GHG Emissions Takeaways
Takeaways are key points detailed and referenced in the Greenhouse Gas Emissions section
U.S. Share of Total GHG Emissions
The U.S. is responsible for the largest share of historical GHG emissions; through 2021, the U.S. generated ~17% of historical global emissions.
The U.S. share of global annual emissions in 2024 was ~11%, while China’s share was ~29%.
On a per capita basis, in 2024 U.S. emissions were ~2.6 times the world average.
Understanding the outsized U.S. share of global historical (cumulative) contributions puts U.S. current contributions in a clearer perspective.
GHG emissions anywhere in the world become evenly mixed in the earth’s atmosphere in about a year, thereby redefining “the tragedy of the commons.”
Agricultural Emissions
In 2023, U.S. GHG emissions from on-farm agriculture were 10.5% of total U.S. emissions, including on-farm fuel and electric use.
Total U.S. agricultural emissions were responsible for slightly more than 1% of global GHG emissions.
Although U.S. emissions are mostly from CO2, about 90% of agricultural emissions are from nitrous oxide (N2O) and methane (CH4).
N2O is mostly generated from chemical fertilizers and manure on crops and grazing land; CH4 is from enteric fermentation and the handling of manure on factory farms.
About 15 to 18% of total U.S. GHG emissions is attributable to the entire food system (or food supply chain), including animal slaughter, food manufacturing and distribution, retail, food service, and restaurants.
Animal Ag Emissions
In 2023, animal agriculture’s GHG emissions were ~8% of total U.S. emissions.
About 80% of total agricultural emissions are from animal ag, including on-farm fossil fuel and electricity use, and emissions from feed crops and grazing lands.
The EPA does not explicitly acknowledge that emissions due to grazing and feed crops are attributable to animal agriculture; many industry groups inaccurately claim that emissions from animal ag are about 4% of total U.S. emissions.
There are large uncertainties and potential underestimates of emissions from U.S. agriculture, and therefore from U.S. animal agriculture; they are due to the outsized influence of methane and nitrous oxide, the difficulties in assigning precise impacts to those gases, the vast territory over which widely varying impacts unfold, the uncountable and unmonitored sources, and the climate-changing legacies from centuries of agricultural land transformation along with current day land use changes.