Many biofuels have more climate impact than oil

By Emma Graham-Harrison

BEIJING (Reuters) - Most crops grown in the United States and Europe to make a "green" alternative transport fuel actually speed up global warming because of industrial farming methods, says a report by Nobel prize winning chemist Paul J. Crutzen.

The findings could spell special worries for alternative fuels derived from rapeseed, used in Europe, which the study concluded could produce up to 70 percent more planet-warming greenhouse gases than conventional diesel.

It suggested scientists and farmers focus on crops needing little fertilizer and harvesting methods that were not energy intensive in order to produce benefits for the environment.

Biofuels are derived from plants which absorb the planet-warming greenhouse gas carbon dioxide as they grow, and so are meant as a climate-friendly substitute for fossil fuels.

But the new study shows that some biofuels actually release more greenhouse gases than they save, because of the fertilizer used in modern farming practices.

The problem greenhouse gas, nitrous oxide, is more famous as the dentists' anesthetic "laughing gas", and is about 300 times more insulating than the commonest man-made greenhouse gas carbon dioxide.

"The nitrous oxide emission on its own can cancel out the overall benefit," co-author Professor Keith Smith told Reuters in a phone interview.

The study casts further doubts on the credibility of biofuels as a climate cure, following the revelation of other unintended side effects such as rainforest clearance and raised food prices, from competing with forests and food for land.