Land use change (LUC) may be the single most important factor in determining the sustainability of biofuels. To ensure that legal standards are effective in limiting climate change forcings, it is essential that LUC be given thorough and rigorous treatment. This Article examines the premise that the climate impacts of LUC—as characterized by biofuels life cycle analyses (LCAs)—are completely fungible with the climate impacts of greenhouse gas (GHG) emissions from other sources. LUC affects climate through both ‘biogeochemical’ and ‘biophysical’ forcings, or the climate impacts of LUC through alteration of atmospheric GHG concentrations and through perturbation of water and energy exchange between the land surface and the atmosphere, respectively. This Article presents a method for thoroughly quantifying the GHG effects of LUC and also provides quantitative estimates of the magnitude of biophysical forcings. The Article then assesses the comprehensiveness of the accounting systems used by major fuel standards. Biofuel LCAs are increasingly including the most important elements required to thoroughly quantify the GHG effects of LUC, yet they are not comprehensive in all aspects and generally use improper accounting for the timing of emissions. Biophysical forcings are sometimes more influential than biogeochemical forcings. However, they have never been included in assessments of the impacts of biofuels-related LUC. Thus, biofuels LCAs are not accurately quantifying the climate impacts of LUC.
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