Landfills Belch Climate-Warming Methane. Even the EPA Doesn’t Know How Much.

It’s easy to forget about garbage. We put it out on the curb and it goes away, thanks to some of the hardest-working people around. But garbage continues impacting us — and the planet — long after it leaves our dumpsters. When all of our trash combines in a landfill, it becomes a serious source of climate-warming pollution.

Municipal solid waste landfills are the nation’s largest source of methane emitted by human sources after fossil fuels and agriculture, according to the Environmental Protection Agency. We send our garbage to as many as 2,000 such dumps nationwide.

Over a 20-year period, methane is up to 84 times more powerful than carbon dioxide in terms of trapping heat in the atmosphere.

At the recent COP26 climate summit, the United States and European Union led 100 countries in signing a pledge to slash methane emissions by 30 percent over the next decade. Trapping methane from landfills could help the U.S. keep its word, environmentalists say, but there’s a big problem: We don’t actually know how much methane and other pollutants are being belched by landfills into the atmosphere in the first place.

The EPA reports that municipal landfills were responsible for 15 percent of U.S. methane emissions in the 2019, which is roughly equivalent to the greenhouse gas emissions from 21.6 million cars on the road for a year. However, air pollution from most landfills is not measured at the source, and these figures are just estimates based on a method of modeling emissions that the EPA has not updated in two decades, according to Environmental Integrity Project (EIP) attorney Ryan Maher.

“That bad stuff is getting out, but I think we need to figure out how much is getting out as the first step to managing it,” Maher said in an interview.

Within a year of trash entering a landfill, anaerobic bacteria begin breaking down food waste and other organic garbage, producing methane as a result. Landfills also produce other pollutants, including the greenhouse gas nitrous oxide and volatile organic compounds that can be harmful to human health.

Maher said technologies such as drones and even satellite imaging can measure pollution from landfills directly, but tracking emissions costs money. Federal law requires larger emitters to install gas collection systems, and some landfills even trap methane to generate electricity. However, more accurate data on emissions could force more landfills to invest in pollution controls, which the industry is reluctant to do.

EPA’s current model for estimating landfill emissions is sorely outdated, Maher said, and is probably underestimating the amount of methane and other pollutants entering the air. For the industry, that translates to fewer state and federal regulations.

“It’s the EPA’s methods that decide whether gas control is necessary under those regulations,” Maher said, referring to pollution controls that suck gas from trash heaps through a network of pipes. “We think updating the methods will result in higher emissions estimates, which will result in more pollution controls under the EPA’s federal regulations.”

In 2008, the EPA reviewed its methods for estimating three landfill gases that the agency is required to track by federal law: volatile organic compounds, nitrous oxide and carbon monoxide. The model is based on methane emissions, which is also a good way to gauge climate impact, but the agency concluded that the levels of most pollutants were underestimated by 25 percent, according to a complaint filed by EIP and other environmental groups on Thursday.

The EPA proposed an update to the emissions model in 2009, but the proposal was never finalized or implemented, the groups said. The EPA is required by the Clean Air Act to review and consider updating the model every three years, but that review was not completed during the Trump administration. So, the groups announced their intention to file a lawsuit in order to compel the agency into action. A spokeswoman for the EPA said the agency does not comment on pending litigation.

“The EPA model is basically showing state regulators and the public which facilities are of most concern, and just where landfills fall generally as emitters of various compounds, and how they compare to other industries,” Maher said.

Last year an EIP analysis found emissions from 19 landfills across Maryland were four times higher than the official state estimate, and Maher believes a reworking of the EPA’s methods would yield similar results nationwide. Scientific studies on landfills have also found a gap between EPA estimates and actual emissions, and more accurate modeling would help policymakers make regulatory decisions and develop climate policy, he added.

The EPA, as well as a handful of state and local governments that keep greenhouse gas inventories, uses the data to track contributions to climate change. Measuring the amount of methane could encourage regulators and lawmakers to push for pollution controls that would help the country meet its emissions targets.

Local communities would also have better data for holding operators accountable for pollution from landfills, the majority of which are located near lower-income neighborhoods and communities of color.