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Dairy Operations Make Most of Anaerobic Digesters

09 June 2009

US - As of February 2009, AgSTAR estimates that there are 125 farm-scale digesters operating at commercial livestock farms in the United States. 98 of these installations are systems that provide manure treatment for dairy farms.

Anaerobic digester systems can be installed successfully at commercial scale operations that collect manure as a liquid, slurry, or semi-solid. Existing farms use a variety of different types of digester designs and energy use technologies.

In 113 of the 125 operational systems, the captured biogas is used to generate electrical power, with many of the farms recovering waste heat for the electricity generating equipment for on-farm use. These systems generate about 244,000 MWh of electricity per year. The remaining 12 systems use the gas in boilers, upgrade the gas for injection into the natural gas pipeline, or simply flare the captured gas for odor control.

In total, the combustion of biogas at the digesters prevents the emission of about 36,000 metric tonnes of methane annually (756,000 metric tonnes of CO2 equivalent). In addition, the combustion of biogas displaces the use of fossil fuels, thus achieving additional emissions reductions of greenhouse gases and air pollutants.

Many of the operational, planned and under construction digester systems included in the database were funded in part by USDA Rural Development through the 2002 and 2008 Farm Bills.

Farm Type Number of Digester Projects
Dairy 98
Swine 19
Caged Layer 3
Duck 2
Broiler 1
Beef 1
Mixed 1

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