April 21, 2024


A landfill is a place of perpetual motion, where mountains of garbage can rise over days and crews race to contain the influx of more and more garbage. In the midst of the commotion, an invisible gas often escapes unnoticed, warming the planet and harming our health: methane.

On Thursday, the climate data sleuths at Carbon Mapper published a study in Science showing that the nation’s landfills are releasing that gas at levels at least 40 percent higher than previously reported to the Environmental Protection Agency. At more than half of the hundreds of landfills surveyed – in the largest assessment yet of such emissions – most of the pollution flowed from leaks, creating concentrated plumes. The researchers found that these super-emitting points can persist for months or even years, and are responsible for nearly 90 percent of all measured methane from the landfills. Tackling these hotspots could be a big step in reducing emissions rates, but blind spots in current monitoring protocols mean they often evade detection.

“It’s a very difficult problem to get completely right without any leaks anywhere,” said Daniel Cusworth, an atmospheric chemist and project scientist for Carbon Mapper, a nonprofit that provides data to inform greenhouse gas reduction efforts. Sometimes Cusworth does aerial surveys of landfills and is relieved to find nothing. “And then other times, you know, I’ll see a massive billowing plume that’s three kilometers long.”

Methane is a powerful greenhouse gas that is created by ao rotting rubbish, and it often seeps through the soil and plastic covers meant to contain it. Although federal regulations require large facilities to use gas capture systems, landfills remain the third largest source of these emissions in the United States, accounting for more than 14 percent of the national total. Because methane is 84 times more powerful than carbon dioxide during its first 20 years in the atmosphere, scientists say reduce its quantity floating around up there is the fastest way around to combat global warming. Doing so also benefits communities: a disproportionate number of American landfills are near marginalized neighborhoods, where gas exposure affect health or pose an explosion risk.

Leaks that exceed the Clean Air Act’s limit of 500 parts per million is common, as shown by the hotspots identified by Carbon Mapper. These areas typically appear after unexpected events, such as cracks in landfill covers, valve failures in the major gas gathering systems, and other maintenance or construction issues. “They really dominated the total emissions for the landfill,” Cusworth said. The survey found that average emissions from the most surveyed sites were at least 1.4 times, and sometimes as much as 2.7 times, greater than those reported to the EPA’s Greenhouse Gas Reporting Program.

an aerial view of a landfill in Georgia with an infrared red, green, blue color-coded plume of methane shown from above
Methane plumes observed by Carbon Mapper during aerial surveys at a landfill in Georgia
Carbon Mapper

Although federal guidelines require these facilities to track emissions and provide that data to the EPA, current reporting and monitoring methods just aren’t up to par, according to the study. Most operators report an estimate, using EPA guidelines, based on the amount of waste they ingest, not measured data. Regulators also require facilities to conduct pavement surveys four times a year, but experts like Cusworth say these efforts are neither frequent nor precise enough. Hotspots can easily escape because many areas are too dangerous or inaccessible to walk on, and monitoring sensors only respond to high concentrations on the ground and will not capture dispersed plumes. “You can’t manage what you can’t measure,” Cusworth said, adding that it’s a popular cliché in the air monitoring industry.

In the survey, the Carbon Mapper researchers flew over landfills with aircraft that captured infrared images, revealing the plumes. Similar remote sensing methods, such as drones and satellites, are among others recent technological advances that can contain pollution, that can help facilities find and address leaks quickly. Other innovations for methane capture systems, such as self-calibrating caps on valves and sensors that can detect leaks, further reduce the risk of failures.

“In the waste sector, specifically, we know which technologies to implement – ​​we’ve known for a number of years. They are feasible, readily available, and a number of them are actually quite cost-effective,” said Kait Siegel, waste sector manager of the methane pollution team at Clean Air Task Force. “We need to have regulations in place.” This coming August, the EPA is expected to update its landfill management policy as part of a required 8-year review cycle.

Tom Frankiewicz, a waste sector methane scientist at RMI, who collaborated with Carbon Mapper on the study, said addressing extraordinary methane sources, such as landfills, was urgent because of the short life and extreme strength of the gas, compared to the prolonged carbon dioxide. The world will not see the climate benefits of reducing CO2 emissions for a century, he said. That time frame drops to a decade when methane is curbed. “We have to work on both and lean on methane because it buys us time.” And in the race to mitigate climate change, every moment counts.






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