According to the National Biodiesel Board, biodiesel production last year tripled over 2004 to 280 million litres last year. This year, it is expected to double to 560 million litres.

In comparison, US consumption of traditional diesel fuel extracted from crude oil stands at 227 billion litres per year.

But biodiesel still has country music legend Willie Nelson singing its praises. The 73-year-old songwriter has launched his own brand of the fuel, dubbed "BioWillie," and strongly believes that biodiesel is the way to go.

Nelson and Oscar winning actor Morgan Freeman are on the board of a company called Earth Biofuels which has signed up Roberts to help promote the cooking oil fuel.

"The idea is to do something useful towards eliminating America's dependence on foreign oil. Consumers can now ensure that their fuel money stays in America rather than going overseas," Nelson wrote on his website.