Climate Impacts of Short-Lived Climate Forcers versus CO₂ from Biodiesel: A Case of the EU on-Road Sector

Biofuels are proposed to play an important role in several mitigation strategies to meet future CO₂ emission targets for the transport sector but remain controversial due to significant uncertainties in net impacts on environment, society, and climate. A switch to biofuels can also affect short-lived climate forcers (SLCFs), which provide significant contributions to the net climate impact of transportation. We quantify the radiative forcing (RF) and global-mean temperature response over time to EU on-road fossil diesel SLCFs and the impact of 20% (B20) and 100% (B100) replacement of fossil diesel by biodiesel. SLCFs are compared to impacts of on-road CO₂ using different approaches from existing literature to account for biodiesel CO₂. Given the best estimates for changes in emissions when replacing fossil diesel with biodiesel, the net positive RF from EU on-road fossil diesel SLCFs of 3.4 mW/m² is reduced by 15% and 80% in B20 and B100, respectively. Over time the warming of SLCFs is likely small compared to biodiesel CO₂ impacts. However, SLCFs may be relatively more important for the total warming than in the fossil fuel case if biodiesel from feedstock with very short rotation periods and low land-use-change impacts replaces a high fraction of fossil diesel