Sustainable Aviation Fuel (SAF) Scale-up: From Lab to Commercial Aviation

Aviation accounts for approximately 2-3% of global CO2 emissions. Sustainable Aviation Fuel (SAF) represents a critical pathway to decarbonise the sector and achieve net-zero targets by 2050. SAF is a drop-in replacement for conventional jet fuel (Jet A-1) produced from sustainable feedstocks including waste oils, agricultural residues, and synthetic pathways.

Key Concepts

SAF can be produced through multiple pathways: HEFA (Hydroprocessed Esters and Fatty Acids), ATJ (Alcohol-to-Jet), and Power-to-Liquids (PtL). Each pathway involves different feedstock-to-fuel conversion chemistry with varying maturity levels. HEFA technology is the most commercially mature, while ATJ and PtL remain in pilot and early-commercial phases.

HEFA Technology: The HEFA process hydroprocesses used cooking oils and other lipids, removing oxygen and producing hydrocarbons equivalent to conventional jet fuel. This pathway can reduce lifecycle greenhouse gas (GHG) emissions by 50-80% compared to fossil jet fuel.

ATJ Technology: Alcohol-to-Jet converts ethanol (from biomass or bio-based routes) via dehydration, oligomerisation, and hydrogenation. The process offers flexibility in feedstock sourcing but requires careful control of intermediate product quality.

Power-to-Liquids: Synthetic pathways combining hydrogen (from renewable electricity) and CO2 (from capture or biomass) to produce SAF. This pathway shows promise for hard-to-abate sectors but faces scaling challenges.

Policy & Market: Global SAF demand is expected to reach 6-10 million tonnes annually by 2030, driven by regulatory mandates (ICAO's Carbon Offsetting and Reduction Scheme for International Aviation) and corporate net-zero commitments. SAF currently costs 2-3x more than conventional jet fuel, requiring investment in scale and R&D.

Applications & Research Frontiers 

Co-processing SAF production within existing refinery infrastructure offers capital efficiency advantages but requires compatibility assessments with existing hydrotreating units.

Advanced sustainability metrics beyond GHG accounting: Life cycle assessment (LCA) frameworks increasingly incorporate water stress, biodiversity impact, and social criteria for feedstock sourcing.

Engine performance and compatibility testing remains critical—SAF blends up to 50% are already approved, with research ongoing to achieve higher concentrations and improve lubricity characteristics.

Feedstock diversification strategies are essential: advanced feedstocks (algae, synthetic biology routes) under development to reduce pressure on traditional biomass supplies.

Conclusion

SAF represents a tangible near-term solution for aviation decarbonisation, with HEFA established and ATJ/PtL emerging. Success requires integrated efforts across policy, infrastructure investment, and feedstock development.

Keywords: Sustainable Aviation Fuel, SAF, HEFA, Alcohol-to-Jet, aviation decarbonisation, net-zero, renewable fuels, biofuels, lifecycle assessment