AVIATION has always been regarded as a tougher sector to convert to low carbon fuels than road transport, because of the high intensity burn required to power planes – which traditionally been supplied by fossil-based kerosene. And a lot is burned.

In 2019, before Covid-19 knocked the industry off a seemingly unstoppable growth trajectory, 95 billion gallons of fuel was burned by commercial airlines worldwide said statistical service Statista.

Speaking to Petroleum Review, International Civil Aviation Organisation (ICAO) deputy director for environmental protection Jane Hupe said analysis undertaken by the UN agency found “that, by 2050, it would be physically possible to meet 100 percent of international aviation jet fuel demand with sustainable aviation fuels, corresponding to a 63 percent reduction in emissions.” However, said Ms Hupe, “this level of fuel production could only be achieved with extremely large capital investments in sustainable aviation fuel production infrastructure, and substantial policy support”. She noted that the effort required to reach these production volumes “would have to significantly exceed historical precedent for other fuels, such as ethanol and biodiesel for road transportation”. 

Fortunately, efforts are being made, with civil aviation a prime target of global initiatives to reduce the carbon emissions created by the consumption and production of fuel.

On October 5, a coalition of global air transport players – covering airlines, airports, air traffic control (ATC) and aviation manufacturers adopted a long-term climate goal of net zero carbon emissions by 2050. Signatories included the International Air Transport Association (IATA), Airports Council international (ACI), ATC organisation CANSO and major manufacturers Airbus and Boeing.

Another example is the World Economic Forum’s Clean Skies for Tomorrow Coalition initiative, which includes major airlines, airports, fuel suppliers and other aviation innovators from around the world. In September (2021), 60 of these companies signed a pledge to cooperate to ensure global aviation was drew at least 10% of its power from sustainable aviation fuels by 2030. Much of this ambition includes the development and use of bio-based feedstocks to make aviation fuel or blends with kerosene, and the companies involved have the capacity to achieve this. they include energy majors such as BP, Shell, Suncor and Norsk e-Fuel; airlines British Airways and Delta; airports such as Heathrow and Schiphol; and aviation manufacturers such as Airbus and Rolls Royce.

While sustainable aviation fuels (SAF) have already fuelled more than 250,000 commercial flights, a forum statement recognised the difficulties in scaling up production and use, because manufacturing aviation fuels from bio-based feedstocks especially is much higher than kerosene: “Costs will fall if production scales up, but fuel providers are facing headwinds due to high price pressure on low SAF demand, and high risks associated with policy and investment uncertainty,” it said. One way in which coalition members are trying to bridge that gap is through the development of SAF certificates (SAFc) where aviation consumers, especially corporate customers, can pay more for flights, knowing that this has funded the use of SAFs. These certificates can count towards their own greenhouse gas reduction commitments in regulatory and trading schemes. (3)

Such market-based systems are at the core of one key element encouraging the world’s civil aviation companies to use sustainable aviation fuels, namely the CORSIA (Carbon Offsetting and Reduction Scheme for International Aviation) system that has been in place for the industry since January 2019. Established by the ICAO, it involves airlines buying emission permits from trading systems or funding carbon offset projects that reduce CO2 emissions elsewhere. In this way, there is a financial incentive for the industry to reduce its carbon footprint. Burning sustainable fuels are one way this can happen, as long as their production and use complies with ICAO standards that insist their carbon emissions must be at least 10% lower over their lifecycle than standard fossil-based aviation fuel. ICAO has added some additional criteria, such as feedstocks not replacing food production; not grown on areas that were previously old-growth forest, wetlands and peatbogs (because of the amount of carbon they lock away); and that any increase in carbon emissions caused by a change in land-use when switching to biofuel production is taken into account in greenhouse gas calculations. They also must be as safe as existing fossil-based fuels. Under CORSIA, third party certification organisations are approved to assess and approve aviation biofuel consignments’ compliance with ICAO lifecycle sustainability criteria.

Five fuel conversion processes are recognised by ICAO as being acceptable within CORSIA, which is currently (as of September 2021) recognised by 107 ICAO member states. These are the Fisher-Tropsch (FT); hydro processed esters and fatty acids (HEFA); alcohol (isobutanol) to jet (ATJ); alcohol (ethanol) to jet; and synthesised iso-paraffins (SIP) systems. As for potential feedstocks, the UN agency recognises use of agricultural and forestry residues, municipal solid waste, used cooking oil, tallow, corn oil, soybean oil, rapeseed oil, palm oil, sugar cane, sugar beet, corn grain, poplar, miscanthus, switchgrass, and palm fatty acid distillate. ICAO is particularly keen on the use of miscanthus and switchgrass given that they absorb carbon when grown, and so could deliver a negative carbon balance over their lifecycle. An ICAO document ‘CORSIA Default Life Cycle Emissions Values for CORSIA Eligible Fuels’ which gives guidance on the carbon emission reduction associated with biofuels is updated annually, said Ms Hupe, taking account of new sustainable fuel feedstocks and conversion processes. (4)

Commenting on the overall system, Bruno Silva, ICAO environment officer said: “We expect that this will help facilitate the future deployment of sustainable aviation fuels.” This is just as well, because ICAO currently projects that sustainable fuels will deliver half of the industry’s carbon reductions towards meeting its current goal of ensuring there will be carbon-neutral growth only from 2020 onwards.

As it stands ICAO said commercial production of sustainable fuels increased from an average of 0.29 million litres per year (2013-2015) to 6.45 million litres per year (2016-2018).

ICAO thinks this capacity will grow, projecting that potential global sustainable aviation fuel production will reach 8 billion litres by 2032 – although the extent to which this capacity will be used to make aviation fuel is less clear.

However, certainly, progress is being made. For instance, Finnish paper, pulp and energy conglomerate SCA and Finnish energy group St1 have created a joint venture to produce and sell advanced biofuels, which will include aviation lines. The companies are building a new biorefinery at St1’s current refining complex in Gothenburg (Göteborg), Sweden, able to produce 200,000 tonnes of liquid biofuels annually. While it will be able to use a range of feedstocks, it will have access to access to SCA’s tall oil, a by-product from pulp production at the company’s mills based in Östrand, Obbola and Munksund, also in Sweden, and will operate from 2023. And in the USA, DG Fuels has developed plans to create a manufacturing plant in Louisiana supplying 151 million gallons (571 million litres) of Fischer-Tropsch process-made sustainable aviation fuel per year.

Last month (September 2021), in Russia, the country’s gas major Gazprom has struck a deal with Russian flag carrier Aeroflot on producing Russia’s first ever minimum-carbon-footprint sustainable aviation fuel from plant-based feedstock. The fuel would be adapted for use on various types of aircraft, being certified under Russian and international aviation safety standards said a joint Gazprom/Aeroflot statement.

And in another energy/aviation sector deal announced in September, Italian energy major ENI is to supply hydrotreated vegetable oil (HVO) biofuel to airport operator Aeroporti di Roma (ADR), which runs Fiumicino and Ciampino airports, serving Italy’s capital.

Adam Zampini spokesperson for Airports Council International (ACI), stressed that airports can play an important role in extending the use of sustainable fuels, working with users and suppliers: “They all have to work in a coordinated way to make this possible,” he told Petroleum Review. “Preparations for SAF implementation can take many months or even years. It is likely that current airports wanting to facilitate SAF will need to bring it from across borders.” He said, at present sustainable fuels “should be preferably procured already blended with conventional aviation fuel to minimise customs or transportation barriers”.

Another non-bio sustainable fuel gaining apparent traction is being made by Silicon Valley, USA, electrofuels start-up Prometheus Fuels, which announced in September it was selling 10 million gallons of its zero net carbon Promethean Forged jet fuel to American Airlines. Prometheus uses a novel process it says can capture CO2 and H2O molecules exhaust pollution from the air, recharging and recombining these molecules into hydrocarbons and thence converting them into gasoline, diesel, or – in this case – jet fuel. Founder and CEO Rob McGinnis said: “It’s the world’s first electro-SAF and the first SAF that can beat fossil fuels on price – our jet fuel costs one cent less per gallon than fossil fuel.”

Meanwhile, ICAO is also looking at recognising lowering carbon content through the reduction of flaring, the use or renewable energy in refineries and carbon capture storage and usage (CCUS) tech.

Another focus for the UN agency is the potential contribution to carbon reduction offered by hybrid and electrical aircraft, which are currently focused on general aviation smaller craft – with one major aeronautical issue being the weight of batteries.

Meanwhile, the development of hydrogen-based aircraft is also being considered by ICAO as an emissions reducer, with researchers here assessing the aeronautical design issues associated with the necessary volume of fuel tanks to handle this kind of fuel. European air traffic control organisation Eurocontrol is among the industry bodies taking this concept seriously. It staged a seminar on hydrogen propulsion powered aircraft in May (2021) that highlighted a Clean Sky 2 and Fuel Cells & Hydrogen 2 Joint Undertakings study that confirmed such planes coil emit zero CO2, and reduce climate impact by 50-75%, and if using fuel-cell technology, by 75-90%. (5)

This comes after aircraft manufacturer Airbus in 2020 revealed three concepts for zero-emission commercial aircraft, which could enter service by 2035. (6)

Mr Zampini agreed that all these advances would be needed. “Net zero will require several solutions: new technologies, which will allow for aircraft to fly 100% on SAF, and the development of new electric and hydrogen-powered aircraft, efficiency improvements, additional operational opportunities to reduce emissions, sustainable infrastructure and negative emissions technologies (NETs),” that remove and sequester carbon from the air.





A version first appeared in Petroleum Review, published by the Energy Institute (