BEIJING - Most crops grown in the United States and Europe to make "green" transport fuels 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 particular concern 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.
The study suggested scientists and farmers focused on crops, which required less intensive farming methods, to produce better 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 alternative to fossil fuels.
But the new study shows that some biofuels actually release more greenhouse gases than they save, because of the fertiliser used in modern farming practices.
The problem greenhouse gas, nitrous oxide, is more famous as the dentists' anaesthetic "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 results, published in "Atmospheric Chemistry and Physics Discussions," were based on the finding that fertiliser use on farms was responsible for three to five times more such greenhouse gas emissions than previously thought. http://www.atmos-chem-phys-discuss.net/7/11191/2007/acpd-7-11191-2007.pdf
They cast 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 competition with forests and food for land. Brazil and the United States produce most of the world's bioethanol, as a substitute for gasoline, while the European Union is the main supplier of biodiesel.
