Feasibility and Environmental Impacts of the Production of Biodiesel from Grease Trap Waste
Megan E.
1
Hums ,
Colin J.
1
Stacy ,
Dr. Richard A.
1Chemical
1
Cairncross ,
Dr. Sabrina
2
Spatari
2Civil,
Drexel University,
and Biological Engineering &
Architectural, and Environmental Engineering
3141 Chestnut St. Philadelphia, Pennsylvania 19104: [email protected]
FFA + Alcohol  Biodiesel + Water
Challenges:
1. Waste grease produced in limited quantity and location-dependent
2. Lipid content in grease is highly variable; 2-30% total waste volume
3. Sulfur concentration inhibits production of ASTM grade biodiesel
Biodiesel from Waste Greases:
1. Utilizes a low-value liability to make a high-value product
2. Reduces the processing burden on waste management systems
3. Has the potential to fuel 1 million vehicles
Proposed System to Integrate Biodiesel Production
Method to evaluate energy usage and environmental impacts for a product
Acidic Oil
(FFA)
Operating Conditions:
• At 120 °C - Hotter than
boiling points of:
• Water (H2O)
• Methanol (MeOH)
• Atmospheric pressure
• MeOH rate 0.75 mL/min
MeOH &
H2O Vapor
Harvest
FFA
+
MeOH
H2O
MeOH
H 2O
+
FAME
Use as
Vegetable
Oil
160
(MeOH)
Vapor
140
120
Excess MeOH at 95%
conversion (right axis)
5
100
4
80
3
60
2
40
20
1
0
0
0
0.05
0.1
0.15
0.2
Normalized MeOH Feed Rate (1/min)
Disposal
• Impacts from GTW-to-biodiesel
process is dependent on lipid
content
Fossil Energy Ratio (Right)
From process analysis of each major process FER = a ratio of fuel energy output divided by
fossil energy input:
step
𝐿𝐻𝑉
𝐹𝐸𝑅 = 𝑛
Here steam is produced by burning natural gas High FER values desirable
𝐸𝑖
𝑖=1
0.9
100
7
6
• GTW does not include farming
step, but has a high impact due
to processing
Process steam requirements (Left )
Achieves >95% FFA Conversion in less than 2 hours
Alcohol/Water Content Study
Conversion/Excess MeOH Study
Time to 95% conversion
(left axis)
Distribute
Biofuels are renewable due to the
recycling of biogenic Carbon Dioxide (CO2)
Crude
Biodiesel
(FAME)
180
• Traditional biodiesels have high
negative impact due to
farming/harvesting of crops
CO2
Emissions
90
Pure MeOH
80
90:10 MeOH:H2O
70
Pure EtOH
60
90:10 EtOH:H2O
Lipid content
primarily
affects steam
requirement in
separation step
50
40
30
Below 10%
lipids, process
steam
requirement
increases
steeply and FER
decreases
rapidly
20
10
0
0
50
Time (minutes)
100
*Stacy, C. J.; Melick, C. A.; Cairncross, R. A., Esterification of free fatty acids to fatty acid alkyl esters in a
bubble column reactor for use as biodiesel. Fuel Processing Technology 2014, 124, (0), 70-77.
Short-Path Distillation
Biodiesel is purified through distillation operating under a vacuum
(in collaboration with the USDA)
Crude FOG biodiesel is:
• Dirty
• High in sulfur content
• Difficult to separate
Atmospheric boiling points:
• FAME: 344 °C
• FFA: 360 °C
Crude
• TAG: 884 °C Biodiesel
Short-path distillation purifies biodiesel: Wipers
• Under high vacuum: 1 mbar
Hot wall
• Low temperature:
• 115-190 °C @ 1 mbar
High
Cold wall
• 300-400 °C @ 1 mbar
vacuum
• Reduces sulfur:
• Lipids: 300 PPM
• Crude: 201 PPM
• Residue: 776 PPM
Residue
• Biodiesel: 27 PPM
Biodiesel
(ASTM grade = 15 PPM)
4.0
 For >15%Lipids
GTW Biodiesel
0.8
3.5

0.7
Soybean Biodiesel
3.0
0.6
2.5

0.5
2.0
0.4
1.5
0.3
Petroleum Diesel
Fossil Energy Ratio (FER)
TAG + Alcohol  Biodiesel + Glycerol
Alternative Biodiesel Production:
• Waste fats, oils, and greases (FOG)
• Contain primarily free fatty acids (FFA)
• Low to no feedstock cost
• More complex processing
Reactor developed at Drexel University for biodiesel production
Process Steam Energy Requirement
(MJ-natural gas/MJ-biodiesel)
Conventional Biodiesel Production:
• Refined vegetable oils (Soybeans)
• Contain primarily triglycerides (TAG)
• Expensive feedstock cost
• Cheap processing
Life Cycle Assessment (LCA)
FFA content (%)
Waste greases challenge wastewater treatment processes and lead to clogging and
sewer overflows. Lipids can be extracted from waste greases for production of
biodiesel.
a) Grease Trap Waste (GTW) from commercial kitchen effluent
b) Sewage Scum (SS) from primary tanks at wastewater treatment plants.
Bubble Column Reactor (BCR)*
Unreacted Methanol Ratio
Utilizing Waste Greases for Biodiesel Production
Fuel Life Cycle
BCR is Robust for:
• Waste Greases (FFA)
• Various Alcohols
• Elevated Water Content
Time to 95% FFA Conversion
(min)
Biodiesel is a renewable fuel that can be produced from a variety of vegetable
oils, animal fats, and waste greases. We utilize fats, oils, and greases (FOG)
from commercial kitchen wastewater and convert it into biodiesel. Research at
Drexel has demonstrated the technical feasibility of production of biodiesel
from FOG; however, commercial feasibility is limited by the variability of its lipid
content, which ranges between 2-30%, by volume. This poster presents a
process for conversion of FOG to biodiesel.
Novel Biodiesel Technology
Rising Bubbles
Introduction
GTW Biodiesel has
higher FER than
Soybean Biodiesel
 For > 2% Lipids
GTW Biodiesel has
higher FER than
Low Sulfur Diesel
1.0
0.2
Separation of lipids from grease
0.1
Methanol Recovery
Conversion of lipids to biodiesel
Purification of biodiesel
0.0
0%
5%
10%
15%
20%
25%
Lipid Content of Waste Grease (%)
30%
0.5
0.0
Where, LHV= lower heating
value, E=energy input,
i=process step 1,2,3:
1=harvest/separation
2=conversion/purification
3=biodiesel transport
Conclusions
• GTW-to-biodiesel is competitive with alternative biodiesels and low sulfur diesel
• Producing biodiesel under 10% lipid content is unfavorable due to process steam
requirement to separate lipids from grease
• Trap grease biodiesel FER is more favorable than soybean biodiesel >15% lipids
Future Work
•
•
•
•
Determine low lipid content cut-off where biodiesel production is unfavorable
Perform techno-economic analysis on biodiesel from trap grease
Analyze FER sensitivity to allocation methods for co-products
Optimize distillation conditions to reduce sulfur content, producing ASTM
biodiesel
Acknowledgments
Russell Reid * United States Department of Agriculture * Philadelphia Water Department
EPA P3 Design Award—SU-83352401 * GAAN RETAIN— Award No. P200A100117
EPA SBIR Grant—EP-D-14-09 * WERF Grant—U3R13