California Policy Should Distinguish Biofuels by Differential Global Warming Effects

California Policy Should Distinguish Biofuels by Differential Global Warming Effects Richard J. Plevin Energy and Resources University of California, Berkeley Biofuels such as ethanol offer potential greenhouse gas (GHG) reductions compared to petroleum-based liquid fuels. However, while the combustion of biomass is considered carbon neutral, the production of biofuels can result in considerable GHG emissions. These emissions are highly variable and determined by a range of factors such as agronomic practices (for energy crops), conversion technology, and fuel choice. The state of California recognizes the potential for biofuels to reduce GHG emissions from the transport sector, yet state policies treat each type of biofuel as homogenous. Maximizing the climate benefits of biofuels will require life-cycle assessment (LCA) of all biofuel production pathways and regulations or incentives based on the differential global warming effects of each pathway. Certifying fuels requires monitoring and tracking the global warming intensity of each phase of production, for each pathway. Emissions for the agricultural phase of crop-based pathways, however, are highly sitespecific; measuring and monitoring these specifics may not be worth the significant effort required. Instead, average values based on feedstock and region can be used to compute agricultural phase GHG emissions. In contrast, biorefineries, which are relatively few in number and far less complex, should be monitored individually. Once each pathway has been analyzed, the net GHG reductions from large-scale biofuel use can be estimated. However, existing life-cycle analyses of the GHG emissions from biofuels production are inadequate and methodologically flawed. These analyses ignore complex market dynamics such as feedbacks (e.g. increased fuel use due to lower prices) and thresholds (e.g. saturation of coproduct markets) that occur at non-marginal production levels. Existing analyses also implicitly assume a “zero GHG” baseline, attributing all GHG emissions from crop-based biofuel production to the biofuel as if no emissions would occur absent biofuel production. A second generation GHG accounting model is proposed to correct these flaws, integrating market equilibrium analysis with life-cycle assessment to produce better estimates of the GHG reductions attributable to each biofuel pathway under a realistic (i.e. non-marginal) production scenario. The improved model lays the groundwork for regulations and incentives to encourage greater GHG reduction benefits from biofuels, and perhaps to deny incentives for pathways yielding zero or negative benefits.