The big question is, do biofuels really contribute to reducing greenhouse gas emissions?
Research suggests that once the greenhouse gases produced by the the process of growing the crops for biofuel are factored in - from ploughing the fields, making the fertiliser, harvesting the crops, processing them, to transporting the finished fuel - the environmental benefits are seriously compromised.
One recent study investigated the impact of fertiliser on biofuel production. Using sugar cane, according to the research, does offer greenhouse gas savings of between 10% and 50%.
But using rapeseed and corn for biofuel manufacture can actually produce between 50% and 70% more greenhouse gases than using fossil fuels. Professor Keith Smith, one of the team of scientists who worked on the research, says he is "concerned that the adoption of biofuels so enthusiastically means we're running ahead of the science".
In February, transport secretary Ruth Kelly announced an enquiry into biofuels before committing the UK to any higher targets than those already set.
The fuels' future seems uncertain, yet in a step that even green campaigners support, the industry is now investing to develop "second generation" biofuels from non-food crops like straw, woodchips and even algae.
This is still some years off. Until then, the quest to find an alternative to petrol and diesel will continue to fuel debate, even if it does not fuel all our cars.
