Nitrous oxide emissions from liquid biofuel production in life cycle assessment

Estimated life cycle nitrous oxide (N2O) emissions of current biofuel production are strongly dependent on cropping system, climate, and the choice of the reference land-use system. The calculation of climate footprints of biofuels due to N2O emissions further depends on the time horizon of the impacts considered and the allocation of the emissions to co-products. Estimated life cycle nitrous oxide (N2O) emissions of current biofuels can contribute substantially to the effect of life cycle greenhouse gas emissions of biofuels (up to 80%). The estimated percentage of the contribution of N2O emissions to the overall effect of biofuel life cycle greenhouse gas emissions may, however, vary by about two orders of magnitude. Life cycle emissions of N2O can be reduced by improving nitrogen use efficiency in the cultivation of biofuel crops.

► N2O emissions of biofuel production highly depend on cropping system and climate.
► Subjective choices in the models also influence predicted N2O emissions of biofuel production.
► N2O emissions contribute substantially to climate footprints of biofuels.
► Efficient nitrogen use in biofuel crop production is vital to reduce N2O emissions.