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The AgSTAR Program has been very successful in encouraging the development and adoption of anaerobic digestion technology. By the end of 2012, the number of operational digester systems had reached 201 systems across the United States. Learn more about AD Projects.
AD System Designs and End Uses
Operational AD systems use several types of technologies to generate power. Half of the projects (10 of 20) that became operational in 2012 use a mixed plug flow design and 35 percent (7 of 20) use a complete mix design. As shown in the chart below, mixed plug flow and complete mix designs account for 65 percent of all operational AD systems.
Captured biogas is used to generate electricity, as a fuel for boilers or furnaces, treated to create compressed natural gas, or for a combination of uses. Combined heat and power continues to be the most common use for biogas followed by electricity generation, as illustrated below.
The growth in the agricultural AD market has produced significant energy benefits. In 2012 alone, approximately 625,000 MWh equivalent of energy was generated.
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.
In 2012, AD systems directly reduced emissions by 1.38 MMTCO2e and approximately 0.38 MMTCO2e was avoided, producing a total emission reduction of 1.76 MMTCO2e.
|Benefits||Estimates for 2012||Equivalents*|
|Direct Emissions Reductions||1.38 MMTCO2e||
|Avoided Emissions||0.38 MMTCO2e||
*Equivalency results calculated at www.epa.gov/cleanenergy/energy-resources/calculator.html.