In the guide below, we discuss sustainable aviation fuel.
We outline what it is, what it’s made of, the different types of this fuel, potential pros and cons, and more.
This guide compliments our separate guide on whether sustainable air travel is possible.
Summary – Sustainable Aviation Fuel
What It Is
Sustainable aviation fuel (also referred to as SAF) is a type of fuel that is claimed to have sustainability benefits over conventional jet fuel (which is a kerosene fuel type) when used in aircrafts
Although there’s no one agreed upon definition of SAF, the main sustainability feature of SAF according to several reports is that it reduces the carbon footprint of aviation and aviation fuel
What It’s Made Of
It’s generally fuel derived from renewable biomass or sustainable feedstock
There’s a range of different biomasses and feedstock types that can be used to make the fuel
It involves biomass or feedstock being sourced, and then converted into fuel
Some sustainable aviation fuels are blended in different % shares with conventional jet fuel in the final fuel product (currently up to 50% of each type of fuel according to several reports, although higher % share sustainable aviation fuel shares might be possible in the fuel)
A summary list of the pros outlined in the guide below:
– May Have Environmental Benefits, & Resource Management Benefits
– May Not Have To Compete For Land Use
– A Range Of Biomass Sources Can Be Used For Biofuel
– Can Be Blended With Conventional Fuel
– Might Use Some Existing Fuel Infrastructure & Aircrafts
– Commercial Airlines Have Already Used It, & A Certain Level Of Future Use/Demand Is Already Guaranteed
– There Are Reasonable Feedstock Supplies Available To Make Biofuels In The US
– May Help Extend The Useful Lifespan Of Older Aircrafts
– May Create New Economic Opportunities
– Some Feedstocks May Show Promising Potential
– Can Be Quality Tested & Certified
– Can Be An Alternative To E-Fuels
A summary list of the cons outlined in the guide below:
– May Currently Be More Costly Than Traditional Jet Fuel
– Consumers Will Likely Bear The Increased Cost For Sustainable Aviation Fuel
– May Only Be Effective For Specific Types Of Flights
– Still Uses Conventional Jet Fuel In The Final Fuel Product
– The Scale Of Use Of Sustainable Aviation Fuel Is Not Yet Where Conventional Jet Fuel Is, & There Might Be Barriers To Growth
– Has Some Practical/Technical Challenges
– Some Question How Renewable Some Feedstocks Actually Are
– Some Question How Sustainable Some Feedstocks Actually Are
– Is Not The Only Sustainability Solution For The Aviation Industry
– Some Reports Indicate That Hydrogen Planes Are The Mid To Long Term Solution
What Is Sustainable Aviation Fuel?
A fuel (which some reports refer to as a type of biofuel) used to power aircrafts that has claimed sustainability benefits compared to traditional aviation fuel (i.e. petroleum-based jet fuel)
Although there isn’t yet an internationally agreed upon definition of sustainable aviation fuel, there’s a commonly listed sustainability benefit that it reduces carbon emissions
Currently, the reduction might be for short to medium haul flights
There can be other claimed sustainability and environmental benefits of SAF too (which we outline in the guide below)
popsci.com indicates that SAFs are chemically identical to conventional jet fuel (or kerosene).
However, SAFs and conventional jet fuel come from different feedstock and are produced/converted to fuel in different ways than conventional jet fuel
What Is Sustainable Aviation Fuel Made Of?
The Feedstock Used
This fuel is usually derived from renewable biomass (i.e. renewable organic matter), or sustainable feedstock
Examples of different biomass or sustainable feedstock used can include:
– Plants (and dedicated crops like corn)
– Microorganisms like algae
– Oils (like cooking oils, plants oils, etc)
– Animal waste or animal fat
– Organic wastes
– Agricultural residues
– According to bp.com, sometimes solid wastes from homes and businesses are used too (although some question that some types of solid waste are actually renewable)
wikipedia.org lists the different sources of biomass that can be used for aviation biofuel, including a range of plant sources, solid biomass sources, and waste sources
popsci.com also indicates that some SAFs are ‘fully synthetic fuels, or e-fuels, made from carbon dioxide and hydrogen’
The Final Fuel Product Used In Airplanes
The final sustainable aviation fuel product (which is made after the feedstock is sourced, and then converted to fuel) can be a blend of sustainable aviation fuel, and also conventional jet fuel
Currently, the blend can be up to 50% aviation fuel according to several reports.
Although, further developments may allow higher shares in the future
Types Of Sustainable Aviation Fuel
Different types of sustainable aviation fuel can be made by adjusting the following variables:
– The type of biomass used (which can impact factors such the CO2 emissions of the fuel)
– The technology used to develop or convert the fuel
– After sourcing feedstock and converting the feedstock to SAF, the final fuel product can be blended with different % shares of conventional jet fuel, and sustainable aviation fuel
The type of aviation fuel used can impact things such as the sustainability, performance and cost of the fuel.
As an example, wikipedia.org lists that the biofuels with the highest emission savings are ‘those derived from photosynthetic algae (98% savings, technology not yet mature) and from non-food crops and forest residues (91–95% savings).
popsci.com also indicates that there are different SAF products available, and each one has different pros and cons to consider.
What Is The Cost Of Sustainable Aviation Fuel?
Several reports indicate that SAF is more costly than traditional jet fuel for producers and consumers, and there’s several reasons for this.
Some reports indicate it could become more affordable in the future though as it develops, improves, and there is more demand and scaling.
Having said that, some reports say SAF may never be as affordable as traditional kerosene jet fuel.
The cost of SAF could become more compounded in planes and jets that are fuel inefficient.
bp.com indicates that:
SAF is currently more costly than traditional fossil jet fuel [and that’s because of] a combination of the current availability of sustainable feedstocks and the continuing development of new production technologies.
As the technology matures it will become more efficient and so the expectation is that it will become less costly for customers.
cnbc.com indicates that:
‘[SAF was about] two and a half times the price of jet kerosene [in 2022] When you factor in the cost of carbon, you’re looking at maybe … twice the price of kerosene’
Sustainable fuels are about twice what you’re paying for … the traditional jet kerosene, so it does represent a significant hike in the airline industry’s cost base
popsci.com indicates that ‘[most SAFs are] two to four times as expensive as traditional jet fuel’, and ‘it’s not likely SAFs will ever be as cheap as fossil fuels are’ even though ‘… prices can likely come down a bit when technology scales and becomes more common’.
popsci.com also mentions that these costs might be a significant issue in less fuel efficient plane models per mile the plane has to fly (because the planes are using more fuel per mile).
wikipedia.org: ‘As of 2020 aviation biofuel is more expensive than fossil jet kerosene, considering aviation taxation and subsidies at that time’
Why Might Sustainable Aviation Fuel Be Important?
There might be three general reasons:
– A desire to reduce carbon emissions to address a changing climate
– Although aviation as an industry might not produce the most total carbon emissions compared to other industries in some countries (popsci.com for example indicates that aviation only makes up about 3% of worldwide emissions), cnbc.com indicates that ‘[air travel is] currently the most carbon intensive activity an individual can make’
– According to bp.com ‘… the aviation industry [is] expected to double to over 8 billion passengers by 2050’. So, getting more sustainable with an expected increase in future capacity and demand might be a priority.
In addition to the above points, SAF may be one solution amongst several other solutions that might help in making air travel more sustainable.
Potential Pros Of Sustainable Aviation Fuel
May Have Environmental Benefits, & Resource Management Benefits
Some of the benefits might include:
– The reduction of carbon emissions for air travel compared to conventional jet fuel
Actual reduction in carbon emissions may depend on the type of biomass used, and other variables.
In terms of the potential reductions in of emissions that could be seen by the use of SAFs, some of the estimates are …
wikipedia.org indicates that some biofuels ‘could lower CO₂ emissions by 20–98% compared to conventional jet fuel’.
bp.com indicates that ‘SAF gives [a] reduction of up to 80% in carbon emissions over the lifecycle of the fuel compared to traditional jet fuel it replaces, depending on the sustainable feedstock used, production method and the supply chain to the airport’
qantas.com indicates that for one of their routes where blended SAF is used, carbon emissions are reduced ‘by around 10 per cent’.
Further to that, both qantas.com and iata.org indicate that SAF has ‘the potential to reduce lifecycle emissions by up to 80 per cent compared to conventional jet fuel’
energy.gov notes that ‘Some emerging SAF pathways even have a net-negative GHG footprint’
– Using renewable resources in the form of biomass to produce the fuel
This is in comparison to fossil fuel used to produce traditional aviation fuel (which include hydrocarbons)
This depends on the feedstock and processes used though, and whether they truly are more sustainable or renewable, or are just marketed that way
– Potentially reducing air pollution
wikipedia.org indicates that ‘Biofuels do not contain sulfur compounds and thus do not emit sulfur dioxide’
Depending on the location though, sulfur dioxide emissions may or may not be a significant issue
– Other potential environmental benefits
energy.gov indicates that biomass crops may help control erosion, improve water quality and quantity, increase biodiversity, store carbon, and reduce pollution pressure of watersheds
wikipedia.org indicates that Jatropha oil may be able to use marginal land that most plants would produce low yields on.
Another potential sustainability benefit might be that solid wastes don’t go to landfills or incineration when they are used as feedstock for SAFs.
May Not Have To Compete For Land Use
wikipedia.org indicates that sustainable biofuels don’t have to ‘compete with food crops, prime agricultural land, natural forest or fresh water’
This might be a case by case basis analysis though on the individual biofuel operations in a given geographic area
A Range Of Biomass Sources Can Be Used For Biofuel
Such as plants, solid biomass, and organic waste sources
Algae (a plant like organism) can also be used
Can Be Blended With Conventional Fuel
Biofuels can be blended in different % shares with conventional aviation fuel after sustainable feedstock has been sourced, and converted to SAF
This allows some flexibility in getting the desired balance of fuels in the final fuel product
Might Use Some Existing Fuel Infrastructure & Aircrafts
Aside from the feedstock, biorefineries and conversion of feedstock into fuel, blended SAF might make use of some of the same infrastructure and aircrafts as traditional jet fuel according to some reports
Many Airlines Have Already Used It, & Some Level Of Future Use/Demand Is Already Guaranteed
– When It First Started Being Used
[The first test flights using blended bio fuel were in 2008, and 2011 saw 50% blended biofuels used for commercial flights] (wikipedia.org)
– Airlines & Locations That Have Experience Using SAF
iata.org indicates that over 45 airlines now have experience with sustainable aviation fuel, and there’s already forward purchase agreements locked in for it’s future use
bp.com indicates that ‘Air bp has supplied SAF at over 20 locations across three continents’
– Pre-Orders Of SAF For Use In The Future
cnbc.com indicates that ‘… airlines had ordered 14 billion liters of SAF’
May Be Used For A Range Of Aircrafts
bp.com mentions that ‘Any aircraft certified for using the current specification of jet fuel can use SAF’ and also mention that they have supplied SAF to a range of aircrafts from ‘… small private jets to large passenger aircrafts’
It’s worth noting that SAF used in aircrafts should be quality tested and certified
There Are Reasonable Feedstock Supplies Available To Make Biofuels In The US
energy.gov indicates ‘An estimated 1 billion dry tons of biomass can be collected sustainably each year in the United States, enough to produce 50–60 billion gallons of low-carbon biofuels’
May Create New Economic Opportunities & Jobs
For example, growing dedicated biofuel crops, or harvesting biomass feedstock may present new economic opportunities to farmers and other producers.
There may also be an opportunity for farmers to create an additional income.
There may also be new economic opportunities and jobs in biorefineries, and the aviation industry.
May Help Extend The Useful Lifespan Of Older Aircrafts
Older aircrafts with less sustainable aircraft systems may be able to increase their ‘in the air’ lifespan by lowering their carbon footprint with sustainable aviation fuel.
Can Be Quality Tested & Certified
bp.com mentions that SAF is quality tested, and blends are certified and re-certified
After this testing and certification, some SAFs can be handled in the same way as a traditional jet fuel
The sustainability of aviation fuels can be certified as sustainable according to certain criteria by a third party
bp.com also mentions that this means ‘… no changes are required in the fuelling infrastructure or for an aircraft wanting to use SAF’
Some Feedstocks May Show Promising Potential
biofuelsdigest.com goes into detail about how algae biomass might show potential for SAF in several ways in their resource
They also indicate that algae feedstock production could be used in other markets other than aviation too.
On the other hand though, wikipedia.org mentions that fuel oil extraction from algae between 2005 to 2012 did not produce any significant results, despite dozens of companies receiving hundreds of millions of dollars in venture capital.
Can Be An Alternative To E-Fuels
Electrofuels are another type of aviation fuel that aims to reduce the carbon emissions from aviation fuel and air travel.
They store energy from renewable energy in liquids or gases
Sustainable aviation biofuels might be an alternative to electrofuels
Potential Cons Of Sustainable Aviation Fuel
May Currently Be More Costly Than Traditional Jet Fuel
Several reports indicate this to be the case
Some reports indicate it may get cheaper in the future as demand, scaling, technology, etc. increase or improve, but, other reports say it may never be as cheap as kerosene based jet fuel
bp.com goes as far as to indicate that higher costs might be limiting wide uptake right now: ‘At the moment, production of SAF is limited as the higher cost for SAF is preventing wider uptake. Air bp is working on helping create more demand in the short-term which will lead to more production and hopefully lower costs in future’
cnbc.com indicates that SAF is currently more expensive than traditional jet fuel
Consumers Will Likely Bear The Increased Cost For Sustainable Aviation Fuel
cnbc.com indicates that the increased costs for SAF over traditional jet kerosene will ultimately be paid for by the consumer
This obviously makes air travel more expensive for consumers, and they may have no choice on certain flights that use SAF
There’s also the query of whether this adds increased pressures on lower income citizens who usually travel on budget flights
May Only Be Effective For Medium To Long Term Haul Flights
Some reports indicate sustainable aviation fuel may only help significantly lower the carbon footprint of medium to long haul flights.
Therefore, there may not be as beneficial from a carbon reduction perspective for shorter flights.
Having said this, qantas.com notes that ‘… medium and long-haul flights, together account for the bulk of CO2 emissions from aviation’, so, this con may not be as significant as others at this point in time.
Still Uses Conventional Jet Fuel In The Final Fuel Product
Several SAF products don’t use 100% sustainable aviation fuel – they are blended with conventional jet fuel
bp.com indicates that ‘SAF can be blended at up to 50% with traditional jet fuel’
Although there might still be a reduction in carbon emissions with blended fuels, they still partially use petroleum based fuels (with hydrocarbons in them) in the final product when they use conventional jet fuel
Some of the reasons fuels might be blended might include for efficiency, performance, and cost, and other reasons
Conventional jet fuel is energy dense for its weight for example
The Scale Of Use Of Sustainable Aviation Fuel Is Not Yet Where Conventional Jet Fuel Is, & There Might Be Barriers To Growth
The quantities of sustainable aviation fuel used in aviation are currently not near the quantities of traditional jet fuel used in the industry.
There’s a range of barriers that have to be overcome first in order for SAF to match conventional jet fuel quantities on a commercial level.
Some of these barriers might include advances in technology, increases in scale, changes in policies and tax credits, consumers paying for increased prices of SAFs compared to traditional jet fuel, and more.
Another barrier might be that aviation can be trickier implement clean energy solutions in than for cars and stationary power plants for example. It’s hard to match conventional jet fuel for energy density when it comes to keeping planes in the air.
biofuelsdigest.com indicates that as of 2022, SAF makes up less than 1% of fuel used in aviation
biofuelsdigest.com also lists ‘the scalability of the feedstocks to reach the needed targets of national scale fuel output’ as a barrier for SAF production
cnbc.com indicates that:
‘… 100 million liters of sustainable aviation fuel [were used] in 2021 [and] that’s a very small amount compared to the total fuel required for the industry.’
[cnbc.com also indicates that in order for quantities of SAF to increase, consumers would have to be willing to pay for the extra price, and even with appropriate government support, SAF may only make up around] 2% of the overall fuel requirement … by 2025]
cnbc.com indicates that ‘… production would jump to 449 billion liters, or 65% of the sector’s needs by [2050, but this is obviously some amount of time away]
cnbc.com also indicates though that ‘… no technology [is] going to replace … carbon, jet aviation … before 2030’
bp.com mentions that aside from a need to reduce the cost of SAF, government policy and policy incentives that reduce investment risk in increased production and supply, ‘… research, development and commercialization of improved production technologies and innovative sustainable feedstocks’, and ‘… advanced technologies to process feedstocks more efficiently at greater scale and investment in the development of sustainable and scalable feedstock options’ may also be short to long term barriers to the growth of SAF.
biofuelsdigest.com identifies scale as the main barrier for SAF
They indicate that ‘SAF production facilities are tiny compared to the economies of scale available to fossil fuels’
They also indicate that more production plants, more physical infrastructure and capital, policy support (and tax credits), a willingness to wait for some feedstock and production facilities ‘[to materialize] a meaningful ROI …’, and public-private partnerships, might all help with the large scale production and commercial viability of SAFs
popsci.com indicate that some of the main barriers/problems for SAFs right now might be limited supply, inability to scale up infrastructure, and the cost of fuel
Tax credits and providing other motivations for companies to invest in SAFs could help scale up production and make SAFs more cost competitive
Has Some Practical/Technical Challenges
wikipedia.org lists issues with rubber seals and hoses, and finding harmful bacteria and fungi in aircrafts as problems that have been encountered with some biofueled aircrafts
Some Question How Renewable Some Feedstocks Actually Are
For example, SAFs that are made from solid waste feedstocks from homes and businesses such as packaging, textiles and other solid waste, may not be truly renewable.
Plastics for example aren’t produced from renewable feedstocks, and neither are synthetic fibres used in textiles.
Some Question How Sustainable Some Feedstocks Actually Are
In order to be sustainable, feedstocks can’t compete with land use or food production, and existing critical forests and rainforests can’t be cut down to supply feedstock.
From cnbc.com: ‘There are major concerns in some quarters that an increased uptake of SAF could, among other things, result in significant deforestation and create a squeeze on crops crucial to the production of food’
Some Question If Some Sustainable Aviation Fuels Actually Decrease Emissions At All
popsci.com has a good article outlining this point
They outline how because SAFs are chemically identical to conventional jet fuel, they emit the same amount of CO2 when burnt.
They point out that the way the fuel is sourced and produced is where emissions might be saved.
Fuels that don’t contribute to deforestation, and that use renewable energy to produce the fuel might emit less CO2.
Crop based biofuels that contribute to deforestation and don’t use renewable energy could have higher CO2 emissions.
popsci.com explains several scenarios where fuels can reduce emissions by 50% up to 99%, depending on the type of feedstock used, the energy used, and other variables.
wikipedia.org also points out how Jatropha oil used as biofuel may either reduce greenhouse gas emissions, or increase them, depending on the type of land used (agro-pastoral vs converted natural woodland)
Is Not The Only Sustainability Solution For The Aviation Industry
Some reports indicate that SAF can’t be relied upon as the only solution to increase sustainability or reduce carbon emissions in the aviation industry.
Other solutions have to be pursued alongside SAF.
bp.com mentions that: There are several broad opportunities for carbon reduction across the industry such as more efficient aircraft design, smarter operations and the development of future technologies like electrification
Having said this, popsci.com mentions that other solutions like electric aircrafts and hydrogen powered planes may have limitations such as shorter flight ranges, being smaller in size than traditional planes, and in the case of hydrogen powered planes, being a while off of commercialization and scaling.
Other solutions like more efficient fuel use per passenger may be potential solutions too.
Some Reports Indicate That Hydrogen Planes Are The Mid To Long Term Solution
cnbc.com indicates that ‘… hydrogen planes represent the “ultimate solution” for the mid and long term’ in order to decarbonize the aviation industry
Therefore, biofuel type SAFs might not be the main mid to long term solution
cnbc.com also notes that ‘… [a lot of] engineering, research and capital commitments would be required’ for hydrogen planes, and at this point in time thy are mainly a concept plane
Commercializing hydrogen hybrid planes and using them on a wide scale would present large challenges
Some reports indicate that hybrid hydrogen planes could enter service by the year 2035
How Does Airplane Fuel Actually Affect The Environment, & Is It Bad For The Environment?
We’ve addressed this elsewhere in this guide.
Airplane fuel has to be sourced from a feedstock, then refined and processed/converted into fuel, then made into a useable fuel product (blended or not blended), then burnt/used on aircrafts.
One of the main focusses of airplane fuel when it comes to the environment is it’s carbon footprint.
Fossil fuel based fuels are extracted as carbon from the ground, and then that carbon is released into the atmosphere when they are burnt.
Biomass based fuels absorb carbon during product, but release that carbon when they are burnt.
All fuels also use energy during production (fossil fuel or renewable energy), and some feedstocks may contribute to deforestation at the land use stage.
All airplane fuel products (and there are a range of different ones) have different variables involved in their lifecycle, and this impacts their sustainability and how they affect the environment.
Environmental impact is not the only impact that has to be considered – economic, practical, social and other impacts have to be considered too.