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CEIC-05-03

"A broad assessment of manure to power technology and investigation of a potential wind-biogas synergy"

Kyle Meisterling

Abstract:
The purpose of this paper is to present a broad assessment of animal manure to power technologies, and to investigate the possibility that manure to power could be coupled with a wind generator on-farm to produce more dispatchable power than with either technology alone. Flexible engineering and economic models are developed to determine the amount of energy available from manure; to characterize operation of anaerobic digesters; and to model a farm-level generating system which includes a wind turbine, digester, and methane storage. Maximum electrical generating capacity from manure in the U.S. is approximately 5.4 GW, with 2.7 GW coming from manure handled as solids (incineration or gasification), and 2.7 GW from anaerobic digestion of liquid manure. The cost of electricity from anaerobic digestion is approximately $ 0.06 / kWh for a farm with 700 dairy cows. Methane emissions from agriculture account for 7% of anthropogenic methane emissions in the U.S. Therefore, greenhouse gas reductions from anaerobic digestion, due to avoided methane emissions from manure storage, are substantial on a per kWh basis. A model of a digester system coupled with wind generation is presented, and a case study is carried out for a representative hog farm in NW Iowa. Compared to the stand-alone digester system, the coupled system provides 65% more baseload power in summer, and 170% more during spring. The cost of this electricity is approximately $0.075 / kWh. This cost is comparable to a stand-alone digester system operated as a peaking unit operated 12 hours per day.

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