Biogas, a low-tech fuel with a big payoff

No wastes: The fermentation of pig and cattle manure generates organic fertiliser and biogas (for electricity generation). This biogas plant about 150km south of Santiago, Chile, generates up to 4MW of electricity for the farm’s own use. — Photos by AFP

Whether at household operations or at industrial facilities, a centuries-old technology is increasingly being used to extract energy from crop waste, kitchen scraps and sewage.

IN villages across China, tens of millions of families use farm and household waste to make clean cooking fuel in backyard fermenters. Germany generates as much electricity as two nuclear power plants with the gas produced by decaying plant matter and animal slurry. Near San Francisco, a landfill extracts enough energy from its stewing garbage to power 300 trucks on their daily runs.