Two technologies that are proposed as part of the solution to reducing greenhouse gas (GHG) emissions from the transportation sector are biofuels and electric vehicles (EV). Both technologies have come under the microscope as to their long-term benefits. For example, the effect of increased biofuel feedstock production on land use world-wide has received a great deal of attention because of the potential carbon penalty should carbon-rich lands be transitioned to feedstock production. Further, some question whether the production of EV batteries outweighs their lower carbon footprint during the use phase. We use life cycle analysis (LCA), a quantitative tool that holistically assesses the impacts, such as greenhouse gas (GHG) emissions, of a technology over the course of its life cycle, to investigate these potential hot spots.
In the case of biofuel feedstock production-induced land use change, we have developed estimates of the changes in carbon stock that would occur should volumes of corn, corn stover, miscanthus, and switchgrass ethanol be produced to meet RFS2 targets. These estimates incorporate state-level, feedstock-specific emission factors, calculated with the CENTURY model, that reflect changes in soil organic carbon (SOC) from land transitions. Combined with factors for above-ground domestic carbon changes from the Carbon On-line Estimator database and international land-use change emission factors from Woods Hole, we have developed estimates of land-use change GHG emissions for cellulosic ethanol produced from these four feedstocks.
To determine the influence of battery production on overall EV life cycle GHG emissions and energy consumption, we have investigated the production of five different cathode materials that could be incorporated into lithium-ion batteries for all-electric vehicles and plug-in hybrid electric vehicles. The materials are lithium manganese oxide, lithium cobalt oxide, lithium iron phosphate, lithium nickel manganese cobalt oxide, and an advanced cathode material under development at Argonne. Results of this analysis indicated that battery production is not a major element of the GHG emissions of an EV over the course of its lifetime when a conventional electricity grid is used to charge the battery. Cathode materials that contain cobalt or nickel, however, do have a higher GHG and SOx impacts than materials that exclude those metals.
Dr. Jennifer Dunn is an Environmental Analyst at Argonne National Laboratory. She investigates life cycle energy consumption and environmental impacts of advanced transportation and fuel technologies, including biofuels and battery-powered electric drive vehicles. Through this work, Jennifer contributes to the development of Argonne’s GREET (Greenhouse gases, Regulated Emissions, and Energy use in Transportation) software model for life-cycle analysis of advanced vehicle technologies and new fuels. At present, GREET has more than 20,000 registered users worldwide. Prior to joining Argonne, Jennifer led life cycle analysis projects in the United States for URS Corporation and supported mobile source emission reduction programs at the United States Environmental Protection Agency. She holds a Ph.D. in Chemical Engineering from the University of Michigan.