Reported emissions from the minerals sector increased from 103.2 million metric tons (MMT) CO₂e in 2011 to 109.3 MMT CO₂e in 2020, an increase of 6 percent. Reported emissions reached a maximum of 117.0 MMT CO₂e in 2014. Emissions for the sector decreased by nearly 5 percent in 2020 from 114.8 MMTCO₂e in 2019 to 109.3 MMTCO₂e in 2020. Emissions from all subsectors were lower in 2020 compared with 2019.

The cement production subsector accounts for nearly 61 percent of total 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 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 19.6 percent, from 55.5 MMT CO₂e in 2011 to 66.4 MMT CO₂e in 2020. From 2019 to 2020, emissions decreased slightly, about 1 percent, from 67.1 to 66.4 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. According to the USGS [1], cement production was temporarily idled in many countries and localities in response to national lockdowns imposed in response to the COVID-19 pandemic. Disruptions to construction corresponded with reduced cement demand, and some planned cement plant openings and expansions were delayed. As shown in the table below, there is a high correlation between clinker production and emissions.

Lime Manufacturing. The 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 27.7 MMT CO₂e reported in 2016 to a high of 31.6 MMT CO₂e in 2014. Emissions for this sector increased between 2016 and 2018 likely due to increased lime production.[2] Emissions decreased slightly in 2019 and continued to decrease in 2020 down to 25.1 MMT CO₂e due to a decrease in lime production since 2018. [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. The majority of commercial glass produced is container and flat glass. [3] From 2011 to 2020, reported annual emissions from the glass production subsector has decreased from 8.4 MMT to 7.4 MMT CO₂e per year (12.0 percent). However, there were 9 fewer glass production facilities reporting in 2020 than in 2011. From 2019 to 2020, the annual emissions related to glass production decreased from 7.8 MMT to 7.4 MMT CO₂e (5.1 percent). In general, these fluctuations were related to the behavior of the export market and the U.S. economy. However, some commercial food and beverage package manufacturers are reportedly shifting from glass containers towards lighter and more cost-effective polyethylene terephthalate (PET) based containers, putting downward pressure on demand for glass. [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 17% in 2020 from 2019 levels primarily due to the COVID-19 pandemic. [4] The annual 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 and 2017. Emissions in 2020 were 4.8 MMT CO2e, a 9.4 percent decrease from 5.3 MMT CO₂e in 2019.

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 2019, the emissions reported for the other minerals production subsector increased by 60 percent (2.1 MMT CO₂e) from 3.5 MMT CO₂e to 6.2 MMT CO₂e. This increase was due to both an increase in the number of facilities reporting (32 more facilities reported in 2020 than in 2011) and an increase in the average annual emissions per facility (up from about 45,000 MT per facility in 2011 to 50,000 MT per facility in 2020). Emissions in 2020 decreased by nearly 10 percent from 6.2 MMTCO₂e in 2019 to 5.6 MMTCO₂e in 2020. The decrease was likely due to reduced demand for products and production disruptions caused by the COVID-19 pandemic.

References

[1]     U.S. Geological Survey (USGS), Minerals Yearbook, Cement, 2010 – 2019; Mineral Industry Surveys, Cement. July 2021; and Mineral Commodity Summaries, Cement, January 2021.

[2]     USGS, Lime, Mineral Commodity Summaries, January 2021.

[3]     U.S. Environmental Protection Agency (USEPA), Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2017, 2019.

[4]     U.S. Geological Survey (USGS), Soda Ash. Mineral Commodity Summaries, January 2021.