Methane and manure: Feasibility analysis of price and policy alternatives

Anaerobic digestion has a number of benefits as a manure treatment technology, including greenhouse gas and odor reduction, increased nutrient availability, and reduced pathogen risk. There is also a potential for electricity generation and energy recovery, although this is only achieved at additional cost. The economic feasibility of the energy conversion technology varies significantly with scale, with significant advantages for larger facilities. This study examined the feasibility of anaerobic digestion and methane recovery by applying the AgSTAR model to the full range of scales of swine and dairy producers in Iowa, under 24 policy scenarios. Based on these scenarios and accounting for model assumptions, it appears that both swine and dairy operations offer opportunities for installing either plug-flow or complete-mix digesters. For swine operations, farrow-to-finish and finishing operations needed more than 20,000 head and 5,000 head, respectively, to be economically feasible in the Midwestern U.S. Dairy operations hold considerably more economic promise, with feasible herd counts in the 150 to 350 head range for electricity prices of $0.12/kWh. Results indicate that increased energy prices and financial assistance will be needed to encourage significant numbers of facilities to recover energy from manure.