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Converting Dairy Manure into Energy. An introduction to anaerobic digestion of farm waste

Converting Dairy Manure into Energy. An introduction to anaerobic digestion of farm waste. Stefan Grimberg Associate Professor Dept. Civil Environ. Eng Clarkson University. Thank you to Floyd Schanbacher. Anaerobic Digester Potential Benefits. Odor Control Reduced liability

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Converting Dairy Manure into Energy. An introduction to anaerobic digestion of farm waste

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  1. Converting Dairy Manure into Energy.An introduction to anaerobic digestion of farm waste Stefan Grimberg Associate Professor Dept. Civil Environ. Eng Clarkson University

  2. Thank you to Floyd Schanbacher

  3. Anaerobic Digester Potential Benefits • Odor Control • Reduced liability • Manure stabilization • Help with nutrient management • Soil stability • Energy generation • Offset farm electricity requirements from grid • Sale of extra energy • Heat generation to reduce fuel required • Reuse of bedding solids • Offset bedding cost

  4. Plug Flow Digesters • Little mixing • Few mechanical parts • Simple

  5. Mixed Digesters Mechanical mixing in tank More gas production Slightly higher capital cost

  6. Community Digester Behringen co-fermentation plant in Germany

  7. Digester Feed

  8. Large-scale Digester Performance

  9. Capital Cost of Manure Management Technology Source: AgStar Publication:

  10. Digester economics • Dr. Fick’s estimated fixed of $660 per cow is a little low for the farms we are looking at. • Tinesdale farm (in Minnesota), with1800 cows, invested about $1,000 per head. • Good estimate $1,000 per cow? • At this capital assumption AD system become economical based on sold energy alone at power sale price of $0.09/kWh. (Mehta, 2002)

  11. Case Study • Gordondale Farms, Nelsonville, WI • 750 head dairy • Sell biogas to utility that generates electricity on site, utility owns and operates generator • Sell at 0.015 $/kWh generated Martin, J.H., 2005. An evaluation of a mesophilic, modified plug flow anaerobic digester for dairy cattle manure. Final report for EPA contract GS10F-0036K

  12. Summary

  13. Martin, 2005

  14. Martin, 2005

  15. Martin, 2005

  16. Martin, 2005

  17. Martin, 2005

  18. Martin, 2005

  19. Martin, 2005

  20. Martin, 2005

  21. Economic Evaluation • Capital costs with co/gen: $748,000 • Annual sale of power: $18,396 • Avoided annual bedding cost: $60,000 • Sale of extra solids: $8,600 • Total benefits: $86,996 • Payback period: Approx 6 years.

  22. Digester Systems Model Electricity offset Surplus electricity Surplus heat Cogen Biogas Heat Digester Solids Sep. Manure Other Input Spread liquid fraction Solids for bedding Sale of solids Solids field application

  23. Example • 500 cow dairy • Free stall barn • Scraped manure • Include flush from milking parlor • Northern NY

  24. Model Estimate: 500 cow dairy

  25. Run Digester Model • Demonstrate: • Effect of size • Power cost • Bedding off set • Any scenarios of interest?

  26. Conclusions • Anaerobic digestion of manure has significant potential to decrease fossil fuel use in rural areas. • Community digesters may be very cost effective due to larger scale and mixed feed composition

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