Greenhouse Gas Reporting Program (GHGRP) emissions reported for the minerals sector increased from 103.2 million metric tons (MMT) CO₂e in 2011 to 114.3 MMT CO₂e in 2021, an increase of 11 percent. Reported emissions reached a maximum of 117.0 MMT CO₂e in 2014. Emissions for the sector increased by 4.4 percent in 2021 from 109.4 MMTCO₂e in 2020 to 114.3 MMTCO₂e in 2021. Emissions from all subsectors were higher in 2021 compared with 2020, except the other mineral production subsector.

The cement production subsector accounts for 60 percent of total reported emissions from the minerals sector and is largely responsible for trends in the minerals sector. Emissions from the lower-emitting glass and lime subsectors also affect the overall emissions trends for this sector.

Cement Production. The reported emissions for cement production include both the process emissions from the calcination of limestone and the combustion emissions from the burning of fuels. The process emissions consist of CO₂ generated during the calcination of limestone in a kiln to produce clinker. Emissions from calcination and the combustion of fossil fuels each account for about one-half of the total CO₂ emissions from kilns. Reported emissions from the cement production subsector have increased by 24 percent, from 55.6 MMT CO₂e in 2011 to 69.0 MMT CO₂e in 2021, even though there were 6 fewer cement production facilities reporting in 2021 than in 2011. From 2020 to 2021, emissions increased by about 4 percent, from 66.4 to 69.0 MMT CO₂e.

Increases and decreases in clinker production can be attributed to an increase or decrease in demand for cement in new residential and non-residential construction. Clinker production decreased in 2020 and CO₂e emissions declined by 0.86 MMT compared with 2019.  Production increased slightly in 2021 due to improved economic conditions following the COVID-19 pandemic; however, growth continued to be constrained by closed or idle plants, underutilized plant capacity, production disruptions due to upgrades, and relatively inexpensive imports. [1]

Lime Manufacturing. The reported emissions for lime manufacturing include both the process emissions and the combustion emissions from the burning of fossil fuels. The process emissions consist of CO₂ generated during the calcination of limestone. Major uses of lime include industrial, chemical, and environmental applications. Reported emissions from the lime production subsector have remained relatively steady as demand for lime has remained fairly stable. The emissions have varied from a low of 25.1 MMT CO₂e reported in 2020 to a high of 31.6 MMT CO₂e in 2014. The average emission rate from 2011 to 2021 is 29.0 MMT CO₂e. The lowest emissions occurred in 2020 and was likely due to plant shutdowns cause by the COVID-19 pandemic. Annual emissions for this subsector have no consistent upward or downward trend Emissions decreased from 29.7 MMT in 2018 to 25.1 MMT in 2020. Emissions increased again to 26.8 MMT CO₂e in 2021. The reported emissions correlate with lime production, which declined from a high of 18,000 million tons in 2018 to a low of 15,800 million tons in 2020. Lime production rebounded in 2021 to 17,000 metric tons due to improved economic conditions. [2]

Glass Production. Glass production is an energy and raw-material intensive process that results in the generation of CO₂ from both the energy consumed and the glass production process itself. The U.S. glass industry can be divided into four main categories: containers, flat (window) glass, fiber glass, and specialty glass. Most commercial glass produced is container and flat glass. [3] From 2011 to 2021, reported annual emissions from the glass production subsector has decreased from 8.4 MMT to 7.8 MMT CO₂e per year (8.0 percent). There were 12 fewer glass production facilities reporting in 2021 than in 2011. From 2020 to 2021, the annual emissions related to glass production increased from 7.4 MMT to 7.8 MMT CO₂e (4.5 percent). In general, these fluctuations were related to the behavior of the export market and the U.S. economy. Due to the COVID-19 pandemic, glass production dropped in the spring of 2020 but rebounded in 2021. [3] 

Soda Ash Manufacturing. CO₂ is generated as a byproduct of calcining trona ore to produce soda ash. Commercial soda ash is used as a raw material in a variety of industrial processes and in many familiar consumer products such as glass, soap and detergents, paper, textiles, and food. [3] Approximately 50 percent of soda ash is used for glass production. Soda ash production remained relatively steady between 2016 and 2019, however, production decreased by 11% in 2020 from 2019 levels primarily due to the COVID-19 pandemic and returned to pre-pandemic levels in 2021. [4] The emissions reported include both the process emissions and the emissions from burning fossil fuels. The reported emissions have varied from a low of 3.8 MMT CO₂e in 2016 to a high of 5.4 MMT CO₂e in 2014. Reported emissions in 2021 were 5.3 MMT CO₂e, an 11.7% percent increase from 4.8 MMT CO₂e in 2020, coinciding with a return to pre-pandemic levels of production.

Other Mineral Production. The other mineral production facilities are those operating under NAICS codes beginning with 327 (non-metallic mineral product manufacturing). Unlike the other subsectors, these facilities report only GHG emissions from stationary fuel combustion sources. Between 2011 and 2021, the reported emissions increased by 49 percent (1.74 MMT CO₂e) from 3.5 MMT CO₂e in 2011 to 5.3 MMT CO₂e in 2021. This increase was due to both an increase in the number of facilities reporting (30 more facilities reported in 2021 than in 2011) and an increase in the average annual emissions per facility (up from about 44,000 MT per facility in 2011 to 49,000 MT per facility in 2021). The maximum emissions for this sector were reported in 2019 (6.3 MMT CO₂e). Reported emissions have decreased since then with 5.7 MMT CO₂e reported in 2020, and 5.3 MMT CO₂e reported in 2021. The decrease in emissions observed between 2019 and 2021 is due in part to a decrease in the number reporting facilities, which decreased from 115 in 2019 to 114 in 2020 and 110 in 2021. The average emissions per facility also decreased from 49,213 MT in 2019 to 41,588 MT in 2021.

In recent years, this subsector has seen a reduction in emissions from combustion of coal and petroleum products. In 2018, emissions from coal combustion were 947,664 MT. By 2021, the number of facilities reporting coal combustion had dropped from 13 to 12 and reported CO₂e emissions had decreased to 446,351 MT. In 2019, emissions from coal combustion comprised about 13 percent of the total reported emissions for this subsector, but by 2021, coal combustion accounted for only 7.8 percent of the reported emissions. Emissions from combustion of petroleum products decreased from 287,829 MT in 2019 to 1,703 MT in 2021. However, emissions from all fuel types decreased between 2019 and 2021, with emissions from natural gas combustions decreasing from 5.1 MMT to 4.8 MMT. Natural gas combustion remains the largest contributor to emissions from this subsector, accounting for approximately 86 percent of emissions in 2011 and increasing to 90 percent in 2021.

References

[1]     U.S. Geological Survey (USGS), Minerals Yearbook, Cement, Advance Data Release, 2020 Annual Tables; Mineral Industry Surveys, Cement. March 2022; and Mineral Commodity Summaries, Cement, January 2022. Available https://www.usgs.gov/centers/national-minerals-information-center/cement-statistics-and-information.

[2]     USGS, Lime, Mineral Commodity Summaries, January 2022. Available at https://pubs.usgs.gov/periodicals/mcs2022/mcs2022-lime.pdf.

[3]     U.S. Environmental Protection Agency (USEPA), Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2020, 2022.

[4]     U.S. Geological Survey (USGS), Soda Ash. Mineral Commodity Summaries, January 2022.