Landfill methane is a major climate threat; city in focus

Mumbai: Methane is 80 times more potent than carbon dioxide in the short term, and is responsible for nearly half of the recent global warming, say researchers. The UCLA's STOP Methane Project report comes ahead of the UN climate summit COP31 scheduled in Nov. The findings are based on data from Carbon Mapper, which tracked nearly 3,000 methane plumes across more than 700 waste sites worldwide. Researchers said these "super-emitting" sites represent the most acute and actionable sources of methane leaks. Topping the list is a landfill in Buenos Aires Province, near Argentina's capital, emitting 7.6 ton of methane per hour -- equivalent in warming impact to over a million SUVs.The finding revives long-standing concerns over Mumbai's dependence on large dumping grounds such as the ones at Deonar and Kanjurmarg, which have drawn criticism for fires, toxic emissions and inadequate scientific waste processing. BMC officials said methane capture systems, biomining and waste-to-energy measures are being scaled up to curb emissions, with officials pointing to ongoing landfill remediation and legacy waste clearance targets. "We have already taken note of this issue (air pollution due to landfill gases). The Bombay High Court, which is hearing a number of PILs on the Kanjurmarg facility, is already watching and has appointed a monitoring committee to recommend remedial measures and we are working on them," said deputy municipal commissioner Kiran Dighavkar.Environmentalists argue that progress remains uneven and stress the need for stricter enforcement of solid waste management rules, decentralised waste segregation and faster deployment of landfill gas recovery systems. With India pushing climate commitments ahead of COP31, the report is likely to intensify scrutiny on urban local bodies to demonstrate measurable reductions in methane emissions from waste. "These are seriously dangerous levels of methane coming from waste sites across a wide variety of countries," said Cara Horowitz of UCLA Law. "Many of these landfills are located close to cities, posing real risks to public health. The encouraging part is that practical solutions exist to curb these emissions."The report highlights that countries across income levels -- from Brazil and Chile to Saudi Arabia, Turkey and the United States -- feature in the rankings, underscoring the global nature of the waste-sector methane challenge. Notably, Turkey -- which will host COP31 -- has multiple high-emitting landfill sites, including one near Istanbul that did not make the main list but was flagged as a "dishonourable mention" due to even higher emissions recorded after 2025. For India, the inclusion of sites near major urban centres raises fresh concerns over waste management practices and landfill gas capture systems. With cities like Mumbai already grappling with pollution and climate risks, the report adds urgency to efforts aimed at scientific landfill management and methane mitigation.The study also points to early signs of action. Two landfill operators in Chile have already initiated mitigation steps after being identified in earlier versions of the rankings. "Making reliable data public can drive accountability and prompt corrective action," said Juan Pablo Escudero.Experts say tackling methane emissions from landfills is among the fastest ways to slow global warming. Unlike carbon dioxide, methane has a shorter atmospheric lifespan, meaning emission cuts can yield quicker climate benefits. (With inputs from Clara Lewis)