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Four Things to Know About Sustainable Aviation Fuel (SAF)

September 13, 2021 | by Chelsey Levingston
Avid aviation watchers are likely seeing more and more discussion about Sustainable Aviation Fuel (SAF), as increased supply and use of alternative fuels is critical to helping the aviation industry reach its goals to reduce, and even eliminate, net carbon emissions from commercial flights around the world.

All GE Aviation and CFM International* engines can operate with approved SAF, which is produced from sustainable feedstocks and other alternative processes, lowering lifecycle carbon emissions up to 80% compared to petroleum-based fuels.

GE has been actively involved in assessing and qualifying SAF since 2007 and works closely with producers, regulators, and operators to help ensure that sustainable fuel can be widely adopted for use in aviation.

GE Aviation’s engineering leader for aviation fuels and additives, Gurhan Andac, answers our top questions below about the importance of SAF.

1. What is SAF and why is it so important?

Andac: Sustainable Aviation Fuel, or SAF for short, is actually jet fuel. It is Jet A, Jet A-1 — the same kerosene end product that we have been burning in our engines for decades.

SAF is synthetically derived from alternative renewable sources and developed in a more sustainable fashion, as opposed to conventional petroleum-based fuels. SAF can start from various feedstock sources, such as oils from plants, algae, greases, fats, waste streams, alcohols, sugars, and captured CO2, but ends up being the same hydrocarbon mixture called kerosene that we know as jet fuel.

It is sustainable in the sense that it can be resourced in a way that is consistent with socio-economic and environmental goals that preserve an ecological balance by avoiding the depletion of natural resources. The use of SAF can lower the lifecycle carbon footprint compared to commercial jet fuel and therefore, really has a vital role in meeting the aviation industry’s environmental and sustainability goals.

2. Where does GE Aviation play in this space?

Andac: We are now engaged in nearly all aspects of the SAF space, from research and development, to policy, standardization, customer collaborations, and more. That said, one of the major roles we are playing is in evaluating and qualifying SAF pathways and different SAF production processes We need to make sure that the candidate production pathway produces a SAF that is indeed equivalent to Jet A/A-1 and that there will be no adverse impact on engine operation and performance with the use of it. As a result, we are very engaged and active in generating and evaluating data to support SAF qualification.  This includes, for example, conducting both engine component-level and system-level testing at GE Aviation facilities in Peebles and Evendale, Ohio, and Lynn, Massachusetts, as well as at other global sites.

We are also deeply involved with various industry bodies that are in charge of developing and maintaining SAF fuel standards. GE is currently leading the efforts in standardization that will enable, in the near future, the use of SAF at higher blend ratios than currently allowed, even up to 100%.

Additionally, we are engaged with various government offices and forums in the U.S. and Europe to drive transition from petroleum to SAF and help shape the related policy and regulation. We also support our customers who are willing to use SAF by providing assistance and guidance, as needed.

3. Can GE and CFM commercial jet engines use SAF?

Andac: All GE and CFM engines have already been certified to Jet A/A-1. SAF being Jet A/A-1-equivalent means engines do not require recertification to burn SAF. 

An operator does not need to ask us whether they can use industry-approved SAF in our engines, just as they do not ask us whether they can use conventional Jet A/A-1, as the engines are already certified for Jet A/A-1. All they have to do is ensure that the SAF meets the requirements of the ASTM D7566 synthetic fuel standard. Every SAF pathway that is in D7566 is in there because the industry, including GE and CFM, already approved it. Also, it is worth mentioning that since SAF is equivalent to Jet A, Jet A-1, there are no additional engine maintenance and service requirements that come with the use of SAF. It is really that simple.

4. Why isn’t SAF being used everywhere today?

Andac: About a decade ago, the aviation industry established a robust SAF evaluation protocol. We approved seven SAF production pathways. More than 350,000 commercial flights have already been operated using SAF since 2011, according to Air Transport Action Group. This is considerable progress. Still, SAF availability is limited at the moment. Current production is less than 1% of the global jet fuel demand. However, more facilities are coming online, and the projections are that about 2% replacement of conventional jet fuel with SAF is possible by 2025. The cost is still the challenge, with SAF being considerably more expensive than traditional jet fuels. However, there are mechanisms, incentives, policies and regulations being put in place that will help SAF use to become more economically viable for the operators.

*CFM International is a 50-50 joint company between GE and Safran Aircraft engines and produces CFM56 and LEAP commercial aircraft engines.

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GE Aerospace is a world-leading provider of jet and turboprop engines, as well as integrated systems for commercial, military, business and general aviation aircraft.