Nobel scientist in biofuel warning
Updated on 13 December 2007
A Nobel Prize-winning scientist has warned that switching from fossil fuels to biofuels could do the planet more harm than good.
Prof Paul Crutzen calculated the global warming effects of the fertiliser needed to grow energy crops like biodiesel and bioethanol were much worse than has been estimated.
He believes a larger proportion than thought of the nitrogen in fertilisers is converted into nitrous oxide, a potent greenhouse gas, New Scientist magazine reported.
The Intergovernmental Panel on Climate Change has suggested that 1-2% of nitrogen added to fields becomes nitrous oxide.
But Prof Crutzen and his colleagues calculated the true figure was closer to 3-5% - enough to negate the savings in carbon dioxide emissions made by switching from fossil fuels.
They estimated that biodiesel made from rapeseed was the least efficient biofuel, potentially having a significantly greater warming effect than fossil fuels.
Only bioethanol made from sugar cane was clearly more beneficial to the fight against climate change, they found.
Prof Crutzen, of the Max Planck Institute for Chemistry in Mainz, Germany, won the 1995 Nobel Prize for chemistry for his work on the threat to the ozone layer.
Prof Crutzen told New Scientist: "Here and there the numbers may change. But the principle doesn't.
At present about 12 million hectares - or around 1% of the world's fields - are devoted to energy crops.
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