The aviation sector will employ a range of technologies to decarbonise, according to panellists at last week’s FT Hydrogen Summit.

While smaller aircraft are likely to be powered by battery engines, compressed hydrogen and hydrogen fuel cells, the global fleet of larger planes will likely opt for sustainable aviation fuel (SAF) and, later, liquid hydrogen, according to David Morgan, director of flight operations at airline Easyjet.

“There will be a number of different fuels: it is not either/or,” he says.

This means developing dual-fuel infrastructure—although this should not be an issue as SAF is effectively a drop-in fuel and a liquid hydrogen network could be built up slowly.

“We will see a [liquid hydrogen] network develop from a small number of city pairs,” Morgan says.

SAF remains the best way to significantly reduce emissions in the short term, according to Grazi Vittadini, chief technology and strategy officer at engine manufacturer Rolls Royce. “But hydrogen holds great promise because you can abate to zero,” she says.

“Hydrogen holds great promise because you can abate to zero” Vittadini, Rolls Royce

To encourage these developments, UN regulating body the International Civil Aviation Organisation (Icao) would need to support both technologies and some form of carbon-pricing regime would need to be introduced for aviation, she adds.

Icao is expected to make a decision on whether to adopt a long-term emissions reduction goal at its next assembly in late September. Any policy implementation would not happen until after that agreement.

Models in a report by Icao’s committee on environmental protection on the feasibility of a long-term reduction goal show that drop-in fuels have the largest impact on residual CO₂ emissions, driving the bulk of reductions by 2050. Hydrogen is not expected to have a significant contribution before 2050—with only 1.9pc of the energy share by that date.

“But this may increase in the 2050s and 2060s if technically feasible and commercially viable,” the report says.

There is good reason that many scenarios only see a limited role for liquid hydrogen, according to Alan Epstein, professor of Aeronautics at MIT.

“For aircraft I don’t think liquid hydrogen makes sense. The fear is it would drive up the cost of travel to the retro age of the [Boeing] 707s,” he says. “Why throw away $1.5tn of commercial airplanes?”

Epstein adds it might be possible to make SAF from green hydrogen instead.

Earlier this year technology firm Johnson Matthey unveiled a new technology called Hycogen that is able to efficiently convert CO₂ and green hydrogen into SAF.

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Author: Tom Young