Greenhouse Gas Emission Mitigation Pathways for Light-duty Vehicle Fleets under Ambitious Climate Targets

Abstract

Mitigating greenhouse gas (GHG) emissions from light-duty passenger vehicles (LDVs) will be necessary to maintain global warming below 2 °C, and ideally below 1.5 °C. In this dissertation, methods to estimate the life cycle GHG emission implications of LDV-focused mitigation strategies and to outline mitigation pathways under ambitious climate targets are developed at national and urban scales. First, a fleet-based life cycle model, the FLAME (Fleet Life cycle Assessment and Material-flow Estimation) is developed to examine the life cycle GHG emission implications of mitigation strategies, such as lightweighting the U.S. LDV fleet or deploying mid-level ethanol blends (15-30% ethanol by volume) in Canada's LDV fleet. The model combines the high technological resolution of life cycle assessment (LCA) with the temporal and dynamic perspectives of LDV fleet models. Recommendations are provided on the most effective timing of the mitigation strategies, and on their contributions to national GHG emission reduction pledges. Then, the FLAME model is augmented with a backcasting procedure to outline GHG emission mitigation pathways for LDV fleets to maintain global warming below 2 °C, and the electrification of the U.S. LDV fleet is used as a case study. The backcasting procedure relies on an innovative approach based on Integrated Assessment Models (IAMs) to quantify national and sectoral GHG emission budgets. Finally, the CURTAIL model (Climate change constrained URban passenger TrAnsport Integrated Life cycle assessment) is developed and applied in Singapore to integrate all passenger land transport modes at an urban level and to seek associated combinations of mitigation strategies that are consistent with maintaining global warming below 2 °C or 1.5 °C. The methods developed in this dissertation bridge gaps between the refined perspectives of LCA and the global perspectives of IAMs to support the development of national and urban policies for LDVs to respect ambitious climate targets. The findings suggest that there is no technological silver-bullet, there is an urgency to act, and all mitigation efforts should be pursued.