The waste sector consists of municipal solids waste (MSW) landfills, industrial landfills, solid waste combustion, and wastewater treatment. Total emissions from the waste sector decreased from 114.9 MMT CO₂e in 2011 to 105.5 MMT CO₂e in 2020 (approximately 8 percent). The decrease in emissions is likely due to the notable drop in reporters (in 2020 there were 180 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 86 MMT CO₂e in 2020 (approximately 8 percent). The decrease in emissions is due to a number of factors, including a reduction in the number of reporters (117 fewer MSW landfills reported in 2020 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 methane emissions and are given the choice of which results to report. Landfills choosing to report the lower of the two estimates is likely contributing to lower reported emissions. In 2020, annual reported waste disposal as well as annual emissions decreased by 5 percent and 4 percent, respectively. Since 2011, waste disposal had been slightly increasing year to year.

In addition to MSW landfills, emissions also decreased from the other waste subsectors. Emissions from industrial waste landfills decreased 12 percent between 2011 and 2020 while emissions from solid waste combustors decreased 7 percent during this time, and wastewater treatment facilities dropped 10 percent.