Greenhouse Gas Emissions from Livestock and Poultry

In 2008 the Environmental Protection Agency (EPA) estimated that only 6.4% of U.S. greenhouse gas (GHG) emissions originated from agriculture. Of this amount, 53.5% comes from animal agriculture. Agricultural activities are the largest source of N2O emissions in the U.S. accounting for 69% of the total N2O emissions for 2009. In animal agriculture, the greatest contributor to methane emissions is enteric fermentation and manure management. Enteric fermentation is the most important source of methane in beef and dairy production, while most of the methane from poultry and swine production originates from manure. The main cause of agricultural nitrous oxide emissions is from the application of nitrogen fertilizers and animal manures. Application of nitrogenous fertilizers and cropping practices are estimated to cause 78% of total nitrous oxide emissions. Based on the life cycle assessment of beef cattle, 86.15% of the GHGs are emitted during the production stage, while 68.51% of emissions take place during the production of pork and 47.82% of GHG emissions occur during the production stage of broiler chickens. The majority of the emissions from the beef cattle production comes from enteric fermentation while manure management is the major source during swine production and propane use during broiler poultry production.