One hundred years ago, the Italian aviator Francesco de Pinedo was attempting the unprecedented feat of crossing the Indian subcontinent in a flying boat. He later splashed down on the Tiber in Rome to national acclaim, having flown via Asia to Australia and back over seven months, taking off and landing in water 80 times.
Aviation has been marked by stop-start journeys on hitherto uncharted courses to unlikely, if not unreachable, destinations. Today’s collective act of faith – amid much scepticism – is in following an uncertain path to sustainability, through green fuels that are yet to be widely produced.
Most in the aviation industry, even if only through self-interest, are on board with the theory. Of the identified emissions cuts needed for carbon neutrality, 70% rely on sustainable aviation fuels, or SAF. “Without it,” says Tim Alderslade, of Airlines UK, “we cannot get anywhere near net zero by 2050.”
This year, the first steps were imposed by mandate in the EU and the UK, requiring 2% of jet fuel to be sustainable – by 2030, that reaches 6% in the EU and 10% in Britain.
However, airlines have questioned whether supplies will be available and at what price. A fissure is developing between those that have secured sources of SAF and invested in technologies, and others with a ferocious eye on the bottom line.
Michael O’Leary, the chief executive of Ryanair, dismisses SAF as nonsense. He says: “It is all gradually dying a death, which is what it deserves to do. We have just about met our 2% mandate. There is no possibility of meeting 6% by 2030; 10%, not a hope in hell. We’re not going to get to net zero by 2050.”
More measured voices among SAF’s champions also have concerns. Willie Walsh, director general of the worldwide airline trade body Iata, had pushed for fuel tanks to contain 5% SAF by 2030. He admitted last week to disappointment in progress, adding he did “not believe that target can be achieved given where we are in terms of SAF production”.
At least, he said, the case for SAF had been proved: “We now need to turn what we know is technically possible into something that’s commercially possible and commercially viable for the industry.”
The UK is trying to create the framework with a revenue certainty mechanism. A bill currently going through parliament will guarantee a price for SAF, to encourage investment in production. The Department for Transport in July allocated £63m to 17 companies looking to make SAF in Britain. A spokesperson said there were “encouraging early signs towards meeting the mandate”. But only Phillips 66 in Humberside is making SAF at scale, with the five plants promised under Boris Johnson’s “jet zero” strategy yet to appear.
Carrots and sticks are needed, with big oil companies having ever less incentive to go green when invited to drill for easy profit. Shell’s decision to stop construction of a Rotterdam biofuel plant, expected to be one of Europe’s biggest converters of waste to jet fuel, will make SAF rarer and dearer. Meanwhile, Donald Trump’s “big beautiful bill” slashes US incentives for SAF production introduced by Joe Biden’s Inflation Reduction Act – although, in a concession to American crop farmers, some subsidies on homegrown SAF feedstocks will continue for two more years.
Philip New, a former BP alternative energy executive and government adviser on SAF, says: “I’m very pessimistic about SAF in the US. There’s no mandate or regulations or reason to use it.”
Beyond the US, geopolitics could weigh on supplies in various ways, he says. Tariffs could divert more Chinese cooking oil for SAF in Europe; meanwhile, Asian countries introducing their own mandates and quotas may not want to export.
New still believes SAF will come but warns: “It is going to be a lumpy transition.”
Current UK and EU mandates can be met entirely with HEFA (hydrotreated esters and fatty acid) based SAF, made from sources such as recycled cooking oil – though its provenance has been questioned. The bigger hurdles come as governments demand second generation (2G) SAF, made of feedstocks such as household rubbish.
Alderslade says production of 2G is “the great unknown”. Missing the mandate, he says, will bring financial penalties “which inevitably will be passed through to passengers”.
New says: “In theory this is a really great way of getting rid of our waste.” The challenge is getting the right level of support to back up the very high-risk first generations of these technologies.” Even with government backing, the 2G targets for 2030 are unlikely to be met, he adds.
Despite the risks, investors see the long-term value. One global asset manager, who declined to be named, said the US was an outlier in abandoning net zero, with mandates coming to Asia as well as Europe. “For oil majors, SAF is lower priority, it’s hard – some people are giving up. But airlines can’t abandon it. It’s going to be bumpy – but is it all coming down? No.”
Differing views among airlines, he suggests, may reflect the ease of access and price paid for SAF at the airports they use: “There’s no shortage in the hubs.”
The British Airways owner, IAG, says it has a “long-term commitment”, with some justification – it announced plans in 2011 for a pioneering waste-to-fuel plant in Essex, although it admitted defeat by 2017. IAG says there will be enough SAF to meet EU and UK mandates until 2030. But a spokesperson added: “Second and third generation SAFs do require more investment and development [and] support … Mandates are one lever to stimulate demand but investment in production is key.”
Green shoots are still appearing: a Belfast company, Catagen, last month launched patented modular technology which it said could produce SAF at quantities needed in the vicinity of smaller airports, a development endorsed by Ryanair.
For BA’s home airport, the debate has particular urgency: if the sustainable aviation roadmap crumbles, Heathrow’s third runway becomes ever more politically difficult.
Matt Gorman, director of carbon strategy at Heathrow, insists: “SAF is not hypothetical. Heathrow is already leading globally in SAF use, 17% of the world’s SAF in 2024 was used here. This is real progress, not a future promise.”
Some environmental campaigners, while remaining firmly against Heathrow expansion, have shifted on SAF, accepting it as a potential route to future decarbonisation – even if many fear it acts as a fig leaf to deflect environmental concerns today. But plenty of campaigners and scientists still question the fundamental premise of SAF and its calculations of carbon reductions.
Planes will continue to emit CO2 as usual at the tailpipe – and in the broader context, will still be depleting resources. Matt Finch, in a report for the Aviation Environment Federation, said: “The blunt truth is that there is not a single SAF feedstock that can’t be used in another sector where it would bring a desirable environmental outcome. And in some cases, that outcome is already what a large proportion of the waste is used for. “
That caveat applies even for the gold standard fuel, third generation, or e-SAF, created via CO2 capture and renewable electricity. It has been synthesised in small quantities, and tested in a Swiss “solar fuel” flight this July. But e-SAF requires green hydrogen, supplies of which, Walsh says, are “very limited, and also extremely expensive”. Investors in e-SAF right now, according to the City insider, “will probably lose their money”.
Where the technology goes is unclear, history suggests. De Pinedo was to die eight years after his seaplane feats, in a conventional plane taking off from a runway in New York in 1933. Flying boats were superseded by the advent of jet aircraft during the second world war.
“Predicting the future will always involve some uncertainty,” Gorman says. “But what we’re doing is not guesswork. It’s based on evidence, expert consensus, and a clear roadmap.”
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