GM's biofuel initiative

General Motors' investment into almost every type of green technology continues apace, with its latest move taking it into the area of producing greener ethanol.

At present, the bulk of ethanol is made from corn. However, as demand to use the crops as biofuel has increased, so too have concerns about the environmental and social impact of the process.

As a result, GM has forged a partnership with US company Coskata, which is developing technology to produce ethanol from household waste, including wood chippings, food and plastics.

The process requires one-third of the amount of water compared to the current method of ethanol production and, as a result, each unit of energy used to make the fuel returns 7.7 units in ethanol. Present production methods release about 1.6 units per unit of energy.

GM will have the fuel ready for mass production by 2011, by which time it estimates there will be enough ethanol-powered cars in the USA to save up to 29 billion gallons of petrol a year.