You may not have noticed, but Britain’s green fields are turning yellow. Look out of your car window a few years from now and all you’ll see is acre upon acre of golden oilseed rape. These are the 21st century’s oilfields. Farmers will become the new oil barons as climate change and diminishing oil supplies turn plants into the environmentally friendly wonder fuel.

This is the vision of the biofuels lobby, until recently dismissed as being as far-fetched as El Dorado. But the biofuels solution to eco-motoring is gradually becoming a reality.

While hybrid petrol-electric motors such as the Toyota Prius hog the headlines, many believe the environmental benefits of hybrids have been overplayed. And the holy grail of clean motoring — the hydrogen fuel cell — is at least 20 years away from becoming a commercial reality.

This, according to the British Association for Biofuels and Oils (Babfo), leaves biofuels as the only current viable solution to cutting carbon dioxide emissions.

There are two types of biofuel: biodiesel made from plant oils and bioethanol made by fermenting grains. These can be used in unmodified diesel and petrol engines respectively when blended with conventional diesel and petrol. The vast majority of biofuels on sale in Britain actually include no more than 5% biodiesel or bioethanol to 95% conventional fuel, in compliance with British and European Union approved standards.

Most manufacturers argue higher concentrations would damage conventional engines, although critics point out that they are used elsewhere — in the United States, for example, where blends are usually 10% bioethanol. With minor modification engines can be converted to run on even higher concentrations of biofuel and a handful of independent garages currently sell 100% biodiesel — about nine around the UK, according to www.biodieselfillingstations.co.uk — and claim most diesel cars can run on it without alteration. The price per litre is about 89p: comparable with the price of conventional diesel.

Carbon dioxide (CO2) emissions are about the same (comparing biodiesel with diesel and bioethanol with petrol) but the equivalent amount of CO2 released when the fuel is burnt will be reabsorbed through photosynthesis by the next crop of plants, so the CO2 is effectively recycled. Engines that run on biodiesel also produce lower particulate pollution and nitrogen oxide emissions.

“For the next 50 years at least, biofuels are likely to be the most effective alternative to fossil fuels,” says Peter Clery, chairman of Babfo.

It is not just lobby groups that say so. Last month the EU increased pressure on the British government to meet its biofuel targets. The EU would like 2% of all fuel sold within its borders to be biofuel by next year and just under 6% by 2010. Unlike Germany and France, which are on course to hit the 2% target, Britain currently plans to achieve just 0.3% by the end of the year.

The government is expected to announce a more ambitious 2010 target before the new year and is considering placing a legal requirement on oil companies to produce a certain quantity of biofuel.

Critics claim that because conventional fuels are needed in the production and refining process, the ultimate benefit of biofuels to the environment is not clear-cut. Even their supporters acknowledge the problem but say biofuels can still cut CO2 emissions realistically by between 50-60%.

On the ground the change in thinking on biofuels is evident. The number of hectares of oilseed rape leapt by 100,000 to just under 1.5m between 2004 and 2005, according to Babfo. It predicts a similar increase next year as farmers switch from putting food in our stomachs to juice in our tanks.

British sales of biodiesel, although still a fraction of traditional fuels, more than doubled between April 2004 and May 2005 — up from less than 1.5m litres per month to almost 3m litres, according to Department for Transport figures. Sales of bioethanol reached 7.8m litres in the same month, up from virtually nothing and boosted by the introduction of a 20p tax rebate (biodiesel has had one since 2002) at the beginning of the year.

The number of garage forecourts stocking the fuel is also rising. Tesco is leading the way among petrol retailers — of its 381 fuel stations, more than half have replaced conventional unleaded petrol with petrol that includes 5% bioethanol.

“We hope to have bioethanol included in all our unleaded petrol within the next few years,” said a Tesco spokesman. “We can sell it for the same price as conventional unleaded so there was no reason not to take the green option.” Tesco also has 23 stations offering a 5% biodiesel blend.

Car makers too are being converted. Earlier this summer Saab launched its first flexible-fuel model, a version of the Saab 9-5 that can handle bioethanol concentrations of up to 85% as well as pure petrol. The car is currently only on sale in Sweden but Saab hopes to take British orders early next year. A flexible-fuel version of the Ford Focus will be available next April.

Right now the dream of a clean biofuel future remains just that. But as the momentum of government, petrol companies and motorists builds behind it, Clery’s vision appears increasingly plausible. “Every field in Britain could become a potential oilfield,” he says.