Establishing “green flight paths” on key long-haul airline routes could help speed the uptake of sustainable aviation fuels, according to a new proposal.

The idea borrows from “green shipping corridors” in the maritime industry, which are rapidly scaling up to help roll out new technology needed for net-zero shipping.

Sustainable aviation fuels (SAFs) are necessary for the airline industry to achieve net-zero emissions by 2050. These non-petroleum-based fuels have lower emissions than standard jet fuel and can be used in existing aircraft engines and fueling infrastructure.

The net-zero target will require 449 billion liters of sustainable aviation fuel in 2050, but 2022 production was just 300 million liters, or 0.1% of the volume necessary. In turn, that more than 1,500-fold increase in production by 2050 will require 5,000 to 7,000 new production facilities and an investment of US$1.1-1.45 trillion.

Ramping up production is also necessary to achieve economies of scale and bring down the price of sustainable aviation fuels, which are currently 2.5 times as expensive to produce as conventional jet fuel.

That’s where the potential for green flight paths (GFPs) come in, researchers argue in a perspective published in Energy & Environmental Science. They propose that specific busy, long-haul aviation routes commit to using 100% sustainable aviation fuels.

The guaranteed customer base would reduce risks for sustainable aviation fuel producers and spur them to make the investments needed to scale up production and establish commercially viable supply chains, the researchers say.

Sustainable aviation fuels face “limited production capacity and we need governmental supportive measures,” says Mercedes Maroto-Valer, a sustainable energy researcher at Heriot Watt University in the UK and one of the authors of the paper. “However, this is also where GFPs can become a game changer.”

Green flight paths could “kick-start SAF implementation through targeted support from key international partner countries,” Maroto-Valer and her collaborators write. They zero in on London-Dubai as a promising candidate for the first GFP.

London-Dubai is a long-haul route that carries a high volume of passengers and is served mostly by large, wide-body jets. It represents precisely the type of route that will be difficult to decarbonize via other technologies such as batteries or hydrogen, and therefore will likely continue to rely on sustainable aviation fuels for the forseeable future.

More broadly, Dubai and London Heathrow are among the busiest airports in the world. They are associated with the highest and second-highest carbon emissions from international flights of any airports in the world, and are also first and second in the total number of international passengers that transit through. Plus, Heathrow has already set a target of 11% sustainable aviation fuel use by 2030.

There’s a climate justice angle here, the researchers point out: by seeding GFPs on routes like Dubai-Heathrow, the countries that benefit the most from long-haul aviation take responsibility for the investment to make the industry sustainable.

And there’s also a practical argument for this approach. “We have identified countries and regions where SAF production can be certifiably and rapidly scaled-up by leveraging existing production capacity for conventional aviation fuels and where support for near-commercial SAF technologies can rely on wider initiatives for clean fuels adoption in industrial contexts,” says Maroto-Valer.

What’s more, if the proposed route is successful, this might inspire the establishment of more GFPs between Singapore and European cities; East Asian cities in Japan and Korea and the East Coast of Canada and the U.S; and East Asia and Australia, the researchers suggest. In other words, the sky’s the limit.

Source: Griffiths S. et al. “Green flight paths: a catalyst for net-zero aviation by 2050.” Energy & Environmental Science 2024.

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