Significantly decarbonizing road transport by 2050, in line with Paris Agreement objectives and the current research from the Intergovernmental Panel on Climate Change,1 will require (a) identifying and supporting the technology pathways capable of delivering deep greenhouse gas (GHG) emissions reductions on a life-cycle basis and (b) understanding the related policy challenge of time. The ICCT has conducted a comprehensive life-cycle assessment of GHG emissions from a variety of alternative passenger car powertrains and fuels, and this briefing presents an overview of the findings and the implications for policy.

The evidence shows there is no realistic pathway to full decarbonization of internal combustion engine vehicles. Natural gas does not offer climate benefits compared to gasoline and diesel, and many biofuel pathways do not, either. There will not be sufficient supply of very low-GHG biofuels, biogas, and e-fuels to decarbonize internal combustion engine vehicles. E-fuels, also known as electrofuels and power- to-liquids, are produced from carbon dioxide (CO2) and electricity. Drivers of plug-in hybrid electric vehicles rely too much on the gasoline engine for this pathway to be a long-term climate solution. Only full battery electric vehicles (EVs) and hydrogen fuel-cell EVs have the potential to be very low-GHG pathways, and the emissions from manufacturing batteries, solar panels, and wind turbines are small when compared to the GHG savings from the greater efficiency and cleaner energy supply of EVs compared to conventional vehicles.

Importantly, battery EVs can be expected to operate with progressively fewer upstream emissions over their lifetimes as electricity grids “green.” The average useful lifetime of a passenger car is between 15 and 18 years (for trucks and buses, it is often even longer),2 and this study finds the bulk of a vehicle’s life-cycle GHG emissions come from fuel and electricity production and consumption. Thus, decarbonization policies will be most impactful if they reflect passenger cars transitioning to all EVs for new sales by the early 2030s, in order to achieve deep decarbonization of the transport sector by 2050.

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