The CI associated with biomass and biofuel transportation and distribution was estimated by multiplying the mass of biomass or biofuel and transport distance by transportation emission factors for a diesel truck (expressed in kg CO2e×kg-km -1 ) from ecoinvent 3.8 and the TRACI 2.0 impact assessment methodology. Because there are only two operational SAF refineries and zero operational cellulosic ethanol refineries in the U.S., a range of biomass and biofuel transport distances (see SI Table ) were evaluated to characterize the potential consequences of this parameter on the overall CI of SAF production. The median biomass and biofuel transport distances were 100 and 600 kilometers, respectively, which accounts for two trips (i.e., one full transport trip and one empty return trip). The CI of both transportation and distribution stages was added to the CI of the biomass conversion stage calculated using BioSTEAM and BLocS.