China and India are the world’s biggest methane polluters

BENGALURU: Landfills are releasing large amounts of planet-warming methane gas into the atmosphere from the decomposition of waste and are a significant 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 locations in each city that persistently emit high methane levels, all of which were landfills.

The cities’ overall methane emissions from all sources were 1.4 to 2.6 times higher than previous estimates, reported international media. The study, published in Science Advances on Wednesday, is aimed at helping local governments carry out targeted efforts to limit global warming by pinpointing specific sites of major concern.

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

Although methane only accounts for about 11% of greenhouse gas emissions and lasts about a dozen years in the air, it traps 80 times more heat in the atmosphere than carbon dioxide does. Scientists’ estimate that at least 25% of today’s warming is driven by 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 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 city sizes, are responsible for a large fraction of total emissions from a given area,” he said. Satellite data to detect emissions is still a relatively new field, but it’s being used more and more to observe gases across the world. It means more independent organisations are tracking greenhouse gases and identifying big emitters, whereas previously local government figures were the only source available.