Thin air: Sceintists say car fuel could be created from thin air using an enzyme from a common soil bacterium. It is hoped this will lead to a cheap way of making environmentally friendly, carbon-neutral "green" fuel that can be used without major redesigns of car engines.
Sunlight: New technology for "photosynthesising" fuel could lead to cars running on "petrol" made from carbon dioxide and sunlight. Solar-powered reactors can take carbon dioxide and turn it into carbon monoxide. The same reactors can also be used to turn water into hydrogen and oxygen. The two can then be reacted together with a catalyst to form hydrocarbon fuels, in a technique known as the Fischer-Tropsch process.
Hydrogen: Hydrogen fuel-cell cars are to be tested on British roads by the public for the first time. Thirty of the vehicles, which have a top speed of 50mph and can go 200 miles on one tank of hydrogen, will be leased to motorists in Leicester from spring 2012. The two-seater car has been developed by Riversimple, a small British manufacturer based in Ludlow, Shropshire.
Chip fat: An eco-friendly car enthusiast claimed to he transformed his vehicle to run on recycled chip fat. Alan Collins, 47, from Chesterfield in Derbyshire, wanted a environmentally-friendly alternative to diesel that would not detract from the car's performance. When he made his eco-conversion in 2002, his £13,000 Audi A4 had notched up more than 1,000 miles of trouble-free motoring by using fuel harvested from a quarter of an acre of sunflowers. As sunflower oil and fat are not mineral-based fuels, the emissions were considered less harmful to the environment.
Alcohol: Ethanol was the next big thing, according to General Motors. GM said at the 2008 Detroit motor home we need to invest in these fuels because, in the immediate future, nothing else will reduce the fast rising demand for oil.
Vegetable oil: Thousands of motorists in 2007 were "home brewing" fuel for their cars, at a tenth of the price at the pump. The "DIY diesel" is tax free and costs just about 9p a litre to produce, compared with about 96p at a garage, experts said. Companies producing the kits, which are similar in appearance to home-brew sets for making beer, reported soaring sales. The main ingredient is vegetable oil, usually obtainable free from restaurants and takeaways which must otherwise dispose of a hundred litres a week.
Chocolate: A new racing car made of vegetables and powered by chocolate can hit speeds of 145 miles per hour. Designers hoped the environmentally-friendly technology used in their car, launched last year, will be adopted by Formula 1 teams such as McLaren and world champions Ferrari. The car, named ecoF3, has a steering wheel made of carrots, a body made of potatoes and a seat made of soybeans.
Steam: Last year the British Steam Car team successfully carried out two test runs ahead of its bid to break the century-old world land speed record for steam-powered vehicles. The 25ft-long British Steam Car reached speeds of more than 80mph on tarmac at the Ministry of Defence's Thorney Island facility in Emsworth, Hants.