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Crop Biotech Update

Biofuels May Contribute to Global Warming, Says Study

September 28, 2007

Rather than lowering greenhouse gas emissions, growing and burning biofuels may contribute to its accumulation, as shown by a new study led by Nobel laureate Paul Crutzen. Crutzen and his colleagues have computed that growing a number of commonly used biofuel crops releases about twice the amount of the greenhouse gas, nitrogen oxide, than previously thought. The research paper appears in Atmospheric Chemistry and Physics and is currently subject to open review. Crutzen, known for his works on nitrogen oxides and the ozone layer, declined to comment before the paper is officially published. The paper suggests that microorganisms convert the nitrogen from fertilizers to nitrogen oxide twice as much as the figure used by the International Panel on Climate Change (IPCC). For rapeseed and corn biodiesel dominant in Europe and US, respectively, the relative warming due to nitrogen oxide emission is 1.5 to 1.7 times larger than the quasi-cooling effect due to reduced fossil CO2 emission.

In the study, only sugarcane biodiesel, with 0.5 -0.9 relative warming, presents a viable alternative to fossil fuel use. Other experts are critical of Crutzen’s approach. Simon Donner, a nitrogen researcher based at Princeton University, says the method is elegant but Crutzen’s basic assumption may prove to be wrong. Stefan Rauh, an agricultural scientist at the Institute of Agricultural Economics and Farm Management in Munich, questions the values chosen by Crutzen to calculate his budget, and says that the rates for converting crops into biofuel should be higher.

Read more at The open access article can be read at