More and more airlines are betting on sustainable aviation fuel (SAF) to make aviation greener. Despite the slow uptake due to its cost, some technologies are already in place to produce greener fuels for aviation.
1. Collection and production
One or multiple sources can compose the feedstock that produces SAF — waste products, such as vegetable oils or household waste, or specifically grown plant material.
For the time being, fats, oils and greases are the major sources of SAF. A concrete example is Neste, a Finish oil refining and marketing company, which has a contract with McDonald’s to collect the used cooking oil from its Dutch restaurants.
In addition, biomass and municipal solid waste are expanding in use as sources. These have the potential to reduce overall greenhouse gas emissions even furtherover their lifecycle, from 85% to 95%, compared to traditional fossil-based jet fuel. The lower-point is that these sources have a lower energy density and require larger volumes of feedstock.
We used about 100 million liters of sustainable aviation fuel in 2021 — that’s a very small amount compared to the total fuel required for the industry.Willie Walsh, IATA Director General
According to Neste, SAF could reduce greenhouse gas emissions by up to 80% compared to normal fossil jet fuels. The Finish-based company has also made a 2.5 million liters SAF deal with the Virgin Atlantic airline. The fuel will be delivered to London Heathrow by ExxonMobil in the first half of 2022 and it brings the company a bit closer to its sustainable fuel target.
2. Technologies for conversion
After completing the separation process, these feedstocks are refined to produce fuel through the use of different technologies for conversion. For fats, oils and greases, the technical process widely used is HEFA — Hydrotreated Esters and Fatty Acids. The process consists of exposing purified liquids to a chemical reaction with hydrogen and catalysts for further distillation.
For solid biomass, FT-SPK — Fischer-Tropsch Synthetic Paraffinic Kerosene is the leading process currently. It consists of the gasification of solid biomass at high temperatures, producing a synthesis gas that is converted into hydrocarbon chains.
The blending process requires strict safety measures and requirements. SAF is not used directly as a fuel but it can be used in existing jet engines after mixing with traditional jet fuel. The blending process guarantees a similar performance and handling characteristics.
SAF is blended with traditional fuel in ratios up to 50%. Currently, most fuels use much lower proportions of SAF, but it is expected that this will increase over time. Last year, Air France-KLM, Total, Groupe ADP and Airbus have joined forces to carry out the first long-haul flight powered by SAF produced in France.
KLM started adding 0.5% SAF for flights departing from Amsterdam and it’s offering its customers the option of purchasing an extra amount of sustainable fuel.
Overall, SAF cost is a major factor preventing the full uptake of this type of fuel. This landscape should reduce as collection and production availability expands.
Airports will have to invest in infrastructure and will for sure pass that bill onto airlines, and they will pass it onto the customers, so it is all going to find its way.Arjan Meijer, Embraer’s CEO quoted by Simple Flying.
In a recent interview to CNBC, the director general of the International Air Transport Association, Willie Walsh, said that the main challenge associated to SAF relates “to volume rather than airlines’ desire to use it”. Walsh noted that “consumers will be willing to pay the extra costs associated with its uptake.