In a fire engine fuelled by Chilean chip fat, Mexican lard and Colombian palm oil, Seth Warren and Tyler Bradt have completed the longest journey made without diesel or petrol.

Nine months and about 21,000 miles after setting out from Alaska, the Americans drove their “veggie vehicle” into Ushuaia, in Tierra del Fuego, Argentina.

“This is proof, hands down, that vegetable oil works,” said Mr Warren, a 29-year-old professional kayaker from Montana.

With Mr Bradt, 20, his fellow kayaker, he secured funding from camping gear, clothing and energy food sponsors. They bought a Japanese fire engine and designed a green fuel system.

Rising oil prices, declining fossil fuel reserves and concerns about environmental damage have been raising the profile of biofuels. Biodiesel – which is made from vegetable oil and can be mixed with, or replace, diesel – and ethanol, which is made chiefly from sugar cane and corn, can be used in petrol vehicles.

Mr Warren and Mr Bradt, who have set up the Biofuels Education Coalition, a non-profit group, began their trip in July 2006 heading down the PanAmerican highway, through mountains, deserts and 16 countries. “We used any kind of oil we could find,” Mr Warren said.

That meant feeding their truck such innovations as salmon oil in Alaska and the rendered-down lard left over after frying pork snacks in Mexico, as well as waste grease from restaurants. and more conventional soya oil in Argentina.

Vegetable oil is cheaper than fossil fuels and the truck did as many miles to the gallon, Mr Warren said. The only difference is the smell. “It smells of food,” he said. “It’s better than a whiff of diesel but it just makes you a little more hungry.”