23/01/2008 (Crash.net, UK) - Biofuels have been hailed as a renewable alternative to fossil fuels in transport, but recent reports have raised concerns they are not always as green as they seem.

The renewable fuels come from organic materials ranging from sugar beet and cane, to wheat or palm oil and because they have taken in carbon dioxide during growth, they are low carbon-emitting compared to the fossil fuels they replace.

But biofuels from plant crops have a big question mark hanging over them amid fears they can compete for land with food, lead to forest clearance which destroys natural habitat and release more carbon, In addition, they can contribute to greenhouse gas emissions through the fertilisers used to grow them and the methods of transporting them.

Initial enthusiasm for the apparently green fuel led to the EU setting targets of meeting 10% of petrol and diesel needs through renewables by 2020, which in the UK translates into the RTFO.

Researchers writing in the journal Science last August said the target was less effective in curbing carbon emissions than a programme of restoring forests and protecting plant habitats.

And just last week a report from the Royal Society warned there was a risk that biofuels could fail to deliver hoped-for reductions in greenhouse gas emissions and could damage the environment.

It has been calculated that reductions in greenhouse gases of anywhere between 10% and 80% compared to fossil fuels could be delivered by converting wheat to ethanol in the UK depending on the processes used, and the Royal Society urged the Government to ensure biofuels are produced in a way that is sustainable and actually delivers CO2 cuts.

The Department for Transport says it is determined only to support biofuels that have a genuine environmental benefit, and the RTFO requires mandatory reporting on the sustainability and carbon impact of the fuels by suppliers.

But earlier this week, the Environmental Audit Committee called on the Government to scrap measures to promote biofuels, describing them as "reckless" and demanded an immediate moratorium in favour of more sustainable ways of achieving emissions reductions.

Scientists are currently developing a new generation of fuels which use the by-products of agriculture - such as straw - so removing the fears over competition with food and minimising the emissions associated with their production.

Fuels from household waste, specially grown algae and even woody crops or grasses which would provide much higher energy yields per hectare than current crops are also being developed.

But the technology is still currently at a demonstration stage and the fuels are not yet on the commercial market.

The UK's Renewable Transport Fuels Obligation (RTFO), which comes into force in April, requires 5% of fuels for vehicles to come from renewable sources by 2010, with bioethanol and biodiesel being blended into conventional petrol and diesel respectively to cut their carbon footprint.