Waste Lipids Conversion to Sustainable Aviation Fuel

The decarbonization of the aviation sector requires scalable, drop-in sustainable aviation fuels (SAFs) capable of meeting stringent performance specifications while achieving substantial lifecycle greenhouse gas reductions. Among certified SAF pathways, the upgrading of waste lipids—such as used cooking oil, animal fats, and acid oils—via catalytic hydroprocessing has emerged as the most technologically mature and commercially deployed solution. Owing to their intrinsic molecular similarity to long-chain hydrocarbons, triglycerides and free fatty acids provide a structurally favorable platform for jet fuel production. However, compositional heterogeneity, high free fatty acid content, contaminant-induced catalyst deactivation, and hydrogen-intensive deoxygenation pose significant upgrading challenges. Catalytic conversion toward jet-range hydrocarbons involves an integrated network of hydrogenation, hydrodeoxygenation, decarboxylation/decarbonylation, hydroisomerization, and selective hydrocracking reactions. Balancing hydrogen efficiency, carbon retention, and product selectivity within the C8–C16 range is central to achieving aviation-grade fuel specifications. Advances in multifunctional metal–acid catalysts, hierarchical porous materials, and hydrogen management strategies are improving jet fuel yield and process stability. Although feedstock availability limits long-term scalability, waste lipid valorization provides a critical near-term pathway for aviation decarbonization and serves as a technological foundation for future SAF innovations. Continued progress in catalyst design, renewable hydrogen integration, and process intensification will determine its evolving role within a low-carbon aviation ecosystem.