Standing on the Brogborough landfill site in Bedfordshire, Kevin, a gasfield operating manager at Infinis, has 70 metres of rotting rubbish under his feet.

"It's like a big pie," he says, explaining that the rubbish is encased all the way around by a thick layer of clay that acts a bit like a pastry crust. Kevin's job is to make sure that the noxious fumes that the rubbish gives off as it rots get siphoned off the dump through big black pipes. Engines powered by the gas drive generators producing electricity that is sold back to the grid.