Sources: U.S. Environmental Protection Agency; CMCM staff

The Environmental Protection Agency’s just-published Inventory of U.S. Greenhouse Gas Emissions and Sinks cites 5.586 billion metric tons (mt) of carbon dioxide equivalent (CO₂e) emissions for 2021, a 6 percent increase over the prior year. EPA assigns CO₂e metrics by UN Intergovernmental Panel on Climate Change-designated global warming potential, where carbon dioxide, methane and nitrous oxides are respectively weighted 1, 28 and 265, while certain hydrofluorocarbons reach into the four- or five-digit range. 

2021 U.S. GREENHOUSE GAS EMISSIONS BY SECTOR, COMPOUND

The Inventory spans six economic sectors; the third largest, Industry, accounted for 24 percent, or 1.34 billion mt of CO₂e in 2021. Within Industry, EPA reports emissions for two key construction inputs: Cement Production, 41.3 million mt; Iron and Steel Production, 38.4 million mt. In comparison to widely adopted metrics suggesting the sectors each account for 7-8 percent of global GHG emissions, cement and iron/steel each contributed about 0.7 percent of the U.S. 2021 output. EPA researchers calculate CO₂e totals for cement and steel by factoring fuel or source mixes behind combustion phases and process electricity. 

“For 30 years EPA has worked with researchers, federal partners, and stakeholders to produce a detailed and complete inventory of U.S. greenhouse gas emissions and sinks,” says EPA Office of Air and Radiation Principal Deputy Assistant Administrator Joseph Goffman. “This work reflects our commitment to transparency, data quality, and timeliness as we meet our inventory obligations under the United Nations Framework Conventions on Climate Change.”