Manure digesters offer great opportunities for some livestock operations, but adoption of the technology can be challenging. A presentation at the 2010 World Dairy Expo in Madison, WI, outlined some of the advantages and drawbacks interested livestock producers may face.
Anaerobic digestion systems consist of a manure collection system, a digester, a gas-handling mechanism and a gas use device that captures and combusts biogas to produce electricity, heat or hot water, explains Chris Voell, program manager of the AgSTAR Program, climate change division of the Environmental Protection Agency (EPA). Biogas is produced when the organic matter in manure decomposes anaerobically, in the absence of oxygen. Biogas typically contains 60-70% methane, which is the primary constituent of natural gas. This clean-burning fuel can be collected and burned to supply on-farm energy needs for electricity or heating. Voell says as of April 2010 there were an estimated 150 manure-based digester projects operating in the United States. Of that total, around 110 were in use on dairy farms, with 15 digesters operating on swine farms and the remainder in use in poultry and beef operations.
The four states of Wisconsin, New York, Pennsylvania and California comprise approximately 50% of the working digesters. These states have generally tended to have energy suppliers that support adoption of the technology – and pay competitive rates for the power. Voell says as of July 2010, total energy production from operating digester projects was estimated at 404 million kilowatts/year in the United States.
However, widespread adoption of the technology in this country is limited, in part because the energy policies at local, state and national levels can sometimes make the process of connecting to the power grid and selling energy somewhat difficult. As Voell points out, the rates paid by energy companies varies greatly from state to state. “In Vermont, producers are paid $.14 to $.18 per kilowatt, compared to payments of around $.03 in the Midwest. So consequently the industry in Vermont is growing very fast. If we can fix some of the energy policy challenges in different parts of the country, I’m convinced the number of digesters will go up,” Voell says. He cites the example of Germany, which has approximately 5,000 manure digesters. Government support means German producers are paid $.20 to $.25 per kilowatt for the energy being generated.
Other major hurdles to adoption include the cost to set up a digester system, limited access to construction capital and federal incentives, and permitting and regulatory obstacles.
AgSTAR is an outreach program that is part of the U.S. Environmental Protection Agency and is charged with helping producers find information and learn about funding options. Designed to assist livestock producers in the evaluation and implementation of methane recovery systems, the AgSTAR program provides information about resources and possible funding sources that may be available for anaerobic digestion projects. Learn more at www.epa.gov/agstar/.