A paper by Nobel laureate Paul Crutzen (P. J. Crutzen, A. R. Mosier, K. A. Smith, and W. Winiwarter (2007) N2O release from agro-biofuel production negates global warming reduction by replacing fossil fuels Atmos. Chem. Phys. Discuss., 7, 11191 - 11205,) finds that:
When the extra N2O emission from biofuel production is calculated in ’CO2-equivalent’ global warming terms, and compared with the quasi-cooling effect of ’saving’ emissions of 15 fossil fuel derived CO2, the outcome is that the production of commonly used biofuels, such as biodiesel from rapeseed and bioethanol from corn (maize), can contribute as much or more to global warming by N2O emissions than cooling by fossil fuel savings.
Crops with less N demand, such as grasses and woody coppice species have more favourable climate impacts. This analysis only considers the conversion of biomass to 20 biofuel. It does not take into account the use of fossil fuel on the farms and for fertilizer and pesticide production, but it also neglects the production of useful co-products. Both factors partially compensate each other. This needs to be analyzed in a full life cycle assessment.
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