Emission characteristics of alternative drive technologies regarding type and number of condensation nuclei for contrail formation

Kurzfassung

Aviation remains one of the most challenging sectors to decarbonize, not only because of its reliance on liquid hydrocarbon fuels but also due to its substantial non-CO2 effects, especially contrails. Understanding how contrails form under alternative propulsion and fuel technologies is therefore of major scientific and policy interest. This study systematically compares contrail formation from hydrogen combustion, SAF, and conventional kerosene, drawing on experimental campaigns and advanced modeling. Contrail ice crystal number emissions are evaluated across pathways, providing quantitative ranges and highlighting the large uncertainties involved. Results show that hydrogen combustion generally produces fewer ice crystals than kerosene or SAF, but nucleation regimes strongly influence the outcomes. SAFs do not consistently reduce soot emissions or contrail ice crystal numbers across blends, though synthetic fuels with optimized composition and lean-burn combustors hold potential for improvement. Fuel cells, on the other hand, avoid particle emissions altogether. The findings underline that contrail impacts depend not only on fuel type, but also on combustion processes, atmospheric conditions, and nucleation pathways. For policy and technology roadmaps, this means neither SAF nor hydrogen can yet be assumed to mitigate contrail forcing without targeted optimization and further field data.