摘要：Much research has estimated induced land use changes (ILUCs) and emissions for first generation biofuels. Relatively little has provided estimates for the second generation biofuels. This paper estimates ILUC emissions for the first and second generation biofuels. Estimated ILUC emissions are uncertain not only because their associated land use changes are uncertain, but also because of uncertainty in the land use emission factors (EFs). This paper also examines uncertainties related to these factors. The results suggest that converting crop residues to biofuel has no significant ILUC emissions, but that is not the case for dedicated energy crops. Use of dedicated energy crops transfers managed natural land and marginal land (cropland-pasture) to crop production. Producing biogasoline from miscanthus generates the lowest land requirement among alterative pathways. The largest land requirement is associated with switchgrass. The difference is due largely to the assumed yields of switchgrass and miscanthus. The three major conclusions from uncertainty in emissions analyses are (1) inclusion or exclusion of cropland-pasture makes a huge difference; (2) changes in soil carbon sequestration due to changes in land cover vegetation play an important role; and (3) there is wide divergence among the emission factor sources, especially for dedicated crop conversion to ethanol.
