http://www.epa.gov/nitrousoxide/sources.html Nitrous Oxide
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Climate Change
Nitrous Oxide
Sources and Emissions
Sources and Emissions
Photo collage of selected nitrous oxide emission sources: agriculture, stationary combustion, and mobile sources.
Where Does Nitrous Oxide Come From?
Human-Related Sources in the United States
Natural Sources - Global Emissions
Where Does Nitrous Oxide Come From?
Nitrous oxide (N2O) is produced by both natural and human-related sources. Primary human-related sources of N2O are agricultural soil management, animal manure management, sewage treatment, mobile and stationary combustion of fossil fuel, adipic acid production, and nitric acid production. Nitrous oxide is also produced naturally from a wide variety of biological sources in soil and water, particularly microbial action in wet tropical forests.
Nitrous oxide emission levels from a source can vary significantly from one country or region to another, depending on many factors such as industrial and agricultural production characteristics, combustion technologies, waste management practices, and climate. For example, heavy utilization of synthetic nitrogen fertilizers in crop production typically results in significantly more N2O emissions from agricultural soils than that occurring from less intensive, low-tillage techniques. Also, the presence or absence of control devices on combustion sources, such as catalytic converters on automobiles, can have a significant affect on the level of N2O emissions from these types of sources.
Emission inventories are prepared to determine the contribution of emissions from different sources. The following sections present information from inventories of U.S. human-related and natural sources of N2O globally. For more information on international emission of N2O from human-related sources, visit the International Analysis section of this site.
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Human-Related Sources in the United States
Table 1 shows the level of emissions from individual sources for the years 1990, 1995, 2000 and 2005 to 2008.
Table 1 U.S. Nitrous Oxide Emissions by Source (TgCO2 Equivalents)
Source Category 1990 1995 2000 2005 2006 2007 2008
Agricultural Soil Management 203.5 205.9 210.1 215.8 211.2 211.0 215.9
Mobile Combustion 43.9 54.0 53.2 36.9 33.6 30.3 26.1
Nitric Acid Production 18.9 21.0 20.7 17.6 17.2 20.5 19.0
Manure Management 14.4 15.5 16.7 16.6 17.3 17.3 17.1
Stationary Combustion 12.8 13.3 14.5 14.7 14.5 14.6 14.2
Adipic Acid Production 15.8 17.6 5.5 5.0 4.3 3.7 2.0
Wastewater Treatment 3.7 4.0 4.5 4.7 4.8 4.9 4.9
N2O from Product Uses 4.4 4.6 4.9 4.4 4.4 4.4 4.4
Forest Land Remaining Forest Land 2.7 3.7 12.1 8.4 18.0 16.7 10.1
Composting 0.4 0.8 1.4 1.7 1.8 1.8 1.8
Settlements Remaining Settlements 1.0 1.2 1.1 1.5 1.5 1.6 1.6
Field Burning of Agricultural Residues 0.4 0.4 0.5 0.5 0.5 0.5 0.5
Incineration of Waste 0.5 0.5 0.4 0.4 0.4 0.4 0.4
Wetlands Remaining Wetlands + + + + + + +
International Bunker Fuels 1.1 0.9 0.9 1.0 1.2 1.2 1.2
Total for U.S. 322.3 342.5 345.5 328.3 329.5 327.7 318.2
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Scanning that page from EPA, it would appear N20 is a concern associated with factory farming (industrial quantities of animal poops) and with car emissions.