Sorry, Rachel Reeves: This is the inconvenient truth about ‘green airports’ and ‘sustainable aviation’
As the government finally gives Heathrow’s airport expansion the green light, flight-free former travel editor Helen Coffey talks to the experts to bust the myths that technology and sustainable aviation fuel can really lead to environmentally friendly flights in the midst of a climate crisis
I can confirm today that this government supports a third runway at Heathrow and is inviting proposals to be brought forward by the summer.” These words, stated proudly by UK chancellor Rachel Reeves as part of her grand plan to reinvigorate the country’s flagging economy, were not universally welcomed earlier this week. Promising an assessment to “ensure that a third runway is delivered in line with our legal, environmental and climate objectives”, her proposals immediately raised more questions than they answered in terms of the UK’s emissions targets.
“The chancellor’s decision to grant another airport expansion is dystopian,” responded Anna Krajinska, UK director at the NGO European Federation for Transport and Environment (T&E). “How can the government aim to meet net zero by 2050 and simultaneously greenlight the expansion of a heavily polluting sector?”
Reeves’s own colleagues raised objections too, with London mayor Sadiq Khan saying he remains opposed to the plan due to the “severe impact it will have on noise, air pollution and meeting our climate change targets”.
Heathrow was not the only airport to receive a nod and a wink. The government also looks set to back expansion at London Gatwick, which has proposed turning its standby runway into a live one. And London Luton is looking to up capacity by adding more terminal space and taxiways. We’re talking significant increases here: the latter is hoping to double passenger numbers, while the former expects a 50 per cent increase in capacity. Heathrow projects that runway number three will increase flight capacity by 54 per cent, totalling 712 more flights a day.
London City airport’s plans to expand to 9 million passengers per year by 2031 were already approved in the summer, while London Stansted has confirmed an additional £1.1bn investment into extending its terminal. If this is all looking a little (or a lot) London-centric, fear not – Doncaster Sheffield airport has received official support for plans to reopen in 2026.
The immediate and obvious question for many was this: how on earth does all the above fit into the UK’s climate targets, specifically our legally binding agreement to hit net zero carbon emissions by 2050?
Passenger numbers in the UK have tripled since 1990 and are forecast to grow by 49 per cent from 2018 levels by 2050. In 2023, the aviation sector was responsible for 32 million metric tons of carbon dioxide in the UK, a 23 per cent increase from the previous year. Last year, UK aviation emissions were on track to reach a record high, reported The Guardian. As a parliamentary report puts it: “The UK aviation industry appears to be recovering from the effects of the pandemic, but at a corresponding cost to the UK’s net carbon emissions.”
At a time when every other industry has been forced to slash emissions, it’s hard to see how airport expansion isn’t at odds with our wider efforts to tackle the climate crisis; every government report, after all, highlights how fiendishly difficult it is to decarbonise aviation. But don’t worry, Rachel Reeves has a cunning plan up her sleeve: sustainable aviation fuels, or SAFs. They have thus far been her main justification when tasked with explaining how more flights and carbon reduction go hand in hand.
“We are already making great strides in transitioning to greener aviation,” reads the latest Department of Transport aviation report. “Earlier this month, the Sustainable Aviation Fuel (SAF) Mandate became law, requiring 2 per cent of this year’s aviation fuel supply to be from sustainable sources, with the targets reaching 10 per cent in 2030 and 22 per cent in 2040. SAF is one of the key measures required to reach net zero emissions from aviation by 2050: it reduces GHG emissions by around 70 per cent on average when replacing fossil kerosene (jet fuel).”
It sounds like a promising solution, doesn’t it? Though, straight off the bat, it’s clear that regular jet fuel is going to continue to power the vast majority of our flights for the foreseeable – 78 per cent of them will still be flying on kerosene in 15 years’ time. And that’s if the targets above are met, far from guaranteed at present.
In the short term, the numbers don’t quite seem to add up either. We’re aiming for a 9 per cent increase in SAF use in five years, while the aforementioned airports are aiming to double their capacity.
The chancellor's decision to grant another airport expansion is dystopian
The plot thickens further from there. First up, the term “sustainable aviation fuel” is something of a misnomer. It suggests that the fuel itself doesn’t emit carbon in flight – an entirely false assertion. SAFs produce just as many emissions as kerosene when burned; the reduction in carbon comes, instead, during the life cycle of the fuel. This can be in terms of using a feedstock that has removed carbon from the air during its lifetime, therefore negating the carbon it releases back out when it’s burned as fuel (called closing the carbon loop), or we could be talking about a source that was destined for landfill – the methane emissions avoided by using it to make fuel instead are taken into account. For example, used cooking oil (UCO) comes under the former, recycling carbon dioxide that was absorbed by the oil while the crop it’s made from was growing.
The number crunching regarding a particular SAF’s life cycle, therefore, needs to be extremely robust. “You have to be sure that those savings are happening before the fuel gets on the plane because once it’s been burned, the CO2 is back out there,” says Celeste Hicks, policy manager at the Aviation Environment Federation (AEF). “People hear sustainable aviation fuel, and they think low-carbon fuel, but it’s not. It’s as carbon-intensive as any fuel but it’s only the backstory of the fuel that provides these magical savings.”
This “backstory” is rooted in even more confusion. Not all SAFs are created equal – far from it. SAF is itself an umbrella term, and the 60 or more fuels that fall underneath it can vary wildly in terms of how much carbon they really save during their life cycle, and how environmentally friendly the production process is. Each country has its own methodologies, too, for calculating these carbon savings, and there are limited auditors to check each claim.
Thankfully, the UK has, unlike the EU, omitted biofuels from its recent SAF mandates. These often involve using great swathes of land – growing energy crops would require at least half of all UK agricultural land to meet the country’s jet fuel needs, for example – and have been associated with deforestation and high water usage. But other SAFs come with their own issues.
Take, for example, a new SAF plant that’s planned to open in Sunderland in 2026, turning used tyres into jet fuel. “This is where the narrative for SAF completely falls apart because you look at the tyres and that’s an absolute zero reduction in emissions,” claims Anna Hughes, director of campaign group Flight-Free UK. “You were going to burn the tyres anyway [most used tyres are incinerated], and you’re still burning the tyres, but to burn them as fuel you are now using a highly energy- and carbon-intensive process to turn them into oil. How is that better than using kerosene?”
Currently, despite different production processes resulting in differing emissions savings, there is little transparency. Leading figures, including Reeves, keep parroting the “70 per cent reduction on average” blanket statistic instead of talking specifics. “The line is still, ‘SAF reduces emissions by 70 per cent,’ because a few types of SAF do that,” adds Hughes. “It’s really strange that this number is not being scrutinised.”
Even when it comes to genuinely revolutionary SAFs with clean credentials, there are hefty hurdles. Synthetic or e-fuels – whereby electrolytic (green) hydrogen, made by electrolysing water using renewable electricity, is combined with captured carbon or nitrogen – are a game-changing, carbon-neutral proposition. But just as biofuels have the downside of requiring land, this production process uses huge amounts of renewable energy. According to a 2023 Royal Society Report, e-fuel production, when done sustainably, would require an estimated five to eight times the UK’s entire 2020 renewable electricity capacity.
Every time I listen to the airlines talking, they’re all saying they can’t get their hands on enough SAF
Which leads us to scalability – the biggest issue in claiming that aviation expansion can be offset by using SAFs. As Ryanair’s own Michael O’Leary put it in 2023, “There isn’t enough cooking oil in the world to power more than one day’s aviation,” while Ecotricity founder Dale Vince responded to Virgin Atlantic’s 100 per cent SAF-powered flight the same year by saying that “we’d need three more planets for SAF to be used by the entire industry globally. It’s not the answer, just a green herring.”
The infrastructure is in its infancy, despite Reeves pledging an investment of £63m for the Advanced Fuels Fund over the next year. “There are 50 SAF plants planned for Europe, five in the UK, but zero have got the final investment decision needed to start building – so we’re not even in a position to start producing the most sustainable type of aviation fuels,” says T&E’s Anna Krajinska.
And it’s not just the UK that’s looking to aggressively scale up its use of SAFs. The minimum SAF volume required by 2030 in the EU, for example, is around 2.8 million tonnes. However, a European Union Aviation Safety Agency (EASA) report deemed the SAF production market “inherently volatile” due to feedstock supply chain limitations and the risks to investors. “While many projects are announced, some may not reach commercialisation,” it said.
“You get into the question of the availability of the feedstocks, and everybody competing for those feedstocks,” Hicks tells me. “Every conference I go to, and every time I listen to the airlines talking, they’re all saying they can’t get their hands on enough SAF.”
When there’s more demand than supply, conditions become ripe for exploitation. One T&E report highlighted the issue of UCO fraud, whereby biofuels made from unsustainable feedstocks, such as palm oil, are fraudulently reported as being made from used cooking oil. “If you’ve got a huge demand being pushed by legal mandates, it’s very likely that you’re going to get fraudulent supply chains,” warns Hicks.
If that already seems like enough issues to be going on with, I regret to inform you that there are more. Firstly, at present, commercial planes are not even allowed to fly on 100 per cent SAF (Virgin Atlantic had to get a special one-off dispensation). The maximum amount airlines can legally use is a blend of 50 per cent SAF and 50 per cent kerosene due to safety concerns. So, scalability obstacles aside, even the small proportion of flights that are using SAF will still be powered by at least half traditional jet fuel.
And then, finally, there’s cost. EASA 2023 figures put the market price of kerosene at €816 a tonne, compared to €2,768 a tonne for biofuels. The cleanest fuel alternatives are also the most expensive to produce: synthetic fuel produced with CO2 captured from the atmosphere averaged €8,225 per tonne, more than 10 times the market price of conventional jet fuel.
Do we really anticipate that airlines won’t pass some of that significant extra operating cost onto the passenger? Which in turn would make flights more expensive, which would dampen consumer demand, which would mean we... probably don’t need those bigger airports anyway.
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