Accomplishments
U.S. Farm Anaerobic Digestion Systems: A 2011 Snapshot (PDF) (2 pp, 720K) provides a summary of the data and trends for manure projects last year.
The AgSTAR Program has been very successful in encouraging the development and adoption of anaerobic digestion technology. The program was established in 1994, and by the end of 2011 the number of operational digester systems had reached 176 systems across the United States. This growth has produced significant environmental and energy benefits, including in 2011 alone, approximately 541,000 MWh equivalent of energy generation.
Total Energy Production (As of December 2011)
Numbers represent total annual energy production in MWh equivalent
Number of Operating Digesters (As of December 2011)
Total farm-scale projects: 161
Total regional/centralized projects: 15
The development of anaerobic digesters for livestock manure treatment and energy production has accelerated at a very fast pace over the past few years. Factors influencing this market demand include: increased technical reliability of anaerobic digesters through the deployment of successful operating systems over the past five years; growing concern of farm owners about environmental quality; an increasing number of state and federal programs designed to cost share in the development of these systems; increasing energy costs and the desire for energy security; and the emergence of new state energy policies (such as net metering legislation) designed to expand growth in reliable renewable energy and green power markets.
Financial incentives have increased the deployment rate of manure digester systems. For example, grants and loans awarded by USDA Rural Development through the Farm Bill have been one of the primary methods for farms to partially fund installation of commercially proven livestock waste digestion technologies.
Estimated Annual Emission Reductions from Anaerobic Digestion
*Avoided emissions calculated based on EPA eGRID national average emission rates for electricity projects and EPA's "Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2006" for non-electricity projects. EPA eGRID data unavailable for 2001, 2002, 2003, and 2006 so values were extrapolated based on a linear decrease from 2000 to 2004 and from 2005 to 2007. EPA eGRID data for 2007 and EPA greenhouse gas inventory data for 2006 were assumed for subsequent years as these are the most recent data available.
Anaerobic digesters reduce greenhouse gas emission reductions in two ways. The first is the direct methane emission reduction from the capture and burning of biogas that otherwise would escape into the atmosphere from the waste management system. For projects that generate energy, a second benefit is the avoided emissions of greenhouse gases (CO2, methane, and nitrous oxide) and other pollutants from the use of biogas to displace fossil fuels that otherwise would be used to generate energy. The graph above shows the annual emission reductions, including both direct reductions and avoided emissions, resulting from anaerobic digesters since 2000.