NOAA Study: Landfills a key source of methane

Decomposing food waste is releasing thousands of tonnes of planet-warming methane gas at landfills in Buenos Aires, Delhi, Mumbai, and Lahore, new research finds.

With about 570 million tonnes of the greenhouse gas emitted every year from both industrial and natural processes, the concentration of methane in the atmosphere has been increasing at a record pace, according to the US National Oceanic and Atmospheric Administration.

In some countries, the biggest source is agricultural fields and farm animals — particularly cows but also livestock and chickens. In the United States, the oil and gas industry is largely responsible.

Yet there is another major global source – garbage.

With data from a satellite-mounted detector showing high methane levels over cities in India, Pakistan and Argentina, a team of scientists looked more closely to pin down the emissions sources.

A landfill in Mumbai, for example, was putting out about 9.8 tonnes of methane per hour, or 85,000 tonnes per year, according to the study's findings.

Landfill waste – responsible for about 11% of global methane emissions – is expected to increase about 70% by 2050, according to the World Bank.

Methane is 80 times more powerful than CO2 over a 20-year period.

Satellite technologies are a boost to scientists, said Jean Bogner, a University of Illinois environmental scientist not involved in the research. This new approach helps to "adequately capture site-specific emissions, which for landfills can vary by orders of magnitude" depending on everything from soil conditions to whether mitigation measures are in place.