Landfills are drivers of the climate crisis – 04/01/2024 – Environment

Open air landfills — where household waste ends up, be it vegetable scraps or old appliances — emit, on average, almost three times more methane than reported to United States authorities. The conclusion is from a study published on Thursday (28) in the journal Science.

The study measured emissions of methane, a gas that contributes greatly to global warming, in around 20% of the approximately 1,200 large landfills operating in the US. The work adds to a body of evidence that landfills are a significant factor in climate change, says Riley Duren, founder of the public-private partnership Carbon Mapper, who participated in the study.

“Until now, as a society, we have largely been in the dark about the real emissions from landfills,” says Duren, a former engineer and scientist at Nada. “This study highlights the gaps.”

Methane emissions from oil and gas production, as well as livestock farming, have been increasingly studied in recent years. Like carbon dioxide, the main greenhouse gas warming the world, methane acts like a blanket in the sky, trapping heat from the sun.

And although methane lasts less time in the atmosphere than carbon dioxide, it is more potent. Its warming effect is more than 80 times more powerful than the same amount of carbon dioxide over a 20-year period.

The Environmental Protection Agency (EPA) estimates that landfills are the third-largest source of human-caused methane emissions in the U.S., emitting as much greenhouse gas as 23 million gasoline cars driven in a year. . Organic waste, such as food scraps, can emit large amounts of methane when it decomposes.

But these estimates were largely based on computer modeling rather than direct measurements. The reason: it is difficult and even dangerous for workers to measure methane emissions in these locations with methane “sniffers”, having to walk on steep slopes or near active dump sites.

For the new study, scientists gathered data from airplane flyovers using a technology called an imaging spectrometer, designed to measure methane concentrations in the air. From 2018 to 2022, they flew over 250 sites in 18 US states, about 20% of the country’s open-air landfills.

In more than half of the landfills they surveyed, the researchers detected emission hot spots, large concentrations of methane that sometimes lasted for months or years.

This suggests something is wrong at the site, such as a large methane leak caused by long-buried layers of decomposing trash, researchers say.

“Sometimes you can have decades of trash in the landfill,” says Daniel H. Cusworth, a climate scientist at Carbon Mapper and the University of Arizona who led the study. “We call it ‘garbage lasagna’.”

Many landfills are equipped with specialized pits and pipes that collect the methane gas that escapes from decomposing trash to burn it or otherwise generate electricity or heat. But these wells and pipes can leak.

Researchers say identifying leaks not only helps scientists get a clearer picture of emissions, but also helps landfill operators fix leaks. Keeping more waste out of landfill, for example by composting food scraps, is another solution.

Abroad, the situation may be less clear, especially in countries where landfills are not strictly regulated. Previous surveys using satellite technology have estimated that, globally, methane from landfills represents almost 20% of methane emissions linked to human activities.

“The waste sector will clearly be a critical part of society’s ambition to reduce methane emissions,” says Duren. “We’re not going to meet global methane reduction targets just by cutting oil and gas emissions.”

There is a growing constellation of methane-detecting satellites designed to provide a more complete picture. Last month, another nonprofit organization, the Environmental Defense Fund, launched MethaneSat, a satellite dedicated to tracking methane emissions around the world.

Carbon Mapper, with partners including NASA’s Jet Propulsion Laboratory, the Rocky Mountain Institute and the University of Arizona, aims to launch the first of its own methane-tracking satellites later this year.