Proceedings available at: http://www.extension.org/67610 To improve the energy production and revenue generation, many farm digester operators are including off-farm feedstocks in the blend. Off-farm feedstocks are raw materials with high carbon concentrations that can be degraded anaerobically. Common off-farm feedstocks include food service or retail waste, food processing byproducts, residuals from biofuels production and FOG (fat, oil & grease) resulting from food preparation. Typically, off-farm feedstocks have a higher energy potential when compared to manure. Manures generally have biogas potential in the range of 280 to 500 L of biogas/kg of VS, compared to off-farm feedstocks which can range from 300 to 1,300 L of biogas/kg of VS [1]. In addition to the increased biogas production, revenue can also be generated from tipping fees collected for feedstock brought onto a farm. The tipping fee is typically comparable to the cost of disposing of the material at a landfill or wastewater treatment plant.

1. Valuing Feedstocks for Anaerobic
Digestion – Balancing Energy
Potential and Nutrient Content
April, 2013
Dana Kirk, Ph.D., P.E.
Louis Faivor
Steve Safferman, Ph.D., P.E.
Wei Liao, Ph.D., P.E.
Anaerobic Digestion Research and Education Center
Biosystems and Agricultural Engineering

2. Industry growth – on-farm anaerobic digesters
2012 –192 operating systems
Up from 151 systems in 2010

3. • Revenue generation
• Low value of products
• Assessing value of environmental benefits
• Access to markets
• Location
• Utilities
• Capital cost
• Manure & nutrient management
• Feedstock availability
• Technological gaps
• Nutrient recovery
• CNG vehicle conversion
Challenges with anaerobic digestion

4. • Pro’s & con’s
• Energy potential
• Nutrients
• Tipping fees
• Infrastructure
• Regulatory
• Management
Non-farm feedstock as a way to address revenue

5. Disclaimer

6. Energy Potential

7. ADREC classification of feedstock
Values
Feedstock Count (n) Avg, TS raw (%) Avg, VS raw (% of TS)
Avg of Normalized
per Initial VS, Biogas
Production (mL/mg) Max Methane (%)
Acid food 3 5.74% 58.77% 0.427 70.67%
Algae 1 1.01% 50.29% 0.051 60.00%
Bakery 1 92.86% 71.51% 0.169 15.91%
Blend
Beef 6 92.86% 71.51% 0.433 66.92%
Chicken 3 0.85% 59.04% 0.477 60.33%
Dairy 141 14.01% 68.56% 0.466 63.19%
Pomace 16 0.135 25.81%
Swine 16 0.110 25.83%
Undisclosed 3 19.54% 88.07% 2.913 70.67%
Blend Total 185 16.94% 68.87% 0.445 56.92%
Dairy
Cheese whey 3 28.16% 82.19% 1.204 70.28%
Whey 3 6.06% 68.38% 1.218 64.17%
Dairy Total 6 17.11% 75.29% 1.211 67.23%
Dairy food 1 6.60% 74.63% 0.452 75.00%
Food manufacture 10 25.63% 80.96% 1.469 69.20%
Food waste
Cafeteria
(blank)
Cafeteria - breakfast 1 20.31% 77.04% 0.451 74.00%
(blank) Total 1 20.31% 77.04% 0.451 74.00%
Cafeteria Total 1 20.31% 77.04% 0.451 74.00%
Food waste 6 27.37% 80.32% 1.445 59.11%
Food waste Total 7 26.20% 79.78% 1.303 61.24%
Formic acid 1 0.17% 78.70% 0.199 0.00%
• 14 general categories of non-farm substrate
• 558 data points as of June, 2012

8. Energy potential of non-farm feedstock
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BiogasPotential(ft3/tonVS)
Substrate

9. Feedstock
Biogas Potential (ft3/ton VS) TS VS
Low High % %
Liquid dairy manure 16,018 3.3% 2.3%
Cheese Whey 22,746 32,000 5.3% 4.5%
Fish offal 28,833 35.4% 29.2%
FOG/food grease 15,378 29,794 60.2% 58.3%
Mixed food waste 14,417 20.3% 15.6%
Food processing waste 21,785 26,590 52.3% 50.6%
Fruit & Vegetable waste 16,659 18,902 11.2% 10.6%
Glycerin 27,872 32,000 29.8% 26.8%
Switchgrass, fresh 10,892 51.0% 48.8%
Waste Potatoes 17,300 23.2% 16.5%
Energy potential of non-farm feedstock

10. Energy potential of non-farm feedstock
0
2000
4000
6000
8000
10000
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BiogasPotential(ft3/tonasis)
Substrate

11. Digester feedstocks & nutrients

12. Feedstock
P2O5
(lb/ton)
TN
(lb/ton)
Fish offal 59 317
FOG 3 to 16 24 to 37
Mixed food waste 20 to 118 116
Food processing waste 8 to 43 32 to 42
Glycerin 19 to 33 38
Meat 31 to 69 69 to 300+
Milk 51 44
Nutrient composition of non-farm feedstock

13. Feedstock nutrients: benefit or liability?
Acres Needed to Utilize P2O5
Feedstock P2O5
(lb/ton of
feedstock)
Alfalfa
(8 ton/ac)
Corn Grain
(180 bu/ac)
Corn Silage
(20 ton/ac)
Soybean
(60 bu/ac)
Wheat
(75 bu/ac)
Fish offal 59 0.6 0.9 0.9 1.2 1.3
FOG 3 to 16 <0.2 <0.2 <0.2 <0.3 <0.3
Mixed food waste 20 to 118 0.2 to 1.1 0.3 to 1.8 0.3 to 1.8 0.4 to 2.5 0.4 to 2.5
Food processing
waste
8 to 43 0.1 to 0.4 0.1 to 0.7 0.1 to 0.7 0.2 to 0.9 0.2 to 0.9
Glycerin 19 to 33 0.2 to 0.3 0.3 to 0.6 0.3 to 0.5 0.4 to 0.7 0.4 to 0.7
Meat 31 to 69 0.3 to 0.7 0.5 to 1.0 0.5 to 1.1 0.7 to 1.4 0.7 to 1.5
Milk 51 0.5 0.8 0.8 1.1 1.1
Agronomic land base for required for phosphorus utilization
Nutrient Recommendations for Field Crops in Michigan. (Warncke et al., 2004a)

14. Feedstock nutrients: benefit or liability?
Acres Needed to Utilize TN
Feedstock TN
(lb/ton of
feedstock)
Alfalfa
(8 ton/ac)
Corn Grain
(180 bu/ac)
Corn Silage
(20 ton/ac)
Soybean
(60 bu/ac)
Wheat
(75 bu/ac)
Fish offal 317 0.9 2.0 1.7 1.4 3.5
FOG 24 to 37 0.1 0.2 <0.2 <0.2 0.3 to 0.4
Mixed food waste 116 0.3 0.7 0.6 0.5 1.3
Food processing waste 32 to 42 0.09 to 0.1 0.2 to 0.3 0.2 0.1 to 0.2 0.4 to 0.5
Glycerin 38 0.1 0.2 0.2 0.2 0.4
Meat 69 to 300 0.2 to 0.8 0.4 to 1.9 0.4 to 1.6 0.3 to 1.3 0.8 to 3.3
Milk 44 0.1 0.3 0.2 0.2 0.5
Nutrient Recommendations for Field Crops in Michigan. (Warncke et al., 2004a)
Agronomic land base for required for nitrogen utilization

15. Substrate
P2O5
(lb/ton)
P2O5 value
($/ton)
Fish offal 59 $30
FOG 3 to 16 $2 to $8
Mixed food waste 20 to 118 $10 to $60
Food processing waste 8 to 43 $4 to $22
Glycerin 19 to 33 $10 to $17
Meat 31 to 69 $16 to $35
Milk 51 $26
Feedstock nutrients: benefit or liability?
Feedstock nutrient fertilizer values

16. Substrate
P2O5
(lb/ton)
P2O5 value
($/ton)
TN
(lb/ton)
TN value
($/ton)
Fish offal 59 $30 317 $200
FOG 3 to 16 $2 to $8 24 to 37 $15 to $23
Mixed food waste 20 to 118 $10 to $60 116 $73
Food processing waste 8 to 43 $4 to $22 32 to 42 $20 to $26
Glycerin 19 to 33 $10 to $17 38 $24
Meat 31 to 69 $16 to $35 69 to 300+ $43 to $189
Milk 51 $26 44 $30
Feedstock nutrients: benefit or liability?
Feedstock nutrient fertilizer values

17. Tipping fees

18. • Landfill1
• National average tip fee of $18.43 per ton MSW
• Largest public and private landfills is $49.27 per ton
• Least cost in the western US, highest cost in the east
($100+/ton)
• Cost associate with waste characteristics
• Wastewater2
• FOG tip fee ranges from $0.05 to $0.15 per gallon ($12 to
$36/ton)
• Fee vary depending on waste characteristics
• Availability can be an issue
Tipping fees
1 2012. Tipping fees vary across the U.S.
http://www.wasterecyclingnews.com/article/20120720/NEWS01/120729997/tipping-fees-vary-across-the-u-s
2 Partanen, W.E. 2008. Fats, Oils & Grease to Green Energy

19. It could be worse!

20. • Planning since 2006, seriously since 2010
• MSU South Campus anaerobic digester planning (2006)
• Goals energy, odor control, renewable energy credits
• MSU feedstock only 150 to 180 kW
• Not economically viable
• Including non-farm feedstocks (2010)
• MSU + non-farm (campus) feedstock 380 to 450 kW
• Capital cost increased $500,000
• Tipping fees = 37% of the revenue
• Disposal cost increased by $50,000 ($0.32/gal)
• Non-farm feedstocks & net metering allowed the
business plan to work
South Campus AD Proposed Feedstock Blend

21. MSU South Campus Anaerobic Digester

23. • Non-farm substrates do impact project financials
• Do your homework on non-farm substrates
• Energy potential
• Composition (solids, COD, nutrients…)
• Consistency
• Current management practice/tipping
• Plan for changing feedstocks
• Don’t forget the digestate
• Understand the regulatory constraints
Conclusion

24. Questions?