It is the best use-case for green hydrogen of the entire energy transition, and the volumes at stake are “insane” if only a tiny fraction of the market is penetrated – Manuel Kuehn’s enthusiasm could almost fuel an A380 by itself.

Head of new energy for Middle East and Africa at Siemens Energy, Kuehn is evangelical about the potential of a newly-announced push by the German technology giant and other partners to deliver a sustainable, cost-effective solution to an aviation sector that is keen to decarbonise, and shed its image as one of the bad boys of climate change.

Siemens Energy, along with Abu Dhabi clean energy group Masdar and others including airlines Etihad and Lufthansa, hopes by mid-decade to have developed a viable synthetic ‘e-fuel’ made by combining captured CO2 with hydrogen – the latter itself produced via solar-powered electrolysis – that can begin to replace kerosene-based jet fuel in the global aviation industry.

In Kuehn’s view, the greening of aviation fuel represents pretty much the best use-case for green hydrogen from renewables of all the myriad applications being explored globally for the key energy transition fuel.

“[Where hydrogen is concerned] for every possible use case you can discuss now, there is at least one alternative.

“The only use case where there is just one solution is aviation fuel, the one where you say for sure the market’s going to come,” says the Siemens Energy executive, who will bring the Germany-based group’s considerable expertise in electrolysis and associated processes to bear on the project.

Kuehn’s conviction rests on the sheer volumes of fuel required by the global aviation sector, which – provided it recovers from its pandemic-induced stall and resumes anything like its former growth path – will be vast.

The International Air Transport Association (IATA) says Sustainable Aviation Fuels (SAFs) could make up 2% of the total used by the commercial airline industry by 2025. Bear in mind that the industry burned through 360 billion litres in 2019 (pumping out 900 million tonnes of emissions in the process), and you begin to see why Kuehn is thinking big.

“Two percent in production litres is insane amounts compared to the [pilot projects] underway. The 2% will be achieved with all the projects we know and some we don’t. And that’s just 2%,” he tells Recharge.

As Kuehn’s remark suggests, the Siemens Energy/Masdar group is far from the only one pushing to satisfy the green needs of the aviation sector – Recharge has previously reported various projects involving EDF, Air Liquide and Rolls-Royce, to name but a few – which alongside the end-user’s urgent demand is another reason speed is of the essence.

Our ambition is to be fast. There is no reason to wait.

“Our ambition is to be fast. There is no reason to wait,” he says.

“Considering the need to build the technology, understand the value chain, certify all this, and get the fuels approved in the airline industry, you’d better start today.”

The solution Siemens Energy and its partners are pursuing involves developing a kerosene synthesis plant that can with maximum efficiency combine PV-produced hydrogen and CO2 to produce a viable e-fuel.

Apart from efficient operation, the demonstrator will need to show one virtue above all others – scalability. Scale will be the key to driving down the cost of e-fuels from levels that are currently seen as way too high compared to standard jet fuel, Kuehn says.

Oh, and “it must be 100% green or it doesn’t help us”, although the Siemens Energy executive says “some pragmatism” may be needed over the provenance of the captured CO2 during the early stages of the project while a large-scale supply arrangement is worked out.

The project is also not yet committing to a scale of PV plant to power the demonstrator, which will be sited at Abu Dhabi’s Masdar City innovation hub, with Kuehn explaining it will “work backwards” to the power supply from the sharp end of the synthesis process.

The project team has received “very positive feedback” for its pursuit of a green synthetic fuel, which Kuehn claims offers distinct advantages over alternative approaches.

One other option is to directly fuel the aircraft with hydrogen itself – Airbus has a project aiming to achieve just that. But using liquid H2 would require substantial reimagining of the entire design of aircraft – not least through the need for much larger fuel tanks – whereas green e-fuels are physically not too different from the kerosene used now.

“It’s an oversimplification to say you can take it as it is today [but] the airplane that’s going to use the synthetic fuel in 20 or 30 years is going to look the same as the airplane today – combustion engine, fuel tank, liquid fuel – the basic system stays the same,” says Kuehn.

Another alternative is to create biofuels that can act as SAFs. According to Kuehn, the problem there, given the volumes needed, is the same as that facing all forms of bioenergy – can the feedstock be genuinely sustainable in the long run, in the way that a supply of hydrogen made using renewables assuredly can?

Then of course there are batteries, which may be an option for lighter, short-haul aircraft but “at least for long-distance aviation there is no other way [than e-fuels],” asserts Kuehn.

Such is the ambition of the aviation fuel project – if successful it may take a shot at the equally massive target of shipping – it is easy to overlook the fact that it is significant in another way, as the first fruit of a wider tie-up between Siemens Energy and Mubadala, the Abu Dhabi sovereign investment group that also controls Masdar.

The two could well end up working together on equally significant hydrogen initiatives in other areas, said Kuehn of a partnership that is slated to be crucial to establishing a green H2 economy in the United Arab Emirates.