FAQ
Sustainable Aviation Fuel (SAF) is a next-generation jet fuel derived from renewable feedstocks that can significantly reduce aviation’s carbon footprint. Energy companies, airlines, and government agencies are investing in SAF as an important solution to make air travel more sustainable. Below is a list of frequently asked questions about SAF covering how it’s produced, its environmental benefits, and its use in today’s aircraft.
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Sustainable Aviation Fuel (SAF) is an alternative jet fuel produced from non-petroleum, renewable resources, such as plant oils, animal fats, used cooking oils, and agricultural waste. SAF is designed as a “drop-in” fuel, meaning it is nearly identical in chemistry to conventional jet fuel and, when blended with conventional fuel, can be used in existing aircraft engines and fuel infrastructure without modification.
Boeing, Airbus, and other airplane and engine manufacturers are making future products compatible with 100% SAF (by 2030 or earlier).
Source: Aerospace Manufacturing and Design
An important difference is that producing and combusting SAF yields much lower greenhouse gas emissions relative to traditional conventional jet fuel on a lifecycle basis.
Source: US Department of Energy. “FAQ: SAF.” Bioenergy Technologies Office.
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SAF is produced by refining renewable and waste materials into fuel that meets jet fuel specifications. There are multiple technological pathways to create SAF, all of which involve converting biological feedstocks into hydrocarbon molecules similar to those in conventional jet fuel. The common method used today is the HEFA process (hydroprocessed esters and fatty acids), which processes oils or fats (like used cooking oil or plant oils) into jet fuel. Additional approved pathways include alcohol-to-jet (ATJ) (converting renewable ethanol or isobutanol into jet fuel) and synthetic iso-paraffins from fermented sugars.
Source: U.S. Department of Energy. "Sustainable Aviation Fuel." Alternative Fuels Data Center
Despite the many production routes available, all SAF must meet the same strict specifications as conventional Jet A fuel. The final product is a hydrocarbon fuel that, when blended with conventional jet fuel, meets all standards for compatibility and is nearly indistinguishable in performance from the fuel used by today’s aircraft.
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Only 8 million gallons of SAF were sold in California in 2021, which made up 0.3% of the total Low Carbon Fuel Standard (LCFS) credits sold.
California aims to increase SAF availability to 200 million gallons by 2035, which would translate to 40% of its aviation fuel needs for air travel within the state.
Source: National Renewable Energy Laboratory
Source: California Air Resources Board
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SAF can be made from a wide range of renewable feedstocks and waste materials. Current approved SAF production pathways utilize feedstocks such as:
Waste oils and fats – used cooking oil, waste animal fats, and greases (called FOG - fats, oils, greases) are commonly used feedstocks
Agricultural and forestry residues – crop residues like corn stover or wood wastes, such as wood chips and sawdust
Municipal solid waste– the biogenic portion of household waste, such as food scraps and yard trimmings
Sugars and starches – plant sugars (sugarcane, sugar beets, or corn) can be fermented into alcohols that are then chemically converted to SAF via the alcohol-to-jet pathway
Algae and energy crops – algae with high oil content and dedicated energy crops, which are grown specifically to produce energy, not food, are being explored and a certified algae-to-jet pathway has been approved
Other biomass and wastes – any renewable biological material with suitable carbon content could be a feedstock candidate, including woody biomass, grasses, and industrial waste gases
Source: U.S. Department of Energy. "Sustainable Aviation Fuel." Alternative Fuels Data Center
The diversity of feedstocks is a major advantage of SAF. It provides flexibility and allows use of wastes and non-food resources. All feedstocks must be evaluated for sustainability and the produced fuel must meet stringent standards before being used in aircraft. As technology advances, the list of viable feedstocks for SAF will grow and help scale up production.
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The primary environmental benefit of SAF is a reduction in lifecycle greenhouse gas emissions, which is the total amount of greenhouse gases released over the entire life of a product. By using renewable feedstocks, SAF can reduce over 80% GHG emissions from air travel compared to conventional jet fuel on a lifecycle basis. SAF combustion also has the benefit of producing less sulfur dioxides and reducing the formation of particulates in the air. All of this is determined with rigorous audits and standardized calculations of the life cycle benefits to net CO2.
Other environmental benefits include:
Improved Air Quality Near Airports
Lower particulate matter (PM): SAF combustion produces fewer soot particles compared to conventional jet fuel, which can improve air quality around airports.
Reduced sulfur oxides (SOx): SAF contains little to no sulfur, leading to lower SOx emissions that contribute to acid rain and respiratory issues.
Reduced Contrail Formation and Non-CO₂ Climate Effects
SAF can reduce the formation of contrails and cirrus clouds, which contribute significantly to aviation’s short-term climate impact.
Lower soot emissions reduce ice crystal formation, leading to fewer persistent contrails that trap heat in the atmosphere.
Waste Reduction and Circular Economy Benefits
Many SAF pathways use waste feedstocks (e.g., used cooking oil, municipal solid waste, agricultural residues), diverting materials from landfills and reducing methane emissions from decomposition.
This supports circular economy goals by turning waste into a valuable product.
Water Use Efficiency
Some SAF production processes, especially those based on algae or cellulosic biomass, can be more water-efficient than fossil fuel extraction and refining.
Wastewater or non-arable land can be used in production, minimizing competition for freshwater resources.
Sources
U.S. Department of Energy. "Sustainable Aviation Fuel." Alternative Fuels Data Center
Phillips 66. "Aviation Products: Jet Fuel and Lubricants." Phillips 66 Aviation
Life-Cycle Water Consumption and Water Use Efficiency of Biofuels (ANL/ESD/12-4)
Stettler, M.E.J., et al. (2022). Air quality co-benefits of low-carbon aviation fuels. ICCT Working Paper 2022-17.
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SAF production and use offers other benefits, both for the aviation industry and the broader economy, particularly in agriculture and waste management sectors.
Job creation and economic growth: Developing a SAF supply chain can stimulate job growth in multiple sectors, from farming and forestry (supplying feedstocks), to construction and operation of renewable fuels production facilities, to transportation and logistics.
Energy security and diversification: SAF diversifies the fuel supply for aviation by reducing reliance on petroleum. Using domestic renewable resources for fuel enhances energy security. It also provides farmers and producers with new revenue streams and adds value to wastes that were previously discarded.
Airline and industry competitiveness: Airlines investing in SAF are positioning themselves to meet future emissions requirements and avoid carbon offset costs. In addition, there are policy incentives that make SAF financially attractive. As production scales up and technology matures, the cost of SAF is expected to come down, potentially creating a large new market worth billions of dollars per year.
Source: US Department of Energy. “FAQ: SAF.” Bioenergy Technologies Office
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SAF must meet stringent aviation fuel specifications and certification standards before it can be used in aircraft. SAF is blended with conventional jet fuel and must be certified to have identical properties to conventional jet fuel.
The global fuel standard organization ASTM International has a specific standards for aviation turbine fuels containing synthesized hydrocarbons. This standard outlines the approved SAF production pathways and the maximum blend percentage (up to 50%) allowed for each. These limits ensure the resulting fuel blend has all the characteristics needed to perform well in aircraft engines.
Once SAF is blended with fossil jet fuel, the mixture is certified under the ASTM standards to ensure it meets all the normal requirements of jet fuel. This is why SAF is referred to as a drop-in fuel.
Every batch of SAF and SAF blend is rigorously tested. Fuel producers must ensure the SAF meets all chemical and performance criteria before it’s delivered to airports. The entire supply chain for jet fuel is tightly controlled to ensure safety, so SAF goes through the same pipeline, storage, and fueling infrastructure after it’s certified, with no changes needed at airports.
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Many major airlines around the world have begun using SAF as part of their sustainability initiatives. In the US United Airlines, Delta Air Lines, American Airlines, Alaska Airlines, JetBlue, and others have all operated flights using SAF.
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The SAF Grand Challenge is an ambitious multi-agency commitment by the United States to scale up the production of SAF to 35 billion gallons per year by 2050, with a near-term goal of 3 billion gallons per year by 2030. In addition, SAF produced under this challenge much achieve a minimum of 50% reduction in greenhouse gas emissions. This strategy is led by the U.S. Department of Energy (DOE), U.S. Department of Agriculture (USDA), and Department of Transportation (DOT) with support from the Environmental Protection Agency (EPA) and other federal partners.
A Third Way report projects that reaching the U.S. SAF Grand Challenge could result in up to 153,000 direct jobs, supporting nearly 250,000 additional jobs across the broader economy
Source:
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Fly with airlines that use SAF. By choosing to fly those airlines, consumers send a demand signal that sustainability matters
Purchase carbon offsets or SAF contributions. A number of airlines have programs where customers can pay a little extra to fund SAF or carbon offset projects.
Support corporate sustainability initiatives. If you travel for business, encourage your company to join corporate SAF programs.
Advocate and stay informed. Consumers can also support SAF by advocating for policies that promote clean fuels.
While one passenger’s actions might feel small, collectively passengers have influence. Showing that passengers value low-carbon flights will further incentivize carriers to invest in SAF.
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SAF is engineered to match the performance characteristics of conventional jet fuel, so it does not negatively impact aircraft or engine performance.
Engine and Aircraft Compatibility – SAF, being a drop-in fuel, has to meet the same specifications as standard jet fuel. When blended and certified, it provides the same thrust, fuel efficiency, and range as the equivalent amount of traditional fuel.
Source: US Department of Energy. “FAQ: SAF.” Bioenergy Technologies Office
Material Compatibility – Jet fuel has certain properties that help swell seals in fuel systems. Manufacturers have confirmed that current engines and fuel systems can use SAF blends without modifications. Future aircraft and engines are planned to be compatible with 100% SAF without the need for blending.
Emission and Combustion Characteristics – One performance benefit of SAF is that it tends to burn cleaner than fossil jet. Lower sulfur content means less sulfate pollution, and lower aromatic content means reduced particulate emissions.
Operational Use – Airlines that have used SAF blends report no required changes to flight operations. Fueling with a SAF blend is the same as fueling with normal jet fuel.
SAF has no detrimental impact on aircraft performance and is designed to be a direct substitute for fossil jet fuel. The main constraints on SAF use today are supply and certification limits, not technical performance issues.
ABOUT THE COALITION
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The Sustainable Aviation Advisory Council was created to to advance the production and use of Sustainable Aviation Fuel (SAF) in California by supporting sensible policies and incentives and providing clear and accurate information to policymakers and other stakeholders.
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From labor unions to businesses, aviation companies, and fuel producers, our diverse members and stakeholders are all calling for reasonable incentives in California.
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We differ in that our council comprises members from beyond the aviation and production sectors. However, we aim to complement the efforts of others advancing the adoption of SAF.
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Our mission is to accelerate the production and use of Sustainable Aviation Fuel (SAF) in California by supporting sensible policies and incentives and providing clear and accurate information to policymakers and the public. We support and participate in public discourse on SAF production and use, ensuring decisions are informed by robust science and stakeholder input.