Evaluating Lifecycle Assessment models in a Low Carbon Fuel Standard

Abstract

To avoid and/or reduce the risk of the various potential irreversible impacts associated with global climate change, many policies have been proposed to create reductions in greenhouse gas (GHG) emissions in all sectors of the United State’s economy. Several US States and the Federal government are considering, or have already considered, adopting a policy called a low carbon fuel standard (LCFS) that seeks to reduce the average GHG intensity of fuels measured across the full fuel cycle. There is significant controversy over the selection of a life cycle assessment (LCA) model to measure full fuel cycle emissions because of the potential impacts on an LCFS policy. There is a debate over whether or not full fuel cycle emissions are useful standards for use in policies designed to set and reach GHG emission reduction goals. This paper compares structural differences within existing LCA models, and the impacts of the emission intensity scores produced by these models. It then introduces these results into a LCFS policy in a system dynamics (SD) model of the Minnesota transportation sector. A comparison between the full fuel cycle intensity emissions as produced by LCA models show that full fuel cycle emissions matter in evaluating fuel choices under the LCFS and differ with regard to pollutants, fuel choice, and jobs created from fuel choices. From the SD modeling scenarios, criteria were developed to help policy makers select an LCA model for use in an LCFS (or potentially other policies). Selection of an LCA model is driven by situation specific issues, values, and goals of policy makers; therefore, criteria developed in this paper will be helpful in determining which LCA model should be adopted under different political and social contracts.