Every year, Americans dump over 250 million tonnes of garbage into landfills, where it seems to magically disappear from our lives. In reality, our rubbish either gets fossilised or digested by vast populations of methane-emitting bacteria.

Over a 20-year horizon, every pound (454g) of methane emitted has 80 times the heat-trapping power of the same amount of carbon dioxide (CO2 lasts much longer in the atmosphere). And America’s 1,200 landfills are producing more methane than we realised, according to a group of scientists who recently used an aerial remote sensing system to fly over 200 of them. They measured methane emissions 1.4 times what had been officially recognised by the US Environmental Protection Agency (EPA). The journal Science published their findings in March.