FUEL for the JOURNEY Is Sustainable Aviation Fuel the Answer?

FUEL for the JOURNEY Is Sustainable Aviation Fuel the Answer?

Although affected by the pandemic, the commercial aviation industry will inevitably recover and continue to grow. At the same time, it will have to take serious steps to reduce CO2 emissions.

Sustainable Aviation Fuel (SAF) has been around for about 15 years. It was originally known as biofuel. The very first biofuel flight took place on February 1, 2008, with a three-hour flight by an Airbus A380 prototype from Filton, UK, to Toulouse, France, using a 60/40 blend of jet fuel and synthetic fuel. This was followed by some serious interest in biofuels produced from a variety of raw materials, but the financial crisis of 2009 resulted in many airlines’ giving a lower priority to reducing CO2 emissions, to focus on reducing fuel consumption to save money.

The very first biofuel flight (shown above) took place on February 1, 2008, with a three-hour flight by this  Airbus A380 prototype from Filton, UK, to Toulouse, France, using a 60/40 blend of jet fuel and synthetic fuel. Airbus image.
The very first biofuel flight (shown above) took place on February 1, 2008, with a three-hour flight by this
Airbus A380 prototype from Filton, UK, to Toulouse, France, using a 60/40 blend of jet fuel and synthetic fuel. Airbus image.

However, between 2011 and 2015, according to IATA, 22 airlines performed over 2,500 commercial passenger flights using blends of up to 50% biojet fuel from feedstock including used cooking oil, jatropha, camelina, algae and sugar cane. But some of the feedstocks for biofuel could have competed with food production (oilseed and soya beans), while the use of palm oil is criticized for causing deforestation. The result was a dropoff in research.

The world has changed significantly since then. Now, there is no alternative but to look at reducing reliance on fossil fuels and to look for cleaner alternatives. However, for all the talk of radical new propulsion systems for aviation — electric, hybrid, hydrogen — it is clear that they are unlikely to be available in the near term. In fact, IATA estimates that it will not be until 2035 that electric and/or hydrogen aircraft will be available for the regional market (50-100 seats, 30- to 90-minute flights), and an additional five years until there are hydrogen aircraft for the short-haul market (100-150 seats, 45- to 120-minute flights).

That leaves larger narrowbody and widebody aircraft reliant on conventional engine technology, with a continuing demand for jet fuel. Even though continuous development has brought some significant improvements in fuel consumption, with parallel reductions in CO2 emissions, those aircraft are used for the vast majority of current airline networks and will see a substantial increase in numbers in the future. To overcome the associated rise in CO2 emissions, the entire aviation industry, manufacturers and operators, needed to find an alternative solution. This has turned out to be sustainable aviation fuel, which offers a lifecycle carbon reduction of around 80% compared with traditional jet fuel, and is now being produced by more environmentally friendly methods than in the beginning.

The IATA estimates were part of an announcement in October 2021 of the approval of a resolution to achieve net zero carbon emissions by 2050, aligning with the Paris Agreement goal of keeping global warming below 1.5°C. With 10 billion people expected to fly in 2050, at least 1.8 gigatons of carbon must be offset in that year, while the net zero commitment implies that a cumulative total of 21.2 gigatons of carbon will be offset between now and 2050.

SAF annual production

IATA predicts that 65% of this will be abated through the use of SAF, with production steadily rising over the years (see Chart 1). The rest will come from new propulsion technology, such as hydrogen (13%), carbon capture and storage (11%), offsets (8%) and efficiency improvements (3%).


All well and good, but the limiting factor right now is availability.

Take the example of Delta, which signed an agreement in March with Colorado-based Gevo that aims for a goal of using SAF for 10% of its operations by 2030. That involves roughly 75 million gallons of SAF annually for seven years but is only anticipated to start in mid-2026. However, the airline will need to secure 400 million gallons annually by the end of 2030 to meet its 10% SAF procurement commitment, and approximately 4 billion gallons annually if it were to fly solely on SAF. However, in addition to high costs, there is limited supply — only enough SAF is available on the market currently to support one day of Delta’s operations at pre-pandemic levels.

The day before the Delta agreement, Gevo signed up with the oneworld alliance (Alaska Airlines, American Airlines, British Airways, Finnair, Japan Airlines and Qatar Airways) to supply up to 200 million gallons of SAF per year for five years. This will be used only for operations in California, including San Diego, San Francisco, San Jose and Los Angeles international airports, and will start in 2027 as three facilities are still to be built in the U.S. Midwest.

Reflecting Delta’s concerns about availability, this agreement followed another by oneworld in November 2021, with renewable fuels company Aemetis, to purchase more than 350 million gallons of blended SAF for operations at San Francisco International Airport. This is due to start in 2025 for seven years, but it has to meet current certification standards, so it will be a less sustainable blend of 60% conventional jet fuel and 40% SAF. In March, Finnair signed up for 17.5 million gallons, worth approximately $70 million over the seven- year term of the agreement. The airline has its own target to fly carbon neutral by 2045.

Gevo’s SAF, to be produced in the U.S., will use inedible corn products that will be processed to create ethanol that will then be converted into sustainable aviation fuel. The entire supply chain will be certified by the Roundtable for Sustainable Biomaterials standard, which is widely recognized as the most robust certification scheme for bioenergy.

Aemetis is building a facility in Riverbank, Calif., that will use scrap agricultural products from orchards and vineyards, combined with renewable vegetable oil and animal fats. Through gasification, the wood fibers will be distilled to create hydrogen. This is then combined with vegetable oil and animal fat to produce SAF and renewable diesel. The facility, which will be co-located with a carbon capture and storage facility, can adjust to produce either renewable diesel only or a mix of renewable diesel and up to 50% SAF.

Of course, oneworld member British Airways is part of the International Airline Group, which also has a target of 10% SAF by 2030 and is investing $400 million over the next 20 years into the development of SAF. At the end of last year, the airline signed its own multiyear agreement for SAF produced at the Phillips 66 Humber Refinery near Immingham in North Lincolnshire, UK. This has already started to be delivered to the airline via the existing pipeline infrastructure that feeds directly into UK airports.

It is an encouraging sign, but it must be regarded as something of a symbolic move. The total amount to be purchased will only be enough to reduce lifecycle CO2 emissions by about 100,000 metric tons, the equivalent of powering 700 net zero CO2 emissions flights between London and New York by Boeing 787 aircraft. The airline currently operates around 40 flights a week on this single sector, using Boeing 777s.

Another airline committing to SAF is Qantas. Its most recent investment, in March, with Aemetis, was for 35 million gallons of blended SAF to be delivered to San Francisco Airport over the seven-year term of the agreement. The value of the contract including incentives is approximately $250 million. Before that, in December 2021, Qantas signed an agreement with Air bp to purchase 10 million liters of SAF in 2022, with an option to purchase up to another 10 million liters in 2023 and 2024, representing up to 15% of the airline’s annual fuel use out of London. This will be a 50/50 blend.

Establishing Supply Chains

Andreea Moyes, Air bp’s global aviation sustainability director, says the company has supplied SAF to customers at over 20 locations across three continents, and it has been used to fuel many different types of aircraft, from small private jets to large passenger aircraft. It has also established supply chains across the Nordic region and supply into other areas of Europe and the U.S., which are used to meet both mandated and voluntary demand.

Air bp has established supply chains across the Nordic region and supply into other areas of Europe and the U.S. Air bp images.
Air bp has established supply chains across the Nordic region and supply into other areas of Europe and the U.S. Air bp images.

The company’s refinery in Castellon, Spain, is co-processing waste-based sustainable feedstocks with fossil fuel to produce synthetic low-carbon fuel that can be certified using International Sustainability and Carbon Certification PLUS procedures, which are approved as part of ICAO’s Carbon Offsetting and Reduction Scheme for International Aviation. This calls for at least 10% net reduction in greenhouse gases compared with conventional aviation fuel on a life cycle basis and no land use change to produce feedstock that involves land with high carbon stock (primary forests, wetlands and peatlands). Since July 2021, a major user of this fuel has been NetJets Europe, the fractional ownership operators, and it has been supplied to airports in Munich, Germany, and Biggin Hill, Bristol and Airbus-owned Hawarden in the UK.

Andreea Moyes Global Aviation Sustainability Director, Air bp
Andreea Moyes
Global Aviation Sustainability Director, Air bp

Moyes says Air bp is not standing still. In February 2022, the Lingen refinery in Germany, operated by parent company bp, produced SAF by co-processing used cooking oil with crude oil. It is also aware that much of the feedstock is from HEFA (hydrotreated esters and fatty acids). As supplies are limited, bp announced a 10-year strategic partnership in February with U.S.-based Nuseed to use carinata oil. Carinata (also known as Ethiopian mustard) is a nonfood cover crop that grows when weather limits main crop production, protects the soil between harvest and the next season’s planting, and does not compete with food production or require additional farmland. It also removes carbon from the air while growing, restoring it to the soil. The company will continue to look at new pathways. For example, in 2016, it invested in California-based Fulcrum BioEnergy, a company commercializing municipal solid waste as a feedstock.

Air bp’s latest customer is DHL Express, which recently signed another composite deal involving Finnish supplier Neste. Together, over five years, they will provide 800 million liters of SAF, split equally. Neste’s SAF is produced from sustainably sourced, 100% renewable waste and residue raw materials. With the expansion of its Singapore refinery and modification to its Rotterdam refinery, it will have an annual production capacity for SAF of 1.875 billion liters by the end of 2023. The company has been working with DHL since 2020, starting with operations from San Francisco International Airport and Amsterdam Airport. In 2021, this was extended to East Midlands airport in the UK. In its Sustainability Roadmap, parent company Deutsche Post DHL Group has committed to using 30% of SAF blending for all air transport by 2030. The combined deal means that it will exceed 50% of a separate target to reach 10% SAF blending by 2026.

OEMs Jump In

Manufacturers are also getting involved. Fourteen years after that first biofuel flight took place, the first prototype A380 took off from Toulouse on March 25 with one of its four Rolls-Royce Trent 900 engines powered by 100% SAF. As well as Rolls-Royce, Pratt & Whitney is providing support for the APU, while TotalEnergies is supplying the unblended SAF, made from HEFA, which generally consists of used cooking oil and other waste fats. That flight looked at takeoff characteristics, while another flight three days later looked at landing.

This follows an A350 flight in March 2021 as part of the Emission and Climate Impact of Alternative Fuels project (in collaboration with Rolls-Royce, German aerospace research center DLR, and oil refining company Neste) and an A319 flight in October 2021 as part of VOLCAN (VOL avec Carburants Alternatifs Nouveaux, a joint project between Airbus, Safran, Dassault Aviation, ONERA and the French Ministry of Transport).

Interestingly, that same prototype is now grounded, as it is to be converted into the ZEROe Demonstrator. This is another leap into the future, as it will become a testbed for hydrogen combustion technology, with the aim of bringing the world’s first zero-emission aircraft to market by 2035.

This is a cooperative venture with CFM, which will modify the combustor, fuel system and control system of a GE Passport turbofan to run on hydrogen. The engine, to be mounted on a pylon extended from the upper fuselage on the port side, was selected due to its physical size, advanced turbo machinery, and fuel flow capability. Caudal position, as well as a hydrogen combustion engine mounted along the rear fuselage. A distribution system will feed liquid hydrogen from four tanks in the lower rear fuselage into a conditioning system that will transform the hydrogen into gaseous form before it is introduced into the engine and combusted for propulsion. The first flight is expected to take place in the next five years.

Also in March. Pratt & Whitney successfully tested the GTF Advantage engine configuration at its facility in West Palm Beach, Fla., to validate its performance on 100% SAF in thrust transients, starting and operability, a key element to achieve EIS in 2024. The fuel used was 100% Hydroprocessed Esters and Fatty Acids-Synthetic Paraffinic Kerosine (HEFA-SPK) fuel acquired from World Energy for the test.

Of course, the GTF is one of the new generation turbofans that provided a step change in fuel consumption and emissions, reducing them by 20%. As a result, GTF engines have saved more than 2 billion liters of fuel and more than 6 million metric tons of CO2 since entering service in 2016.

The company says it has been actively involved in testing SAFs for almost two decades and helped to establish the technical standards that allow engines to operate on SAF blends of up to 50%, and is still working closely with the Commercial Aviation Alternative Fuels Initiative and ASTM International to reach 100% SAF approval. A new partner is Air bp, with an MoU to work collaboratively to explore the viable supplies of SAF up to 100% until 2024. In addition, the two companies will collaborate on researching the performance of 100% SAF to provide insights and data into fuel performance and emissions reductions.

Nearer the Destination?

It is clear from the number of events in March 2022 that the pace of SAF development is picking up. It is also clear that demand is far outstripping supply and that there are a number of possible pathways to producing the fuel. We are still some way from the day when SAF is readily available at airports around the world, and it is likely that there will be partnerships between aerospace manufacturers, airlines and fuel suppliers that will shift and move in the future.

It is also clear that the aviation industry is taking its environmental concerns seriously this time and has made a serious commitment to cleaning up its act. SAF may be a good example to use in fending off criticism and pointing the finger at other sectors, like maritime, that are more polluting and resistant to change.