Sustainable aviation fuel and whether the math actually works for decarbonizing the sky

Sustainable aviation fuel (SAF) is the aviation industry’s primary strategy for decarbonizing flight, offering 60 to 80 percent lifecycle carbon reductions compared to conventional Jet-A. The chemistry works, the fuel is approved, and it requires zero engine modifications. But global SAF production in 2025 reached roughly 600 million liters, just 0.2 percent of the 300 billion liters the world’s airlines burn annually. Closing that gap is the defining challenge of aviation’s climate commitment.

Why Can’t Aviation Just Electrify Like Cars and Trucks?

Aviation accounts for two to three percent of global CO2 emissions, and that share is growing precisely because other sectors are shifting to electric power. Batteries remain far too heavy for anything beyond short-range regional aircraft. Hydrogen faces massive infrastructure and storage challenges. That leaves fuel as the variable the industry can change without replacing the global fleet of turbine-powered aircraft.

A single transatlantic flight on a Boeing 767 burns roughly 30,000 gallons. The global airline industry consumes approximately 100 billion gallons per year. SAF is the pragmatic path because it is a drop-in replacement — same chemical properties, same energy density, same performance. The difference is the carbon source: instead of ancient hydrocarbons pulled from the ground, SAF is produced from feedstocks that captured carbon recently.

What Is SAF Actually Made From?

SAF can be produced through several pathways, each with distinct feedstocks, costs, and scaling limits.

HEFA (Hydroprocessed Esters and Fatty Acids) is the most mature pathway. It converts used cooking oil, animal fats, and vegetable oils into jet fuel. Neste, the world’s largest SAF producer, operates refineries in Finland, Singapore, and Rotterdam. World Energy supplies SAF to Los Angeles International from its Paramount, California refinery. Montana Renewables converted a former petroleum refinery in Great Falls, Montana, to produce renewable fuel from waste fats.

HEFA works today but has a hard ceiling. Global waste fat and oil supplies could yield an estimated 15 to 20 billion liters of SAF per year — only five to seven percent of what the industry needs.

Alcohol-to-Jet converts ethanol into jet fuel through a series of chemical reactions. LanzaJet built its Freedom Pines facility in Georgia and has attracted investment from Microsoft, Airbus, and several major airlines. The existing ethanol supply chain is an advantage, but food-crop-based ethanol raises serious land use and water concerns.

Power-to-Liquid (e-fuel) is the pathway with the most long-term potential. It combines carbon dioxide captured directly from the atmosphere with green hydrogen produced by renewable-powered electrolysis, then synthesizes liquid hydrocarbons through a Fischer-Tropsch reactor. The result is jet fuel chemically identical to Jet-A with lifecycle emissions approaching zero.

The feedstock — CO2 and water — is essentially unlimited. The problem is cost: power-to-liquid SAF currently runs five to ten times the price of conventional jet fuel, with cost parity unlikely before 2040 to 2045. HIF Global (Chile), Infinium (Texas), and Twelve (backed by the U.S. Air Force) are all operating at demonstration scale. Demonstration and commercial scale are two very different things.

Gasification converts municipal solid waste, agricultural residue, or forestry waste into synthesis gas, then into liquid fuel. The feedstock is abundant — humans produce garbage at enormous scale — but every batch of waste is chemically different, making process control extremely difficult. Fulcrum BioEnergy attempted this in Nevada and went through bankruptcy.

How Big Is the Production Gap?

IATA has set a target of net-zero carbon emissions by 2050, with SAF expected to deliver roughly 65 percent of the required carbon reductions. That means scaling from 600 million liters to approximately 450 billion liters per year — a 750-fold increase in about 24 years.

For context, the investment required is measured in hundreds of billions of dollars in new refinery infrastructure, renewable electricity capacity, and direct air capture facilities that largely do not exist yet.

What Regulations and Incentives Are Driving Adoption?

The mandates and financial incentives are arriving. The European Union’s ReFuelEU regulation requires SAF to comprise 2 percent of jet fuel at EU airports by 2025, rising to 6 percent by 2030 and 70 percent by 2050. The United Kingdom has its own parallel mandate.

In the United States, the Inflation Reduction Act offers up to $1.75 per gallon in blender’s tax credits for SAF meeting carbon intensity thresholds. Major carriers are making commitments: United Airlines has invested in multiple SAF producers, Delta has signed long-term offtake agreements, and JetBlue, Alaska Airlines, and several European carriers have all secured supply deals.

What’s the Realistic Timeline?

By 2030, SAF will likely represent three to five percent of global jet fuel supply. That is meaningful but nowhere near the trajectory required for net zero by 2050. HEFA and alcohol-to-jet will carry the near-term load because they work today. Power-to-liquid will remain mostly at demonstration scale through the end of this decade.

The critical scaling window is 2035 to 2045, and it depends almost entirely on two factors: the cost of renewable electricity and the cost of direct air capture. If both drop far enough, power-to-liquid becomes the endgame. Those remain two enormous uncertainties.

Does SAF Matter for General Aviation Pilots?

Most GA pilots burn 100LL avgas, not Jet-A, so the unleaded avgas transition is a separate issue. But turboprop and light jet operators should pay attention. SAF is already approved for blending up to 50 percent with conventional Jet-A. At the handful of FBOs that carry it, the blended fuel performs identically — same burn rate, same engine behavior, no modifications required.

The Contrail Factor Most People Miss

SAF doesn’t only reduce CO2. Research suggests it also reduces particulate emissions, which means fewer contrails. This matters more than it might seem: contrails — the white lines jets leave across the sky — may contribute more to aviation’s total warming effect than CO2 emissions alone. The science on contrail climate forcing is still being refined, but if SAF significantly reduces contrail formation, its total climate benefit could be substantially larger than carbon reduction numbers suggest.

Key Takeaways

• SAF is real and flying today, but production covers just 0.2 percent of global jet fuel demand — a 750-fold scale-up is needed by 2050.
• Used cooking oil pathways (HEFA) dominate current production but can supply only 5-7 percent of demand due to limited feedstock.
• Power-to-liquid is the long-term answer because its feedstock (CO2 and water) is unlimited, but costs must drop 5-10x before commercial viability.
• Regulatory mandates in the EU and tax credits in the U.S. are accelerating investment, with major airlines already signing offtake agreements.
• Contrail reduction may be SAF’s hidden advantage, potentially delivering climate benefits beyond what CO2 lifecycle numbers capture.