Frequently Asked Questions


What is CAAFI?
CAAFI is an acronym for the Commercial Aviation Alternative Fuels Initiative. CAAFI is a coalition of aviation stakeholders who are interested in bringing commercially viable, sustainable, alternative jet fuels to the marketplace. CAAFI is engaged in various activities to enable and facilitate the near-term development and commercialization of such fuels. For details about CAAFI, its stakeholders and partners, functions, focus activities, and accomplishments, visit About CAAFI.

Who are CAAFI’s stakeholders (sponsors and participants)?
CAAFI is co-sponsored by the Aerospace Industries Association (AIA), Airports Council International-North America (ACI-NA), the Airlines for America (A4A), and the Federal Aviation Administration (FAA). In addition, CAAFI membership consists of approximately 600 organizations and 1800+ stakeholders. These include members of other U.S. and non-U.S. government agencies and trade associations, as well as energy producers, university faculty, nongovernmental organizations, and consultants. View a partial list of our member organizations. CAAFI is not a participant-funded organization, rather operating funds come from CAAFI sponsors. Participation in CAAFI is free of charge; we simply strongly encourage participants to engage in the efforts of the broader CAAFI community.

Why and how was CAAFI formed?
CAAFI was formed in 2006 in response to three concerns regarding aviation fuels: 1) supply security, 2) affordability and price stability, and 3) environmental impacts. These concerns prompted the FAA Office of Environment and Energy R&D Advisory Board to request action on aviation alternative fuels from the FAA Office of Environment and Energy. Following initial presentations by the manufacturing sector and the U.S. Air Force at a Transportation Research Board (TRB) forum in January 2006, FAA, A4A, and AIA elected to form a coalition of interested parties to foster alternative jet fuel development, later formalized as CAAFI; ACI-NA joined shortly thereafter.

How does CAAFI function?
CAAFI serves a primary role as a clearinghouse, facilitating the exchange of information about, and coordination of, private-sector and governmental initiatives supporting the development and commercialization of “drop-in” alternative aviation fuels (i.e., fuels that can directly supplement or replace petroleum-derived jet fuels). CAAFI members execute on in-kind work programs, while CAAFI sponsors (and their members) and other public-private partners provide resources for the execution of various work elements. CAAFI often serves as an industry voice that communicates progress and the need for the execution of a broad range of efforts by the entire jet-powered aviation enterprise.

What is the long-term goal of CAAFI?
CAAFI aims to facilitate the development and deployment of sustainable aviation fuels (SAF) in commercially meaningful quantities that will significantly reduce emissions associated with aviation operations while improving price stability and supply security. The availability of fuels produced from renewable feedstocks and/or other waste-streams will help operators reduce aviation’s net carbon footprint, even as aviation activity increases.

How is CAAFI organized?
CAAFI has an Executive Director who acts as an overall coordinator and instigator for the work of CAAFI. The Executive Director is supported in his execution of CAAFI work programs by an Assistant Director and Administrative Leadership Team, which includes a Head Advisor for Strategy and Implementation from FAA, a Head Advisor for Research & Technical from U.S. Department of Transportation/Volpe, and other support team members.

  • CAAFI Members are individuals and/or entities who are interested in supporting and/or engaging in the work of CAAFI forming a public-private partnership. CAAFI is ultimately a cooperative initiative. There is no cost to becoming a CAAFI member.
  • CAAFI Work Teams are led by volunteers from the CAAFI membership who are approved by the Sponsors and Executive Director. At present, there are four Work Teams: Research and Development, Certification/Qualification, Sustainability, and Business.
  • CAAFI’s Steering Group (SG) guides CAAFI’s overall strategy and efforts. The Steering Group is comprised of CAAFI’s Executive Director, Administrative Leadership Team, sponsors and key partner representatives, and leaders of the various CAAFI Work Teams.
  • CAAFI’s Sponsors include:
    • Federal Aviation Administration (FAA), Office of Environment and Energy
    • Airlines for America (A4A)
    • Aerospace Industries Association (AIA)
    • Airports Council International-North America (ACI-NA)

What has CAAFI accomplished to date?

  • Fuel Specification Approvals. The CAAFI Certification and Qualification team works within established processes to help move promising alternative aviation fuels through industry evaluation to approval by ASTM International and other recognized certifying bodies. Government agencies, fuel manufacturers, aircraft and engine manufacturers, and airlines are stakeholders in CAAFI, and many participate on the certification team. The industry has agreed that these alternative fuels should “drop-in” to commercial engines, pipelines, fuel farms, and all other distribution and storage channels, thus requiring no new equipment or infrastructure. With assistance from the CAAFI Certification and Qualification Team, several drop-in alternative jet fuels have already been certified for commercial use.
  • Fuel and Feedstock Readiness Tools. CAAFI has developed a collection of tools that facilitate assessment and advancement of fuel and feedstock readiness with respect to ASTM approval, R&D and deployment activities, environmental sustainability, and commercialization. See our Fuel Readiness Level Tool page and our Feedstock Readiness Level Tool page. The Feedstock Readiness Level tool has also been used to develop a public repository of feedstock readiness evaluations on the USDA’s National Agricultural Library website.
  • Stakeholder coordination and communication. CAAFI enhances communication among government agencies, aviation sector trade associations, industry, fuel producers, feedstock producers, academic researchers, and non-governmental organizations via the CAAFI Biennial General Meeting, webinars, coordination with other public-private partnerships around the globe, conference presentations, and other venues.
  • Strategic thought leadership. CAAFI participates domestically with interagency working groups and strategic initiatives (e.g., SAF Grand Challenge, Biomass Research and Development Board, Billion Ton Bioeconomy, collaborative forums, and sustainable aviation fuel research consortia (e.g., FAA’s Aviation Sustainability Center (ASCENT)).
  • State Initiatives. CAAFI has facilitated formation of supply chains for sustainable aviation fuel deployment through the CAAFI State Initiatives.

How does CAAFI interact with the other global alternative aviation fuel coalitions?
CAAFI collaborates with sustainable aviation coalitions across the globe, including formal and informal work plans and partnerships. Under the umbrella of the CAAFI Biennial General Meeting, CAAFI initiated an ongoing “global exchange” of ideas to facilitate complementary work programs and help aviation present a united framework to facilitate development and deployment of advanced alternative jet fuels.

What is the focus of current CAAFI activity?
CAAFI supports the development and deployment of sustainable aviation fuels for use by the entire jet-powered aviation community. See CAAFI’s current Goals and Priorities.

When should we expect to see alternative fuels in commercial production?
In the U.S., the first commercial-scale SAF-producing facility opened in March of 2016 (AltAir, now World Energy, Paramount, CA). View a map of the current and anticipated commercial-scale deployment and the pathways currently approved under ASTM. CAAFI continually facilitates the convening of task forces and ongoing evaluation of new fuel pathways for ASTM qualification.

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Jet Fuel

What is jet fuel?
Conventional jet fuel is a blend of hydrocarbons (molecules comprised of chains of hydrogen and carbon) that is produced from the distillation and refinement of petroleum. This product stream coming out of the refinery is often referred to as a “middle distillate” fuel (between the streams produced for gasoline and diesel) or more specifically, kerosene-type jet fuel. The hydrocarbon molecules are typically in the C7 to C18 range, and consist of three general molecular forms: paraffins, cyclo-paraffins, and aromatics. Each type of molecule has unique attributes, but when blended together they deliver the characteristics needed and required for safe and efficient use in a turbine engine. Other compounds may also be added to jet fuel (usually in very small amounts) to improve its overall suitability for aircraft use, including additives such as antioxidants, metal deactivators, electrical conductivity additives, static inhibitors, icing inhibitors, corrosion inhibitors, biocides, lubricity enhancers, and thermal stability improvers. The jet fuel specifications used by the industry do not prescribe the exact composition or production methodologies to be used to make the fuel, but rather simply define the final physical properties that the fuel must exhibit.

What are the jet fuel types?
Jet fuel carries several common commercial and military names, including Jet A, Jet A-1, Jet B, JP-5, JP-8, TS-1, or ATF (aviation turbine fuel). These fuels differ slightly in a few discrete properties, for instance, in minimum freeze point or maximum flash point. Commercially, Jet A is used primarily in the United States, while Jet A-1 is primarily used outside the United States. Jet B is considered an alternative to Jet A-1 in cases of extremely cold climates, but not often supplied because it has a higher flammability than Jet A-1. However, all of these fuels have detailed specifications for physical properties and performance characteristics that must be met, and these are defined by international bodies, the most common of which are ASTM D1655 and DEF STAN 91-91. Physical properties (e.g. D1655 Table 1 Properties) include such properties as: acidity, maximum aromatics, volatility, flash point, density, and energy content. Performance characteristics (e.g. D1655 Table X1 Properties) include such elements as combustion characteristics and atomization. Additives are also controlled (e.g. D1655 Table 2), usually by min or max volume requirements.

How is jet fuel used on an aircraft?
The jet fuel loaded onto an aircraft constitutes a large fraction of the overall takeoff weight of the aircraft, and aircraft are less efficient at heavier weights, so the industry attempts to keep the amount of required fuel or energy onboard to a minimum. Because weight is a key consideration, fuel also serves several functions onboard the aircraft, other than just a chemical source of energy, including as a heat transfer medium, a hydraulic fluid, a lubricant, a ballast medium, a conductivity agent, a swelling agent for seals, etc. The fuel is injected as a continuous, atomized stream into a combustor where it mixes with air while burning to deliver a stream of hot, energetic gas to a turbine. The turbine converts the gas energy to mechanical energy (i.e. a rotating compressor, booster, and fan), producing power for the aircraft. As a result of the above, aircraft system manufacturers are genuinely concerned about carefully controlling the properties of jet fuel.

How much energy is in jet fuel?
For commercial applications, ASTM D1655 requires jet fuel to produce a minimum amount of energy of 42.8 MJ/kg, with densities between 775-840 kg/m3 (or 18,400 BTU/lbm, with densities of 6.47-7.01 lb/usg).

What are the products of jet fuel combustion?
Similar to any pure hydrocarbon fuel, when pure jet fuel is burned under ideal conditions (with pure oxygen), its combustion by-products are carbon dioxide and water. In real world applications (less than ideal, and in the presence of air, which contains nitrogen), the combustion may also result in the trace release of carbon monoxide, unburned hydrocarbons (in gas and particulate form), nitrogen oxides, and sulfur oxides (as a direct function of how much sulfur is in the fuel). Regulations exist that limit the amount of pollutants that can be produced. Jet fuel combustion produces ~3.16 pounds of CO2 per pound of fuel burned.

What makes jet fuel different from automotive fuel?
Automotive fuels for spark and compression ignition engines typically include gasoline (and/or alcohols) and diesel fuel. These fuels contain shorter and longer carbon chain lengths, respectively, than jet fuel. The shorter chain lengths typically result in higher volatility and the longer chain lengths typically result in a higher freeze point, amongst other physical and performance-based property changes, making both types unsuitable for aviation use. Automotive fuels are produced to their own unique specifications. Jet fuel is generally produced to tighter specifications than gasoline or diesel (e.g. to guarantee operability, eliminate contaminants, etc.).

How much jet fuel is consumed in the U.S.?
Based on data supplied by the U.S. Energy Information Administration, civil and military aviation consumed approximately 27.1 billion gallons of jet fuel in 2019 (102.4 billion liters, 1.8 million barrels per day). The pandemic significantly influenced the use of jet fuel in 2020 when approximately 16.6 billion gallons of jet fuel were burned. In 2021, jet fuel use was again over 20 billion gallons a year. We expect quantities to continue to increase over the years. The Bureau of Transportation Statistics indicates that U.S. commercial carriers consumed 19.2 billion gallons for domestic and international operations in 2019. The difference between the two values above reflect fuel usage by foreign carriers (who don’t submit BTS data), as well as operations of the military, business aviation, general aviation, and miscellaneous special uses (e.g. firefighting, law enforcement).

How much jet fuel is consumed in the world?
Various sources estimate that the total production/consumption of jet fuel is about 100 billion gallons worldwide, increasing annually by an average 3.6% per year over the last decade.

Who produces jet fuel, and how?
Most of the large international petroleum producers/refiners produce jet fuel from their standard refinery operations, as do a significant group of regional producers. Crude oil is converted into conventional jet fuel through several processes. First, the oil is heated, then distilled to separate raw feedstock into different output streams based on boiling point. While in separate streams, impurities are removed (e.g. acids, sulfur, etc.), after which the streams are blended to ratios to achieve the specific composition of the desired jet fuel type (e.g. Jet A). Finally, certain additives are installed to improve fuel performance and stability to meet the final specifications.

How does jet fuel get transported to the airport?
Typically, large commercial airports have jet fuel delivered by pipeline systems from the refineries to a “fuel farm” adjacent to the airport. But jet fuel is also delivered by rail, road (tanker trucks), and water (tankers and barges). Read more about the transportation issues associated with alternative jet fuel.

Can commercial aircraft burn fuels other than jet fuel?
Commercial aircraft can only use fuel that is approved for use in the engine and aircraft operating manuals, as only this type fuel is proven to enable the performance and operability guaranteed by the certification of the aircraft. All of the major engine and aircraft manufacturers require usage of fuel which meets the requirements of ASTM D1655 (at a minimum).

What other fuels (alternative fuels) could work for aviation?
At present, based on today’s certifications, no other fuel types, other than jet fuel, satisfy the needs of the jet-powered aviation enterprise. It is not an issue of a gas turbine being physically unable to burn the fuel, but rather that the overall safety and performance of the aviation system cannot be matched by other fuels. Gas turbine engines are regularly used to power ships and provide power for other heavy machinery or power production, and do so using a wide range of fuels, from hydrogen to heavy oils. But use of such fuels cannot today deliver the same level of performance, safety, and cost as jet fuel for aircraft. Going forward, aircraft producers are investigating a wide range of fuel and energy systems to power aircraft, but none of those systems have proven feasible, or appear to be feasible, for several more decades due to the need for advances in energy storage to enable sufficient power per unit weight of the fuels as well as the need to adjust fueling and airport infrastructure globally to accommodate non-drop-in fuels. Significant progress is being made on small general-aviation aircraft operating on hybrid or electric propulsion using fuel cells and/or batteries, but such systems still appear to be severely deficient in key performance attributes of delivering sufficient energy density (by a factor of 50) or cost competitiveness to be reasonable for commercial aircraft. As of 2022, electric aircraft and aircraft powered by hydrogen and other fuels would likely be limited in range to around 200 nautical miles. As such, the jet-powered aviation enterprise expects to continue the use of jet fuel through the middle of this century.

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Alternative Jet Fuels (AJF) and Sustainable Aviation Fuel (SAF)


Foreword: a primer on the different terminology used for the non-petroleum fuels being pursued by the industry (see also CAAFI’s Glossary of frequently used terms).

Sustainable Aviation Fuel (SAF): a general term used to describe the class of non-petroleum-based turbine (or jet) fuel blending components that are being pursued by the industry to:

  • Reduce net life-cycle carbon dioxide (CO2) emissions from aviation operations.
  • Enhance the sustainability of aviation by being superior to petroleum-based jet fuel in economic, social and environmental aspects.
  • Enable drop-in jet fuel production from multiple feedstocks and conversion processes, so no changes are required in aircraft or engine fuel systems, distribution infrastructure, or storage facilities. As such, SAF can be mixed interchangeably (is fungible) with existing jet fuel.

The SAF terminology has been adopted by the International Civil Aviation Organization (ICAO) in their efforts associated with addressing aviation greenhouse gas emissions under CORSIA, and the rest of the industry is adjusting to the new terminology. Previously:

  • ICAO had defined “aviation alternative fuel” as “a drop-in fuel obtained from sources other than petroleum, such as coal, natural gas, biomass, and hydrogenated fats and oils.” This definition was also broad, and includes some fuels that could have environmental impacts worse than conventional jet fuel. SAF then has a “potential to be sustainably produced and to generate lower carbon emissions than Conventional Aviation Fuel (CAF) on a life cycle basis.”
  • CAAFI previously referred to the fuels of interest to the aviation community as Sustainable Alternative Jet Fuels (SAJF), i.e. a sustainable subset of all possible alternative methods of production.
  • The scientific portion of the aviation community refers to these fuels in ASTM D7566 as Aviation Turbine Fuel Containing Synthesized Hydrocarbons, simply focusing on the technical aspects of the fuel, and not on the concept of sustainability.

SAF is also sometimes referred to as bio-jet, renewable jet, bio-kerosene, alternative jet fuel, non-conventional jet fuel, etc., or specifically, by the several names for the conversion pathways outlined in ASTM D7566 (e.g. HEFA). Any SAF compliant with the requirements of D7566 is recognized as meeting the characteristics of traditional petroleum-based jet fuel approved under ASTM D1655 (see below).

So, SAF is sustainably produced non-conventional turbine fuel, refined from non-petrochemical sources, and may be derived from many resources whose chemical constituents can be converted to the set of pure hydrocarbons that comprise jet fuel. These substances are also processed (or synthesized) into jet fuel molecules in an alternative manner to simply refining crude oil (via thermochemical, biochemical, and catalytic production processes). Feedstocks for SAF are also varied, ranging from cooking oil, plant oils, solid municipal waste (trash), wood waste, waste gases, sugars, purpose-grown biomass and agricultural residues, among others.

It is important to note that different types of SAF, depending on their source and manner of production, will have different levels of perceived sustainability (because there are also multiple sustainability platforms via which SAF types get evaluated). So, all SAF are considered to be alternative jet fuels, but not all alternative jet fuels are necessarily SAF.

There is an additional nomenclature being propagated right now, primarily in the EU, where people are starting to distinguish between two types of SAF: those produced from biogenic sources (as biofuels or renewable fuels) and those produced from carbon dioxide and hydrogen directly (as “synthetic fuels”). Time will tell if the latter terminology is more broadly adopted.

What do we mean by the term alternative jet fuel?
Generally, the aviation industry means jet fuel derived from a source other than petroleum. Specifically, CAAFI and the aviation community mean a fuel produced to the requirements of ASTM D7566. It can include drop-in jet fuels produced from a broad range of hydrocarbon sources (feedstocks) using a wide range of conversion processes. We sometimes refer to these fuels as synthetic fuels, too—fuel produced from sources other than petroleum via biochemical or thermochemical processes. Just because a fuel is an alternative fuel, it does not mean it meets the various definitions of sustainability the industry is seeking (e.g. jet fuel produced from coal).

What is the difference between an “alternative fuel type” and an “alternative jet fuel?”
An alternative fuel could be any generic fuel derived from a source other than petroleum. It could include compressed natural gas, liquefied natural gas, hydrogen, alcohols, biodiesel, etc. However, none of these fuels are suitable for jet-powered aviation. The aviation community needs jet fuel for safe and efficient operation, whether that is produced from petroleum, or sources other than petroleum. Currently, the aviation sector is focused on drop-in alternative jet fuels and, more specifically, sustainable aviation fuels (SAF).

What is a drop-in AJF?
Drop-in alternative jet fuels are Jet A/A-1 fuels that meet requirements per ASTM D1655 (US), Def. Std. 91-91 (British) and CAN/CGSB-3-23 (Canadian) jet fuel specifications, whose origin is ASTM D7566 (Aviation Turbine Fuel Containing Synthesized Hydrocarbons) and is re-identified as D1655 Jet A or Jet A-1 fuel. Drop-in alternative jet fuels are completely compatible with a conventional (typically petroleum-derived) jet fuel in terms of materials, safety, and composition. A drop-in fuel does not require adaptation of the fuel distribution network or the engine fuel systems; it can be used “as is” in vehicles and engines that have historically operated with only conventional fuel. All alternative jet fuel blending components may become “drop-in” only after being blended with a conventional fuel to a certain prescribed proportion. The currently approved fuels and blend levels can be found on our Fuel Qualification page. Drop-in fuels align with CAAFI’s goal of expanding SAF deployment in the near term.

What is a sustainable aviation fuel (SAF)?
Sustainable aviation fuel, or SAF, is a subset of drop-in alternative jet fuels that is produced from renewable or waste-based feedstocks. SAF is a globally accepted term used by the International Civil Aviation Organization to refer to “renewable or waste-derived aviation fuel that meets the [Carbon Offsetting and Reduction Scheme for International Aviation] CORSIA Sustainability Criteria” included in the Standard and Recommended Practices. CAAFI will continue to describe alternative jet fuels as AJF (e.g. in questions above and below) until such time as the AJF are shown to meet sustainability criteria, and then will refer to such fuels as SAF.

What are key challenges relating to AJF development?
General challenges include navigating the path of technology development from laboratory benchtop to pilot facility (fuel chemistry as a function of conversion process and operating conditions, impacts of scaling), defining products and coproduct potential, developing comprehensive techno-economic understanding, and initial life cycle analysis (LCA) evaluations, to name a few. The CAAFI R&D Team has developed a series of white papers addressing the key challenges related to alternative jet fuel development. CAAFI’s webinar series also regularly addresses key challenges.

What are key challenges relating to AJF deployment?
General challenges include the development of requisite supply chains, including feedstock availability for viable production capacity, detailed life cycle analysis (LCA) evaluations, cost competitiveness, addressing funding needs, performing siting studies (community acceptance, blending options, and transport), and acquiring offtake agreements with airlines and fuel suppliers, to name a few. The CAAFI Leadership Team and Business Team work directly with producers on these issues, or work collaboratively through various CAAFI initiatives to help address these issues on an individual or prospective basis.

How are feedstocks converted into AJF?
The industry has determined that there are several ways to convert the carbon or hydrocarbon content of various sources into the chemical components of jet fuel. These can include biological processes (fermentation or microbial conversion), or thermochemical processes (gasification, torrefaction, pyrolysis, catalytic conversion, hydroprocessing, etc.).

Before aircraft can use any alternative jet fuels, those fuels must meet rigorous criteria spelled out in aviation fuel specifications, both physical properties and fit-for-purpose properties. The specifications for alternative jet fuels are defined in ASTM Standard D7566 and specific annexes to the Standard apply to individual processes for producing alternative jet fuel (see our Fuel Qualification page).

How long have commercial aviation entities been pursuing alternative jet fuels?
Alternative aviation fuels activity had been developing slowly since the 1970s, largely through the efforts of the U.S. Air Force and a group of engine companies. When CAAFI formed in 2006, the ASTM committee had begun the process of streamlining their certification processes for alternative jet fuels. A blend of synthetic and conventional jet fuel produced by the South African producer Sasol was approved by ASTM and began being used on flights in and out of Johannesburg in 1999. In 2009, approval of the new ASTM D7566 specification for synthetic aviation fuels, with the ability to add annexes to it for new alternatives, once proven, heralded the true dawn of the era of alternative aviation fuels.

What is the U.S. government’s SAF Grand Challenge?
In September 2021, the U.S. government announced a “SAF Grand Challenge” with the goal of producing three billion gallons per year of sustainable aviation fuels in the U.S. by 2030, reducing GHG emissions from aviation by 20% by 2030, and fully replacing jet fuel with SAF by 2050 (estimated at 35 billion gallons). To achieve these goals, the U.S. government developed a SAF Grand Challenge Roadmap outlining government-wide activities to facilitate the deployment of SAF. The roadmap was released in September 2022 at the Global Clean Energy Action Forum. Six action areas are outlined in the Roadmap:

  1. Feedstock Innovation
  2. Conversion Technology Innovation
  3. Building Regional SAF Supply Chains
  4. Policy & Valuation Analysis
  5. Enabling End Use
  6. Communicating Progress & Building Support

CAAFI will develop team activities and initiatives to support these action areas leading up to 2030.

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AJF/SAF Certification and Qualification

What is the process for jet fuel development and approval?
See the fuel approval process on our Fuel Qualification page. For an overview on jet fuel development and approval, as well as links to helpful resources, see CAAFI’s Path to Alternative Jet Fuel Readiness document.

Is SAF approved by the FAA and other Aviation Authorities?
These fuels are acceptable for use on those aircraft and engines that are approved to operate with Jet A or Jet A-1 fuels that meet the D1655 standard. The same is true for the European Aviation Safety Agency (EASA) as per CM-PIFS-009. Transport Canada has not released any formal guidance documentation. However, if the SAF enters the fuel distribution system as D1655, no formal guidance is required for operations already meeting their regulatory compliance (engine or aircraft manuals, or operating certificates) via the use of D1655 fuel.

What alternative jet fuels can be used today?
See the list of approved alternative aviation fuels on our Fuel Qualification page.

What drop-in alternative jet fuels are on the way to evaluation and approval?
See our Fuel Qualification page. A process has been established to regulate the sequence in which the current roster of alternative fuels and additives will be reviewed by the OEMs. Progression through the process is based on the technical substantiation and test work accomplished by the producer and the task force that has been assisting with the development and review of the product. CAAFI has worked closely with the research community and OEMs to establish prescreening procedures to ensure fuels that enter the ASTM process have suitable basic characteristics, and has worked to develop a “Fast Track” approach to streamline initial fuel qualification at low blend levels. CAAFI continues to work with the ASTM community to improve the fuel qualification process, while other industry participants continue to focus resources on timely qualification.

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AJF/SAF Compatibility with Existing Equipment and Operations

Does an airline or business aviation operator need special approval for their aircraft to fly with alternative jet fuels and SAF?
Special aircraft approval is not needed if the fuel is produced to the requirements of ASTM D7566 and thereby re-identified as ASTM D1655 jet fuel. FAA Special Airworthiness Information Bulletin (SAIB) NE-11-56R2 summarizes:

…jet fuel made from…synthetic blending components that meet the requirements of ASTM International Standard D7566 are acceptable for use on aircraft and engines certificated for operation with D1655 Jet A or Jet A-1 fuel if they are re-identified as D1655 fuel…When D7566 jet fuels are re-identified as D1655 fuel, they meet all the specification requirements of D1655 fuel and, therefore, meet the approved operating limitations for aircraft and engines certificated to operate with D1655 fuel, unless otherwise prohibited by the engine or aircraft type certificate (TC) holder.

The same bulletin states the following in its recommendations:

  1. These fuels are acceptable for use on those aircraft and engines that are approved to operate with Jet A or Jet A-1 fuels that meet the D1655 standard.
  2. Aircraft Flight Manuals, Pilot Operating Instructions, or TCDs that specify ASTM D1655 Jet A or Jet A-1 fuel as an operating limitation do not require revision to use these fuels.
  3. Current aircraft placards that specify Jet A or Jet A-1 fuels do not require revision and are acceptable for use with these fuels.
  4. Operating, maintenance, or other service documents for aircraft and engines that are approved to operate with ASTM D1655 Jet A or Jet A-1 fuel do not require revision and are acceptable for use when operating with these fuels.
  5. There are no additional or revised maintenance actions, inspections or service requirements necessary when operating with these fuels.1

Does an airline or business aviation operator need to register aircraft any differently to use alternative jet fuels or SAF?
No changes in registration are required if using a SAF qualified under the ASTM specification.

Will aircraft perform the same under all conditions (for example, extreme hot and cold temperatures) using AJF/SAF?
SAF blended fuel is fully approved to meet the specifications of petroleum-based fuels. This means that it performs just like conventional fuel as it meets the specifications contained in ASTM D1655.

SAF blend stocks (i.e., synthetically produced hydrocarbons defined in ASTM D7566 prior to blending with conventional jet fuel) generally have a lower mass density than conventional fuels, but final SAF blended fuels still fall within ASTM D1655 specification. Paraffinic types of AJF also have had slightly higher energy mass content. Operators should be aware of the specifics of the fuel and validate their flight planning is performed with appropriate assumptions on density (just as is done today when dealing with fuel differences at different airports around the world).

Do operators need to fly differently on AJF/SAF fueled flights?
No, SAF does not affect how an operator flies the aircraft. Flight planning should consider the appropriate fuel density just as it does for conventional jet fuel.

Does an operator need to obtain a certificate of analysis?
No, an approved fuel certificate of analysis is not required. However, for the business aviation community, a pilot can obtain a certificate, upon request, from the fuel supplier.

Does flying on SAF require a special placard for a business aviation aircraft?
No special placard is required.

How does SAF impact the defueling processes? Is there a special procedure?
As with all defueling operations, fuel removed from an aircraft containing SAF should be either disposed of or returned to the aircraft from which it was removed. Persons defueling an aircraft should also contact their fuel supplier to ensure proper defueling procedures are followed.

Can alternative jet fuels coming from multiple feedstocks, conversion processes, or producers be blended together?
Yes, following its initial blending, SAF is a “drop-in” fuel and can therefore be co-mingled with other equivalent specification fuel (e.g., ASTM D1655) without limitations in railway cars, fuel trucks, airport fuel storage facilities, and aircraft fuel tanks.

Can biocide additives be added to AJF/SAF blended fuel?
Yes, SAF, once blended correctly to ASTM D7566 requirements and distributed to the end user, is a drop-in fungible fuel and is considered ASTM D1655 jet fuel. Approved biocides (i.e., Kathon FP1.5 or Biobor) may be added at aircraft manufacturer’s required dosages, the same as allowable in Jet-A ASTM D1655 fuels.

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AJF/SAF Benefits

How does SAF perform with respect to life cycle greenhouse gas (GHG) emissions?
Depending on the feedstock and production pathway used, alternative jet fuels may offer reductions in GHG emissions when compared to conventional fuels. Land-use change can be critical with any biomass, as converting tropical or peatland rainforest to biomass production can increase the life cycle emissions by several orders of magnitude over that of traditional Jet A (see Stratton et al. PARTNER report). Find more about land use change on the EPA’s Sources of Greenhouse Gas Emissions webpage. CAAFI and the aviation community have committed to carbon neutral growth starting in 2020, which is being implemented through the ICAO Carbon Offsetting and Reduction Scheme for International Aviation (CORSIA), and therefore, are interested in alternative jet fuels that have GHG reductions compared to standard petroleum-based jet fuels. CORSIA-Eligible Fuels are defined as having at least 10% reduction in life cycle GHG emissions compared to a petroleum-based fuel baseline. The crediting of SAF within CORSIA is determined by the compliance with the CORSIA sustainability criteria and the life cycle greenhouse gas footprint of the fuels. ICAO has published a set of default SAF life cycle emissions values that can be used by an operator, or the operator can pursue an actual value using the published CORSIA life cycle analysis methodology.

What sort of actual emissions reductions can be expected from using SAF?
An illustrative example: a large-cabin modern business jet on a 1,000 nautical-mile mission might burn enough fuel to produce approximately 22,787 pounds of CO2. If such a flight were to use SAF (HEFA-SPK pathway) at a blend of 30% SAF to 70% conventional Jet-A fuel, the same mission would result in a net reduction of CO2 emissions of approximately 4,100 pounds (18%) on a lifecycle basis.

How do AJF perform with respect to local air quality pollutant emissions?
Synthetic fuels afford the opportunity to lower local air pollutant emissions through the reduction of sulfur and aromatic compounds. Thus, when blended with traditional fuel, overall sulfur and aromatic content is reduced. Research also suggests that some alternative fuels may produce less particulate matter (a growing concern for local air quality).

Do AJF affect aircraft performance?
Effects can be slightly positive and negative, but overall operability and safety are maintained. For example, lower density fuels can improve fuel burn, but adversely affect an aircraft’s maximum payload range. Various members of the civil aviation community are exploring all performance impacts, and none are found to be outside the range of expected results based on common planning methodologies (e.g. flight planning, dispatch) of the industry.

How will AJF affect airports?
Benefits to airports are possible with alternative fuels. Airports that own and operate ground service equipment can also see environmental improvements in the operation of their own equipment, as alternatives for such equipment can reduce greenhouse gas and local emissions as well. Project 02-07 of the Airport Cooperative Research Program (ACRP) developed the Handbook for Analyzing the Costs and Benefits of Alternative Aviation Turbine Engine Fuels at Airports.

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AJF/SAF in Technical Operations

Does the use of AJF have an impact on APU and main power plant performance, other components including fuel tanks and fuel systems, airframe, maintenance procedures/requirements, and/or product warranties?
Selected aircraft OEMs, engine and APU manufacturers, as well as manufacturers of other components, participated in the testing process and that testing found that AJF is compatible for use in their products with no modifications required and with no need for recertification or additional validation. These manufacturers and other interested parties are participants to the final industry approval of new D4054 pathways, and any one individual has the ability to stop the approval with any valid technical objection.

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AJF/SAF Financial Considerations

Are AJF economically viable?
The two chief barriers to deployment (in many cases) are the availability of capital to construct the required initial infrastructure and the availability of reasonably priced feedstocks and supply chains. CAAFI, through its members, partners, and work programs are attempting to drive down these barriers to implementation. In the long run, most parties involved in CAAFI understand that being the first transportation mode to move forward with drop-in, sustainable, alternative fuels will help ensure aviation’s economic viability and environmental acceptability.

Is SAF more expensive than traditional jet fuel?
As of late 2022, the cost of a blended SAF is typically higher than the price of petroleum-based Jet-A. Additionally, transportation costs for the fuel will vary and can add to the overall cost of the fuel.

What financial incentives or other credits are available to help reduce the cost of SAF relative to traditional jet fuel?
In the U.S., there are three main sources of financial incentives to deploy SAF associated with the Renewable Fuel Standard (RFS), the California Low Carbon Fuel Standard (LCFS), and the U.S. SAF blenders tax credit codified in the Inflation Reduction Act of 2022.

The Renewable Fuel Standard mandates volumes of renewable fuels within the U.S. fuel pool and provides for Renewable Identification Numbers are assigned to each batch of fuels that meet the criteria of the program; the number of RIN credits per gallon of fuel vary. Once assigned, RINs can be separated from the fuel and sold separately on the open market. RIN prices vary by fuel category and over time; in 2021 RIN prices were around $1.30-$1.50/RIN. Qualified SAF pathways can be assigned RINs under RFS but are not specifically mandated under the program.

The California Low Carbon Fuel Standard sets annual life cycle carbon intensity (CI) standards for gasoline, diesel, and biomass-based alternatives. Through LCFS, per-ton credits are generated and can be traded in the LCFS market. Per-ton credit values have historically ranged from $65-200 per ton.

The SAF Blenders Tax Credit provides a credit to blenders for incorporating SAF into their fuel pool, providing $1.25 per gallon for SAF meeting a minimum of a 50% reduction in life cycle GHG emissions, and providing for an additional $0.01/gallon for each percentage point of GHG reduction beyond 50%, up to a maximum of $1.75/gallon. It should be noted that the Blenders Tax Credit will be phased out in favor of a producers credit in 2024, the details of which have not been established.

Together, these incentives in the U.S. provide potential mechanisms for SAF to become more economically viable in spite of higher current production costs than petroleum-based jet fuel.

Is financial compensation or a tax break available to airlines or business aviation operators to fly on SAF?
There are currently no direct financial incentives for airlines or business aviation operators to fly on SAF. However, those operators who may be subject to CORSIA have the option to meet their carbon neutral growth obligations via the purchase of SAF.

Given that SAF costs more and that a small-to-medium-sized business aviation operator may not be subject to ICAO’s CORSIA scheme; what is the value of those operators in using SAF?
The business aviation industry, as a whole, committed in 2009 to improve its efficiency and do its part to mitigate the industry’s effect on climate change.

There is considerable political pressure in many parts of the world to reduce emissions from aviation by restricting flying or imposing severe extraneous costs on it. Business aviation is often portrayed as an inefficient and wasteful mode of transportation used only by rich people. It is important for the long-term economic survival of business aviation to demonstrate through concrete measures that it is a responsible steward of the environment.

The aviation industry is at the forefront of environmental responsibility and is the first industry to have developed international environmental standards for both manufacturers and operators. The industry’s proactive stance has helped stave off significantly more restrictive environmental standards and regulations globally; the industry has been instrumental in designing environmentally meaningful standards, as well as supporting national and regional regulations that also allow the industry to grow in a sustainable manner. The civil aviation sector (business and commercial) is aggressively promoting the use of SAF in recognition of the importance of ensuring that the industry can grow sustainably.

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Implications for Fixed Base Operators (FBOs)

If an FBO is interested in purchasing and selling SAF, what should it do?
It is important for an FBO desiring to sell SAF to:

  • Contact your fuel supplier for information on SAF.
  • Become well acquainted in advance with the relevant ASTM D7566 standard, to ensure that only qualified fuels are involved in any supply transactions.
  • Understand how, if at all, the FBO could participate in the acquisition and handling of fuel to facilitate the introduction of SAF (e.g., enabling blending of fuels near the airport; taking SAF from multiple producers or suppliers).

How does an FBO receive SAF?
The fuel supplier will arrange transportation of SAF to the FBO. Normal fuel acceptance procedures should be used.

How does an FBO store SAF?
The FBO should contact its fuel supplier to determine how to best store and deliver SAF. A key factor to consider is whether the SAF is purchased for a single client (who may desire sequestration of the fuel for fueling their specific aircraft) or for general use.

Are there special quality control procedures required for storage and delivery of SAF?
FBOs should follow the quality control procedures recommended by their fuel supplier for the SAF, which should tend to be identical to those used for other approved jet fuels.

Is special training required for FBO employees to handle SAF?
All FBOs should provide comprehensive training in the handling of aviation fuels. FBOs should coordinate with their fuel supplier to identify any unique training requirements based upon their specific operating conditions. FBOs should educate their staff on the values of SAF and to have staff promote the adoption of SAF when available.

Is there an industry standard for defueling an aircraft using SAF?
As with all defueling operations, fuel removed from an aircraft containing SAF should be either disposed of or returned to the aircraft from which it was removed. The FBO should also contact its fuel supplier to ensure proper defueling procedures and certification processes are followed.

How should an FBO handle client concerns regarding compatibility of SAF with aircraft components?
Aircraft OEMs, engine and APU manufacturers, as well as manufacturers of other components, participated in the testing process and that testing found that SAF is compatible for use in their products with no modifications required, and with no need for recertification or additional validation. FBOs can provide a Certificate of Analysis for the SAF, which is available from the FBO’s fuel supplier.

If clients still have concerns, the FBO should direct clients to contact their OEM regarding any compatibility issues.

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