Biofuels such as biodiesel from soy beans can create up to four times more climate-warming emissions than standard diesel or petrol, according to an EU document released under freedom of information laws.

The EU has set itself a goal of obtaining 10 per cent of its road fuels from renewable sources, mostly biofuels, by the end of this decade, but it is now worrying about the unintended environmental impacts.

Four major studies are under way.

Chief among those fears is that biofuel production soaks up grain from global commodity markets, forcing up food prices and encouraging farmers to clear tropical forests in the quest for new land.

Burning forests releases vast quantities of carbon dioxide and often cancels out many of the climate benefits sought from biofuels.

Biodiesel from North American soybeans has an indirect carbon footprint of 339.9 kilograms of CO2 per gigajoule - four times higher than standard diesel - said the EU document, an annex that was controversially stripped from a report published in December.

Editing the report caused one of the consultancies, Fraunhofer of Germany, to disown it partly in a disclaimer.

But it has now been made public after Reuters used freedom of information laws to gain a copy.

The EU's executive European Commission said it had not doctored the report to hide the evidence, but only to allow deeper analysis before publishing.

"Given the divergence of views and the level of complexity of the issue... it was considered better to leave the contentious analysis out of the report," the Commission said in a statement. "The analysis prepared under this study applied a methodology which by many is not considered appropriate."