How quickly can a synthetic aviation fuel industry emerge?

In late April, the European Parliament and EU Member States reached agreement on new mandates for sustainable aviation fuels through to 2050. Under the final agreement, the percentage of sustainable aviation fuel (SAF) that must be blended with kerosene will start at 2% by 2025, moving to 6% by 2030, 20% by 2035, 34% by 2040, and reaching 70% by 2050. A dedicated sub-target for synthetic fuels derived from green hydrogen will also come into force from 2030. Although the final wording and requirements for these mandates have yet to be released, the headline numbers are clear even if the detail isn’t – starting at 1.2%, the synthetic fuel requirement will be scaled up to 5% by 2035, reaching 35% by 2050.

SAF is going to require a huge effort and should rightly be the immediate focus of attention, largely because of the state of technology and the amount of effort that has gone into preparing the groundwork for a SAF industry. But while the overall SAF target is challenging, given the small quantities produced today, the synthetic fuel mandate looks daunting. In EU parlance, synthetic fuels are renewable liquid and gaseous transport fuels of non-biological origin, meaning liquid or gaseous fuels which are used in the transport sector other than biofuels or biogas, the energy content of which is derived from renewable sources other than biomass. In the aviation industry this presumably means two types of fuel;

1. Hydrogen as a direct fuel derived from renewable energy sources.
2. Synthetic kerosene (also known as an e-fuel), produced by combining hydrogen derived from renewable energy sources (via electrolysis of water) and carbon from the atmosphere (via direct air capture or DAC), with the energy required for the capture and final synthesis also coming from renewable sources such as wind and solar PV.

For 2030, hydrogen as a direct fuel is a non-starter given that the planes don’t yet exist and probably won’t do so until 2040 at the earliest, although we might see some small commuter versions before that. So for 2030 and probably 2035, this mandate is really only about e-fuels. The synthesis of such a fuel is discussed in detail in a paper by Kraan et al., An Energy Transition That Relies Only on Technology Leads to a Bet on Solar Fuels, Joule (2019), with the energy schematic they developed shown below. This is to produce one barrel of fuel (5.5 GJ solar fuel on the right of the schematic).

The illustration above presumes feasibility and the availability of a wide range of thechnologies at large scale. In reality, that isn’t the case today. Clearly solar PV and synthesis technologies exist at scale, but Direct Air Capture (DAC) is still to be demonstrated at scale (i.e. 1 million tonnes per annum or more) and hydrogen electrolysis is only just reaching the sort of scale required for synthetic fuel production. As such, the discussion below should be viewed in that context and not just be a question of quickly building the necessary facilities.

In 2023 we can expect EU aviation fuel consumption to be somewhere around 1 million barrels per day, which includes both internal EU demand and international aviation bunkers for flights departing from the EU, for passenger and freight movements. So a 1.2% synthetic fuel mandate means the production of at least 12,000 barrels per day of e-fuel within seven years, or over 4 million barrels (600 kt) produced in 2030.

Jet fuel is mainly carbon in terms of weight, so 600 kt is about 500 kt carbon and 100 kt of hydrogen. This amount of hydrogen (but in practice more is needed) will require multiple 200 MW electrolyser projects, each similar to the project recently announced by Shell in Rotterdam that will produce 60,000 kg per day of green hydrogen, currently Europe’s largest such project. The Shell project will begin operation in 2025 after two years of construction, along with offshore wind capacity built in the Hollandse Kust Noord area.

The 500 kt carbon equates to nearly 2 million tonnes of atmospheric carbon dioxide capture in 2030, which is a scale of capture that doesn’t currently exist in the world. However, Occidental and its subsidiary 1PointFive announced in late 2022 they plan to begin detailed engineering and early site construction for their first large-scale DAC facility with start-up expected in late 2024. Upon completion, the DAC plant will be the world’s largest of its kind and is expected to capture up to 500,000 metric tons of carbon dioxide per year.

However, the provisions of the EU Directive on these types of fuels allows for other sources of CO₂ to be used, but in some cases for a limited time period. Up until 2041 it will be possible to use CO₂ from sources such as industry where allowances have already been surrendered against such emissions. It is also permissible to use the captured CO₂ from the production or the combustion of biofuels, bioliquids or biomass fuels. These provisions mean that an immediate relaince on DAC as a source of carbon for synthetic fuels isn’t required.

Producing sufficient hydrogen and capturing enough carbon dioxide is energy intensive and is just the start. These then must be combined to make the synthetic fuel, which takes even more energy and more hydrogen than the molecular weight of jet fuel points to. For example, a hydrogen based reaction is required to convert the carbon dioxide to carbon monoxide, which is required for the subsequent synthesis reaction. If the facilities designed to do this make use of Fischer-Tropsch technology, jet fuel won’t be the only product. Its yield might be as much as 67% (with the other 33% being lighter and heavier hydrocarbons, but this will require an optimised catalyst), which means that for the above jet fuel requirement the picture becomes more complex and bigger. The required production of synthetic fuels rises to 18,000 barrels per day, of which 12,000 is jet fuel.

The synthesis plants are not simple projects either, although the underlying technology is tried and tested in facilities such as the Shell gas-to-liquids synthesis plant in Qatar. That unit takes natural gas and breaks it down into hydrogen and carbon monoxide (synthesis gas) before recombining these into longer chain hydrocarbon molecules such as for jet fuel. That facility operates on a very large scale, producing some 150,000 barrels per day of product (of which some is suitable for jet fuel use). Building smaller versions is possible, although even the first Shell synthesis pilot plant, built 30 years ago in Malaysia and still operating today, produces 14,700 barrels of oil product per day. Even smaller scale gas-to-liquids is also possible, with Petrobras operating such a unit in a remote location as a pilot for the conversion of associated gas from oil production into useful liquids.

Given the rapid scale up of the synthetic fuel mandate (4x from 2030 to 2035), the sensible approach will be for the EU to build reasonably large from the start. A first facility might be the size of the Shell Malaysia unit (the illustration shows an 18,000 b/d unit but this is still small by global refining standards), but would also require about 3 GW of green hydrogen capacity and three million tonnes per annum of DAC. Apart from the synthesis unit which is arguably smaller than the desirable scale for modern refining, the hydrogen and DAC units are unprecedented in size. However, both hydrogen and DAC are scalable technologies, with the latter currently deployed on a modular basis, and as noted above DAC isn’t an immediate requirement.

Building an 18,000 b/d synthesis facility, 3 GW of hydrogen electrolyser capacity and 3 MT per annum of DAC combined with large scale renewable energy production (say 6 GW of offshore wind) is a formidable project, costing many billion euros and taking years in terms of planning, approvals, financing and construction. Such a project will also stretch the available technologies, given that DAC in particular doesn’t yet operate at scale anywhere. But the EU needs to start at least five such projects over the coming 2-5 years, not just to meet the synthetic fuel mandate of 2030, but also with an eye on the 2035 mandate and beyond.