From biorefinery synergies to sustainable aviation fuel: A critical review of twenty years of renewable fuel pathway evolution

Sustainable aviation fuel (SAF) production must scale by two orders of magnitude to meet legally binding mandates such as ReFuelEU Aviation and CORSIA, yet the optimal combination of production pathways remains contested. In 2006–2007, Corma, Huber and co-workers proposed that existing petroleum refinery infrastructure could serve as the primary platform for renewable fuel production, a thesis that shaped a generation of research. This critical review traces the evolution of seven SAF-relevant pathways over 2006–2026 and evaluates them against five criteria, feedstock simplicity, infrastructure compatibility, product slate alignment, regulatory qualification timing, and scale economics, through a structured technology scorecard complemented by a parametric levelised cost analysis, drawing on 81 peer-reviewed and institutional sources. Hydrotreating of triglycerides (HVO/HEFA) validated the refinery integration thesis and currently constitutes the largest share of global SAF output, but faces a structural feedstock ceiling of approximately 30–40 Mt/year of available lipids. FCC co-processing has seen limited uptake owing to coking penalties and product slate mismatch with jet fuel specifications. The two fastest-growing pathways, alcohol-to-jet and power-to-liquid, emerged outside the original refinery-centric paradigm. Sensitivity analysis shows that HEFA remains the lowest-cost route below a used cooking oil (UCO) price of approximately 1,028 €/t, beyond which AtJ becomes competitive, while PtL requires regulatory andates rather than cost competitiveness for deployment. Meeting projected SAF demand requires a regionally optimised portfolio of complementary pathways rather than convergence on a single technology, with the refinery repositioned around SAF as its primary product. Global SAF production reached approximately 1.9 Mt in 2025, roughly double the 2024 volume but still less than 1% of total jet fuel consumption. This production level illustrates the scale of the challenge ahead.