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Energy and Economic Assessment of Anaerobic Digesters and Biofuels for Rural Waste Management
Citation:
Abeles, T., D. Freedman, L. DeBaere, AND D. Ellsworth. Energy and Economic Assessment of Anaerobic Digesters and Biofuels for Rural Waste Management. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/7-78/174.
Description:
A technological and socioeconomic assessment of anaerobic digester feasibility for small to mid-size livestock operations was undertaken. Three full scale digesters and one pilot scale facility were under various degrees of monitoring and evaluation to assess design and operational problems as they affect the adoption and establishment of farm scale anaerobic digestors. Materials handling presented the greatest obstacle to satisfactory operation of the full scale systems. Conversion of the biogas to electricity via standard engine-generator sets is capital and maintenance intensive. Electrical conversion requires engine-generator sets which can add 30% to the cost of the system, and which have conversion efficiencies of only 10-25%. The system becomes more economical if the biogas can be used on site for direct thermal loads, suggesting that the economic feasibility of anaerobic digesters is site specific and should be closely integrated with the total farming operation. If excess engine heat can be recovered from electrical conversion equipment, and if provisions can be made on the farm to level electrical loads and conserve energy, then the economics are enhanced. Analysis was performed for farms with 100 animal units.