Greenhouse gas inventories from animal agriculture for the United States

The 2005 EPA greenhouse gas emissions inventory estimates that in 2003 total U.S. greenhouse gases were 6900.2 Tg CO2 Eq. of which 486.4 Tg CO2 Eq. was from agriculture. The contribution of greenhouse gases from agriculture was estimated to be 7.0% of the total emissions. Using the same methodology, EPA estimated that 1990 contributions from agriculture were 418.4 Tg CO2 Eq. In EPA estimates, contributors to the inventory include methane from enteric fermentation and manure management, and N2O from manure management and agricultural soils management. The category agricultural soils management includes N2O emissions from pasture, range and paddock distribution, synthetic fertilizer use, sewage sludge application, and some other cropping practices. Other contributors to the agriculture sector include livestock facility fuel and power associated emissions, as well as fuel-CO2 and N2O from growth and processing of the crops consumed by livestock. To date, these other contributions are not separately identified by economic sector in any available U.S. inventory. Adding the categories currently unaccounted for into the agricultural inventory would be expected to increase the total from 486.4 to approximately 670 Tg CO2 Eq. and the livestock sector contribution could reach approximately 380 Tg/year CO2 Eq.