Chapter 5, Key Finding 1
Agricultural greenhouse gas (GHG) emissions in 2015 totaled 567 teragrams (Tg)1 of carbon dioxide equivalent (CO2e)2 in the United States and 60 Tg CO2e in Canada, not including land-use change; for Mexico, total agricultural GHG emissions were 80 Tg CO2e in 2014 (not including land-use change) (high confidence). The major agricultural non-CO2 emission sources were nitrous oxide (N2O) from cropped and grazed soils and enteric methane (CH4) from livestock (very high confidence, very likely).3
1 Excludes emissions related to land use, land-use change, and forestry activities.
2 Carbon dioxide equivalent (CO;2e): Amount of CO;2 that would produce the same effect on the radiative balance of Earth’s climate system as another greenhouse gas, such as methane (CH4) or nitrous oxide (N;2O), on a 100-year timescale. For comparison to units of carbon, each kg CO;2e is equivalent to 0.273 kg C (0.273 = 1⁄3.67). See Box P.2 in the Preface for more details.
3 Estimated 95% confidence interval lower and upper uncertainty bounds for agricultural greenhouse gas emissions: –11% and +18% (CH4 emissions from enteric fermentation) and –18% and +20% and –16% and +24% (CH4 and N;2O emissions from manure management, respectively; U.S. EPA 2018).