The document discusses anaerobic digestion of farm waste to convert dairy manure into energy. It describes some benefits of anaerobic digestion including odor control, manure stabilization, and energy generation. It also discusses different types of digester systems, capital costs, case studies, and an example economic model of a 500 cow dairy farm converting manure into biogas through anaerobic digestion.

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

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

17. Community Digester Behringen co-fermentation plant in Germany

18. Digester Feed

19. Large-scale Digester Performance

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

23. Summary

24. Martin, 2005

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31. Martin, 2005

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

35. Model Estimate: 500 cow dairy -$1.8 Annual Net Benefit per Cow without excess heat and methane credits $13.54 Annual Net Benefit per Cow if excess heat cannot be sold $38.27 Annual Net Benefit per Cow $111,463 Total Annual Benefits $10,000 Onsite Fiber value $16,739 Tax Offset $8,495 Farm savings-Thermal (internal) $25,171 Farm savings-Electric (internal) $4,203 Renewable Energy Tax Credit $7,646 Methane Credit $12,368 Thermal Sales (surplus) $17,707 Electric Sales (surplus) $9,133 Fiber sales Potential Annual Benefits $23,553 Maintenance, Repair Annual Operating Costs $68,774 Total Annual Cap. Cost over 10 yrs $656,180 Digester/Cogen system Capital Cost Cost/Benefit Item