Carbon Sequestration through Sustainably Sourced Algal Fertilizer: Deep Ocean Water Abstract ID: 12622 Final Paper Number: V23A-4783 By Martin T. Sherman 1. The draw-down of carbon dioxide from the atmosphere happens in the oceans when marine plants are growing. This is due to the use of CO2 during photosynthetic biological processes that raise the pH of the water. Macro- and microscopic marine photosynthesizers are limited in their growth by the availability of light and nutrients (nitrogen, phosphorous, iron, etc.) Deep ocean water (DOW), from below about 1000m, is a natural medium for marine algae, which contains all (except in rare circumstances) necessary components for algal growth, except sunlight. DOW represents ~90% of the volume of the ocean. The introduction of DOW to a tropical or summer sea can increase chlorophyll from near zero to 60 mg per M3 or more. Oceanic thermal energy conversion (OTEC) can utilize DOW to produce electricity and high value drinking water. DOW, with its access to a sustainable source of nutrients and concomitant products, represents the logical long-term solution for algal feedstocks for biofuels. Importantly, the large-scale growth of marine plants has the added benefit of reducing oceanic acidification, effectively adding to the ocean’s ability to absorb carbon before biological calcificating processes are interrupted. 2. The form of the utilization infrastructure for DOW can roughly be divided into two types; the unconstrained release, and the open pond system (There is a third type: DOW pumped into bio-reactors made of transparent materials, but as they are energy-intensive due to pumping, suffer from biofilm clogging and have limited economies of scale, this class is discounted). Unconstrained release has the advantage of having low infrastructure investment and is available to any area of the ocean. However, there are many questions about ecologic impact. The open pond system has high infrastructure costs but enables intensive use of DOW for harvesting macro- and microalgae and sustainable mariculture. It also enables greater concomitant production of DOW’s other potential products, such as electricity. Unlike an unconstrained release, the open pond system can capture much of the biomaterial from the water, which limits the impact to the surrounding ecosystem. 3. The Tidal Irrigation and Electrical System (TIESystem), is an open pond that is to be constructed on a continental shelf. It harnesses the tidal flux to pump DOW into the pond on the rising tide and then uses the falling tide to pump biologically rich material out of the pond. This biomaterial represents fixed CO2 and can be used for biofuel or fertilizers. The TIESystem benefits from an economy of scale that increases at a rate that is roughly equal to the relationship of the circumference of a circle (the barrier that creates the open pond) to the area of the pond multiplied by the tidal flux on that particular area of the continental shelf. Despite the large construction costs of artificial islands and structures robust enough to withstand the conditions of the continental shelf, 1 2 1)Palm Island, Dubai. Courtesy Wikepedia 2) TIESystem, top down view lagoon/ tidal pump/open pond bioreactor. 3) TIESytem with grid connection and ship for export. 4) TIESystem on a continental shelf 3 4 the system will become economic as it grows in size. However, extensive research will be required to maximize the output of each subsystem, minimize interference between these subsystems, and minimize the risk of anoxic events or bio-toxin releases. Current Use Soaring anthropogenic concentrations of carbon dioxide in the atmosphere have lowered oceanic pH in the temperate oceans by 30%. In the process, about a quarter of the CO2 has been transferred1. The growing of marine plants absorbs carbon dioxide in the building of their bodies and in their respiration. Wageningen biologist Ronald Osinga theorized that growing 180,000 square kilometers of sea-lettuce (ulva lactuca) would be enough to reverse ocean acidification. Sealettuce is one of many fast-growing edible species of marine plants. Macroscopic algae like kelp grows 20 times as fast as their terrestrial counterparts, and microscopic organisms, 30 times as fast. The limiting factor in marine plant growth is the availability of fertilizers like nitrates, phosphates, carbon dioxide and micronutrients like magnesium and iron. Experiments to in- (Left panels) simulated latitude-depth distribution of changes in pH(relative to pre-industrial values) in year 2100. (Right panels): simulated horizontal mean pH as a function of year and depth(refer to Table 1 for simulation setup). It is shown here that ocean iron fertilization accelerates deep ocean acidification. Courtesy Cao · Caldeira 2010 Terrestrial-based approaches to growing algae for utilization consume large water resources and have low efficiencies due to energy inputs for pumping and fertilizers. For instance, a gram of nitrogen takes at least 30 kJ to produce and a typical kg of algae has 60g of nitrogen and 6g of phosphates. Despite cultivation rates reaching 5-50g per day, relative to photovoltaics and wind, this approach is land intensive. A middle ground estimate of algal biomass cost is $1.25 per kg to produce and has an energy density of 25MJ per kg (wet). This leads to a best-case scenario of ~$0.68 kWh output for the consumer6. However, most of this cost is created by the expense of generating the biomass. For instance in a Hydrothermal Liquefaction process (1 kg wet algae generates ~5 kWh), 98.5% of the expenses are incurred in growth of the algae. Fertilization with Utilization A tidal pump is created by the mechanism of an artificial atoll where its lagoon’s only access to the incoming tide is via a conduit that descends off the edge of the (tropical or subtropical continental) shelf, drawing up DOW. The lagoon pumps in concert with the natural tidal flux. DOW is a near ideal medium for algal growth and represents ~90% of the world network of ~200 TIESystems each 20 km in radius placed in tidal ranges of 0.7 m or more could grow enough algae to meet world energy demand ~150,000 tWh (2014). Tropical locations such as Pacific Central America or northwest Australia enable OTEC co-generation of ~15,000 tWh, with tidal flow adding a further ~ 750 tWh. This network would absorb ~2.16 bn tons of CO2. Each TIESystem would repay its investment within 7 years. The large energy value of algae make it economically viable to build TIESystems in temperate continental shelves forgoing the OTEC component, due to their higher tidal fluxes. A rough estimate suggests that utilizing less than 5% of world continental shelf under TIESystems could sustainably replace all fossil fuels. Summary DOW fertilization with utilization is a strong CO2 offsetter and ocean acidification reducer. To find best practice of the TIESystem and move toward implementation, further research is called for from the fields of biology, hydrology, sedimentology, engineering, naval architecture, plant design, and logistics. Impact assessment, engagement with NGOs and regulatory bodies are all called for due to the scope of the project. RADIUS of TIESystem in km: Circumference (in km) Area of water at surface (in square km) Volume exchange of Deep Ocean Water (DOW) per flux (cubic m) Non-OTEC production per flux (MWH) OTEC production per flux (MWH) Biomass production kg per flux (Wet) 1 6.283185307 3.141592654 942477.7961 0.48747046 78.53981634 138544.236 10 62.83185307 314.1592654 94247779.61 48.74704601 7853.981634 13854423.6 20 125.6637061 1256.637061 376991118.4 194.988184 31415.92654 55417694.41 CO2 uptake per flux (kg) 10159.91064 1015991.064 4063964.257 Value of Carbon Credits per flux 406.3964257 40639.64257 162558.5703 Value of non-Biomass MWh output (total per flux) 3951.36434 395136.434 1580545.736 CE-CERT biomass conversion biodiesel (gallons per flux) 1282.838566 128283.8566 513135.4264 CE-CERT biomass conversion MWH approx per flux 39.94186012 3994.186012 15976.74405 Grand Total value per flux ($US) 8920.530904 892053.0904 3568212.361 Approx building cost ($US) 942477796.1 9424777961 18849555922 Time to recover approx building cost (years) 153.3420283 15.33420283 7.667101413 This chart shows a suboptimal location for a TIESystem such as the continental shelf Average Tidal Flux in m .3 on the Florida Gulfcoast. Small tidal fluxes & low temperature gradient are overcome Head in m 0.1 so that the system becomes ecconomic as it grows in size. Number of Fluxes per year 689 ***Important Notes 1) Delta is a function of the area of the lagoon unlike a normal Turbine Efficiency coefficient (0-1) 0.95 hydro-electric dam which is based on height 2) Cost is based on the assumption of OTEC turbine efficiency coefficient (0-1) 0.3 $150,000 per meter of atoll wall with plant costs of $5000 meter of atoll wall (because Temperature difference (for OTEC) 20 plant costs decrease rapidly as they are scaled up and $10000 per meter of atoll wall Biomass growth7 (g per m3) 147 for the cold water intake pipe 3) Biomass figures are based on previous studies of Value per kWh ($US) 0.05 DOW, they include bacterial growth 4) CE-CERT figures are based on usage of muValue of 1 Carbon Credit ($US) 4 nicipal waste and it is anticipated that biomass produced by a TIESystem will contain Value of 1 gallon of diesel ($US) 2 more energy. COST per linear m of wall ($US) 150000 crease carbon sequestration through use of open ocean fertilization via iron in the South Atlantic (as iron availability is the limiting factor on phytoplankton growth there) have resulted in primary growth, but this does not result in carbon rich deposits forming on the seafloor. Instead, 99% transfers and accelerates acidification of the deep oceans and only delays acidification of the surface by a few years2. This has important implications for any other system that fertilizes the ocean such as those that create an artificial up-welling of DOW or OTEC. The biomass created by DOW exposed to sunlight initially raises pH by the growth of marine plants and then it lowers the pH as animals who have consumed that biomass respirate. This is mimicked by the seasonal pH variation in the artic ocean3. Many projects are examining growing and harvesting kelp as food and fodder and as source material for fertilizer, fuel and pharmaceuticals. For instance, a kelp farm using an array of specially planted ropes in South Korea reported CO2 capture in the form of algal growth at ~10 t CO2eq per ha per year4 or ~10% of (wet) volume5. It's important to note that most of this biomass increase occurred in the spring. In summer and autumn kelps die back to their holdfasts due to lack of nutrients, releasing the CO2. The lack of nutrients is caused by surface water warming, creating thermocline layers that prevent the mixing of deep, cold, nutrient rich water with sunlight. ocean’s volume. DOW can also be used to generate electricity in the megawatt range through OTEC via a thermodynamic exchange with warm surface waters. OTEC mixes two-thirds warm surface water and one-third DOW. A TIESystem’s DOW moves under tidal forces, which increases OTEC efficiency by a third. The lagoon then concomitantly acts as an open pond bioreactor, exposing pure DOW to sunlight to create nearly ideal conditions for algal growth. The tide flowing out of the lagoon is then harnessed to aid biomass collection, increasing the utilization efficiency of this resource. The construction of artificial islands robust enough to withstand the conditions on the continental shelf is expensive. This technology is typified by the Palm and World Island developments in Dubai. However, as a result of an exponential increase in outputs as the TIESystem grows in size, the large investment costs of the system will, in most locations, become economic if constructed large enough. (See table above) By enclosing a section of the continental shelf in this way, biomass generated is collected for utilization and the carbon dioxide is absorbed and removed from the water before it returns to the ocean. This discharge from the lagoon mitigates ocean acidification by its slight alkalinity. Also, carbon offsetting is made possible by creating replacements for fossil fuels. Based on algal growth of 147g per cubic meter of DOW7, a Ocean Thermal Energy Conversion. Courtesy Wikepedia Time of Investment recoup 2πrVwD+P+C (πr2HfS-M)F r= Radius of the artificial atoll Hf= Height of average tidal flux Vw= Volume of average wall segment S= Sale value of all products M= Maintenance and labour cost D= Average costs of wall per m3 P= Plant construction costs C= Additional construction costs F= Number of tidal fluxes per day Biography Martin T. Sherman is the inventor of the Tidal Irrigation and Electrical System (USPTO 6,863,028). He is CEO of Seavac Ltd, and a regular contributor to debate and discussion on renewable energy developments. He works as an actor, and resides in London, UK. Contact via seavac.org Climatological distributions of pH, pCO2, total CO2, alkalinity, and CaCO3 saturation in the global surface ocean, and temporal changes at selected locations. Taro Takahashi, S.C. Sutherland, D.W. Chipman, J.G. Goddard, Cheng Ho, Timothy Newberger, Colm Sweeney, D.R. Munro. LamontDoherty. Earth Observatory of Columbia University, Palisades, NY 10964, United States Cooperative Institute in Environmental Sciences, University of Colorado, Boulder, CO 80309, United States 2 Climatic Change- DOI 10.1007/s10584-010-9799-4 LETTER: Can ocean iron fertilization mitigate ocean acidification?A letter. Long Cao · Ken Caldeira Received: 30 October 2009 / Accepted: 2 January 2010 © Springer Science+Business Media B.V. 2010 3 Ibid (1) 4 Installing kelp forests/seaweed beds for mitigation and adaptation against global warming: Korean Project Overview. Ik Kyo Chung, Jung Hyun Oak, Jin Ae Lee, Jong Ahm Shin, Jong Gyu Kim and Kwang-Seok Park. ICES J. Mar. Sci. (2013) doi: 10.1093/icesjms/fss206 5 Do trophic cascades affect the storage and flux of atmospheric carbon? Annalysis of sea otters and kelp forests. Christopher C Wilmers, James A Estes, Matthew Edwards, Kristin L Laidre, and Brenda Konar Front Ecol Environ 2012; doi:10.1890/110176 6 A comparison of algae to biofuel conversion pathways for energy storage off-grid. Matthew S. Orosz, David Forney. May 2008 Report 2.62. M.I.T. 7 Effects of deep seawater on the growth of several species of marine microalgae, Journal of Applied Phycology, February 1994, Volume 6, Issue 1, pp 75-77. Tsuneo Matsubayashi, Isao Maruyama, Sumiko Kido, Yotaro Ando,Toshimitsu Nakashima, Takayoshi Toyota 1
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