These are vast spaces that will be as large as cities: open landfills where household waste finally ends up, whether it is vegetable scraps or old household appliances.
These landfills also release methane, a robust planet-warming gas, at a median rate nearly thrice higher than reported to federal regulators, in line with data. study published on Thursday in the journal Science.
The study measured methane emissions at about 20 percent of about 1,200 large landfills operating in the United States. This adds to growing evidence that landfills are a major contributor to climate change, said Riley Duren, founder of the public-private partnership Carbon Mapper, who participated in the study.
“As a society, we have been largely unaware of the actual emissions from landfills,” said Duren, a former NASA engineer and scientist. “This study highlights gaps.”
Methane emissions from oil and gas production and livestock have come under increasing scrutiny lately. Like carbon dioxide, the main greenhouse gas causing global warming, methane acts like a blanket in the sky, trapping the sun’s heat.
And although methane stays in the atmosphere for a shorter time than carbon dioxide, it is more powerful. Its warming effect is greater than 80 times stronger than the same amount of carbon dioxide over a 20-year period.
The Environmental Protection Agency estimates that landfills are the third-largest source of human-made methane emissions in the United States, emitting as much greenhouse gas as 23 million gasoline-powered cars annually. Organic waste, reminiscent of food scraps, can emit large amounts of methane because it decomposes.
However, these estimates were largely based on computer modeling slightly than direct measurements. An enormous reason: For employees equipped with methane detectors, measuring emissions on site, climbing steep slopes or near lively landfills will be difficult and even dangerous.
For the recent study, scientists collected data from airplane overpasses using technology called imaging spectrometers, designed to measure methane concentrations in the air. Between 2018 and 2022, they served aircraft to greater than 250 locations in 18 states, representing roughly 20 percent of the nation’s open landfills.
In greater than half of the landfills examined, researchers found emission hotspots, or significant plumes of methane that sometimes endured for months or years.
That suggests something went unsuitable at the site, reminiscent of a big leak of trapped methane from layers of long-buried, decaying garbage, scientists said.
“Sometimes it sits in a landfill for decades,” said Daniel H. Cusworth, a climate scientist at Carbon Mapper and the University of Arizona who led the study. “We call it junk lasagna.”
Many landfills are equipped with specialized wells and pipes that collect methane leaking from rotting garbage to be burned or sometimes used to generate electricity or heat. But these wells and pipes can leak.
The researchers said that locating leaks not only helps scientists get a greater picture of emissions, but additionally helps landfill operators fix leaks. Another solution is to forestall more waste from ending up in landfills, for instance by composting food scraps.
The picture could also be less clear abroad, especially in countries where landfills usually are not strictly regulated. Previous research using satellite technology They estimated it Worldwide, landfill methane accounts for nearly 20 percent of human-caused methane emissions.
“The waste sector will certainly play a key role in achieving society’s ambitions to reduce methane emissions,” said Carbon Mapper’s Duren. “We won’t meet global methane targets just by cutting oil and gas emissions.”
A growing constellation of methane-detecting satellites could provide a more complete picture. Last month, one other nonprofit, the Environmental Defense Fund, launched MamineSat, a satellite to trace methane emissions around the world.
Carbon Mapper and partners including NASA’s Jet Propulsion Laboratory, the Rocky Mountain Institute and the University of Arizona aim to launch the first of its own methane-tracking satellites later this 12 months.
