Over half of U.S. landfills surveyed are significant sources of methane emissions, according to a new study published in the journal Science on Thursday. The research, the largest assessment to date of methane from landfills, highlights an opportunity to tackle climate change by addressing this potent greenhouse gas.
Led by Carbon Mapper, the study included researchers from NASA Jet Propulsion Laboratory, Arizona State University, University of Arizona, Scientific Aviation, and the Environmental Protection Agency (EPA). The team found that approximately 52 percent of landfills had observable methane emission point sources, a stark contrast to the 0.2 to 1 percent of super-emitting sites in the oil and gas sector, which is the largest U.S. source of methane.
Super emitters are defined by the EPA as sources emitting at least 100 kilograms of methane per hour. Notably, 60 percent of large emitting landfills had methane leaks persisting over months or years. In comparison, the majority of leaks at super-emitting oil and gas sites were short-duration events.
“Addressing these high methane sources and mitigating persistent landfill emissions offers a strong potential for climate benefit,” said Dan Cusworth, scientist at Carbon Mapper and lead author of the study. He emphasized that pinpointing these leaks provides a quick way to target and reduce emissions.
While oil and gas industries have been the primary focus of emerging regulations and voluntary programs in the United States and Europe, this study suggests that landfills are a significant and previously underestimated source of methane emissions. The advent of more aerial and satellite surveys enables regulators to measure, quantify, and act on methane emissions from landfills more effectively.
Traditionally, companies and regulators relied on model-based estimates and handheld methane sensors, which offered a less comprehensive view. The study revealed that the EPA’s greenhouse gas reporting system has underestimated methane leaks in landfills, with aerial surveys showing emission rates 1.4 times higher than EPA estimates.
The EPA reported that in 2021, 12 percent of all U.S. greenhouse gas emissions from human activities were due to methane. Given methane’s potency as a greenhouse gas, targeting emissions from landfills could play a crucial role in combating climate change.
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Surveys show U.S. landfills are major source of methane emissions
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