Water footprint and sustainability assessment of sustainable aviation fuel production from castor oil, soybean, switchgrass, and corn stover in the Tongliao region

Decarbonizing aviation through sustainable aviation fuel (SAF) requires pathways that are both resource-efficient and regionally adaptable, particularly in water-limited areas. This study evaluates the life cycle sustainability of SAF produced from four biomass feedstocks—castor, soybean, corn stover, and switchgrass—through Hydroprocessed Esters and Fatty Acids, Fischer-Tropsch, and Alcohol-to-Jet pathways in the semi-arid Tongliao region of Northeast China. Life cycle assessment quantified water footprint (WF), carbon footprint, and soil carbon sequestration, and an eXtreme Gradient Boosting (XGBoost)-based surrogate model was developed using castor as a case study to estimate crop-specific WFs within the observed climatic domain. Castor- and switchgrass-based SAF exhibited the lowest life cycle WFs (0.1571 and 0.1195 m 3 /MJ). Accounting for induced land use change and soil carbon sequestration, switchgrass-based fuel achieved net-negative emissions, whereas castor-based fuel reduced emissions by 88.12% compared with fossil jet fuel. Multi-criteria decision analysis integrating environmental, technical, economic, and social dimensions identified the castor-based pathway as the optimal SAF option, followed by corn stover-based and switchgrass-based pathways. These findings highlight the role of non-food, drought-tolerant feedstocks and AI-assisted modeling in guiding feedstock selection, process optimization, and policy formulation for SAF development in water-stressed regions.