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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.
2014 Use and Benefits of AD in the Livestock Sector
AgSTAR estimates that approximately 247 AD systems were operating at commercial livestock farms in the United States in 2014. Learn more about AD Projects.
Anaerobic digestion of livestock waste reduces greenhouse gas (GHG) emissions in two ways:
- Methane emissions are directly reduced as biogas is captured and used as a renewable fuel.
- The energy generated displaces the use of fossil fuels, further avoiding the emission of GHGs and other pollutants.
Learn more about:
- Environmental and Energy Benefits
- Greenhouse Gas Equivalencies
- Anaerobic Digester System Designs and End Uses of Biogas
Environmental and Energy Benefits
Greenhouse Gas Emission Reductions (2000-2014)
- In 2014, anaerobic digesters on livestock farms reduced GHG emissions by 3.97 million metric tons of CO2 equivalent (MMTCO2e)
- 3.44 MMTCO2e direct emission reductions
- 0.54 MMTCO2e emissions avoided
- Since 2000, anaerobic digesters on livestock farms have reduced emissions by 21.85 MMTCO2e
The chart above distinguishes the portion of the total emissions that were directly reduced and the emissions avoided from the reduction in fossil fuel use.
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 2014 and prior years.
Energy Generation (2000-2014)
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.
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 2014 (3.97 MMTCO2e).
CO2 emissions from one of the following:
Annual GHG emissions from one of the following:
|1,422,939 tons of waste sent to a landfill|
|203,485 garbage trucks of waste recycled instead of landfilled|
Carbon sequestered by one of the following:
|101,794,872 tree seedlings grown for 10 years|
|3,254,098 acres of U.S. forests in one year|
|30,654 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 2014 (Total = 247)
|Induced Blanket Reactor||5||2%|
|Anaerobic Sequencing Batch Reactor||3||1%|
Operational AD systems use several types of technologies to generate power. Complete mix and mixed plug flow designs accounted for 42 percent of all operational AD systems in 2014.
Trends in AD System Designs (2000-2014)
Plug flow and complete mix 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 2014 (Total = 247)
|Combined Heat and Power (CHP)||124||50%|
|Flared Full Time||12||5%|
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 (2000-2014)
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.