THERE are a number of sources for biofuels, but there is one common theme that links them all – oil.

According to Terry de Winne, founder of the Biofuels.fsnet.co.uk website: ‘The essential element of biodiesel is oil – animal or vegetable, used or recovered, oil or tallow.

‘Treated with alcohol and a catalyst, mixed for an hour then left to settle overnight, the result is a pure diesel fuel compatible with currently-manufactured motor vehicle engines. That is a simplification of the transesterification process, but not overly so.’ Possible sources of biofuel include:

Rapeseed oil – the crop of bright yellow flowers is grown, crushed and refined to produce oil

Sugarbeet – the beet is fermented to use as a transport fuel

Sunflowers – some varieties of sunflower contain up to 45% oil, which can be converted into biofuel

Apple – the apples are fermented and can be turned into bioethanol which can be used as a 5% blend with petrol

Beans – certain types of bean can be crushed and refined to produce oil