Three environmental groups are making a move to hold the U.S. Environmental Protection Agency accountable for accurately tracking heat-trapping gases emitted from the nation’s landfills.

The Environmental Integrity Project, Chesapeake Climate Action Network and the Sierra Club have filed a notice of intent to sue the EPA, the first step in a legal process under the Clean Air Act. The groups claim the agency allows landfills to use methods that are more than two decades old, which are underestimating methane emissions by at least 25 percent.

The EPA under the law must review and, if necessary, revise its landfill gas emissions calculation methods every three years, and agency officials have known those emissions factors have been off since at least 2008, according to the 10-page legal notice, which was sent to Michael Regan, the EPA administrator, last week.

“When it comes to pollution, it’s very difficult to manage what you can’t measure,” said Ryan Maher, attorney for the Environmental Integrity Project, in a press release. “EPA needs to fix how it estimates emissions from this massive source of methane and other air pollutants, not only to help us understand the full extent of the landfill problem, but also to make sure that we’re holding polluters accountable and regulating these facilities properly.”

In June, Maher authored a study that found that Maryland’s landfill methane emissions were four times higher than that state had estimated. “It’s not just Maryland, it’s the whole country,” said Tom Pelton, a spokesman for the Environmental Integrity Project.

The EPA has 60 days to attempt to resolve the conflict with the environmental groups. An EPA spokeswoman declined to comment, citing the potential litigation.

Rotting garbage and other waste in municipal landfills are responsible for about 15 percent of the country’s human-caused emissions of methane, a powerful climate super-pollutant that scientists say needs to be reigned in quickly to prevent the worst impacts of global warming. Methane is 86 times more powerful than carbon dioxide over 20 years.

In July, Inside Climate News, WMFE in Orlando and NPR reported that the EPA’s own top expert on methane believed the agency was undercounting landfill methane emissions. 

The EPA has “been understating methane emissions from landfills by a factor of two,” Susan Thorneloe, a senior chemical engineer at the EPA who has worked on the agency’s methane estimation methods since the 1980s, said. Part of the problem, she said, may be that the EPA’s methods for estimating landfill methane emissions are outdated and flawed.

Reducing methane could almost immediately reduce climate change, because it stays in the atmosphere for a short time, unlike carbon dioxide, which lingers for a century or more. 

Landfills are one of three main sources of human-caused methane pollution, along with livestock and the oil and gas industry. The United States is the third-biggest emitter of methane in the world.

A 2018 National Academy of Sciences report placed “low confidence” in EPA estimates for landfill methane emissions due to uncertainties and insufficient measurements. The report concluded that the agency’s method for estimating methane emissions from landfills makes faulty assumptions for methane generation rates and was “never field-validated.”

Jean Bogner, a University of Illinois at Chicago emeritus professor and a co-author of the National Academy of Sciences report, told Inside Climate News earlier this year that methods need to keep pace with science, especially as the world moves into more intensive climate change mitigation strategies.

Following the environmental group’s lawsuit notice, she said in an email that emissions modeling needs to better take into account local climate conditions and landfill operators’ management strategies. She cited a new study she co-authored and published in November in the journal Elementa that showed how landfill operators or regulators could do that by, among other methods, better tracking soil moisture, temperature conditions and the past 30 years of local climate data or predictions.

Jeff Chanton, a Florida State University climate scientist who studies methane, agreed. “The scientific community has the techniques and methodology to quantify methane emissions from landfills,” including more robust modern environmental measurements and better computer modeling, he said in an email. 

Further, EPA allows operators multiple ways to calculate the amount of methane they generate. Depending on which methods an operator chooses, the estimated amount of methane emissions can vary significantly.

Only six of the landfills that EPA listed in the top ten in the nation for methane emissions in 2019 are on that list for 2020. They are Sampson County Disposal, Roseboro, North Carolina; Eagle Point Landfill, Ball Ground, Georgia; Black Warrior Solid Waste Disposal Authority, Coker, Alabama; Brevard County Disposal Facility, Cocoa, Florida; 121 Regional Disposal Facility, Melissa, Texas; and Rumpke Sanitary Landfill, Cincinnati, Ohio.

This may be due to landfill operators using different calculation methods that resulted in lower estimates, as the operators of the Orange County, Florida, landfill said they were going to do. That landfill fell from a 2019 ranking of third in the country in July of last year to 301st now.