Almost every conversation about aviation and climate arrives at the same place within a few minutes. Someone asks what sustainable aviation fuel actually is, and whether it is a real fuel or a piece of accounting.
It is a real fuel. It goes into a real aircraft and burns in a real engine. The part that takes explaining is where the saving happens.
What is SAF?
SAF stands for sustainable aviation fuel, and the two are used interchangeably once the acronym has been introduced. It is jet fuel made from sustainable feedstocks rather than fossil crude. Most of what reaches the market today starts as used cooking oil, waste fats and tallow, or technical corn oil recovered during ethanol production.
The chemistry is deliberately unremarkable. SAF is a drop-in fuel, which means it meets the same technical standard as conventional jet fuel, ASTM D1655, and works in existing aircraft, existing engines and existing airport infrastructure. Nothing needs modifying. In practice it is blended with fossil jet fuel rather than used neat, and the blend is what goes into the wing.
One distinction is worth making from the start. A fuel made from something other than crude oil is an alternative fuel, and alternative does not mean sustainable: coal can be converted to jet fuel, and the result is an alternative fuel with a worse carbon footprint than the fossil kerosene it replaces. Sustainability is a separate test, applied afterwards, by someone independent.
Why is it called sustainable if it still burns?
Because the saving is counted across the fuel’s whole life, not at the point of combustion.
Burning SAF still releases carbon. What changes is where that carbon came from. Fossil jet fuel releases carbon that has been locked in geological storage for millions of years, adding it to the atmosphere for the first time. SAF releases carbon that was in the atmosphere recently, taken up by a crop or embodied in a waste stream that already existed. Set the two against each other across production, transport and combustion, and the lifecycle total is lower.
That is why every honest SAF figure is a lifecycle figure with a stated baseline. In our May 2026 transaction with Delta Air Lines, the reduction was calculated against a fossil baseline and verified before anyone claimed it. A number without a baseline is not a claim, it is an adjective.
Does calling something SAF guarantee a large reduction?
No, and this is the most useful thing on this page.
ICAO’s rule for CORSIA eligible fuel is that it “will achieve net greenhouse gas emissions reductions of at least 10% compared to the baseline life cycle emissions values for aviation fuel on a life cycle basis”. Ten per cent is the floor, not the expectation.
Work through what that permits. Take a fuel with a 50% lower lifecycle footprint, blend it into fossil kerosene at a modest percentage, and the resulting blend can still clear the bar and still be described as SAF. Nobody has broken a rule. The word simply covers a wide range, and on its own it tells a buyer very little.
So “we bought SAF” is the beginning of a conversation rather than the end of one. The questions that follow are what the actual lifecycle reduction was, against which baseline, and which scheme verified it. A supplier who answers those in one breath is selling something different from a supplier who repeats the acronym.
Who decides whether a batch qualifies?
A certification scheme, and not the company selling the fuel.
Fuel enters the system only once a recognised scheme has assessed the feedstock, the production pathway and the chain of custody behind it. The schemes set the sustainability criteria, audit against them, and withdraw certification when they are not met. Future Energy Global is certified by both RSB and ISCC as a trader, and audited externally by SCS Global Services.
This matters more than any adjective a marketer can attach. “Sustainable” is a conclusion a scheme reaches after it has seen the evidence, not a word a supplier awards itself.
Why can’t I just buy it at my airport?
Because supply is concentrated near the small number of plants that produce it, and most airports have none.
That is the practical problem the industry is built around at the moment. Production is growing but it is not evenly distributed, and an airline flying from an airport with no SAF cannot buy what is not there. It is also why Book and Claim exists: it separates the certified environmental attributes from the physical fuel, so the fuel is used where it makes sense and the verified reduction is retired to whoever funded it.
What does this change about what you can claim?
Everything, and it comes down to evidence.
A certified batch comes with a record: where the feedstock came from, how the fuel was made, what the lifecycle reduction was, and who ended up owning it. That record is what survives an audit. When someone asks where your reduction came from, the answer should be a document rather than a reassurance.