Found on US EPA 1990-2020 Report: Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2021, updated 04/2023 (epa.gov).
Total U.S. emissions for 2021 (bottom Table ES-2): 6,340.2 MMT CO2 eq.
Beef Cattle Emissions for 2021:
Total beef cattle emissions 2021: 139.1 + 2.0 + 8.3 = 149.4 MMT CO2 Eq
(149.4 MMT CO2 Eq / 6,340.2 MMT CO2 Eq) = 0.0236 MMT CO2 Eq or 2.36% (rounded to 2.4% if rounding to the nearest tenth, or 2% if rounding to nearest whole number)
Sources:
EPA (2023). Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2021. U.S. Environmental Protection Agency, EPA 430-R-23-002. https://www.epa.gov/ghgemissions/inventory-us-greenhouse-gas-emissions-and-sinks-1990-2021.
Calculations: In the Putman et al., 2023 life cycle assessment, total GHG emissions from beef production (cradle to grave) are calculated as 249.8 Tg CO2e.
[In 2017] 42.7 kg Co2e per kg beef x 5.85 Tg beef produced and consumed = 249.8 Tg CO2e.
*Note Tg is equivalent to million metric tons (MMT)
The U.S. Environmental Protection Agency (EPA) GHG Inventory reports total U.S. GHG emissions in 2017 were 6561.8 MMT CO2e.249.8 MMT CO2e / 6561.8 MMT CO2e = 3.8%
Sources:
EPA (2023). Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2021. U.S. Environmental Protection Agency, EPA 430-R-23-002. https://www.epa.gov/ghgemissions/inventory-us-greenhouse-gas-emissions-and-sinks-1990-2021.
Putman, B., C. A. Rotz, and G. Thoma. 2023. A comprehensive environmental assessment of beef production and consumption in the United States. J. of Cleaner Production. doi.org/10.1016/j.jclepro.2023.136766.