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Aircraft & TechWhat is Sustainable Aviation Fuel?
Sustainable aviation fuel, commonly known as SAF, is a busy buzzword with airline CEOs and environmentalists, but it came in at a mere 600 million liters, or approximately 0.5 Mt, in 2023, according to IATA. Last year, 300 million liters was achieved. Despite this footprint, an increase of 100%, the SAF still represents a minuscule portion of global aviation fuel demand. Airlines extol the greenness of SAF, but the production of sustainable aviation fuel raises important questions, including what it actually is, what it's sourced from, and why it's not more widely used in the aviation industry.
What this piece covers
Sustainable Aviation Fuel Defined
What do companies mean when they talk about sustainable aviation fuel? Here's what major institutions have to say about it:
The International Civil Aviation Organization, or ICAO, the UN aviation agency, defines "sustainable aviation fuel" as "a renewable or waste-derived aviation fuel" that meets specified sustainability criteria under Annex 16, Volume IV. Furthermore, the ICAO states that, to be categorized as a SAF under CORSIA, a fuel must provide environmental benefits in terms of a net CO₂ reduction of at least 10% on a life‑cycle basis compared to conventional aviation fuel and must be produced by fuel producers certified under an ICAO‑approved sustainability certification scheme.
Furthermore, the European Union defines sustainable aviation fuels (SAFs) as synthetic aviation fuels, aviation biofuels, or recycled carbon aviation fuels.
The International Air Transport Association (IATA) defines SAF as a non‑fossil alternative to conventional aviation fuel that can be produced from various sustainably sourced feedstocks, including used cooking oil, biomass waste, and renewable energy with captured carbon. SAF, according to IATA, can reduce life-cycle carbon emissions by about 80% compared to conventional aviation fuel.
In addition, the European Civil Aviation Conference (ECAC) believes that SAF must be non‑conventional, not petroleum-based, and that it must reduce life‑cycle greenhouse gas emissions.
Inside the Supply Chain
Where does sustainable aviation fuel come from? Here, too, multiple official frameworks describe the feedstocks and production pathways that qualify:
According to IATA, SAF can be produced from feedstocks such as used cooking oil, biomass waste and residues, and renewable energy with captured carbon, and it can be "typically" reduce lifecycle carbon emissions by around 80% compared to conventional aviation fuel, depending on the fuel type IATA says.
Meanwhile, the European Alternative Fuels Observatory highlights three routes: Jet fuel produced from biomass, synthetic aviation fuel made from renewable or low-carbon electricity and captured CO2, and recycled carbon aviation fuel made without petroleum.
The U.S. Department of Energy's Alternative Fuels Data Center adds municipal solid waste and wet wastes to the list of SAF feedstocks, as well as fats, oils, and greases.
Product Certification and Blending
When sustainable aviation fuel enters the aircraft fuel system, its integration is controlled in a variety of ways:
"Drop-in" is the term used to describe SAF that has been approved as a substitute for fossil jet fuel.
For one, only certified "CORSIA SAF" qualifies for operators' claimed emissions reductions under ICAO's CORSIA program—other "eligible fuels" are not counted toward reduction targets.
Second, SAF producers must be certified under an ICAO-approved sustainability certification program to allow SAF to contribute to CORSIA emissions reductions. ICAO manages the approval of certification schemes based on sustainability requirements it sets.
Finally, ECAC emphasizes that SAF must meet "drop-in" requirements—meaning it must be mixable with typical fossil-based jet fuel, have similar performance specifications, and have no adverse effect on aircraft fuel systems or operation.
How Much Is There?
IATA reported that global SAF production reached "over 600 million liters (0.5 Mt)" in 2023, up from 300 million liters (0.25 Mt) in 2022, according to the company's press release on December 6, 2023.
When describing this volume, IATA explicitly notes that SAF would account for only about 3 percent of aviation's fuel needs by 2030 under announced capacity, implying that SAF still accounts for a very small percentage of aviation fuel.
IATA also expresses concern about policy hurdles in that press release. According to IATA,
IATA designates three factors as critical for increasing the share of aviation fuel provided by SAF: First, expanding feedstock supplies, including used cooking oil, animal fats and devoted energy crops, the organization writes. Second, Increasing refinery and blender capacity for SAF is critical, as is making device integration easier. Third, government backing through tax incentives, R&D investment, public-private partnerships, and offtake agreements is required.
Current Cost Gap
SAF is similarly priced according to multiple recent comparisons:
In November, Reuters reported that SAF costs 2.5 to 3 times as much as kerosene. Mexico Business News also reported in November that SAF costs 2 to 5 times as much as traditional jet fuel worldwide, based on a RMI report from 2023. * And the cost of SAF in the United States is currently about $6.69 per gallon, compared to $2.29 for traditional jet fuel, according to RMI. Mexico Business News gives a worldwide price of $6.00 per gallon. Both estimates imply a price that is roughly 2.5 to 3 times higher than the $2.29 per gallon rate.
Why we published this. A grounded sense of what SAF can and cannot do this decade.
