The waste sector consists of municipal solids waste (MSW) landfills, industrial landfills, solid waste combustion, and wastewater treatment. Total emissions reported to the Greenhouse Gas Reporting Program by the waste sector decreased from 114.9 MMT CO₂e in 2011 to 103.3 MMT CO₂e in 2021 (approximately 10 percent). The decrease in emissions is likely due to the notable 11 percent drop in reporters (in 2021 there were approximately 190 fewer reporters than in 2011), along with a drop in emissions from MSW landfills.

Over 80 percent of emissions from the waste sector come from municipal solid waste (MSW) landfills. Reported emissions from MSW landfills decreased from 94 MMT CO₂e in 2011 to 85 MMT CO₂e in 2021 (approximately 10 percent). The decrease in reported emissions is due to several factors, including a reduction in the number of reporters (in 2021 there were approximately 108 fewer reporters than in 2011), along with changes to the rule for calculating methane emissions from MSW landfills. Starting in reporting year 2013, MSW landfills are allowed to assume that a higher percentage of methane generated by the landfill is oxidized to CO₂ as it passes through the landfill soil cover, resulting in lower reported methane emissions. Landfills are provided two equations for calculating annual methane emissions and are given the choice of which results that best represent the emissions from the landfill to report each year. More landfills choosing to report the lower of the two estimates is likely contributing to lower reported emissions. Another factor that may be contributing to lower emissions is a reduction in degradable waste disposed in MSW landfills since 2011. [1]

In addition to MSW landfills, reported emissions also decreased from the other waste subsectors. Emissions reported by industrial waste landfills decreased 17 percent between 2011 and 2021 while emissions reported by solid waste combustors decreased 3 percent during this time, and wastewater treatment facilities dropped 27 percent.

[1] EPA, Advancing Sustainable Materials Management: Facts and Figures 2018. December 2020. Available online at: https://www.epa.gov/sites/production/files/2020-11/documents/2018_tables_and_figures_fnl_508.pdf.