New study assesses hundreds of US landfills to quantifying methane emissions

More than half the landfills in the United States are “super-emitters” of methane.

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Image Credit: Mohammed Saber/EPA-EFE

According to a new study, more than half the landfills in the United States are “super-emitters” of methane. Methane, a heat-trapping greenhouse gas (GHG), is 28 times more powerful than carbon dioxide.

The study, “Quantifying methane emissions from United States landfills,” was led by nonprofit Carbon Mapper and published in the journal Science.

“Methane is the most important trace greenhouse gas after carbon dioxide, and anthropogenic emissions account for more than half of the global total,” H. Jesse Smith, the study’s author, said. “Landfills containing solid waste are potentially major sources of methane, but their importance has remained poorly constrained.”

The study “quantified emissions at hundreds of large landfills across 18 states in the United States between 2016 and 2022 using airborne imaging spectrometers.” Between 2018 through 2022, the research team, made up of scientists from NASA’s Jet Propulsion Laboratory, University of Arizona, Arizona State University, the U.S. Environmental Protection Agency (EPA) and airborne atmospheric research company Scientific Aviation, used advanced aircraft direct measurements of more than 200 active municipal landfills participating in the EPA’s Greenhouse Gas Reporting Program (GHGRP).

Spanning 20 percent of open United States landfills, the study “represents the most systematic measurement-based study of methane point sources of the waste sector,” according to the study. It identifies major sources of emissions that have not been detected in traditional accounting and need mitigation.

“Cusworth et al. report data gathered by airborne imaging spectrometers from about 20 percent of open U.S. landfills to show that considerable point source emissions can be detected at a majority of sites,” Jesse Smith. “These results underline the need for better monitoring of landfill emissions to help guide climate change mitigation policy.”

The study revealed that GHGRP and other reporting systems were missing major sources of methane and emphasized the enormous impact of landfill emissions. According to the EPA, “landfills are the third largest human-caused methane emissions source in the country.”

“Addressing these high methane sources and mitigating persistent landfill emissions offers a strong potential for climate benefit,” Dr. Dan Cusworth, lead author of the study and a program scientist with Carbon Mapper, said. “The ability to precisely identify leaks is an efficient way to make quick progress on methane reduction at landfills, which could be critical for slowing global warming.”

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