Current Life Cycle Analysis (LCA) models indicate that crop-based biofuels generate greenhouse gas savings, compared with fossil fuels. We argue that they do so only because they ignore the emissions of CO2 from vehicles burning the biofuels without determining if the biomass is “additional,” and because they underestimate the ultimate emissions of N2O from nitrogen fertiliser use. Taking proper account of these factors would result in very different findings. It would be far better to derive biofuels from biomass, from waste feedstocks or highyielding bioenergy crops with low nitrogen demand, grown on currently unproductive land.
Smith K A and Searchinger T D (2012). Crop-based biofuels and associated environmental concerns, GCB Bioenergy, doi: 10.1111/j.1757-1707.2012.01182.x