From Blend Limits to Net-Zero Flight: Comparing SAF Pathways, Costs, and the Scale-Up to 2050

Abstract

Aviation’s reliance on energy-dense liquid fuels makes deep decarbonization challenging, and Sustainable Aviation Fuel (SAF) remains the most immediately deployable lever because it can be used within existing aircraft and fueling infrastructure. This paper reviews SAF as a portfolio of routes rather than a single solution, synthesizing the techno-performance, lifecycle impacts, certification status, and deployment constraints of today’s leading pathways. We compare lipid-based HEFA, waste/residue-enabled Fischer–Tropsch (FT), Alcohol-to-Jet (ATJ), and Power-to-Liquid (PtL) e-kerosene, highlighting how yield/efficiency, upstream energy inputs, and feedstock availability jointly determine climate benefit and cost. Reported performance spans high HEFA yields (80–90%) versus lower FT yields (35–45%) and PtL electricity-to-liquid efficiencies (35–45%), while lifecycle GHG reductions vary from ~40–70% (ATJ) to ~90–100% for PtL under fully renewable electricity and atmospheric CO2 sourcing. Economic barriers persist: SAF costs commonly exceed fossil jet fuel, with pathway-dependent ranges that can reach multiple dollars per liter, especially for PtL dominated by hydrogen cost. Finally, we frame deployment as a scale problem: moving from today’s sub-billion-liter production to hundreds of billions of liters by 2050 requires sustained, policy-backed capacity growth and rapid infrastructure learning curves.