Life Cycle Assessment of Greenhouse Gas Emissions from Plug-in Hybrid Vehicles: Implications for Policy

TLDR

Plug‑in hybrid electric vehicles can cut transport GHGs, but their benefit depends on low‑carbon grid electricity and long‑term power‑sector choices that shape future emissions. The study models PHEV life‑cycle emissions, accounting for lithium‑ion battery production (2–5 % of total GHGs) and varying electricity carbon intensities, including cellulosic ethanol use. PHEVs cut life‑cycle GHGs by 32 % versus conventional cars, though only modestly better than hybrids, and their lower liquid‑fuel use could help conserve scarce cellulosic ethanol supplies.

Abstract

Plug-in hybrid electric vehicles (PHEVs), which use electricity from the grid to power a portion of travel, could play a role in reducing greenhouse gas (GHG) emissions from the transport sector. However, meaningful GHG emissions reductions with PHEVs are conditional on low-carbon electricity sources. We assess life cycle GHG emissions from PHEVs and find that they reduce GHG emissions by 32% compared to conventional vehicles, but have small reductions compared to traditional hybrids. Batteries are an important component of PHEVs, and GHGs associated with lithium-ion battery materials and production account for 2–5% of life cycle emissions from PHEVs. We consider cellulosic ethanol use and various carbon intensities of electricity. The reduced liquid fuel requirements of PHEVs could leverage limited cellulosic ethanol resources. Electricity generation infrastructure is long-lived, and technology decisions within the next decade about electricity supplies in the power sector will affect the potential for large GHG emissions reductions with PHEVs for several decades.