In North Wales, bio-fuel pioneer John Nicholson runs his Mercedes on pure duck fat obtained from a firm that makes Chinese meals for supermarkets. Meanwhile, in the US, Alabama farmer Wayne Keith uses a pick-up truck with a wood burning stove that provides hydrogen to power the engine.
Both men are grappling with one of the biggest questions facing the planet: where do wefind alternatives to fossil fuels? The answer may lie not only in wood and duck fat, but also in cooking oil, rapeseed, palm oil, sugar cane and even wheat. All are natural forms of hydrocarbon waiting to take their place as fuels that can power our vehicles without upsetting the delicate balance of the planet.
Road transport emissions rose by 50 per cent between 1990 and 2003; these account for about a quarter of all Britain's fossil carbon emissions.
Nicholson, whose company sells bio-fuels made from used cooking fats says: "To run a car on duck fat, all you have to do is cut into the fuel supply pipe; and the engine just sucks it in. It works best on cars like Mercedes, which are well built."
Nicholson discovered alternative fuels a few years ago during the fuel price blockades. "It is amazing what some engines will run on. Although the fact that an engine will run on an unusual form of bio-fuel does not always means that it is running cleanly or efficiently.''
Bio-fuels were once only the preserve of those either in the know or enthusiasts concocting bio-diesel from used vegetable oils in their sheds. But almost unheralded, there has been increased acceptance of bio-fuels among bodies such as police forces and local authorities, with several police forces already trialling bio-diesel.
Environmentalists hope they will help increase demand for biofuels and prompt the Government towards greater support, currently limited to a tax break of 20p per litre.
Biofuels break down into two types. Bio-diesel is made from used or fresh vegetable oils by a simple conversion process. It can then be used in most diesel engines. It is possible to use the oils without the conversion process for short periods, but most engines tend to clog up after a while, so converted fuel is preferable for long term use.
Recycling used oil results in around 85-90 per cent of fossil fuel emissions being removed; the level reduces to about 50-75 per cent using freshly made oil.
About 150 places sell bio-diesel in Britain and conversion plants are springing up, although most of the fuelis actually a blend of conventional diesel and 5 per cent pure bio-diesel. But while campaigners such as Nicholson argue that diesel engines in many cars such as Mercedes, Volkswagen and Renault can run happily on pure bio-diesel, manufacturers say that, because of doubts about purity, the limit must be 5 per cent.
Bioethanol, a petrol substitute, is more problematic. It is essentially alcohol distilled from renewable sources - including, as Wayne Keith discovered, wood. In Brazil, many cars run on bioethanol made from by-products of the sugar cane industry. But, unlike bio-diesel, it cannot usually be used in petrol engines without adaptation.
So what should the Government do to encourage greater use of biofuels? Richard Hill, of the British Association for Bio-Fuels and Oils says: "We want the Government to impose a mandate on fuel suppliers to ensure that a proportion of all sales will be bio-fuels. And an increase of 1p a litre on diesel would be enough to remove all duty from bio-diesel. The Government badly needs an environmental success story and this is one that could be easily and quickly make a massive impact."