Institute for Molecular Science and Engineering

New podcast alert!

This month I talked to two of the authors of the latest IMSE briefing paper about low carbon fuels for aviation. This was launched on 1 March 2023. I spoke to Andrea Fantuzzi and Nadine Moustafa about their experience writing the paper.

The challenge of low carbon fuels for aviation

The aviation industry is responsible for 2.1% of global CO₂ emissions. This represents 12% of CO₂ emissions from all transport sources. One decarbonisation solution is to use an alternative “sustainable” fuel, such as hydrogen, biofuels or power-to-liquid (PTL or “synthetic”) fuels. The CO₂ emissions from burning hydrogen are zero. In contrast the CO₂ emissions from burning biofuels and PTL fuels are calculated to be net zero, because the carbon in these fuels has come from the atmosphere.

So why aren’t we already flying in planes using these fuels? Currently, the UK does not produce very much of any of these fuel types and doesn’t use them for powering planes. This is because:

• Kerosene is much cheaper.
• Aircraft engines have to be adapted to operate on biofuels and PTL fuels. Both the engine and the body of the aircraft have to be completely redesigned to work with hydrogen. As you might imagine, the safety testing requirements are stringent.
• There isn’t enough spare electricity to produce hydrogen and PTL fuels in useful quantities.
• There isn’t enough spare plant material to produce biofuels in useful quantities.

And more worryingly, there are still questions about whether using these fuels really would reduce CO₂ emissions overall. Though they may produce zero or net zero CO₂ emissions when they are combusted, what about when they are produced, stored and distributed?

Key questions in the briefing paper

The paper looked at the three fuel types mentioned above and asked three questions:

What are the total CO₂ emissions for a fuel type, including the whole production process? This uses a tool called life cycle analysis. It turns out that CO₂ emissions can vary widely for hydrogen and biofuels, depending on the raw material and the technology used. Some modes of production produce less CO₂ than kerosene, which is good. Some do not – so these are not worth investing in.

What resources are required to make each fuel type on the right scale to meet current UK fuel demand? Do we actually have the raw materials and infrastructure to produce them at this scale? The short answer, right now, is no, and we’re not even close. Long term, it’s harder to say.

Biofuel raw materials will not ever be enough to replace very much of UK fuel demand. But we currently have the technology to make fuel with these, so the government is keen. We don’t have the infrastructure to make hydrogen and PTL fuels at scale. Both would require a big increase in renewable electricity generation in the UK. We would also need to build CO₂ capture facilities for PTL fuels, as there are currently no commercial CO₂ capture plants in the UK. And additionally, no large scale PTL production plants for aviation fuel exist anywhere in the world at the moment– so all this technology needs to be developed and tested, which takes time.

If we want to scale up fuel production, what policies does the government need to put in place in order to achieve this? The most important thing here is for the government to set a high standard. Development should focus only on fuels that really are greener and really are scalable, to meet full demand. Exactly how we might do this is different for each fuel type, because it depends on the molecular and thermodynamic reality of each fuel. The molecule dictates the challenge…

Writing the paper

IMSE organised an online workshop to start the process of developing the paper in 2021. Then a core writing team, each of whom are specialists in a particular fuel type, or in the policy arena, met every few weeks to write the paper. This was a super multidisciplinary process! As Nadine says in the podcast, we all needed to not be afraid to ask questions, and as Andrea says, we all needed to be aware of where we might be using the same word to mean two different things…

Read the paper here

Read about the launch here

So when do you think you’ll be getting on a plane powered by something other than kerosene? Have you changed your flying habits to reduce your carbon footprint?