SAF can be produced in several ways, but the end product must meet at least the same requirements as fossil jet fuel. Once approved, the fuel can be used in existing aircraft, storage tanks and pipelines. The four most obvious methods are 1. HEFA, primarily based on used cooking oil. 2. Fischer Tropsch gasification based on waste as well as wood and residuals. Alcohol to jet (AtJ), mostly based on residual products from sugary raw materials or enzymatic processes. 4. Electrofuels, also called PtX or PtL, produced on electricity, carbon and hydrogen. Common to all those mentioned is that a maximum of 50% may be mixed into the conventional fuel. Efforts are being made to lift or remove this restriction. Airbus and Boeing as well as some airlines have completed successful test flights with 100% SAF.
It is crucial that the fuel is sustainable. This is not included in the technical approval but separately by independent organizations that apply a comprehensive set of sustainability criteria for the raw materials, transport and production method used.
Today, there are only two producers that can continuously supply SAF. World Energy and Neste. Both with HEFA oil based on used cooking oil. SAF accounts for just half a per mille of aviation fuel consumption globally. 2-3 producers are expected to be on the market during 2022-23, also with SAF produced on used cooking oil, namely Total, Repsol and ENI. In 2023-25, a further number of manufacturers are expected to be ready with the first AtJ, Fischer/Tropsch catalytic or PtX/electrofuel products.
Used cooking oil is the dominant SAF raw material. A disadvantage is that there is a natural limit to how much is available. Critics have also pointed out that it is not possible to ensure sustainability all the way back in the supply chain. Limited access to raw materials is a risk for all methods, however to a lesser extend electrofuels, that do not use biogenic raw materials but electricity, hydrogen and carbon. Here, access to renewable energy is a challenge, but is expected to be manageable in an expansion of renewable energy.
Electrofuels/PtX is supposed to be the future fuel. Several development projects are underway both in the Nordic region, internationally and in Denmark. The EU and several international analyzes finds that electrofuels will become dominant within the next, or few, decades.