Emission Trends in Metals Production

Reported emissions from the metals sector decreased significantly from 112 million metric tons (MMT) CO2e in 2011 to 78 MMT CO2e in 2020, a decrease of 30 percent. Reported emissions decreased steadily between 2011 and 2016, with the largest decrease occurring in 2015 (13%). Emissions have remained below 2014 levels in recent years. Annual emissions from the metals sector decreased in 2016 to 88 MMT CO2e, and then increased slightly in 2017 (89 MMT CO2e) and 2018 (92 MMTCO2e). Emissions then decreased again in 2019 and 2020. Emissions in 2020 were 12 MMT CO2e (13%) lower than 2019. Metals production experienced decreased demand from the manufacturing industry related to impacts of the COVID-19 pandemic. [1] Capacity utilization within primary metal manufacturing (NAICS codes beginning with 331) declined each month from January through May (from 70% to 51%) and then began to gradually recover through December (to 65%). [2]

Iron and Steel Production. Iron and steel production are responsible for approximately 80 percent of the reported emissions in the sector. Crude steel production is closely tied to economic conditions and can vary from year to year, with corresponding fluctuations in emissions. Since 2011, iron and steel production has decreased as shown in the table below. The decrease in emissions for this industry can also be attributed to restructuring of the industry, technological improvements, and increased scrap steel utilization, which resulted in a corresponding drop in emissions.[3] The number of reporters in the iron and steel subsector also decreased during this period from 129 facilities in 2011 to 123 facilities in 2017. In 2020, production of pig iron and raw steel decreased by 19 percent and 18 percent from 2019, respectively, while CO2e emissions decreased by 10.0 MMT (14 percent), and the number of reporters remained the same at 122.

Emission Source

Annual Production (million metric tons)











Pig Iron Production











Raw Steel Production











Note: Data obtained from United States Geological Service Mineral Commodity Summaries 2021, available at: https://minerals.usgs.gov/minerals/pubs/commodity/iron_&_steel/

Aluminum Production. For 2020, aluminum production accounts for 4.9 percent of the total CO2e emissions reported for the metals sector. Emissions in this subsector have decreased from a high of 7.3 MMT CO2e in 2011 to a low of 2.7 MMT CO2e in 2017. In 2018 and 2019, emissions steadily increased to 3.4 MMT CO2e and 4.0 MMT CO2e, respectively. From 2019 to 2020, emissions decreased by approximately 5 percent to 3.8 MMT CO2e. The decrease in emissions from 2011 to 2017 was due to industry emission reduction efforts and lower aluminum production. [3] The increases in emissions reported in 2018 and 2019 are likely due to increased aluminum production resulting from improved market conditions for U.S. aluminum plants. After declining each year since 2012, primary aluminum production increased in 2018 and 2019 by 20 percent and 23 percent, respectively. Primary aluminum production facilities were exempted from COVID-19 lockdown orders and estimated production in 2020 decreased only slightly from 2019 levels (0.9%). [4]

Ferroalloy, Lead, Magnesium, and Zinc. Ferroalloy, lead, magnesium, and zinc production account for about 5 percent of the total CO2e emissions reported for the metals sector in 2020. The combined emissions reported for the ferroalloy, lead, magnesium, and zinc subsectors have decreased from 6.1 MT CO2e in 2011 to 4.1 MMTCO2e in 2020. The largest reduction was in the magnesium production subsector, which decreased by 913,000 MT CO2e (about 62 percent). The reduction in emissions for the ferroalloy, lead, magnesium, and zinc subsectors is partly due to industry emission reduction efforts and to an overall decrease in the number of reporters, which decreased from 38 in 2011 to 34 in 2020. The emissions in 2020 were about 7 percent lower than reported in 2019, although the number of facilities reporting emissions remained unchanged.

Other Metal Production. The other metal production facilities are those operating under NAICS codes beginning with 331 (primary metal manufacturing) that are not otherwise subject to a metal subpart under Part 98, and includes iron foundries, facilities that engage in secondary smelting and alloying of aluminum, and facilities that manufacture finished products from purchased metals by rolling, drawing, and/or extrusion. This subsector accounts for about 10 percent of the total CO2e emissions from the metals sector. Unlike the other subsectors, these facilities report only GHG emissions from stationary fuel combustion sources. Overall, emissions reported by this subsector slightly increased from 9.4 MMT CO2e in 2011 to 9.5 MMT CO2e in 2019 before decreasing to 8.0 MMT CO2e in 2020. The number of reporters increased from 121 in 2011 to 131 in 2020. Emissions for this subsector increased between 2011 and 2014 by 13 percent (1.2 MMT CO2e) from 9.4 MMT CO2e to 10.6 MMT CO2e. This increase was due to both an increase in the number of facilities reporting (8 more facilities reported in 2014 than in 2011) and an increase of 4,570 MT CO2e in the average annual emissions per facility. Beginning in 2015, the average annual emissions per facility declined from 82,170 MT CO2e in 2014 to 68,421 MT CO2e in 2019. In 2020, average annual emissions per facility were 61,069 MT CO2e.

[1] U.S. Geological Survey, Annual Aluminum Mineral Commodity Summary, January 2021, Available at: https://www.usgs.gov/centers/nmic/mineral-commodity-summaries

[2] Board of Governors of the Federal Reserve System (US), Capacity Utilization: Manufacturing: Durable Goods: Primary Metal (NAICS = 331) [CAPUTLG331S], retrieved from FRED, Federal Reserve Bank of St. Louis; https://fred.stlouisfed.org/series/CAPUTLG331S, September 15, 2021.

[3]  U.S. Environmental Protection Agency, Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2019. April 14, 2021. EPA 430-R-21-005. Available at: https://www.epa.gov/sites/default/files/2021-04/documents/us-ghg-inventory-2021-main-text.pdf

[4] U.S. Geological Survey, Annual Aluminum Mineral Commodity Summary, January 2021, Available at: https://pubs.usgs.gov/periodicals/mcs2021/mcs2021-aluminum.pdf

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