Is Sustainable Aviation Fuel the Future of Flight? Exploring Its Potential and Limitations

Download this background briefing as a PDF: Sustainable aviation fuel: is it really a game-changer?

Sustainable aviation fuels (SAFs) are key for cutting CO2 emissions in aviation.
SAF can’t compete with fossil jet fuel on price without subsidies.
Scaling up SAF production will be slow and costly due to resource limits.

Why are people excited about SAF? Sustainable aviation fuel is seen as a breakthrough for the aviation industry. It allows planes to fly without using fossil fuels. Test flights have already flown on 100% SAF, and airports worldwide are starting to blend it with traditional jet fuel.

So, what is SAF? It’s a fuel that can replace traditional jet fuel but doesn’t rely on fossil fuels. Instead, it uses materials from the environment, like municipal waste or plant biomass. In recent years, there’s been a push to replace fossil fuels completely, especially as climate change concerns grow. The idea of synthetic fuel dates back over a century, with techniques originating as far back as 1925. But today, the stakes are higher as various sectors rush to cut emissions.

How “green” is SAF? The environmental impact of SAF depends on how it is made. Burning SAF releases carbon, just like regular jet fuel. However, the carbon from SAF comes from renewable sources, aiming for a “net zero” outcome in emissions. But if non-renewable energy is used in production, or if creating the raw materials releases too much carbon, that balance is upset.

Right now, few SAFs are completely net zero. In the UK, a fuel can be labeled “sustainable” with just a 40% reduction in emissions. For commercial flights, SAF must be blended with at least 50% fossil fuel, meaning even a 100% SAF flight isn’t fully carbon-neutral.

Still, nations are optimistic about SAF. The U.S. aims for 3 billion gallons by 2030 and has plans for huge increases by 2050. The UK will require 10% of fuel to be SAF by 2030, growing to 22% by 2040. The EU is following suit with its own goals.

But why isn’t 100% SAF in use yet? A big issue is cost. Producing SAF involves more steps and high energy use, making it expensive. The costs for one type of SAF, called Direct Air Capture (DAC), could range from 190% to 500% compared to fossil fuel prices.

Another obstacle is the limited supply of affordable resources. The cheapest SAF comes from waste, like used cooking oil, but those sources are running low. As countries look to expand SAF production, they risk using resources that could harm the environment, like agricultural land.

Even if SAF becomes cheaper, it may never match fossil fuel prices without ongoing subsidies. If those financial supports disappear, SAF production could stall.

Plus, even a 100% carbon-neutral SAF won’t solve all aviation sustainability issues. It still emits nitrogen oxides, which can be harmful to both health and the environment. While there are suggestions that SAF could mitigate these impacts by up to 44%, it will not be a complete fix.

What does this mean for Heathrow? The airport consumes nearly half of the fuel used at UK airports and accounts for a significant portion of the country’s aviation emissions. Questions arise about expanding Heathrow while meeting climate goals, especially given uncertainties in SAF production and its upcoming scalability.

In summary, while SAF is promising, major challenges remain. Its production will be slow and costly, and it may not live up to the “game changer” hype. The future of aviation’s environmental impact hangs in the balance.

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