U.S. Agriculture and Forestry Greenhouse Gas Inventory: 1990-2013

The U.S. Agriculture and Forestry Greenhouse Gas Inventory: 1990–2013 was developed to update previous USDA greenhouse gas inventories and to revise estimates for previous years based on improved methodologies. This inventory provides a comprehensive assessment of the contribution of U.S. agriculture (i.e., livestock and crop production) and forestry to greenhouse gas (GHG) emissions. The document was prepared to support and expand on information provided in the official inventory of U.S. GHG Emissions and Sinks (U.S. GHG Inventory), which is prepared annually by the U.S. Environmental Protection Agency. Carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) concentrations in the atmosphere have increased by approximately 43 percent, 152 percent, and 20 percent respectively since about 1750. In 2013, total U.S. GHG emissions were 6,673 million metric tons of carbon dioxide equivalents (MMT CO2 eq.), rising 5.9 percent from 1990 estimates. Carbon sequestration in managed forests, urban trees, and harvested wood products (882 MMT CO2 eq.) reduced these emissions to a net 5,791 MMT CO2 eq. in the United States in 2013. Agriculture alone accounted for about 9 percent of total U.S. emissions (595 MMT CO2 eq.). The primary GHG sources from agriculture are N2O emissions from cropped and grazed soils (264 MMT CO2 eq.), CH4 emissions from ruminant livestock production (165 MMT CO2 eq.) and rice cultivation (8 MMT CO2 eq.), CH4 and N2O emissions from managed livestock waste (79 MMT CO2 eq.), and CO2 emissions from on-farm energy use (74 MMT CO2 eq.). The largest managed carbon sink in the United States is managed forests, which sequester 705 MMT CO2 eq. The U.S. agriculture and forestry sector in aggregate provided a net sink of 270 MMT CO2 eq. in 2013 (including GHG sources from crop and livestock production, grasslands, energy use, and GHG sinks for forests and urban trees). This report serves to estimate U.S. GHG emissions for the agricultural sector, to quantify uncertainty in emission estimates, and to estimate the potential of agriculture to mitigate U.S. GHG emissions.