A person picks up rubbish in search of reusable items as a fire rages at the Bhalswa landfill in New Delhi on April 27, 2022.

Manish Swarup/AP

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Manish Swarup/AP

A person picks up rubbish in search of reusable items as a fire rages at the Bhalswa landfill in New Delhi on April 27, 2022.

Manish Swarup/AP

BENGALURU, India – Landfills are releasing far more planet-warming methane into the atmosphere from decaying waste than previously thought, a study has found.

Scientists used satellite data from four major cities around the world – Delhi and Mumbai in India, Lahore in Pakistan and Buenos Aires in Argentina – and found that emissions from landfills in 2018 and 2019 were 1.4 to 2.6 times higher than previous estimates.

The study, published Wednesday in Science Advances, aims to help local governments lead targeted efforts to limit global warming by identifying specific sites of greatest concern.

When organic waste like food, wood or paper decomposes, it releases methane gas into the air. Landfills are the third largest source of methane emissions globally, after oil and gas systems and agriculture.

Although methane accounts for only about 11% of greenhouse gas emissions and persists for a dozen years in the air, it traps 80 times more heat in the atmosphere than carbon dioxide. Scientists estimate that at least 25% of current warming is due to methane from human actions.

“This is the first time that high-resolution satellite images have been used to observe landfills and calculate their methane emissions,” said Joannes Maasakkers, lead study author and atmospheric scientist at the Netherlands Institute. space research.

“We found that these landfills, which are relatively small compared to the size of cities, are responsible for a large portion of a given area’s total emissions,” he said.

Satellite data for detecting emissions is still a relatively new field, but it is increasingly being used to observe gases around the world. This means that more independent organizations are tracking greenhouse gases and identifying large emitters, whereas previously local government figures were the only source available.

“This new work shows how important it is to better manage landfills, especially in countries like India where landfills are often on fire, emitting a wide range of harmful pollutants,” said Euan Nesbit, a scientist at Earth at Royal Holloway, University of London. , which was not part of the study.

Earlier this year, smoke hung over New Delhi for days after a massive landfill burst into flames as the country suffered an extreme heatwave with temperatures topping 50 degrees Celsius (122 Fahrenheit). At least two other landfill fires have been reported in India this year.

Nesbit added that the new satellite technology, combined with on-the-ground measurements, makes it easier for researchers to identify “who is polluting the world”.

China, India and Russia are the world’s biggest methane polluters, according to a recent analysis by the International Energy Agency.

At last year’s United Nations climate conference, 104 countries signed a pledge to cut methane emissions by 30% by 2030 from 2020 levels. India and China do not are not signatories.

The authors plan to conduct more research on landfills around the world in future studies.

“This is a rapidly developing area and we expect more interesting data to come out soon,” Maasakkers said.