetric productivities were strongly affected by the source of the hydrolyzed biomass [18]. Table 2: Effect of the raw source hydrolysates on the conversion factors (Yp/s ) of xylose into xylitol and the volumetric productivities Qp. Raw material hydrolysates Yp/s (g/g) Qp (l/h) Rye bran 0.61 0.33 Corn cob 0.71 0.60 Corn cob 0.52 0.26 Sugar cane bagasse 0.79 0.52 Corn leaves 0.64 0.36 Eucalyptus wood 0.63 0.41 Eucalyptus wood 0.04 0.02 Rice straw 0.72 0.57 Source: [18] 7. Aminoacids production by fermentation Lysine is currently produced by Ajinomoto in Sao Paulo State, by fermentation process, due to the large demand of feed industries. Glutamate is also produced there to attend the demand for flavor enhancers and large part of the production is exported to several countries. Another ADVANCES OF THE BRAZILIAN PRODUCTION OF CHEMICALS... 117 plant for lysine in Sao Paulo state was recently announced by a Korean industry, which should be ready this year. 8. Other products Different products were developed by the former Coopersucar (CTC) and by several research Brazilian groups in order to aggregate value to sucrose and to sugar cane. Technologies were developed for microbial production of xanthan gum, dextrans and other biopolymer, some other organic acids, polyols, aminoacids and enzymes. Also, sugar cane bagasse applications were developed for paper and packing industries as also for composites (already commercialized). Processes for the production of solvents have extensively been studied and more recently, many companies are developing methods on alcohol chemistry to produce solvents, polymers and other products derived from bioethanol. Telma Teixeira Franco Chemical Engineering School, P.O. box 6066, Unicamp, Campinas, 13081-970, Brazil e-mail: [email protected] 118 INDUSTRIAL PERSPECTIVES FOR BIOETHANOL References 1. Motta, R.S The economics of biodiversity in Brazil. Texto para discussao: Ipea, ISSN1415-4765, 1998. 2. Ministério da Agricultura Brasil (http://www.agricultura.gov.br) 3. Embrapa (www.embrapa.br) 4. www.biotaneotropica.org.br 5. Vettore, A. L., Silva, F. R., Kemper, E. L., et al. (2003), Genome Res. 13, 2725–2735. 6. Pessoa Jr. A; Roberto, I.C; Menossi, M; dos Santos, R.R; Ortega Filho, S.; Penna, T.C.V.Perspectives on Bioenergy and Biotechnology in Brazil. Applied Biochemistry and Biotechnology 121–124, 2005. 7. www.canavialis.br 8. Pacific Northwest National Laboratory (PNNL) and the National Renewable Energy Laboratory (NREL) of USA in 2004. (http://www.osti.gov/bridge/) 9. Kirchner, M, Chemical industry, white biotechnology and renewables. Renewable resources and biorefineries, Ghent, 2005. 10. Soccol, CR, Marin, B, Raimbault, M, Lebeaut, JM . Breeding and growth of Rhizopus in raw cassava by solid state fermentation. Appl. microbiol.biotech. 41 (3): 330-336, 994. 11. Carta, F.C; Soccol, CR; Ramos LP and Fontana. J. D. Production of fumaric acid by fermentation of enzymatic hydrolysates derived from cassava bagasse. Bioresource Technology 81-97. 2000. 12. Pandey, A, Soccol, CR, Nigam, P, Soccol, V.T. Vandenberghe, LPS, and Mohan.R Biotechnological potential of agro-industrial residues. II: cassava bagasse. Bioprocessing and Characterization of Lignocellulosics Bioresource technology 68 (1): 23-28, 1999. 13. Coopersucar – personal communication. 14. PURAC Sínteses, personal communication 15. Mercocítrico Fermentações S.A. 16. PHB produzirá plástico a partir do açúcar. Jornal Valor Econômico, 21 feb.2006:B15.valor econômico, 2006. 17. Rossell, C.V; Mantelatto, P.E.; Agnelli,J.A.M. Sugar-based Biorefinery – Technology for Integrated Production of Poly(3-hydroxybutyrate), ADVANCES OF THE BRAZILIAN PRODUCTION OF CHEMICALS... 119 Sugar, and Ethanol. Biorefineries Industrial Processes and Products. Staus quo and future directions. Ed. Birgit Kamm, Patrick Gruber and Michel Kamm, 2005.Wiley-VCH, Germany. Roberto, I.C. Biotecnologia ciência e desenvolvimento 2002. http://www.biotecnologia.com.br/revista/bio28/28_produ.asp Section 3 Role of Bioethanol in the Energy Landscape Conversion of lignocellulose biomass (bagasse and straw) from the sugar-alcohol industry into bioethanol Carlos Eduardo Vaz Rossell Introduction The purpose of this study is to evaluate lignocellulose-based raw materials that remain after cutting, harvesting and processing sugarcane, to obtain sugar and ethanol (and in the future other products), by hydrolyzing those materials into a mixture of reducing sugars, followed by fermentation and recovery of the products. Most studies on hydrolysis of lignocellulose derivatives performed in the last 100 years were directed towards the use of wood or wood wastes as raw materials. The advent of sugarcane to produce bioethanol from sugarcane extractable sugars has generated a large surplus bagasse that can be potentially converted into ethanol and increase significantly the offer of this fuel without requiring a proportional increase in cultivation areas. Under this new condition, sugarcane will be fully used. An analysis of the characteristics of the sources of lignocellulosic matter included in the sugar processing remains is fundamental to develop a hydrolysis technology specific for the sugar and alcohol sector. The lignocellulosic matter left over after the sugarcane is processed consists of bagasse and harvest wastes [1]. At the current stage, sugar mills and distilleries do not recover harvest residues, but partially burn them during the sugarcane destalking to serve as soil coverage, the surplus being incinerated in the field. 124 INDUSTRIAL PERSPECTIVES FOR BIOETHANOL This situation will gradually be modified due to changes occurred during the cutting and harvesting practices, where the destalking with fire will be eliminated according to schedules designed to reduce the environmental impact of land burning [2]. The increasing interest in using lignocellulosic matter as primary fuel will also significantly contribute to further valuation of lignocellulosic wastes that are left over after cutting down and harvesting the cane. Thus, bagasse is the lignocellulosic residue currently available to be converted into ethanol. Sugarcane bagasse Sugarcane bagasse is the resulting biomass fraction obtained after the procedures of cleaning, preparation (reduction, using sets of leveling rotating blades and defibering using sets of oscillating hammers) and extraction of sugarcane juice (using sets of three roller crushers or diffusers). Bagasse is not a homogeneous biomass, and shows changes in composition and morphological structure, due to the cut procedure and industrial processing. The following factors influence significantly bagasse composition: ·· · · Straw removal (or not) by fire, previous to cutting. The harvesting and loading procedures, with more or less soil, sand and vegetal waste dragout, such as manual cut, mechanical cut, sugarcane crushing, cut including the top, and so on. The type of soil where sugarcane is cultivated (latosoils, sandy soils, others). There are different procedures for cane cleaning, such as dry cleaning using revolving tables, dragout cleaning and pneumatic cleaning. The geometry and other constructive details of the revolving tables, as well as the water volume per ton of sugarcane (cane stems after the cut) can influence the bagasse composition. The efficiency of the extraction equipment influences directly the residual sugar content in the bagasse, and the ether extract content is · 125 CONVERSION OF LIGNOCELLULOSE BIOMASS (BAGASSE AND STRAW)... in inverse proportion to the percentage of sugarcane burnt before being cut. The most important morphological characteristics of bagasse are dimension and form, which are fundamentally associated with the procedures to prepare and extract cane juice. Several authors describe typical compositions for bagasse [1, 3]. Table 1 shows the typical results according to studies conducted at ICICDA, the Cuban Institute for Research on Sugarcane Derivatives. Composition % Bagass Fiber Kernel Straw Cellulose 46.6 47.7 41.2 45.1 Pentose polymer 25.2 25.0 26.0 25.6 Lignin 20.7 19.5 21.7 14.1 Organo-soluble 2-3 Water-soluble 2-3 Ashes 2-3 8 Product humidity 48-52 9.7 (Dry basis) 3.5 Table 1. Sugar cane bagass and straw composition (according to ICIDCA) An inspection of these results shows that the content of moisture in the bagasse is within the 48-52% range (average: 50%), which is typical and some water loss is caused by the roller crushers (or the final water loss associated with diffusers). A water-soluble fraction consisting basically of sugars is the result of the juice extraction procedure; the lower the content of this fraction, the higher the efficiency of the extraction procedure. In South Central 126 INDUSTRIAL PERSPECTIVES FOR BIOETHANOL Brazil, pol sugar values after extraction range from 1.5 to 2.8 %, average: 1.85% [4]. Most of the mineral matter results from mineral impurities from the soil and sand that are dragged out together with the sugarcane; the rest consists of ashes that form the plant, plus ferrous metals and heavy metals produced by the wear and tear of the preparation and extraction equipment. The content of mineral matter varies considerably and is associated with the cutting, harvesting and the extraction and preparation processes. Unpublished data provided by Linero [5] who conducted samplings in several mills located in Sao Paulo state show this variability. The mineral matter content in bagasse ranges from 1.6 to 5.0%. The organo soluble (ethanol + benzene) extract corresponding, among others, to the wax associated with the external surface of the cane stem, has a waterproofing protective function and also varies expressively. This fluctuation is associated with the cutting and harvesting process, and the stems that were not burnt will present higher contents of wax. According to Sousa [6], the ethanol + benzene extract represents 2.7% (w/w) of untreated bagasse. Fatty acids (45%), longchain fatty alcohols (44%) and sterols (5%) are the main fractions of this extract [3]. Sousa [6] and Silva [7] conducted detailed studies about procedures of delignification and fractioning of the bagasse to be employed as source of inputs for the chemical industry. These authors presented data concerning the composition of the three fractions of bagasse, namely, hemicellulose, cellulose and lignin. The studies of this group serve as references to develop a process of saccharification of the sugarcane biomass: whole bagasse or its fractions fiber and medulla, plus harvest wastes, leaves, tops and so on. Sousa [6] analyzed a bagasse sample from Sao Paulo state sugar mills and found that 22% (w/w) content of lignin (dry base and bagasse exempt from mineral impurities) and a 78% content of holocellulose (hemicellulose + cellulose). These data (Table 2) confirmed the previous results described in [1] and [3] and also the fact that, both for hemicellulose and cellulose, the changes of their contents in the bagasse are relatively small from variety to variety of sugarcane, or from region to region. 127 CONVERSION OF LIGNOCELLULOSE BIOMASS (BAGASSE AND STRAW)... The composition of the sugarcane biomass shows that holocellulose prevails, followed by lignin. A more realistic profile of the content of recoverable sugars is shown in Table 3, except for acetyl groups and other non-sugars associated with hemicellulose and also quantifying the hexose fraction. Components of sugar canebagass % Holocellulose 77.8 Acid-insoluble lignin 20.4 Acid-soluble lignin 1.4 Soluble in ethanol-benzene (II) 5.4 Soluble in hot water (III) 10.2 Ashes (I) 3.3 Uronic acid (as anhydride) 4.2 (I) Based on the dry unextracted bagass. (II) Based on the dry unextracted bagass and not corrected for ashes. (III) Based on the dry bagass extracted with ethanol-benzene. Table 2.Chemical composition of sugar cane bagass. According to Sousa (1985), organosolv Polysaccharides: % (I) % (II) Glocose (hexose) 42.9 60.8 Xylose (pentose) 23.1 32.8 Arabinose (hexose) 3.3 4.7 Galactose (hexose) 1.2 1.7 Total 70.5 100 (I) In the ground bagass, extracted, dryed and not corrected for ashes.. (II) Based on total carbohydrates. Table 3. Carbohydrates in sugar cane bagass. According to Sousa (1985). 128 INDUSTRIAL PERSPECTIVES FOR BIOETHANOL These studies also present important data on lignin composition in terms of evaluation of the impact of degradation and formation of undesired lignin by-products during cane processing [1, 6]. Studies by Sousa [6] and Silva [7] allowed us to formulate a standard bagasse composition (Tables 2 and 3), which be used to quantify the potential of using bagasse in the hydrolysis process. Table 4. Standard bagass (calculated composition) Impact of bagasse components on saccharification processes Moisture The moisture associated to the bagasse has no effects either on the conversion of the bagasse into total recoverable sugars, nor in the conversion rate. Most pretreatment processes, such as steam cracking, CONVERSION OF LIGNOCELLULOSE BIOMASS (BAGASSE AND STRAW)... 129 thermal hydrolysis or organosolv processes are performed in the presence of water, usually mixed with an organic solvent. The only exception lies in the pretreatment processes that use concentrated acids (sulfuric acid or mixtures of sulfuric acid + phosphoric acid). Water-soluble fraction The water-soluble fraction, where reducing sugars prevail, is decomposed during the pretreatment processes and produces hydroxymethyl furfural (HMF) due to high temperatures (above 150°C) and pH below 3.5. Thus, these reducing sugars have no effect on the hydrolysis process and are not used. However, if the HMF remains until the hydrolysis fluids are fermented, it will contribute to inhibit alcohol fermentation. Mineral matter Ferrous metals and heavy metals act as catalysts in the organosolv delignification processes [6] and can favor hydrolysis, depending on their content and composition in the bagasse. It seems that the different morphologies of fibers and the medulla can lead to different contents of inorganic impurities, justifying future determinations of the content of these compounds. The presence of dispersed mineral matter (sand and soil) has a deep abrasive effect on the equipment employed in the process, requiring the use of more expensive alloys reducing the useful life of components and increasing the operating costs and investments in fixed capital. Ether extract The possible influence of the bagasse ether extract on the pretreatment and hydrolysis reactions should be evaluated taking into account that its main natural function is to form a protective film on the stem surface. This may interfere with the industrial processes if they are performed at intermediate temperatures, where some components remain solid, preventing the penetration of the solvents used in hydrolysis. 130 INDUSTRIAL PERSPECTIVES FOR BIOETHANOL Similarly, solidification on surfaces of equipment, tubing and parts may cause clogging and loss of thermal exchange capacity, among others. Characteristics of particles present in the bagasse and their impact on saccharification processes Ponce and Friedman [8] analyzed the form and size of bagasse particles. After classifying the samples, the authors found a spongy fraction and a fiber fraction with a high thinness ratio. It was found that rectangular prisms formed both fractions. The size distribution and the characteristic dimensions and properties such as equivalent diameter, specific area, form factor, thinness factor and apparent density were presented. Nebra and Macedo [9] performed measurements in bagasse samples and, unlike previous studies, these authors assigned an ellipsoidal-base prism model to fibers, while the spongy fraction was considered similar to spheres. This study was performed on a bagasse sample from a sugar mill located in the central southern region and prepared using two sets of leveling rotating blades, a defibering device and a 37" × 78" milling set which represent the typical conditions of bagasse production in Brazil. The fiber fraction with equivalent diameter between 150 and 3,210 µm ?and thinness factors between 10 and 60 accounts for 71% of the total mass, while the medulla, with equivalent diameter between 180 and 1,680 µm?and thinness factors between 1.7 and 3.2 accounts for the rest of the initial mass of bagasse. Another interesting fact pointed out by the authors is that the calculated apparent densities (dry base) of the fiber fraction increase from 210 to 600 kg/m³ as the equivalent diameter of the fiber fraction decreases. Their explanation for this increase in density is that the fibers with larger diameters are formed by aggregates of fibers and medulla, which contributes to reduce the apparent density. The characterization of the particles composing the bagasse shows three fractions, namely, fibers, medulla and rind (fibrous particles from the outer cortex of the stalk). The form and size of these three components are considerably different [10]. CONVERSION OF LIGNOCELLULOSE BIOMASS (BAGASSE AND STRAW)... 131 · · · The medulla is formed by spongy particles with relatively regular form and a length/width ratio approximately equal to 1, which means that they can be considered as nearly spherical. The fraction corresponding to the rind is quite larger and looks like near-rectangular blades. The fibers can be represented as cylinders with a thinness factor of approximately 50 and considered similar to cylinder of infinite length. After measuring the apparent density of the medulla, fiber and rind, as well as the real density of the bagasse (density of the skeleton), they reported the methods and difficulty to obtain representative results. Both the bagasse and its fractions have low apparent densities. An apparent density of 220 kg/m³ was found for the medulla, while this value is 520 kg/m3 for fibers and for the rind it is 550 kg/m³. The real density of bagasse reaches the value of 1,470 kg/m³, which is consistent with the 1,380 kg/m³ and 1,510 kg/m³ previously reported (for dry bagasse) respectively by Crawford and Pidduck. These results confirm the statements below: · The porosity of the three components of bagasse is very important and should be taken into account in any study on bagasse pretreatment and saccharification, regardless its nature, considering that the reactions are heterogeneous and involve a solid-fluid interface. The apparent density of the medulla fraction is approximately half the value of the fiber density. This causes an increase in the ration between the mass of the fluid medium and the mass of lignocellulosic matter during the pretreatment and hydrolysis processes to maintain the reaction medium vigorously stirred and the final fluid diluted. It will also negatively influence the separation of finer particles that did not react during hydrolysis and are harder to separate based on differences in density. We assign great importance to the morphology of bagasse particles concerning the optimization of hydrolysis reactions. Preliminary studies to enlighten the possible impact of bagasse morphology on the hydrolysis reaction are commented below [11]. A · · 132 INDUSTRIAL PERSPECTIVES FOR BIOETHANOL sample of bagasse was dried to approximately 12-15% of moisture, demedullated and subjected to a pneumatic classification in order to separate the characteristic fractions. Images of these fractions were scanned (Figures 1 and 2) and visually assessed. Figures 1a and 1b represent fiber samples. Their format support the model earlier [10, 11]. In our case, fibers are quite uniform and compact, in the form of elliptic cylinders and with a thinness factor similar to the one determined by those authors. The form of these fibers should favor the retention of particles inside the reactor, regardless the reduction in diameter. A larger specific area per unit volume would probably favor the hydrolysis reaction. Figure 1a. Bagass fiber CONVERSION OF LIGNOCELLULOSE BIOMASS (BAGASSE AND STRAW)... 133 Figure 1b. Bagass fiber (zoom) Figures 2a and 2b represent medulla samples. Lignocellulosic matter is expanded and has low apparent density. Comparatively, the particle size is quite smaller than the size of fibers. The medulla is darker, indicating its ability to adsorb foreign mineral matter, e.g. clay and metals formed by wear of the preparation and milling equipment. From the morphological perspective, we can suggest that the medulla is not convenient for hydrolysis. Its spongy structure and low apparent 134 INDUSTRIAL PERSPECTIVES FOR BIOETHANOL density will require a higher liquid reaction medium / lignocellulosic matter mass ratio that causes additional dilution in the final fluid, as well as an increase in energy consumption. The particle size will be reduced more rapidly than the fiber size throughout the hydrolysis reaction, achieving the diameter above which they can go through the solid retention system in the continuous reactor. This will translate into a larger fraction of matter that did not fully react and will escape from the reactor, reducing the yield or requiring additional equipment and costs to recover and recycle this fraction. Figure 2a. Bagass kernel CONVERSION OF LIGNOCELLULOSE BIOMASS (BAGASSE AND STRAW)... 135 Figure 2b. Bagass kernel, zoom Data from Table 1 indicated that fiber and medulla have different chemical compositions, the first being richer in cellulose, the preferred polymer for hydrolysis conversion. The medulla presents higher percentages of hemicellulose and lignin. These differences in composition indicate a comparative advantage of fibers in terms of hydrolysis yield. Sugarcane straw These harvest wastes consist of sugarcane green leaves, dry leaves and tops, being also a source of lignocellulosic raw materials. Although this source is not currently used, this situation will be reversed in the 136 INDUSTRIAL PERSPECTIVES FOR BIOETHANOL medium range, given that the environmental legislation foresees gradual extinction of the practice of destalking using fire. References [1] and [3] describe the approximate composition of this residue for other sugarcane regions such as Cuba (see Table 1), but no typical values are available for Brazil. The composition of sugarcane straw is somewhat similar to that of bagasse in terms of cellulose and hemicellulose. However, the lignin content in the straw is approximately 30% lower than that of bagasse or its component fractions. Another feature to be considered for future use of straw for hydrolysis is its high ash content, which is about twice the content in the bagasse. Although no data concerning the shape and size of straw are available, visual inspection shows that it is highly heterogeneous, since it comes from different fractions of the sugarcane plant and was not prepared beforehand. According to studies performed at CTC [4] concerning the potential of straw available, depending on the harvesting procedures, it is possible to recover an amount of dry biomass equivalent to 14% of the sugarcane mass (harvested stems) delivered to the mill. The potential of straw as a source to increase the offer of lignocellulosic biomass, either for hydrolysis processes or as a source of primary energy, justifies deeper studies to determine the composition and physical and chemical properties of straw. Availability of bagasse and straw for hydrolysis processes Nowadays, mills and distilleries do not recover stalk, which is not available for use. The availability of bagasse is linked to the energy efficiency of the mill. Currently, the available surplus bagasse for hydrolysis or other purposes varies from 7 to 10% the total bagasse, which is approximately 280 kg per ton of cane. The rest of the bagasse obtained by processing the sugarcane is employed as primary fuel to generate steam and electric power. This condition is present in sugar mills with annexed distilleries, which operate cycles of steam and power generation with pressure levels of 21 bar. CONVERSION OF LIGNOCELLULOSE BIOMASS (BAGASSE AND STRAW)... 137 Bagasse surpluses up to 50% of the bagasse obtained after the sugarcane is processed can be achieved by optimizing the system of production of steam and power and generating steam at a pressure between 65 and 80 bar and using highly efficient turbines and generators. Potential to convert bagasse into reducing sugars and ethanol The stoichiometric conversion of standard bagasse, as well as its maximum potential to produce ethanol are presented in Table 4. Only the reducing sugars that can be potentially recovered from hemicellulose and cellulose were considered. In order to quantify the potential of bagasse to produce ethanol as a function of technological advances in hydrolysis, we have established five scenarios that gradually incorporate the increases in efficiency of conversion of hexoses and pentoses to be subjected to hydrolysis catalyzed by diluted acids and enzymes, and fermentation of pentoses to give ethanol. These scenarios were drawn upon data on hydrolysis techniques published by Ogier [12]. The results of proposed scenarios are presented in Table 5 and the scenarios are the following. 1. Pretreatment and diluted acid hydrolysis of hexoses at the current technological stage. 2. Pretreatment, diluted acid hydrolysis of hexoses and optimization of the hydrolysis reaction to the best values achieved as reported in literature. 3. Pretreatment, diluted acid hydrolysis of hexoses and pentoses and optimization of the hydrolysis reaction to the best values achieved as reported in literature. 4. Pretreatment and enzyme hydrolysis of hexoses at the current technological stage. 5. Pretreatment and enzyme hydrolysis of hexoses and pentoses with optimized technology. If we refer to one ton of bagasse in natura, the impact of the introduction of hydrolysis processes becomes apparent. Starting with a reasonable optimized technique it is possible to achieve an ethanol production of 69.1 liters per ton of bagasse. 138 INDUSTRIAL PERSPECTIVES FOR BIOETHANOL With optimized saccharification processes, the yield rises to 94.2 97 liters. Once the barrier to alcohol fermentation of pentoses is overcome, the yield will amount to 132.2 – 149.3 liters per ton of bagasse. Considering a 10% surplus of bagasse, the introduction of hydrolysis will represent an 8.1% increase over the 85 liters of ethanol per ton of cane currently obtained in an autonomous distillery. Under the best condition and using fully optimized technology and 50% surplus of bagasse, it is possible to obtain an additional 87.8%. Using the straw, optimizing the cycles of energy generation and possibly introducing fiber-rich sugarcane varieties, can further increase these values. Possible scenario Forcasted conversion Ethanol Ethanol Hexoses Pentoses Ethanol Total [1] hexoses: 60% fermentation: 89% pentoses: 70 % fermentation: 0% distillation: 99,5 % 69.1 0 69.1 [ 2] hexoses: 80% fermentation: 91% pentoses: 78.5 % fermentation: 0% distillation: 99.75 % 94.2 0 94.2 [ 3] hexoses: 80% fermentation: 91% pentoses: 85% fermentation: 50% distillation: 99.75 % 94.2 37.9 132.2 [4] hexoses: 85% fermentation: 89% pentoses: 70% fermentation: 0% distillation: 99.5 % 97 0 97 [5] hexoses: 95% fermentation: 91% pentoses: 85% fermentation: 50% distillation: 99.75 % 111.4 37.9 149.3 Table 5. Transformation potencial of bagass to ethanol (liters/ton of bagass) Conclusions Although some of the results and statements above require experimental determinations and technical and economic studies to be CONVERSION OF LIGNOCELLULOSE BIOMASS (BAGASSE AND STRAW)... 139 validated, it is possible to make a preliminary diagnosis to better use bagasse as source of carbon to produce ethanol on a large scale. The bagasse cannot be considered a homogeneous material and it is necessary to separate it into fractions for saccharification. The inorganic matter (e.g. soil, sand, metals) that is washed out with the bagasse should be removed before starting the treatments, since it would accumulate in the reactor and other equipment of the process and cause abrasive wear. The distribution of these components of mineral origin in the fractions that form the bagasse should be characterized in order to determine their impact on the reactions. Previous treatment is required to remove these impurities both to have a better performance at later stages and to extend the useful life of equipment. The classification of bagasse into its typical fractions, namely fibrous and spongy, is recommended in order to achieve better efficiency in the conversion of holocellulose. A study of the most appropriate processes of classification, as well as their economic evaluation should be performed. The processes of demedullation of bagasse to separate it into fiber and medulla must be evaluated as a first alternative to processing the bagasse in order to improve the performance of hydrolysis. Since the pretreatments and saccharification are catalyzed by mineral acids or by enzymes, the heterogeneous reactions occurring on the solid-fluid interface, as well as the influence of particle size, geometry and porosity should be taken into account in kinetic studies, as well as the reactor design, by introducing concepts of heterogeneous kinetics in porous media. Physical and chemical properties of the fractions that form the bagasse, such as morphology, size, porosity, real and apparent densities, typical pore dimensions, specific area of the particles, friction coefficients, chemical composition of fractions, etc, should be determined. The impact of other components such as waxes and other components that can be extracted with organic solvents should be evaluated in order to check for possible interference with pretreatments, acid or enzyme saccharification, and ethanol production. Analytical methods capable of quickly and accurately establishing the chemical composition of bagasse fractions and the profile of sugars 140 INDUSTRIAL PERSPECTIVES FOR BIOETHANOL and by-products formed during the pretreatments and saccharification must be introduced. Wastes from cutting and harvesting should be typified using the same method employed for bagasse. Based on this information it will be possible to diagnose the potential of straw as a raw material for ethanol production, and establish the pretreatments to be performed if the straw requires adaptation to yield a more effective saccharification. In case the characteristics of straw show that its application in hydrolysis is unfavorable, the straw may be diverted to replace bagasse as primary fuel in the boilers and increasing the amount of bagasse available for saccharification. Due to the advances in the hydrolysis process followed by conversion of reducing sugars into ethanol, the scenarios in this study show the potential of bagasse (and in the future, of straw) as a raw material to increase the offer of ethanol. It is worth noticing that the increase in production of ethanol occurs with no need of additional planted areas and leads to full utilization of sugarcane. Carlos Eduardo Vaz Rossell Grupo Energia - Projeto Etanol (MCT/NIPE), Caixa Postal 6192, Campinas, SP 13084-971, Phone +55 19 3512-1121, e-mail: [email protected] CONVERSION OF LIGNOCELLULOSE BIOMASS (BAGASSE AND STRAW)... 141 References 1. Paturau JM. By-products of the sugar cane industry. Elsevier Science Publishers B.V., The Netherlands, 1989. 2. Macedo I.; editor. A energia da cana de açúcar. ÚNICA. São Paulo, Brazil 2005. 3. Taupier OG, editor. Manual dos derivados da cana de açúcar. ICIDCA/ABIPTI (Cuban Institute for Research on Sugarcane Derivatives / Brazilian Association of Institutions for Technological Research). Brasilia, Brazil 1999. 4. CTC. Relatório do controle mútuo. Piracicaba, SP, Brazil 2001. 5. Linero F. Unpublished data. Piracicaba, SP, Brazil 2000. 6. Sousa MFB. Separação e identificação dos constituintes do bagaço de cana e sua conversão em insumos químicos pelo processo Organosolv. Master’s Thesis, Unicamp, Campinas, SP, Brazil 1985. 7. Silva FT. Obtenção de Insumos Químicos a partir do Aproveitamento Integral do Bagaço de Cana. Doctor’s Degree Thesis, Unicamp, Campinas, SP, Brazil 1995. 8. Ponce N, Friedman P, Leal D. Geometric properties and density of bagasse particles. Int Sugar Journal 1983;205: 291-295. 9. Nebra SA, Macedo IC. An Experimental Study about Typical Shapes and Sizes for Sugar Cane Bagasse Particles and about their Free Settling Velocity. Int Sugar Journal 1988; 90:168-170. 10. Rasul MG, Rudolph V, Carsky M. Physical Properties of Bagasse. Fuel 1999;78:905-910. 11. Olivares E, Roca G. Unpublished data on studies of bagasse particle structure. Unicamp, March 2006. 12. Ogier JC, Ballerini D, Leigue JP, Rigal L, Pourquié J. Production d’ethanol à partir de biomasse lignocellulosique. Oil and Gas Science and Technology- Revue de l’IFP 1999;54:67-94. 142 INDUSTRIAL PERSPECTIVES FOR BIOETHANOL Acknowledgments To FAPESP (Foundation for Research Support in Sao Paulo State) for financial support to the DHR (Dedini Rapid Hydrolysis) project. To Dedini Indústria de Base S.A. for the support provided to this project. To Grupo Energia - NIPE/UNICAMP for the support provided to this project. Author’s note This study, whose objective was to present processing methods and discuss the potential of bagasse as a raw material to produce ethanol (as well as other chemicals) was based on pioneering studies such as those by Nebra SA and Macedo IC, Silva FT. Although these authors are mentioned in the references, we wish to further emphasize that the use of data, figures, definitions and concepts from their publications was fundamental to meet the objectives of the present study. Abbreviations: TC: ton of sugarcane harvested and placed at the conveyor belt of the mill Glossary Biomass: This term refers to fresh organic matter produced by live animal and vegetal organisms. However, within the context of this study, this term will be used to indicate only recent organic matter of vegetal origin, which in our case is limited to bagasse and its fractions and to post-harvest sugarcane wastes. Bagasse: Residue after juice is extracted from milled sugar cane. Demedullation: Process of separation into fiber and medulla. Fiber: Vegetal tissue formed by bundles of lignocellulosic matter that give support to the plant. Medulla: The non-fibrous portion of parenchimal tissue. Harvest wastes: Sugarcane green leaves, dry leaves, and tops. Advanced techniques for generation of energy from biomass and waste H. J. Veringa P. Alderliesten 1. INTRODUCTION Biomass contributes as the world’s fourth largest energy source today up to 14% of the world’s primary energy demand. In developing countries it can be as high as 35% of the primary energy supply. Biomass is a versatile source of energy in that it can be readily stored and transformed into electricity and heat. It has also the potential that it is used as a raw material for production of fuel and chemical feedstock. Production units range from small scale up to multi-megawatt sizes. Development of biomass use contributes to both energy and other non-energy policies. None energy related arguments are: · Environmental and climate change. CO2 is the main gas responsible for climate change, and it is observed that the gas emissions from road transport are the main contributors to the increase of the total level of emission in recent years, in spite of levelling off or even reduction of CO2 emissions from other activities in the European Union. Environmental Policy: The life cycle of biomass as a renewable material has a neutral effect on CO2 emission. It also offers the possibilities of a closed mineral and nitrogen cycle. The environmentally hazardous sulphur dioxide (SO2), which is produced during combustion of fossil fuels, leading to acid deposition, is not a major problem in biomass · 144 INDUSTRIAL PERSPECTIVES FOR BIOETHANOL systems due to the low sulphur content of biomass (< 1% compared to 1 to 5% for coal). Agricultural Policy: CAP (Common Agricultural Policy) and the search for alternative uses of set-aside land. It is estimated that 20 million hectares of agricultural land and 10-20 million hectares of marginal land could already be made available for non-food production by the year 2000. Social Policy: Estimates show that 11 jobs are created per MW of installed biomass conversion capacity so that 5% of coverage of the EU energy needs on the basis of biomass would lead to 160,000 additional jobs (Wright report). Regional Policy: Biomass can be used as a decentralised energy source where conversion plants are located close to the source of biomass. This would lead to stabilisation of employment in rural areas and regional development. Security of supply. 98% of the transport market is dependent on oil. In the case of no policy on the level of the EU, the external energy dependence will reach 70% before 2030. This dependence will be up to 90% when it concerns oil imports. · · · · Energy related motivations for use of biomass are: · Biomass can readily be used in boilers to produce directly heat and/or steam to generate electricity. This is being done at a small scale at remote locations and in a centralized way in large production units of more than 50 Megawatts. Co-firing with coal is an attractive option with a relatively low need for additional investments. Gasification is, although the technology exists already for decades, it is still being developed for advanced uses of biomass and waste. The gas which can be produced this way, a syngas, is a well known commodity in the energy generation and chemical process industry and offers excellent options for high efficiency large scale electricity production and chemicals. The EU has put forward the objective to substitute 20% of traditional fuels by alternatives in the road transport sector by the year 2020, which has lead to a Directive on the promotion of biofuels. This draft Directive contains a proposal for an obligation on member states to · · ADVANCED TECHNIQUES FOR GENERATION OF ENERGY FROM BIOMASS... 145 ensure that, from 2005, a minimum share of transport fuel sold on their territory will be bio-based, whereas the individual member states sell a minimum proportion of biofuel of 2%. This level should grow by a yearly amount of 0.75% in the following years up to a level of 5.75% in 2010. In 2020 8% of the fossil fuel based transportation fuels has to be substituted by biofuels. To meet this 2020 EU-goal large scale robust, reliable and cost-effective biofuel production facilities have to be developed and implemented, with final production costs of 10 Euro/GJ. Biofuel currently represents 0.3% of the total diesel and gasoline consumption in the market, which is basically the result of 6 member countries amounting to a level of 700 ktons in 2000. Major oil companies in the EU have formulated their strategies in view of their responsibilities to contribute to a sustainable development, but also advocate a seamless introduction. This means that any replacement of conventional fuels by biofuel should not induce major changes in the current supply and distribution infrastructure. For the next decades any biofuel should have such properties that they can be blended into the current conventional fuels without major adaptation of the technological infrastructure. This means that carbon based renewable fuels are for the next decades the only option for a substantial replacement of the fuel pool. Obviously, there is a good chance for natural gas to become a transportation fuel, which, however, does need extensive adaptations in the supply infrastructure, but only minor modifications on the car engine. Natural gas has lower CO2 emissions per unit of delivered mechanical energy and consequently less emission. Also dependence on supply from outside the EU is less than in the case of mineral oil. In the long run hydrogen will become important, giving other renewable energy sources a chance to contribute. However, technology is still in its infancy and a distribution and supply infrastructure is non-existent. It is believed that hydrogen will break through after the year 2020 or even later. The major candidates for short term replacement of fuel out of mineral oil like biodiesel (RME), pressed vegetable oils (PVO), and conventional bio-ethanol from starch and sugar crops show manufacturing costs of between 12 and 21 dollar per Gigajoule, which compares with · · · · 146 INDUSTRIAL PERSPECTIVES FOR BIOETHANOL the costs including excise duty and taxation of mineral diesel between 17 and 30 dollar per Gigajoule. This latter depends on the price per barrel of crude oil, which for this analysis is taken between 15 and 25 dollar per barrel. This means that a policy based on exemption of excise duty on biofuels, and an increase of the price of mineral oil, will create the economic conditions for replacement. In the (near) future FischerTropsch diesel and bio-ethanol from lignocellulosic biomass can offer lower prices than current biodiesel and conventional bioethanol fuels. Already a surprising number of actions are undertaken with promising results: · · · · In Austria, the contribution of biomass for district heating has increased 6-fold [1] in Sweden 8-fold [2] during the last decade thanks to positive stimulation at federal and local level. In the USA, already more than 8000 MWe installed capacity based on biomass has been installed, primarily stimulated by the PURPA-Act [3]. In France, direct combustion of wood represents almost 5% of the primary energy use [4]. In Finland, bio-energy already amounts by 18% of the total energy production and if foreseen to grow to 28% by 2025 [5]. It is obvious that the above given arguments underline the dependence of the introduction of biofuels in the transportation sector on external factors like commitment of EU member states to international agreements and directives as well as local circumstances such as industrial infrastructure, crude oil price, availability and contractibility of biomass, taxation policy and choice of the best option for development of renewable energy recourses. On the other hand, the technological development can severely influence the production costs and large-scale availability of biofuels. It is for the time being still in debate which is the best option for the conversion technology starting from biomass supply all the way to the enduse. Further, the actual choice will depend on local circumstances such as potential set aside agricultural land in the EU, the availability of waste vegetable oil and fats and/or other derived organic waste streams. ADVANCED TECHNIQUES FOR GENERATION OF ENERGY FROM BIOMASS... 147 2. PRESENT SITUATION This section summarises the current status of biomass technology from biomass crops, conversion technologies to end products, technologies available and end products of the conversion process. Figure 2.1 gives an overview of the different routes from biomass to end products. This system focuses on distributed production, which is the area where nowadays the very challenging developments are underway. However, particularly in the Netherlands, the main contribution to renewable energy generation is co-conversion with coal-fired stations and in the future with gas turbines. Figure 2.1 Potential paths for biofuel-based distributed energy production (taken from “Energy Visions 2030 for Finland)[5] 148 INDUSTRIAL PERSPECTIVES FOR BIOETHANOL In the year 2004, some 9 PJoule of bioelectricity generated by cofiring is expected besides 20 PJoule generated in small-scale units in the Netherlands. The plans exist to achieve in 20010 34 PJoule by cofiring against 26 PJoule in small-scale operations. Co firing in coal fired power stations is a very attractive option as the biomass or biomass derived waste is taken with the coal into the boiler. This bio-fuel can either be ground down to the size of the pulverized coal particles and mixed up with the coal, or it can be injected in separate units into the same boiler. In both cases the grinding is a critical step and can substantially influence the costs of the electricity generated due to the co-firing. For the rest, the downstream equipment remains the same and no major investments are necessary. R&D work at ECN has resulted in a thermal pre-treatment for bio-fuel (Torrefaction). [21] which gives the fuel similar properties as the coal concerning the ignitability, next to other benefits like hydofobicity and reduced weight. In the end even homogeneous properties can be given to a broad band of bio-fuels and wastes so that the specificity for fuels might become less severe. The negative side obviously is an extra process step. The co-firing potential of current units is the limitation due to the fact that ashes with different properties than coal are mixed up which can lead to unwanted, or at least, not well understood ash behaviour in the applications which it is now being used for. A way out of this problem is to separately gasify the biomass and inject the syngas into the boiler. In this way, in principle, more freedom exists in choosing the balance between coal and biomass input and the ashes are entirely separated. The draw back is the extra gasifier that has to be invested. Figure 2.2 gives an example of a gasification unit for co-conversion with a 600 MW power plant. ADVANCED TECHNIQUES FOR GENERATION OF ENERGY FROM BIOMASS... 149 Figure 2.2 Indirect cofiring by upstream gasification (Amer-9 power plant of Essent) The waste incineration area has recognized that, next to elimination of municipal waste material, the generation of electricity will become more and more interesting from both societal and economic point of view. This is also stimulated by the fact that, for instance in the Netherlands, up to 50% can be considered as renewably generated electricity which has all the benefits of selling price, tax exemption and subsidees. In view of this up to now, some 12 Petajoules of fossil input is replaced by electricity generated from waste. The plans are to increase this amount to 20 Petajoules by the year 2010 [19]. The initiative recently taken by the “Afval Energiebedrijf “in Amsterdam envisages to build a 530.000 tons per year waste incineration unit based on grate combustion and employing flue gas recirculation, improved steam conditions in combination with advanced materials in the hot zones, adding up to an output efficiency of more than 30%. Figure 2.3 shows a schematic of this new unit being build up along with the steam flow and conditions and some other performance factors. 150 INDUSTRIAL PERSPECTIVES FOR BIOETHANOL 2.1 Biomass material The main biomass resources include the following: short rotation forestry (Willow, Poplar, Eucalyptus), wood wastes (forest residues, sawmill and construction/industrial residues, etc.), sugar crops (Sugar beet, Sweet Sorghum, Jerusalem Artichoke), starch crops (Maize, Wheat), herbaceous lignocellulosic crops (Miscanthus), oil crops (Rapeseed, Sunflower), agricultural wastes (straw, slurry, etc.), municipal solid waste and refuse, and industrial wastes (e.g. residues from the food industry). Current and future biomass resources in the EU are given in Table 2.1. It can be seen from the table that in the long term, energy crops can be an important biomass feedstock. At present, however, wastes, either in the form of wood wastes, agricultural wastes, municipal or industrial wastes, are the major biomass sources and, consequently, the priority fuels for energy production. There is also an additional environmental benefit in the use of residues such as municipal solid waste and slurry as feedstocks as these are withdrawn from polluting land filling. Figure 2.3 Flow scheme and characteristics of the new AEB Amsterdam new waste incineration unit ADVANCED TECHNIQUES FOR GENERATION OF ENERGY FROM BIOMASS... 151 Raw Material Current Resources (dry) Mt./yr. Future Resources Mt./yr. Short Rotation Forestry Wood Wastes Energy Crops Agricultural/Wastes MSW/Refuse Industrial Wastes 5 50 100 60 90 75-150 70 250-750 100 75 100 Table 2.1 Current and future EU biomass resources [6], [7], [8] Research on biomass energy crops is concentrating on generating reliable data on potential yield, environmental impact, limitations and economics. Developments are done through networks of research groups such as the Miscanthus Network, the Sweet Sorghum Network etc. There is also a number of other European and national projects which carry out research on a range of biomass materials. 2.2 Conversion processes Biomass combustion or gasification? Biomass combustion results in either heat or electricity. Biomass gasification results in a combustible gas, which can be used for the generation of different products: heat, electricity, synthetic natural gas (SNG), transportation fuels and chemicals. So only if heat and/or electricity is required, combustion and gasification are competing processes. If heat is the only product required, combustion seems to be preferable. Small-scale heat producing plants however suffer from bad economics1, especially if high emission standards are to be met. Large-scale generation of SNG by biomass gasification (and subsequent distribution 1 Small-scale generally is relatively expensive, and also small-scale heat consumers (often space heating) only need heat during the cold season, which means that the “plant” only operates limited time. 152 INDUSTRIAL PERSPECTIVES FOR BIOETHANOL to small-scale users where the SNG is burned to produce heat) is considered to be an attractive alternative. If electricity is the desired product from biomass, combustion and gasification compete. Gasification however, can reach higher electric efficiencies because of Carnot’s law2. The advantage becomes even larger if a fuel cell is added to the gasification system, since the efficiency of a fuel cell does not depend on Carnot’s law. In reality, thermodynamic optimum systems cannot be made due to different losses and non-ideal behaviour. The main conclusion however remains valid: conversion by gasification leads to a higher electric efficiency than conversion by combustion. Furthermore, by gasification more products can be produced (liquid fuels like diesel, methanol and gaseous products like “natural gas” and chemicals like H2). Even if only heat is required, gasification probably plays a crucial role by producing SNG, which can be stored, distributed and burned where and when heat is desired. Combustion Combustion can be represented by: ———> C6H10O5 + 6 O2 Biomass + Oxygen (air) 2 6 CO2 + 5 H2O + 17.5 MJ / Kg. Carbon dioxide + water + heat. Carnot’s law states that the maximum efficiency from heat to work that can be obtained is equal to 1- Tlow/Thigh. A gas turbine is powered by gas with much higher temperatures (up to 1200°C) than the steam powered steam turbines (up to 600°C). This is the principal reason why gasification can reach higher electric efficiencies. Assume the following systems: combustion with 95% efficiency to steam and with 600°C to 100°C steam cycle and gasification with 80% gas yield with combined cycle (1200°C turbine inlet temperature to 100°C steam exit temperature) and 20% heat with steam cycle from 400 to 100°C. The theoretical maximum (thermodynamic) efficiencies are 69% and 54% for gasification and combustion respectively. If the gas from gasifier at 900°C can be used in the gas turbine directly (without intermediate cooling/steam generation), the maximum efficiency even rises to 74%. These are absolute maximum values, but it illustrates the difference between combustion and gasification. ADVANCED TECHNIQUES FOR GENERATION OF ENERGY FROM BIOMASS... 153 The majority of biomass and agricultural waste derived energy comes from wood combustion. There is a constant drive to improve the combustion efficiency up to more than 30% and a reduction in pollutant emissions. The major development in this area is in large combined heat and power plants (CHP). Direct combustion processes for heat production and driving a steam cycle are commercialised already. New developments towards better overall thermodynamic efficiencies of the steam cycle and firing of biomass powder in ceramic gas turbines are envisaged. The amount of heat produced depends on the humidity of the biomass source, the level of excess air required and whether or not complete combustion is accomplished. Today, combustion technology is extremely well advanced, permitting widespread industrial application. Two types of boiler are commonly in use: ·· Boiler with fixed or travelling grates. Boilers with fluidised-beds. The former type is very common, ranging from the household boiler to large scale 50 MW industrial furnaces, and can accommodate heterogeneous combustible material in terms of composition, humidity and granularity. On the other hand, load following is difficult. Figure 2.4 shows the principle of a household boiler of the Herz company in Slovakia, the capacity ranges up to 150 kW. In a fluidised-bed, shown in Figure 2.5, the combustible particles, together with the granular bed material, are carried by a constant flow of gas in upward direction. The fuel is constantly injected into this bed. The bed itself constitutes the major heat capacity of the system and therewith stabilizes the process. In this way, effective heat and mass transfer are being taken care of. Such a system can combust a wide range of materials including fuels of non-biological origin. From an investment point of view, this fluidised-bed technology becomes attractive at plant sizes larger than 10 MW(th). 154 INDUSTRIAL PERSPECTIVES FOR BIOETHANOL 2. Ventilator for off gases 3. Heat exchanger 4. Ash removal 5. Combustion space 6. Burner surface Figure 2.4 The principle of a household boiler of the Herz company in Slovakia. ADVANCED TECHNIQUES FOR GENERATION OF ENERGY FROM BIOMASS... 155 Their main advantage is the possibility to use mixtures of various types of biomass (woody, non-woody) and/or to co-fire them with other fuels. Nevertheless, compared to grate-fired boilers, their operation in partial load is problematic. As already mentioned, a promising development in combustion for efficient biomass conversion is co-combustion. This can be applied in existing coal plants of a large capacity, allowing for high efficiency of electricity production. New boiler concepts, where biomass is combusted together with coal, peat, RDF (refure-derived fuel, i.e., upgraded urban waste fractions) or other fuels can achieve high efficiencies, due scale factors and reduced risks as more than one type of fuel can be used, e.g., to compensate seasonal influences in bio-feedstock availability (see also Figure 2.2). Gasification As the gasification reaction itself is endothermic, heat has to be supplied to the system by external sources. This heat can be brought to the reaction zone through the wall of the reactor, by the bed material itself or through a hot process gas stream. Due to the fact that, usually, no air (or oxygen) is taken up into the process gas, a product gas with middle or high calorific value is produced (10-18 MJ/Nm3). Such a high calorific value gas is attractive since volume streams are reduced making downstream processing like gas cleaning, compression or any kind of catalytic process relatively simple and therefore cheaper. In this respect a wealth of highly advanced processes are being developed and demonstrated or are awaiting demonstration at a sizeable scale [11], [12], [13], [16]. The other way to generate the heat necessary for the gasification reaction is to partially combust the biomass fuel giving the most direct supply of heat to the gasification process itself. The overall reaction reads: C6H10 O5 + 0.5O2 = 6CO + 5H2 + 1.85 MJ/kg but it also produces some CO2 and H2O in the fuel gas stream.R.P. Overend, Battelle, 505 King Avenue, Columbus, OH 43201. 156 INDUSTRIAL PERSPECTIVES FOR BIOETHANOL Figure 2.5 Circulating fluidised-bed. In the simplest system, air is used for the supply of oxygen, so that the syngas produced is diluted with nitrogen. Calorific values are in the range of 3- 8 MJ/Nm3, depending on the system applied. Air gasification itself is relatively cheap, but downstream processing to clean the gas is expensive due to large volumes to be handled. Gasification with pure oxygen requires an oxygen supply, which is expensive, particularly at small scales. Fixed bed downdraft gasification, Figure 2.6B, concerns small scale by definition, the maximum capacity is several tens of MWth. Furthermore, the conversion generally is low. Downdraft gasifiers can also be made “slagging”, which means that inert material leaves the gasifier as a liquid slag and the conversion rises to almost 100%. This generally requires oxygen in order to reach the desired high temperatures. Fixed bed updraft gasifiers Figure 2.6A, are characterized by high conversion and high efficiency. The exit gas temperature is generally ADVANCED TECHNIQUES FOR GENERATION OF ENERGY FROM BIOMASS... 157 100-300°C due to the counter current flow of solid fuel and hot gas. The product gas contains large amounts of hydrocarbons. Tar (large hydrocarbons) make up approximately 15% of the energy content of the gas. The biomass fuel specifications are mild, but there is a risk of too highpressure drops over the bed if too much small particles are fed. Fuels with slagging tendency can cause problems in the hot bottom zone, but updraft gasifiers can also be made “slagging”. This means that inert material leaves the gasifier as a liquid slag. This generally requires oxygen in order to reach the desired high temperatures. Fluidised bed gasifiers, Figure 2.6C are characterized by the presence of an inert heat carrier like silica sand. Fluidised bed gasifiers can be separated in three types: BFB, CFB, and coupled fluidised beds (indirect). BFB (bubbling fluidised bed) is the simplest concept. It also seems suitable for applications where oxygen (and steam) must be used instead of air. CFB: circulating fluidised bed as shown in Figure 2.6C, reactors are often seen as the most suitable for large-scale applications. BFB as well as CFB gasifiers show a limited conversion of 90-95%. This can be increased to approximately 98% by using smaller fuel particles. Indirect gasifiers contain two reactors where gasification and combustion are separated. Two gases are produced: a N2-free product gas and a “conventional” flue gas. Because the conversion is complete, indirect gasifiers seem to be the attractive alternative of oxygen/steam-blown fluidised beds when N2-free gas is required. Entrained flow reactors, Figure 2.6D, are practically empty vessels, where small fuel particles (or liquids) are converted at high temperature. It can either be slagging or non-slagging. Slagging gasifiers are preferable if biomass is used. The conversion is almost complete, but oxygen is needed to achieve the high temperatures needed. Biomass should be pulverized to a size of 1 mm. Entrained flow gasifiers are used to produce syngas to be used either as syngas or for electricity generation. This means that these gasifiers in practice operate at elevated pressure. The entrained flow technology (Figure 2.6D) is primarily developed in the petrochemical industry as a means to gasify heavy residues. It is now being used successfully for high-pressure gasification of pulverized coal and will be applied for centralized gasification of pre-treated and pulve- 158 INDUSTRIAL PERSPECTIVES FOR BIOETHANOL rized biomass. The high temperature reactor in the Carbo V system is an example of such an entrained flow reactor (Figure 4.2). The gas obtained by gasification can be combusted in a diesel, gas or “dual fuel” engine, or in a gas turbine. Several biomass gasification processes have been and are being developed for electricity generation. In BIG-ISTIG (Biomass Integrated Gasifier-Steam Injected Gas turbine), steam is recovered from exhaust heat and injected back into the gas turbine. In this way, more power can be generated from the turbine at higher electrical efficiency. A B C D Figure 2.6 Schematics of different direct gasification reactors. As the gasification temperature is high (up to 2000°C) tar production is absent and a relatively pure syngas is produced which will be used for catalytic biofuel production. Pyrolysis/Carbonisation Pyrolysis is a process of decomposition at elevated temperature (300 to 700 OC) in the absence of oxygen. The products obtained by pyrolysis of lignocellulosic matter are: solids (charcoal), liquids (pyrolysis ADVANCED TECHNIQUES FOR GENERATION OF ENERGY FROM BIOMASS... 159 oils) and a mix of combustible gases. The properties of each of the products is dependent on the reaction parameters i.e. the temperature, heating rate, residence time and the actual pressure at which the process takes place. Pyrolysis has been practised for centuries for the production of charcoal (carbonisation). This process is running at relatively low reaction temperatures and high residence times to maximise solid char yield at around 35%. In recent years more attention has been paid to the production of pyrolysis oils, which have the advantage of being easier to handle than the starting biomass and have a much higher energy density. Yields of up to 80% by weight of liquid may be obtained from biomass material by using fast or flash pyrolysis at moderate reaction temperatures. These liquids, currently referred to as bio-oils or biocrudes, are intended to be used in direct combustion in boilers, engines or turbines. Nevertheless, some improvements on the product are necessary to overcome unwanted properties such as poor thermal stability and heating value, high viscosity and corrosivity. For use as a fuel for combustion engines, or even more advanced applications, extensive upgrading will be necessary liker deoxygenation by catalytic hydrotreating at high pressure or zeolite cracking at atmospheric pressure. Both processes are being developed at laboratory scale [14]. The main advantage of fast pyrolysis for the production of liquids is that fuel production can be done separated from power generation, and can be considered as a densification step to facilitate transportation and inevitable elaborate handling. Although it reduces transportation costs, the extra step of in-site pyrolysu8is offsets the costs involving direct transportation of the raw biomass [22]. Figure 2.7 shows the fast pyrolysis unit based upon the “Rotating Cone Principle” in operation at Biomass Technology Group at Enschede. This unit is now being upscaled to high capacity (> 1 MW output). Here biomass falls in hot sand, which is transported over the inner surface of a spinning cone. Sand takes care of heat transfer and residence time is determined by the cone size and rotation speed. The char is the source of heat in this reactor. 160 INDUSTRIAL PERSPECTIVES FOR BIOETHANOL Features: ! No carrier gas ! High heat transfer ! High solids throughput Characteristics: ! Solids residence time: 0.1-5 seconds ! Gas residence time: 0.1-5 seconds Figure 2.7 “Rotating Cone Principle”. Pyrolysis, either to produce a solid carbon material or a liquid can be of interest in combustion with existing systems for large-scale electricity production. If biomass fuel is to be imported, to meet national goals for introduction of renewables into the energy chain or to achieve emission reduction, it may be argued that pyrolysis is a step to be taken at the location of the biomass production, so that only highly concentrated energy carriers are transported. Also the solid pyrolysis product (char) has properties similar to coal, and therefore can be easily accommodated as a renewable or a CO2 emission free energy carrier, which can be mixed up with coal. Same ADVANCED TECHNIQUES FOR GENERATION OF ENERGY FROM BIOMASS... 161 applies to the liquid pyrolysis product, but in this case separate injection technology is to be applied with coal fired boilers. Further, pyrolysis is applied as a means to reduce the size of waste streams, like electronic scrap, plastics etc. In some processes, even high calorific value gas is generated, precious metals are recovered and environmentally hazardous waste metals are immobilized [15]. A number of technologies combining pyrolysis and gasification are developed to overcome the drawbacks of both technologies separately by combining their respective advantages. Like in the case of advanced gasification technologies, these processes are awaiting demonstration at realistic scales [16], [17]. The largest plant built today is 2 tonnes/h but plans for 4 and 6 tonnes/h (equivalent to 6-10 MWe) are at an advanced stage of planning. Over the past years, it has become less and less obvious whether pyrolysis oil can be a viable feedstock for transportation fuel as it was believed earlier. Liquefaction Hydrothermal upgrading This is a low temperature (250-500°C), high-pressure (up to 150 bar) process in which a reducing gas, usually hydrogen, is added to the slurried feed. The product is an oxygenated liquid with a heating value of 35-40 MJ/kg, compared to 20-25 MJ/kg for pyrolysis oils. Interest in liquefaction is reduced due to the high cost of pressure reactors, the need for feed preparation and problems with feeding slurries. Some R&D is being carried out on batch reactors and catalytic hydro cracking. The so-called hydrothermal upgrading is a similar process. It takes place in a high-pressure reactor close by the critical point of water [18]. During this process biomass decomposes into CO2 and a so-called biocrude. This latter product is easily separated from water in which it forms, but still has to be hydrogenated to become a fuel comparable with conventional ones. The work has been started to generate an alternative to the ever-increasing oil price some decades ago. Now the future of this technology looks uncertain. 162 INDUSTRIAL PERSPECTIVES FOR BIOETHANOL Supercritical gasification The process of supercritical gasification [24]is basically the same as Hydrothermal upgrading, but occurs at more extreme conditions in terms of temperature and pressure. Therefore the product yield will be composed of gaseous products rather than liquid in the case of HTU. Water becomes supercritical at temperatures over 374oC and a pressure of 221 bar and the distinction between gas and liquid phases disappear. Usually the reaction temperature is chosen much higher than this latter. In the phase change from sub to supercritical, the properties of water change dramatically. It becomes highly reactive and can break C-C, C-H and C-O bonds in such a way that smaller fractions are obtained if higher temperatures are applied. The selectivity and efficiency is, however, significantly enhanced by the presence of a catalyst. Under the most extreme conditions temperatures over 600C the organic molecules are split into the smallest possible entities like H2 and CO2, but at more moderate temperatures the selectivity towards CH4 becomes larger. Even lower temperature than say 400oC will yield complicated waxes and higher hydrocarbons. A typical reaction reads as follows: 2C6H12O6 + 7H2O ——> 9CO2 + 2CH4 + CO + 15H2 ÄH = 1.3 MJ/kg It can be seen that the water participates in the reaction, not only as an effective carrier for heat transfer to the biomass, but also as a reagent. Possibly the water is consumed in a reforming process of the large molecular fragments generated by cleavage of the biomass molecules. This might also be the explanation why a reforming catalyst is so important in the process. A possible process is shown in Figure 2.8. Actually the process schedule is rather simple, but the problems are due to the feeding of the wet biomass and the heat exchanging. This latter heat exchanging process becomes more critical when process temperatures are increasing. The advantages of supercritical gasification are: ·· · Complete transformation of all organic material Short residence times: .5-2 minutes Product gas, including CO2 is liberated at high pressure. This CO2 ADVANCED TECHNIQUES FOR GENERATION OF ENERGY FROM BIOMASS... 163 is primarily dissolved in the water phase and can be easily flashed out to a high CO2 concentration, which will be of value when sequestration is foreseen. The yield is relatively clean as gaseous by-products remain dissolved in the water phase. · Process costs can be high as expensive materials and reactor systems are to be used. It may well be that ultimately the process is best for producing Synthetic Natural Gas along with CO2 storage as the economically most viable application in the long run. Figure 2.8 Schematic of the supercritical gasification process. Esterification Esterification is the chemical modification of vegetable oils into vegetable oil esters, which are suitable for use in engines. Vegetable oils are produced from oil crops (e.g. rapeseed, sunflower) using pre-pressing and extraction techniques. The by-product of the oil production is a protein ‘cake’ which is a valuable feedstuff for animal feeding. Esterification is needed to adapt the properties to the requirements of diesel engines. This process eliminates glycerides in the presence of an alcohol and a catalyst (usually aqueous sodium hydroxide or potassium hydroxide). Methyl esters are formed if methanol is used while ethyl esters are formed if ethanol is used. The most common vegetable oil ester for biofuel is RME (rape methyl ester). 164 INDUSTRIAL PERSPECTIVES FOR BIOETHANOL The schedule of the process is represented below. This example considers an initial biomass (raw material) quantity of 3000 kg of rapeseed. During the extraction process this is converted to approx. 1000 kg of rape oil and 1900 kg of protein feedstuff. In the esterification process the rape oil is treated with methanol to produce 1000 kg RME and 110 kg of glycerine. Extraction Esterification Vegetable oil esters can be used in mixtures with diesel fuel up to 100%. The most promising product at present emerges as RME, a methyl ester based on vegetable oil, which is obtained from rapeseed or sunflower and further processed by cross-esterification of fatty acids and alcohol (methanol). Results from the Thermie programme on biofuel utilisation have shown that no special problem have been detected with conventional diesel engines working on mixtures of up to 50% rapeseed methyl ester. Compared to conventional diesel, RME produces lower emissions and therefore contribute to reducing of health problems e.g. respiratory problems and cancer. Rapeseed oil doesn’t produce sulphur dioxide, which impairs lung function and contributes to acid rain. There may, however, be problems with odour (similar to cooking oil) when pure RME is used as a fuel. Biological/Biochemical Processes Anaerobic digestion of wastes produces methane. It is a well-established technology for waste treatment. This is the natural breakdown of ADVANCED TECHNIQUES FOR GENERATION OF ENERGY FROM BIOMASS... 165 organic matter, such as biomass, by bacterial populations in the absence of air into biogas, i.e., a mixture of methane (40-75% v/v) and carbon dioxide. This bioconversion takes place in “digesters,” i.e., sealed, airless containers, offering ideal conditions for the bacteria to ferment the organic feedstock to biogas. A simplified stoichiometry for the digestion of plant carbohydrates follows: C6H10O5 + H2O —— > 3 CH4 + 3 CO2 During anaerobic digestion, typically 30-60% of the input solids are converted to biogas; by-products consist of undigested fibre and various water-soluble substances. Biogas, either raw or usually after some enrichment in methane, could be used to generate heat and electricity through gas, diesel of “dual fuel” engines, at capacities up to 10 MW(e). The average production rate is 0.2-0.3m3 biogas per kg dry solids. Nowadays 80% of the industrialised world ‘biogas production’ is from commercially exploited landfill. R&D is mainly concentrating on factors affecting microbial population growth. High solids digesters are being developed for the rapid treatment of large volumes of dilute effluents (wastes) from agro-industrial processes. This process has the advantage of a low cost feedstock and offers substantial environmental benefits as a waste management method. Figure 2.9 shows an example of an anaerobic digestion plant in the Netherlands. digestion: 55°C 2-3 weeks 10-15% dry matter 230 kt/y gives 92 kt/y ODW, 10 kt/y biogas, 23 kt/y digestate waste water Figure 2.9 Anaerobic digestion for CHP production Vagron Groningen plant. 166 INDUSTRIAL PERSPECTIVES FOR BIOETHANOL Another product from acid and enzyme hydrolysis, fermentation and distillation is ethanol, which is used as a transport fuel, on the European level mainly in the form of ETBE (a mixture of ethanol and isobutane). The process scheme is shown in Figure 2.10. In the USA however, ethanol is used as a mixture called gasohol (ethanol mixed with gasoline), while in Brazil either pure ethanol or gasohol is used. Presently the techniques of hydrolysis, fermentation and distribution are all commercialised for sugar and starch substrates. Acid hydrolysis for (ligno)cellulosic feedstocks is expected to be economical in about 5 to 10 years. Enzyme hydrolysis is at the pre-pilot stage. It is expected to be commercial in 5-10 years and economical in 10-15 years. The economic competitiveness will be increased by improvement of industrial productivity and efficiency. Recently, major enzyme manufacturers (Genencor, Novozymes) have claimed a 20-fold reduction of cellulosic production costs. Acid and enzymatic hydrolysis of cellulosic materials are not commercial technologies, furthermore, they need a strong R&D development before commercial demonstration. 1. raw biomass 2. disclosure 3. hydrolysis 4. fermentation 5. distillation 6. dehydration 7. fuel adaptation and distribution 8. heat and power production Figure 2.10 Bio-ethanol, power and heat from biomass (waste) streams. ADVANCED TECHNIQUES FOR GENERATION OF ENERGY FROM BIOMASS... 167 The raw materials for bio ethanol can be sugars or starch feedstocks such as wheat, sugar beet, potato, Jerusalem artichoke and sweet sorghum. Maize grain in the US and sugarcane in Brazil are the most utilised biomass material for alcohol production. Bioethanol can be used as a pure fuel as it is applied in the Proalcool Programme in Brazil or mixed with motor gasoline*. If bioethanol is used at 100%, engines should be adapted while for mixed utilisation, non-adapted engines can be used. Since the production of bioethanol in Brazil has shown large yearly variations, the availability is experienced to be limited, or at least uncertain. This made people reluctant to invest in new cars with adapted engines. Presently new cars, which run on pure ethanol, are not produced anymore. Ethanol can be used to substitute for MTBE (Methyl Tertiary Butyl Ether) and added to unleaded fuel to increase octane ratings. In Europe, the preferred percentage, as recommended by the Association of European Automotive Manufacturers (AEAM), is a 5% ethanol or 15% ETBE mix with gasoline. Ethanol could in the future also be produced from lignocellulosic feedstocks. ETBE (Ethyl Tertiary Butyl Ether) production A new product derived from the reaction of equal parts of ethanol and the hydro carburant isobutane, which have fuel properties like octane rating, volatility, heat efficiency and corrosivity superior to bioethanol. Instead of MTBE**, ETBE can be added can be added to unleaded motor gasoline to obtain a mixture of up to 15% without technical problems. The resultant mixture exhibits the same performance * Gasohol is the term used in the United States to describe a maize-based mixture of gasoline (90%) and ethyl alcohol (10%). It should not be confused with gas oil, an oil product used to fuel diesel engines. ** MTBE (Methyl Tertiary Butyl Ether). Obtained from fossil methanol (natural gas) and added to unleaded fuel to rating. MTBE output is currently growing at the rate of 10% annually in France. MTBE is the principal competitor of bioethanol and ETBE as an 168 INDUSTRIAL PERSPECTIVES FOR BIOETHANOL characteristics and engines do not have to be modified. ETBE can be manufactured in plants currently producing MTBE. The first industrial ETBE plant came on stream in 1990 at ELF France, using bioethanol supplied by the French producers Beghin-Say and Ethanol Union. 3. ECONOMICS OF BIOMASS SYSTEMS 3.1 Cost of bio-feedstocks The costs of biomass depend on the dynamics of local markets, as well as on agreements, such as contracts between biomass users and producers. This cost includes all necessary transportation and handling, as well as pre-treatment (drying, size changes). Exact estimates are very difficult to make, as the markets are “immature” and changes occur rapidly. On the one end of the spectrum, we find some industrial residues, e.g., from construction sites, that have nil of even negative costs (i.e., the industry is prepared to pay to get rid of them. On the other end, we have biomass from energy plantations. In the middle of the spectrum, forest and farm residues require the application of costly harvesting and handling operations. According to some recent calculations the following results are derived: · In France (1996), the cost of wood transported over a distance of 40 km to be converted to bioelectricity by advanced gasification processes - e.g., BIG-ISTIG, 20-50 MW(e) - is estimated at 1.54 • cents/kWh(e), representing between 35 and 43% of the average cost of electricity. A study (1998) by VTT (Finland) arrives to raw material (wood) cost figures of 2-3 • cents/kWh(e) for transportation between 20 and 40 km; this is to be increased by 30% for transportation up to 100 km. · octane booster, with more than 10 million tonnes produced annually worldwide. The price of MTBE is linked to that of methanol, which exhibited major price fluctuations of between 95 - 190 ECU/tonne between 1987 and 1992. As a result, manufacturers may favour ETBE whose market price is generally more stable. European regulations currently specify maximum MTBE (and ETBE) content in engines as 10% by volume. 169 ADVANCED TECHNIQUES FOR GENERATION OF ENERGY FROM BIOMASS... · A Dutch study (1996) estimates the production costs of biomass in the form of organic residues as 0-45 • /dry t. Energy crops 50-80 • /dry t; to these figures we should add 10-20 • /t for transportation, and another 10-20 • /t for handling and pre-treatment. 3.2 Costs of bioelectricity Many economic evaluations of electricity generation systems utilising biomass as a feedstock have been carried out. In the following Table, a comparison of such calculations for the main technologies available is presented. Technology Applied Efficiency (%) Generation Capacity (MWe) Present Future Investment Cost (k• /kWe) cE/kWh(e) Combustion 15 - 35 1 - 50 100 1.1 - 2.8 2.8 - 10 Co-combustion Of existing power station Of existing power station Of existing power station 0.5 3.6 - 10 Gasification 20 - 35 0.1 - 25 ? 1.5 - 2.0 ? Gasification * Combined cycle 30 - 47 < 12 25-120 1.3 - 2.4 4.4 - 8.4 Flash Pyrolysis * Diesel 30 - 35 15-25 50 0.8 - 1.8 3.9 - 7.8 Biogas * Urban Wastes 20 - 30 1? < 10 9 - 15 23 - 80 Biogas * Landfills 20 - 30 <1 ? 0.5 - 1.2 2.9 - 5.6 Table 3.1 Main technological routes for producing electricity from biomass. In these calculations, the cost of feedstock is assumed to be zero only in the case of landfills; in the other cases the fuel price is assumed to be: ·· · combustion: 2.0 - 2.5 • cents/kWh(e); gasification: 1.9-2.4 • cents/kWh(e); pyrolysis: 37 • /t of biomass. 170 INDUSTRIAL PERSPECTIVES FOR BIOETHANOL Combined heat and power (CHP) generation is considered to be another key potential market (see above). Table 3.2 outlines the economics involved in a CHP plant, which uses willow as a feedstock, and a fluidised-bed combustion system. Specific Investment 1600 •/kW(e) Lifetime 25 years Capacity 10 MW(e) + 17 MW(th) Biomass Costs (Short rotation, willow) 55 E/dry t Bioelectricity Production Cost 7.6 •cents/kW(e) (bio-heat at zero cost) Table 3.2 Costs of CHP plant (fluidised-bed Considering biofuels the Figure 3.1 gives a comparison of different commodity fuels prepared out of biomass. New products like bio-diesel will add another 20-25 $/GJ to the price of petroleum based fuel [19]. Fischer Tropsch diesel produced out of biomass will become competitive when produced centralised at large scale and with significant tax exemptions. Figure 3.1 Estimated production costs of wood-based methanol, ethanol and pyrolysis oil using various technologies (taken from “Energy Visions 2030 for Finland)[5] ADVANCED TECHNIQUES FOR GENERATION OF ENERGY FROM BIOMASS... 171 4. CHALLENGES FOR BIOMASS R&D 4.1 Long-term goals The long-term goal of biomass R&D is to be competitive with fossil fuels without subsidies on a level playing field of full costs, to increase its contribution to energy demand of the EU to more than 20% of the projected primary energy demand in 2025 and more than 30% in 2050. In parallel, it is necessary that the gradual increases of biomass energy contributions have to be realised in an environmentally sustainable way and accepted by the public. Figure 4.1 shows the time path for the subsequent development steps. These will be outlined in the following section. • Maximising direct/indirect cofiring in conventional coal-fired power plants • Indirect cofiring (gasification) in natural gas-fired boilers and CCs • Decentral CHP production (gasification, pyrolysis -> GEs, GTs, FCs) • Gasification/methanation -> “green” natural gas (SNG, LNG) • Hydro-Thermal-Upgrading -> “biocrude” • Supercritical gasification -> H2, CH4 Implementation time Figure 4.1 Short and medium-term developments. The easiest way to implement biomass as an energy resource presently is by producing process heat as it occurs to a large extent in the wood, sugar and paper industry. In Scandinavia, biomass or organic waste is combusted in large scale fluidised-bed boilers to raise steam or hot water for heat supply and to a minor extent for electricity production, basically in back pressure steam turbines. The full potential is not yet completely explored. Further, combustion units of about 50 MW(th) driving condensing steam cycles to produces mainly electricity are in a state of planning or are being started up. These systems will have to become 172 INDUSTRIAL PERSPECTIVES FOR BIOETHANOL economically viable by the fact that subsidies on the “green” electricity or heat are made available, or that customers are willing to pay extra. As a next step, co-firing of biomass or waste (paper or sewage sludge for instance) with existing and highly optimised coal boilers is in a state of development. Presently an input of up to 10% of the calorific value of the fuel is targeted, but values of up to 35% are envisaged. This cofiring is achieved by injecting the fuel into the boiler next to the coal. In this case the biomass will have to be chipped to small particles to make injection possible. In some cases, like for sewage sludge, the waste can be co-injected with the coal. An interesting option is to pyrolyse the biomass or waste to bring it in a form, which resembles the coal so that it is easily injected. The pyrolysis gas can be injected into the system further down steam. Synergistic effect can be attained as it presents a possibility to reduce NOx emissions from the boiler. Another application of co-firing is to gasify the biomass and to inject the syngas into the boiler (Figure 2.2). In this case the residues from the coal-burning unit can be kept separated from the residues of the biomass. This latter technology is also foreseen to be implemented into existing gas fired combined cycle plants. This will open up an enormous potential for introducing biomass and waste into the energy-generating infrastructure. For a county like the Netherlands, for instance, all the options of co-firing mentioned are of importance to meet the goals for CO2 emission reduction as well as generation of energy out of renewables. So far fuel availability, but even more so, contractibility have been experienced as the main obstacle for exploitation of the large-scale potential. Next to this co-firing, at locations where also heat has a significant economic value, stand-alone units may become attractive. Due to high potential the efficiency and attractivity of temperature levels of the process, gasification is the main candidate technology. The size and type of such plants depends on local conditions like fuel availability, its composition and morphology and the heat/power ratio required. In any case, however, gas cleaning will be the critical step. This gas cleaning is not only necessary to meet the demands of local legislation, but also, and may be even more important, to be able to combust the gas in a prime ADVANCED TECHNIQUES FOR GENERATION OF ENERGY FROM BIOMASS... 173 mover. At this moment it is not clear whether or not the costs for the necessary gas cleaning technology to be involved will turn out to be prohibitive for implementation. In this respect it may well be that more advanced gasification technologies giving inherently low tar levels in the product gas will ultimately be the final option for implementation. Figure 4.2 gives an example of an advanced two-step gasification process known as the “Carbo V” process developed at the EUT in Freiberg, Germany. Here biomass is pyrolysed to char and gas. The gas is used to create a high temperature zone in which later the char is injected. This process suppresses tar formation and gives a medium calorific fuel gas. A number of demonstration project in the EU and also elsewhere in the world are planned, started up or running to get more insight into the feasibility of the technology. Figure 4.2 An example of an advanced to step gasification process. Ultimately, biomass as a feedstock will be needed to replace existing fossil recourses. Any kind of technology described here as for producing bio-oil, biogas, or routes involving catalytic chemical synthesis will be necessary to meet this future demand on chemical feedstock and transportation fuel. 174 INDUSTRIAL PERSPECTIVES FOR BIOETHANOL It will be the main task of the biomass R&D community to make this challenge become reality in the coming decades. Figure 4.3 shows the concept of biorefinery, the ultimate integration of biomass and waste in the energy and materials production. This will be the main way to overcome shortage in raw material to combat unwanted emissions and to guarantee a sustainable society for generations to come. Figure 4.3 Biorefinery concept. 4.2 Obstacles Fuels The major obstacle to the large-scale implementation of biomass systems will be the guaranteed supply of biomass feedstock. In this respect distinction has to be made between availability and contractibility. As a rule, 50% of the availability is presently taken for the contractibility, but this number will have to grow to explore its potential. The commercial viability will be based on the financial margin to producer or collector (gate price or production cost). For the energy crops, this must compete with the lowest margin in conventional farming. Acceptance of new crops into the agricultural system can only be achieved ADVANCED TECHNIQUES FOR GENERATION OF ENERGY FROM BIOMASS... 175 if the farmer is confident with the new crop or has experience with the crop for other uses (e.g. rapeseed oil). All demonstrations and field trials should involve agricultural organisations. Making biomass waste streams available is basically a matter of organisation or logistics. Not only the quality like the amount of inorganic material in the stream but also long term guaranteed supply is of importance in relation to the size of the plant where the biomass or waste is processed. For small plants, pre-processing or conditioning can be done on the premises, but for larger ones it can be decided as a consequence of economic optimisation, to partially pre-process the feed at the production site or on the way to the conversion plant. The extreme case is where biomass is imported as a regular fuel. Ultimately biomass is converted on the production place into char, pyrolysis oil or pellets. Local benefits may be achieved in such a case when also at the production site by products can be integrated with the local energy demand (local use of the gas as a by-product of the char production for instance). It will be of high importance to find ways to optimise such energy chains in an environmentally and economic way to achieve a situation where biomass and organic waste is to a large extent implemented. Energy crops An obstacle to the growing of biomass for energy on set-aside land is the possible emergence of new crops, which will be grown for nonfood and non-energy purposes (e.g. paper pulp and chemicals). These crops will be suitable for growing on set-aside land and the products may have higher value than biomass fuel, therefore, allowing the processor to pay more for the biomass. The price offered for the energy crop must compete with prices offered for other crops, which may also be grown on set aside land. Clearly, growing of organic material for energy production needs particular insight into possible ways to maximize soil depletion. Also fertiliser and chemical constituents will have to be minimized. Of particular interest is integration of energy crop production regionally and its economics. 176 INDUSTRIAL PERSPECTIVES FOR BIOETHANOL Wastes Agricultural waste is a by-product and obviously not optimised towards energy production purposes. At present these ‘residues’ are readily available often at very low, zero, or in some situations, negative costs. Some debate exists over the use of these residues and the decision to use them is generally site-specific. Forest fires are a real threat in southern Europe thus necessitating the routine collection of forest residues, which therefore are a potential biomass fuel. However, in other more northern areas where forest fires are not a threat, residues are not harvested because they are considered to be a valuable part of the nutrient cycle of the forest and also contribute to soil structure. In these cases forest residues are usually not considered as a biomass fuel. As a consequence, many of the steams have unfavourable properties like abrasivity, corrosivity, ash and inorganic material content. Further, local legislation leads to assignment of a certain percentage of the fuel as green fuel. This makes the total pool of organic fuel substantial but very inhomogeneous. Development of suitable fuel blends in relation with particular conversion technologies and optimised morphology is therefore of prime importance. It may be foreseen that a new branch of economic activity will emerge: pre processed optimised fuel production with added value like pellets, briquette, chips etc. R&D into conversion technology with these new fuels is then of prime importance. Import/Export For highly urbanized areas, but which still have renewable energy targets, green fuel import can be important. For producing areas this can lead to new economic activity and added employment. The issue of import can mean that collection occurs over large areas. But conversion takes place highly concentrated in co-conversion or dedicated plants but with high capacity. In each particular case it has to be determined how the logistics will look like: to what extent will pre-processing be done and where. Minimization of transport costs is the main issue in this case. But also local benefits may be of importance. ADVANCED TECHNIQUES FOR GENERATION OF ENERGY FROM BIOMASS... 177 4.3 Conversion Processes Combustion The main development has been with fluidised-bed combustors. These combustors have a high efficiency, can burn a mixture of fuels and fuels that can contain up to 60% moisture. The largest boilers are grate systems (up to 100 MW thermal), which can produce about 200 t steam/hr. Direct combustion is commercialised at present and the firing of biomass powder in ceramic gas turbines will be commercialised in the years to come. These turbines will have a capacity of 100 kW - 500 kW. Products are heat and/or high-pressure steam, which can be used to produce power or combined heat and power. The most promising developments in combustion for efficient biomass conversion is co-combustion. This can be done in existing coal plants of a large capacity (which allows high efficiencies for production of electricity). New boiler concepts where biomass is combined with coal, peat, RDF or other fuels offer high efficiencies because of their larger scale and low risks in the power supply since more than one fuel can be used (e.g. to compensate seasonal influences). Most R&D is on technical aspects e.g. stoking, combustion air and fuel conveyance. There have been large improvements in combustion efficiency (>30%), in reduction of pollutant emissions (e.g. fly ash) and in the development of CHP plants. R&D will also be required for Stirling engines and pressurized combustion systems. Main R&D tasks lay in the field of co-combustion: assessment of possibilities of co-combustion in different situations, development and demonstration of advanced boiler concepts. Specific research topics on combustion are corrosion by alkalines and chlorides and options to prevent. Further, slagging prevention and applying difficult biomass fuels such as straw, RDF, and grasses in different combustion systems is important. The main barriers to overcome are the high cost, making use of the economy of scale. The developments will be helped if up-front investment is available. The involvement of industries in the development will be an important issue and part of the R&D should concentrate on demonstra- 178 INDUSTRIAL PERSPECTIVES FOR BIOETHANOL ting the environmental and energy benefits of the technologies to industries. One issue, which must be assessed in the studies, will be how well the utilities meet the CO2 and other emission standards. Gasification Gasification is sensitive to changes in feedstock type, moisture content, ash content and particle size. The gas can be used for internal combustion engines provided it is cleaned of tars, carryover dusts, some of its water content, and cold enough. If cleaning does not take place, tars may precipitate on inlet valves and clog up gas/air mixers. Dust can clog carburettors, cause engine damage and act as a grinding powder between the piston and cylinder wall. The most effective and economical use of the gaseous product is the production of electricity via gas turbines if combined with steam cycles. Gasification produces a higher yield than combustion with respect to electricity production for low power plants (50 kW to 1-10 MW) with internal combustion engines. For higher power (1-10 MW to 50-100 MW) combustion systems with steam turbines are more efficient than gasification systems. For very large-scale power plants (50-100 MW) gasification can reach exceptionally high levels of efficiency through a combined gas turbine-steam turbine system R&D in gasification is aiming at large scale (1000t/day) oxygen and/or air blown systems. Of prime importance is the development of efficient systems for electricity production. IGCC and STIG may ultimately achieve efficiencies of 42-47%. To reach this goal, emphasis in R&D will have to be given to: Development of simple and cheap gas cleaning technologies for dust, NOx or ammonia, hydrochloric acid and alkaline components. This development is needed for both large scale (>10 MW) units as well as small ones. Ultimately stringent standards for fuel quality are needed. Further, emphasis will have to be given to improving the tolerance of gasifiers to different types of biomass and operation of gas engines or gas turbines fired by low calorific gases. Once efficient and cost effective gasification has been achieved, the synthesis gas can be used for deriving of secondary fuels like metha- ADVANCED TECHNIQUES FOR GENERATION OF ENERGY FROM BIOMASS... 179 nol or, more generally, chemical feedstock. The relative demand and cost advantages are unlikely to become evident until after 2010 when liquid fuel may increase in price or environmental requirements may restrict the use of gasoline or petroleum additives. Pyrolysis Flash pyrolysis will produce the largest percentage of bio-oil (6080% by weight). Slow or conventional pyrolysis will produce more charcoal (35%-40%) than bio-oil. Flash pyrolysis is at a demonstration scale. Upgrading processes are at a far lower degree of development than pyrolysis processes. Bio-oil is expensive as a transport fuel (especially if no environmental credits are taken into account), but as a liquid, bio-oil presents the advantage of easy handling, transport and storage. This bio-oil can be combusted for heat and electricity and therefore it may become economically attractive. Char can be used in small gasifiers (kW range) or may become important as import fuel as a transport fuel (diesel substitute), bio-oil needs a stabilising step and maybe upgrading. On the R&D side emphasis is to be given to: · ·· · improving the production of bio-oil (for MW power stations) and upgrading using catalytic hydro-treatment, solving the corrosive and toxic problems, modification of diesel engines, which will be run with pyrolysis oil, development of recovery of fine chemicals. Esterification The process for the production of RME is well developed and the product is commercially available in France, Germany and Italy. EU nonfood oilseed production is confined to 700,000 ha-1.2 million ha and this allocation is being quickly taken up by member states. In 1994 180 INDUSTRIAL PERSPECTIVES FOR BIOETHANOL total EU area of oilseeds for non-food purposes was 0.62 million ha as compared to 0.2 million ha in 1993. Most of this is accounted for by rapeseed which increased to an estimated 0.4 million ha. The major producers are France and Germany with respective areas of 173,000 ha and 152,000 ha (1994). Bio-diesel is expensive as a transport fuel (costing approx. 0.20-0.25 ECU/litre more than its mineral equivalent). In the countries where RME is commercially available, it is competitive with fossil diesel due to tax exemptions. At the EU political life an intensive debate is going on to make biofuels economically competitive through a reduction in excise. The main obstacles to the development of esterification processes are the high production cost of RME, the limited amount of raw material which is allowed to be grown in the EU and the opposition of some Member States and the lack of competitiveness of biofuels in comparison to fossil fuels mitigate against the injection of capital into the development of improved esterification methods. R&D should concentrate on: ·· ·· Testing RME in different types of engines. Testing of engines for emissions (particulates) and reduction of odour problems. Improved Energy Ratios and greenhouse gas benefits. Reduction of production costs, especially by using more efficiently the by products (glycerine, cake). Biological/Biochemical Conversions Acid hydrolysis, fermentation and distillation of sugar/starch-based substrates are all commercialised at present. Enzyme hydrolysis may be commercially available in 5-10 years. Acid and enzymatic hydrolysis of cellulose-based substrates are not commercial technologies. There is still an economic gap between the price of fossil fuels (0.15 • /L) and the price of liquid biofuels (0.4-0.6 • /L for ethanol in Europe). The gap is expected to be reduced by improvement of industrial productivity and efficiency, and use of new species. Methane (used for power) and compost are other products commercially available from biochemical processes. ADVANCED TECHNIQUES FOR GENERATION OF ENERGY FROM BIOMASS... 181 The main product is ethanol, which can be mixed with gasoline up to 10% in normal engines. 100% ethanol can be used in adapted engines. ETBE (a mixture of ethanol and isobutane) can be used as a lead substitute (up to 15%) in diesel/gasoline engines. The main obstacle to the development of bioconversion technologies is the lack of investment in RD&D. In the absence of this investment coordination activities should be initiated, also with the USA. R&D on this topic is still in its infant phase and therefore an extensive list of topics will have to be addressed: Development of advanced methods for the chemical hydrolysis of cellulose and lignocellulosic materials. R&D in fermentation/distillation includes the use of novel yeasts, bacteria and fungi. Pre-treatment is being investigated to increase the ease of hydrolysis. The most cost-effective hydrolysis process developed so far is steam explosion. R&D in acetone-butanol fermentation is being carried out but there has been no breakthrough as yet. One step hydrolysis/fermentation stage where the hemicellulose and cellulose are treated at the same time. Niche markets should be identified and demonstrations should be established to highlight the benefits of the technologies. Example of niche markets are environmentally sensitive areas such as waterways and leisure areas. Development of new types of bioreactors. Development of new strains of microorganisms for fermentations. Development of cheap enzymes for enzymatic hydrolysis of lignin. · · · · · · ·· · H.J. Veringa P. Alderliesten Energy research Centre of the Netherlands (ECN) P.O. Box 1, 1755 ZG Petten, The Netherlands Phone: +31 224 56 4628, Fax:+31 224 56 8487, E-mail: [email protected] 182 INDUSTRIAL PERSPECTIVES FOR BIOETHANOL 5. REFERENCES [1] Biomass technologies in Austria, Market Study Thermie Programme, Action BM62, European Commission DGXVII, July 1995. [2] Energy in Sweden 1994, NUTEK (The Swedish National Board for Industrial and Technical Development). [3] Donald Klass, Excerpt of Biomass in North American, Biomass for Energy, Agriculture and Industry, vol 1 8th EC Conference, eds. P. Chartiers, A.A.C.M. Beenackers, G. Grassi, 1995 pp 63-73, Pergamon Press Oxford. [4] P. Ballaire, Publication Interne ADEME 1996. [5] Energy Visions 2030 for Finland, VTT Energy, ISBN-951-37-35966, 2001. [6] G.T. Wrixon, A. Rooney, W. Palz, Renewable Energy 2000, Springer Verslag, 1993. [7] C.P. 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[12] Production of a bio-gasoline by upgrading biomass flash pyrolysis liquids via hydrogen processing and catalytic cracking, M.C. Samolada, W. Baldauf, I. A. Vasalos, 1998. [13] Staged thermal treatment combined with pyrometallurgical smelting producing energy and products from waste, A.B.J. Oudhuis, H. ADVANCED TECHNIQUES FOR GENERATION OF ENERGY FROM BIOMASS... 183 Boerrigter, J.P.A. Neeft, H. Zanting, Proceedings R’2000, 5th World Congress on Integrated Resource Management, June 5-9, 2000, Toronto, Canada. [14] Upscaled two-stage gasification process; high efficient and low tar gasification process for biomass and waste in small, medium and large scale CHP-plants, COWI. [15] Carbo-V-gasification; fuel gas, heat and electricity from biomass, Umwelt- und Energietechnik Freiberg GmbH. [16] Contributions ECN Biomass to “Developments in thermochemical biomass conversion” Conference, 17-22 September 2000, Tyrol, Austria, ECN-RX-00-026. 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