Meeting U.S. light-duty vehicle fleet climate targets with battery electric vehicles and electrofuels

Abstract

Mitigating greenhouse gas (GHG) emissions from light-duty vehicle (LDV) fleets cannot solely rely on battery electric vehicles (BEVs). This study focuses on a potential complementary solution, electrofuels (e-fuels, produced with electrolytic hydrogen and carbon dioxide) and specifically e-gasoline deployment in the U.S. as a drop-in fuel compatible with existing vehicles and fueling infrastructure. This study uses 1) fuel- and vehicle-level analyses to determine energy and feedstock inputs that would enable e-gasoline to have lower GHG emissions than conventional gasoline or vehicle electrification; and 2) fleet-level analysis to understand whether deploying e-gasoline in the U.S. LDV fleet can help reach 2015-2050 cumulative emission budgets under exogenous BEV deployment scenarios. For each scenario, we analyze required e-gasoline production volumes and associated demands for feedstock, renewable electricity, and critical materials for water electrolyzers and electricity generation. Results show that e-gasoline GHG intensity is most sensitive to electrolysis electricity GHG intensity. Deploying e-gasoline produced from fully renewable energy has the potential to assist the fleet in meeting climate targets. Absent other measures, a slower deployment of BEVs or insufficient low-GHG intensity electricity for BEV charging increases the need for e-gasoline and an aggressive production ramp-up. When e-gasoline is produced through optimistic pathways (e.g., fuel-level GHG intensity as low as 7 g CO2-eq/MJ), meeting a 2 °C climate target would require peak production of 17-400 billion L/yr by ~2040 depending on the BEV deployment scenario (requiring an estimated 2-45 times 2023 U.S. carbon capture capacity, 60-1400 times 2020 U.S. electrolytic hydrogen production, and 0.4-9 times 2022 U.S. renewable electricity production). Without significant recycling of electrolyzer inputs, cumulative material demand could exceed global reserves for iridium, and place pressure on yttrium, nickel, and platinum reserves depending on assumed electrolyzer technology. Mitigating GHG emissions from land passenger mobility cannot solely rely on BEVs and e-fuels; other complementary strategies based on vehicle efficiency, other low carbon fuels, trip avoidance, and modal shift must be considered.