Sustainable aviation fuel isn’t the best route to zero carbon flight – Inside track

This post is by Finlay Asher, aerospace engineer and member of Safe Landing: a global community of aviation workers and enthusiasts.

As an aerospace engineer, I understand the excitement around so-called ‘sustainable aviation fuel’ (‘SAF’). It’s pitched as a climate solution that keeps everything else – airports, aircraft and airline business models – more or less the same. But while the rhetoric can be high flying, the reality is more complex. Not all ‘SAF’ is created equal, and not all regions are equally suited to producing it. In the UK, and beyond, we must take a clear-eyed view of what role ‘SAF’ can and can’t play in the wider challenge of decarbonisation.

There’s no doubt that aviation must change. Jet fuel is a fossil-based product and we won’t meet our climate goals without cutting rising aviation emissions. ‘SAF’ has been held up as a near term solution and, in certain forms, it can help. But we need to be cautious about seeing ‘SAF’ as a magical solution, and potentially look elsewhere for opportunities to harness aviation to deliver economic development.

SAF must be scrutinised
My organisation, Safe Landing, chooses to avoid the term ‘sustainable aviation fuel’ or ‘SAF’ to describe alternative jet fuels (those which aren’t derived from fossil fuels). This is because the ‘sustainable’ label presumes such fuels have a low environmental impact and this claim often doesn’t hold up to much scrutiny.

‘SAF’ is a broad category, covering a range of fuel production pathways. Some are made from waste products and could deliver moderate emissions savings. Others rely on purpose grown farm crops or energy intensive processes like ‘green’ hydrogen or direct air capture (DAC), raising serious questions about their land use consequences, energy requirements and real world scalability.

Every region needs to ask: which pathways make sense here, both environmentally and economically? Investing in the wrong types of fuel production risks diverting scarce global and national resources away from more effective uses in other sectors. It could also increase commodity prices for everybody, while burning through a large heap of taxpayers’ money.

Decarbonisation needs joined up thinking
‘SAF’ can’t be looked at in isolation. We need a joined-up industrial strategy that considers the best use of land, renewable energy, green hydrogen and waste biomass across multiple sectors. For example, should green hydrogen be used to create synthetic aviation fuels or would it deliver greater impact producing either green synthetic fertilisers for farmers or green steel, eg in the UK at Scunthorpe or Port Talbot steelworks?

Or, take anaerobic digestion, using farm and food waste to create biogas and organic fertiliser could be a more environmental and economic use of biomass than converting it into fuel for planes. These trade offs matter, especially in a resource constrained world.

The risk is that a narrow focus on ‘SAF’ could distort our priorities, sucking in subsidies and policy focus at the expense of more cost and time effective decarbonisation routes.

We should focus on our strengths, not wishful thinking
There’s an argument that the UK should become a hub for ‘SAF’ production. But this vision must be grounded in economic and physical realities.

Producing electro-fuels from green hydrogen and direct air capture is extremely energy intensive. The UK’s relatively high electricity costs and limited land availability make it a poor location for this kind of production, compared to regions with abundant, cheap solar and wind and relatively low energy demand. Chasing these ambitions here may not offer the best return on public or private investment.

Instead, the UK’s strength lies in its engineering expertise. Our world class skills in design, systems integration and advanced manufacturing could play a vital role in developing technologies to export for global decarbonisation, not just producing fuels here to burn onboard British aircraft but building the infrastructure, power systems and components that enable cleaner energy and transport systems worldwide.

What kind of future are we fuelling?
Calls to use ‘SAF’ to expand conventional airports may be well-meaning, but they might be misdirected. A truly sustainable regional development strategy should start by asking: what does a zero carbon air transport system actually look like?

Our alternative economic vision is to make the UK a leader in zero carbon aircraft. Public-owned airports in Central England such as Luton and Sheffield-Doncaster are well placed centrally between population centres, eg Bristol in the South, Scotland in the North, Ireland to the West and Amsterdam in the East. We’re blessed geographically to lead as a focal point of an early zero carbon air travel network.

This would provide a clear signal for battery-electric, hybrid-electric and hydrogen-electric aircraft developers to locate their companies here. It would also supercharge innovation, with spillover benefits to other areas of the economy. For example: high performance electric motors and fuel cells that can be used in other industries.

The sky’s the limit for the future of flight, but the UK must choose to back winners which play to our strengths, natural resources and existing expertise if we are to compete in a global market. Let’s invest in the solutions that deliver the most value for the climate, the economy and our communities, not just the ones that appear to promise the (flight) path of least resistance.

Look out for Green Alliance’s report coming soon, exploring the UK’s strong potential to become a world leader in zero emission flight.