Satellite data finds landfills to be methane ‘super emitters’
Landfills release large amounts of planet-warming methane gas into the atmosphere from waste decomposition and are a major contributor to such emissions in urban areas, a study suggests.
Scientists used satellite data from Delhi and Mumbai in India, Lahore in Pakistan and Buenos Aires in Argentina and identified specific sites in each city that emit persistently high methane levels, all of which are landfills. The cities’ total methane emissions from all sources were 1.4 to 2.6 times higher than previous estimates.
The study, published in Scientific progress on Wednesday, aims to help local governments implement targeted efforts to limit global warming by identifying specific places of great concern.
When organic waste such as food, wood or paper decomposes, methane is released into the air. Landfills are the third largest source of methane emissions worldwide, after oil and gas systems and agriculture.
Although methane only accounts for about 11% of greenhouse gas emissions and stays in the air for about 12 years, it traps 80 times more heat in the atmosphere than carbon dioxide. Scientists estimate that at least 25% of current warming is caused by methane from human activity.
“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 author of the study and atmospheric scientist at the Netherlands Institute for Space Research.
“We found that these landfills, which are relatively small compared to the size of a city, are responsible for a large part of the total emissions from a given area,” he said.
Satellite data to detect emissions is still relatively new, but is increasingly being used to observe gases around the world. It means more independent organizations are tracking greenhouse gases and identifying major emitters, when local government figures were the only available source.
“This new work shows the importance of better managing landfills, especially in countries like India where landfills are often on fire and emit a wide range of harmful pollutants,” said Euan Nisbet, an earth scientist 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 caught fire as the country sweltered in an extreme heat wave with temperatures exceeding 50 degrees Celsius (122 Fahrenheit). At least two other landfill fires have been reported in India this year.
Nisbet added that the newer satellite technology, combined with ground-based measurements, makes it easier for researchers to identify “who is polluting the world.”
China and India are the world’s biggest polluters of methane, according to a recent analysis by the International Energy Agency.
At the United Nations climate conference last year, 104 countries signed a pledge to reduce methane emissions by 30% by 2030 compared to 2020. Both India and China are not signatories.
The authors plan to do more research on landfills around the world in future studies.
“It is a rapidly developing field and we expect more interesting data to come out soon,” said Maasakkers.
Methane satellites find landfills with the same climate impact as several hundred thousand cars
Joannes D. Maasakkers et al, Using Satellites to Uncover Large Methane Emissions from Landfills, Scientific progress (2022). DOI: 10.1126/sciaadv.abn9683
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