Chapter 2: Livestock and grazed lands emissions

Authors: OGLE, STEPHEN - Colorado State University; ITLE, COURTNEY - Eastern Research Group (ERG); Del Grosso, Stephen - Steve; EDQUEST, KARA - Eastern Research Group (ERG); ALLEN, AMBER - Eastern Research Group (ERG); STOUT, TARA - Eastern Research Group (ERG)

Submitted to: Government Publication/Report
Publication Type: Government Publication
Publication Acceptance Date: 12/1/2021
Publication Date: 1/19/2022
Citation: Ogle, S.M., Itle, C., Del Grosso, S.J., Edquest, K., Allen, A., Stout, T. 2022. Chapter 2: Livestock and grazed lands emissions. In: Hanson, W.L., Del Grosso, S.J., Gallagher, L. editors. U.S. Agriculture and Forestry Greenhouse Gas Inventory: 1990–2018. Technical Bulletin No. 1957. Washington, D.C.: United States Department of Agriculture, Office of the Chief Economist. p. 12-57.

Interpretive Summary: A total of 345 MMT CO2 eq. of greenhouse gasses (GHGs) were emitted from livestock, managed livestock waste, and grazed land in 2018. This represents about 56% of total emissions from the agricultural sector. Compared to the base year (1990), emissions from livestock sources were about 10% higher in 2018. Enteric fermentation contributed a little more than half (178 MMT CO2 eq.) of all emissions associated with livestock production, while soils from grazed lands (89 MMT CO2 eq.) and managed waste (81 MMT CO2 eq.) accounted for approximately 26% and 23%, respectively, of the total emissions. Grazed lands are estimated to be a small CO2 sink at about 13 MMT CO2 eq. in 2018. The largest total emissions associated with livestock production were from Texas (primarily from beef cattle) and California (mainly from dairy cattle). Emissions were also relatively high in Idaho, Montana, South Dakota, Nebraska, Colorado, Kansas, Oklahoma, Wisconsin, Iowa and Missouri. Beef cattle contributed the largest fraction (55%) of GHG emissions from livestock in 2018 followed by dairy cattle (31%) and swine (10%).

Technical Abstract: A total of 345 MMT CO2 eq. of greenhouse gases (GHGs) were emitted from livestock including enteric fermentation, managed livestock manure (includes solid and liquid waste), and grazed land in 2018. This represents about 56% of total emissions from the agricultural sector. Compared to the base year (1990), emissions from livestock sources were about 10% higher in 2018. There are three main sources of increased emissions: methane (CH4) and nitrous oxide (N2O) emissions from managed livestock manure and N2O emissions from grazed lands. These increases were partially offset because the CO2 sink strength of grazed lands increased. Enteric fermentation contributed a little more than half (178 MMT CO2 eq.) of all emissions associated with livestock production, while soils from grazed lands (89 MMT CO2 eq.) and managed manure (81 MMT CO2 eq.). accounted for approximately 26% and 23% respectively, of the total livestock emissions. All of the emissions from enteric fermentation and about 76% of emissions from managed livestock manure were in the form of CH4. Of the emissions from grazed lands, 87% were in the form of N2O from soils. Grazed lands are estimated to be a small CO2 sink at 13.4 MMT CO2 eq. in 2018. The largest total emissions associated with livestock production were from Texas (primarily from beef cattle) and California (mainly from dairy cattle). Emissions were also relatively high in Nebraska, Kansas, Wisconsin, Iowa, and Missouri. Beef cattle contributed the largest fraction (55%) of GHG emissions from livestock in 2018, with the majority of emissions in the form of CH4 from enteric fermentation and N2O from grazed land soils. Dairy cattle were the second-largest livestock source of GHG emissions (31%), primarily CH4 from enteric fermentation and managed manure. The third-largest GHG source from livestock was swine (10%), nearly all of which was CH4 from manure. Poultry have relatively low emissions, despite being the largest livestock group in number of animals, because this group produces very low enteric fermentation emissions.