Faced with soaring prices at the petrol pumps, ecologically-minded Britons are turning to fish and chips to run their cars -- transforming the leftover frying oil into "green" fuel.
Deep in the southern English countryside, an environmental group spent last weekend teaching 12 men how to transform the abundant vegetable oil from fish and chip shops, but also pubs and restaurants, into biodiesel.
One of the participants, Mike Kempton, who runs a business hiring out limousines, said the prospect of cheap fuel was extremely attractive at a time when oil prices have reached historic highs.
"I want to save money, I don't want to be in a position where I'm isolated from fuel and where I can't drive my vehicle.
"And I genuinely am concerned about what we're doing to the environment," he said.
The courses are organised by the Low Impact Living Initiative (LILI), a group which has already trained more than a thousand people, and applicants for the scheme increase every time the price of fuel rises.
In an added incentive, the government does not tax the production of biodiesel, providing it does not exceed 2,500 litres per person a year.
In a low-tech shed in Winslow near Oxford, Jon Halle, a tutor from the non-profit making company Goldenfuels, gives the participants an elementary chemistry lesson.
By mixing a litre of vegetable oil with methanol and several other ingredients and heating it, he produces a litre of basic biodiesel.
"Some people don't have a clue, some people on the course are chemists but everybody will be able to go away and do it if they spend the time," Halle said.
He insists the danger is low even to people without a scientific background.
"The risks are, you use some dangerous chemicals, you also use electricity so you could have potentially dangerous scenarios but you just have to take care.
"It's not rocket science, it's like cookery but on a big scale."
It is not as easy as Halle makes it look -- some of the participants struggle to properly measure the amount of fatty acids in the oil that must be neutralised for it to become fuel.
But when properly done, the biodiesel can be used in diesel engines without any modification and without the vehicle suffering any loss of performance.
Biodiesel made from vegetable oil contains 75 percent less carbon than its mineral equivalent.
Another participant on the course, Matthew Stephens, from Lincolnshire in eastern England, admitted using the "green" fuel was good for his conscience.
"I have to use the car to work a lot, Lincolnshire doesn't have public transport in a meaningful way," he said.
"And if I use biodiesel, it will make me feel an awful lot better because it's virtually carbon-free."
The re-processing of vegetable oil is relatively rare in Britain, meaning there is a huge glut of raw material and the process does not require much-needed agricultural land to be set aside to growing biofuels crops such as rapeseed.
There is one hitch though -- the basic equipment to turn the oil into fuel costs between 1,000 and 2,000 pounds (1,250 euros and 2,500 euros or 1,950 dollars and 3,900 dollars) and the necessary chemicals cost 15 pence per litre of biodiesel.
That means an individual user would need to produce biodiesel for more than a year to absorb the initial investment.
Colin Hygate, the director of Greenfuels, which claims to be Europe's biggest seller of the re-processing equipment, said business was booming as people take a long-term approach.
"We see an acceleration whenever there is an issue about fuel security or the cost of fuel at the fuel station," he said.
"We are growing year-on-year. Over a four-year period, we have gone from a turnover of less than 100,000 pounds a year to a turnover this year that is looking more like two million pounds.
"The number of people inquiring about our products has increased from about 10 to 15 contacts a day to between 40 to 50 people and we have had to employ additional sales people to try to cope with the increasing demand."