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AgSTAR is one of EPA’s climate-protection partnership programs, which promotes investments in alternative energy technologies by encouraging the development and adoption of anaerobic digestion (AD) technology in the livestock sector. Since 2000, the use of biogas recovery systems with AD in the livestock sector has continued to increase, which has led to meaningful reductions in greenhouse gas emissions.
Learn more about these programs, including AgSTAR, in the Office of Atmospheric Programs: Climate Protection Partnerships 2012 Annual Report (PDF) (48 pp, 4.5 MB)
AgSTAR Annual Emission Reductions (2000-2012)
2013 Use and Benefits of AD in the Livestock Sector
From its preliminary analysis, AgSTAR estimates that approximately 239 AD systems were operating at commercial livestock farms in the United States in 2013. Learn more about AD Projects.
In 2013, AD systems directly reduced emissions by an estimated 2.06 million metric tons of CO2 equivalent (MMTCO2e) and approximately 0.47 MMTCO2e was avoided, producing a total emission reduction of 2.53 MMTCO2e. To complement the Annual Report, the chart below distinguishes the portion of the total emissions that were directly reduced and the emissions avoided from the reduction in fossil fuel use.
- Environmental and Energy Benefits
- Greenhouse Gas Equivalencies
- Anaerobic Digester System Designs and End Uses of Biogas
- Printer-friendly version of the 2013 Use and Benefits of AD in the Livestock Sector (PDF) (3 pp, 618 K)
Environmental and Energy Benefits
Greenhouse Gas Emission Reductions (2000-2013)
AD systems reduce greenhouse gas (GHG) emissions in two ways. First, direct methane emissions are reduced by capturing and burning biogas that otherwise would escape into the atmosphere. Second, AD projects generate energy that displaces the use of fossil fuels, resulting in the avoidance of GHG emissions and other pollutants. In 2013, AD systems directly reduced emissions by an estimated 2.06 million metric tons of CO2 equivalent (MMTCO2e) and approximately 0.47 MMTCO2e was avoided, producing a total emission reduction of 2.53 MMTCO2e.
To be consistent with the Fourth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC AR4) methodology, AgSTAR’s emission reduction calculations have been updated to reflect a global warming potential (GWP) of 25 for methane for 2013 and prior years.
Energy Generation (2000-2013)
AD systems generate usable energy each year by using biogas to generate electricity, as a boiler fuel for space or water heating, or for a variety of other uses. Approximately 840 million kilowatt hours (kWh) equivalent of energy was generated by AD systems on livestock farms during 2013.
Greenhouse Gas Equivalencies
Understanding greenhouse gas emission reductions is challenging, so it helps to think of the environmental benefits in terms that are more relatable. Using EPA’s Greenhouse Gas Equivalencies Calculator, equivalencies are presented below for the total estimated emissions reductions from AD systems on livestock farms in 2013 (2.53 MMTCO2e).
CO2 emissions from one of the following:
Annual GHG emissions from one of the following:
|906,810 tons of waste sent to a landfill|
|129,677 garbage trucks of waste recycled instead of landfilled|
Carbon sequestered by one of the following:
|64,871,795 tree seedlings grown for 10 years|
|2,073,770 acres of U.S. forests in one year|
|19,535 acres of forests preserved from conversion to cropland in one year|
Anaerobic Digester System Designs and End Uses of Biogas
Operating AD System Designs in 2013
Operational AD systems use several types of technologies to generate power. Complete mix and mixed plug flow designs accounted for 65 percent of all operational AD systems in 2013.
Trends in AD System Designs (2000-2013)
Complete mix and mixed plug flow systems continue to be the most common designs. AgSTAR anticipates that the use of complete mix designs will continue to expand as farms take advantage of opportunities offered through codigestion, which refers to the simultaneous anaerobic digestion of multiple organic wastes in one digester.
End Uses of Biogas in 2013
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.
Trends in End Uses of Biogas (2000-2013)
Combined heat and power continues to be the most common use for biogas followed by electricity generation. Visit the projects page to access details about AD projects across the United States.