Methane emissions from municipal landfills are a key contributor to greenhouse gas emission increases, according to a report published May 18 by the Environmental Integrity Project.

Landfill emissions account for more than 14% of the total methane emissions in the U.S., and they result from the breakdown in food scraps, yard trimmings and paper, the report said. This is the third highest source of methane emissions, behind livestock (27%) and natural gas systems (25%).

A total of 295 million metric tons of methane were emitted from U.S. landfills in 2021, which EIP notes is the equivalent of “66 million gasoline- powered passenger vehicles on the road for a year (about a quarter of all American cars, SUVs, vans, and pickup trucks), or from 79 coal-fired power plants.”

The report noted that the methane emission amounts reported by the Environmental Protection Agency are likely to be underestimated because it doesn’t have data on how well the landfill gas collection systems designed to reduce emissions are performing.

Reducing methane emissions is critical in addressing climate change, as methane emissions trap heat in the environment at a much higher rate than carbon dioxide and landfill emissions often continue for decades. “Landfills that stopped accepting waste in the 1980s are still producing methane today,” the report said.

A tangible means of addressing this issue is to encourage households to reduce their food waste, as around 40% of food is thrown away and begins producing methane as it breaks down in landfills. This is a global challenge, the report noted, explaining that “if wasted food were a country, it would be the third-largest emitter of global greenhouse gases.”

Recycling and composting waste are two of the suggestions offered in the report to reduce the volume of methane-producing items finding their way into landfills. The report says these are two of “the best ways to manage waste once it is no longer possible to rethink/redesign, reduce or reuse it.”

California has the highest volume of landfill waste. However, as a result of California’s more stringent regulations, Texas has the highest metric tons of methane emissions from its landfills. The “Lone Star State” also has the highest number of landfills (96), four more than the “Golden State.”

“EPA is failing to adequately control methane from landfills, a huge source of greenhouse gases, and we can no longer ignore this problem with the climate crisis heating up,” said Leah Kelly, senior attorney at EIP and one of the report’s authors, in a press release announcing the report. “Landfills not only contribute to climate change, but they disproportionately impact low-income neighborhoods and communities of color forced to live near dumps.”

The full report is available here.