September 24, 2007

Biofuel crops may raise greenhouse gas emissions, scientist says

Cambridge, England – A new study by Nobel Prize-winning chemist Paul Crutzen suggests that growing and burning biofuel crops may actually raise greenhouse gas emissions, rather than lower them.

The study says that growing some of the most commonly-used biofuel crops release around twice the amount of the potent greenhouse gas nitrous oxide than previously thought. The amount of nitrous oxide – N2O, also known as “laughing gas” – could wipe out any benefits from not using fossil fuels, and probably contribute to global warming.

“The significance of it is that the supposed benefits of biofuels are even more disputable than had been thought hitherto,” says Keith Smith, co-author on the paper. “What we are saying is that (growing many biofuels) is probably of no benefit and in fact is actually making the climate issue worse.”

The work is currently subject to open review in the journal Atmosphere Chemistry and Physics, and Crutzen has declined to comment until that process is complete. The paper suggests that microbes convert much more of the nitrogen in fertilizer to N2O than previously thought, and could be three to five percent, which is twice the widely-accepted figure used by the International Panel on Climate Change to calculate the impact of fertilizers on climate change.

For rapeseed biodiesel, which accounts for about 80 percent of the biofuel production in Europe, the relative warming due to N2O emissions is estimated at 1 to 1.7 times larger than the relative cooling effect due to saved fossil-fuel CO2 emissions. For corn bioethanol, dominant in the U.S., the figure is 0.9 to 1.5 times larger. Only cane sugar bioethanol, with a relative warming of 0.5 to 0.9, looks like a better alternative to conventional fuels.

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