General Motors Corp said it has bought a stake in start-up biofuel company Coskata Inc. which has developed a commercially viable process to bring cellulose-based ethanol to the market in 2011. GM said it would not disclose the size of the stake or how much it had invested in Coskata.

Cellulosic ethanol production currently costs about double that of traditional U.S. ethanol, a plant-based distilled alcohol derived mostly from corn in the United States and from sugar in Brazil. The new U.S. energy bill signed into law by President Bush in December mandates a huge jump in biofuels production for America's automobiles - 36 billion gallons by 2022, with 16 billion gallons from cellulosic ethanol.