By Roger Harrabin
Environment analyst, BBC News
Oil firms have warned that European Union plans on biofuels could damage the world's rainforests.
Plantations for biofuels may threaten forests and wildlife,
Some oil representatives have told the government that they cannot meet the UK target of 5% biofuel on the forecourt by 2010 while also protecting wildlife.
The EU recently announced plans to double the biofuel total by 2020.
One government official told the BBC: "The policy is running ahead of the science; we have to be very careful that this doesn't all go badly wrong."
The biofuel bonanza is being promoted by the car industry as a way of achieving cuts in greenhouse gas emissions.
Biodiesel comes from plant oils, and ethanol from fermenting starchy or sugary plants.
Experts agree it makes sense to maximise wood waste and to grow energy crops on land that is marginally productive for food.
The problem is the scale of the enterprise. Many biologists warn there is simply not enough land on the planet to feed a growing number of people who are hungry for more protein, but also want to run cars on fuel from plants.
Already President Bush's highly-subsidised drive to get fuel from the Prairies has triggered food riots in Mexico because it has pushed up the price of corn.
The biofuels issue is particularly acute in Indonesia where the natural forests are being razed to make way for palm plantations to produce vegetable oil, soaps, shampoos, industrial substances - and now motor vehicle fuel too.
The oil giants have promised they would obtain their palm oil from sustainable sources; but they define this as taking oil from plantations where forests were felled more than five years ago.
Some oil industry experts are now admitting that this makes no sense, because it simply increases overall demand for palm oil.
The UK's overall energy plans have been thrown into disarray by the recent EU heads of government decision on energy supplies.
The forthcoming UK energy white paper plans to cut greenhouse gases by many means, including producing 20% of electricity from renewable sources like wind and solar by 2020.
EU plans effectively quadruple the target for renewable energy
But the EU's recently published strategy is far more prescriptive. It demands that 20% of all energy should come from renewables - that covers not just electricity, but also fuel for cars, domestic aviation, home heating and industry.
As electricity accounts for about a quarter of total energy, this means the EU figure works out as four times more renewable energy than the government had in mind.
The UK's exact share of the EU obligation is still being negotiated; but meanwhile officials are scrabbling to find policies to fit.
I understand that when the white paper is published it will paper over the policy gaps. The government will flesh out more detailed ideas when legislation is proposed in the autumn.