A federal clean fuel standard (CFS) for the USA

A clean fuel standard (CFS) regulates transportation greenhouse gas emissions by establishing a carbon intensity benchmark (the ‘compliance schedule’) against which transportation fuels may be rewarded or penalized depending on their lifecycle emissions scores. This paper examines the potential for a national CFS in the USA to drive cost-effective emissions reductions in road and aviation segments. We introduce the CFS Scenario Compliance Model (CSCM), and two ambitious scenarios of transportation decarbonization which are consistent with economy-wide progress to net zero emissions in 2050. Our ‘High-ZEV’ scenario is characterized by electrification of the vehicle fleet, while the ‘High-Liquid’ scenario emphasizes rapid scale-up of next-generation fuel production. These scenarios achieve an 87–94 % reduction in road transportation carbon intensity by 2050, with High-ZEV offering faster and deeper emissions cuts, as well as being cheaper for motorists. In addition, we model an ∼84 % reduction for aviation fuel carbon intensity (excluding non-CO2 emissions). Even in the High-ZEV scenario, road and air transport together consume 68 % of the USA's 1.5 °C carbon budget by 2050. We review policy considerations for the design of a national CFS in the USA, including the ambition of target-setting, investment support, and use of feedstock caps to mitigate sustainability risks.