Virgin Atlantic 747 to test biofuel in early 2008

Cutting emissions of heat-trapping gases from transportation sources is more difficult than cutting them from stationary sources like power plants. Power stations can switch from coal, the heaviest greenhouse gas emitter, to cleaner burning natural gas.

On Monday, Branson said jets may have problems using ethanol, the most common biofuel, which is made mainly from corn in the United States and sugar cane in Brazil.

He said ethanol freezes at 15,000 feet (4,600 metres) and that butanol, a fuel similar to gasoline that can be made from biomass, may be a better alternative. It is also less corrosive than ethanol.

Virgin Fuels has invested in a small number of U.S. ethanol projects and hopes eventually to produce branded biofuels, the company's managing partner said earlier this year.

Separately, Branson said Virgin would name one of its Galactic crafts -- planned for use in space tourism -- after his friend Steve Fossett, the millionaire adventurer who disappeared in a small private plane in the U.S. West early last month.

Test flights of the Galactic crafts begin next year and passenger service is expected to begin in 2009.