Sustainable aviation fuel

Sustainable Aviation Fuel is jet fuel made from something other than crude oil. Most of it today comes from waste and residue materials such as used cooking oil, animal fats from meat processing and agricultural residues, converted through a process called HEFA. Newer routes make it from captured CO₂ and renewable electricity.

Here is what we commit to for every batch we buy:

• Certified under a recognised sustainability scheme, either ISCC or RSB
• Made from waste or residue feedstocks, never from crops grown for the purpose
• A certified lifecycle emissions reduction of at least 75 % against fossil jet fuel

The exact figure varies by batch, because it depends on the feedstock, the process and how far the fuel travelled. We publish it for every purchase.

SAF is not a complete answer to aviation's climate impact. It's currently 0.8% of global jet fuel, and scaling it depends on demand existing before the price falls. That demand is what your purchase is for.

No. And no service can honestly promise that it will.

Aviation fuel goes into shared airport pipelines, so nobody can direct a specific batch to a specific aircraft. Not us, not the airline, not you. What can be done is to make sure the fuel is produced and put into the aviation system, and that its emissions reduction is allocated to you and recorded.

This is called book-and-claim, and it works like buying renewable electricity. Your particular electrons are not green, but your purchase means more renewable generation exists than otherwise would. The atmosphere does not care which aircraft burns the cleaner fuel. It cares how much fossil kerosene gets displaced.

We buy fuel in batches and allocate against them as customers buy. The fuel is delivered wherever the supply chain puts it, which is rarely the airport you are flying from.

We measure the great-circle distance between the departure and arrival airports, then apply official DESNZ emission factors for economy class. The result includes burning the fuel (TTW), producing the fuel (WTT) and high-altitude effects (RFI).

Read the full methodology on the method page.

Yes. A business seat takes up several times more of the aircraft than an economy seat, so it carries a larger share of the flight's emissions. Our calculator prices an economy seat.

The simplest way to cover the difference is to buy more than one seat:

• Short- and medium haul flights (< 5 hours): select 2 seats for premium economy or business class
• Long-haul flights (> 5 hours): select 3 seats for business class, or 4 seats for first class

These follow the official DESNZ cabin factors, which allocate emissions by how much floor space a seat occupies. Change the seat count before you pay.

It is an honest estimate, not a measurement.

We calculate the great-circle distance between the two airports and apply official DESNZ conversion factors for economy class, including high-altitude effects, plus the emissions from producing the fuel. Real emissions depend on the aircraft, how full it is, the weather and the route flown on the day, none of which any calculator can know in advance.

The largest uncertainty is the high-altitude effects. We use a general add-on of 70%, as recommended by DESNZ, but depending on the engine, route and weather on the day, the real effect could be anywhere between 0 and 200%.

Because we count three things and most calculators count one.

1. Burning the fuel. The CO₂ released by combustion. This is what almost every calculator shows.
2. Producing the fuel. Extracting and refining the fuel and transporting it to the aircraft accounts for around 13% of the total. Official conversion factors publish this separately, so it is routinely left out.
3. High-altitude effects. Contrails and nitrogen oxides warm considerably more when released at cruise altitude than at ground level. This is roughly a third of the total, and it is the component most often omitted.

None of this is unconventional. It is the same underlying data most calculators use. We simply include all of it, and show the three parts separately so you can see exactly where the number comes from.

No.

The EU mandate requires fuel suppliers to blend 2 % SAF. Worldwide, SAF is 0.8 % of jet fuel. Airlines buy the legal minimum and stop, because SAF costs two to five times more than fossil kerosene and every extra litre loses them money.

Nothing moves volume above that minimum except someone paying the difference. That is what your payment does.

It also does more than buy fuel. SAF is expensive largely because it is made in small volumes, so every purchase builds the demand that lets producers scale up and brings down the cost of the next litre. The effect does not stop at the fuel you paid for.

Yes, when that is an option. It is why the calculator shows you what the same trip costs by train, by electric car and by petrol car before it shows you a price.

For short routes the difference is stark. A flight emits around 205 g per passenger-kilometre against roughly 5 g for an electric train. No fuel switch competes with simply not taking off.

But some journeys have no realistic alternative. This is for those.

Your payment buys the same amount of sustainable aviation fuel (SAF) as your seat burns in fossil fuel. That fuel is produced, certified and delivered into the aviation fuel supply. It does not go into the specific plane you fly on, and "Will my flight run on SAF?" explains why. What matters for the climate is that the fuel gets made and burned instead of fossil fuel, not which engine burns it.

Your payment also funds Gold Standard certified climate projects, covering the part of your flight's impact that a fuel switch cannot address.

You receive a Certificate of Climate Contribution in your name or your company's name, along with a receipt for the purchase.

Approximately 70% buys and retires Sustainable Aviation Fuel, 10% buys and retires Gold Standard certified carbon credits, 20% covers payment processing, certification and running this service.

We publish this split because most services in this field don't. These are averages: prices for SAF and carbon credits fluctuate, but we work to keep your price stable.

Partly, and we are explicit about which part.

The SAF portion is not an offset. It is a fuel substitution inside aviation's own supply chain, so less fossil kerosene is burned than would otherwise have been. That is a reduction, and it happens in the sector that caused the emissions.

The remainder is handled with Gold Standard certified climate projects. That covers the emissions from producing the biofuel, plus the high-altitude warming that no fuel switch removes. That part is a contribution to emission reductions elsewhere, and we do not claim it cancels out your flight.

We separate the two because they are different things and deserve different language. Anyone who charges one price and calls the whole thing neutralised is glossing over that distinction.

No. Flying causes warming, and paying afterwards does not undo it.

Roughly two thirds of a flight's climate impact comes from producing and burning the fuel. Switching to SAF removes most of that, currently 75 % for the batch we are allocating from. The remaining third comes from high-altitude effects, meaning contrails and nitrogen oxides, which changing the fuel does not remove.

That works out at about half of your flight's impact addressed by replacing fossil fuel with SAF, and about half by funding Gold Standard certified reductions elsewhere. Your result above shows the exact split for your flight.

The first is a reduction inside aviation. The second is a contribution outside it. Neither erases the flight.

If someone offers to make your flight climate neutral, ask what physically happens to the warming. There is no good answer.