As aviation accelerates out of the COVID-19 crisis, sustainability and emissions will be more of a priority than ever before. Sustainable aviation fuels, including biofuels, are a key weapon in the arsenal for the fight to reduce emissions and the industry’s impact on climate change, with the greenest estimated to reduce lifecycle emissions compared with fossil fuels by up to 80% by some calculations and even higher by others.
We spoke with Freya Burton, chief sustainability and people officer at LanzaTech, which produces these fuels, and Jessica Poole, technology business lead at Rolls-Royce, to learn more about where sustainable aviation fuels have come from — and are going.
Sustainable fuels, or SAFs in the aviation context, have come, as Burton puts it, “a really long way from sugar and corn”, with a truly impressive number of fuel pathways in this new market.
First generation biofuels were creating ethanol, largely from sugar or corn, to add into existing fuels. Later options included feedstocks like jatropha and camelina that can be turned into energy crops, but there are issues here around replacement or reprioritisation of agricultural growing areas. Another option is also wastes and residues, particularly oils and greases or agricultural residues, but these come with reliability and repeatability issues. Recycled carbon is also an option: municipal solid or plastic wastes that can’t be mechanically recycled and would end up in landfill, or processing of waste gases into fuel. And then there’s power-to-X, converting power, usually off-peak, into fuels via conversion and storage.
As a result of all these technologies, says Poole, “there are a range of players in the industry that are looking at lots of different routes. And actually, although they’re all slightly different, and the fuels that are produced will have slightly different properties, we’re going to need a whole range of production methods, because to really scale up production in a way that is sustainable, you need a variety of routes.”
A crucial part is, however, ensuring that sustainably produced fuels are similar enough to the Jet A and Jet A-1 standards that they can be “dropped in” to the mix using the existing infrastructure, which means that existing distribution networks can be used. Successful tests have been carried out for over a decade with lower proportions of fuels, with higher-proportion or even full-SAF tests a more recent development.
“The reason SAFs are so brilliant, and so important to aviation, is that they have really similar properties to the standard Jet-A we use today,” Poole says, comparing them to radically different fuels like hydrogen. “SAFs, because they’re carbon based, have got really similar properties to normal Jet A, which is great, because it means they’re effectively drop-in. The industry has gone through a certification process to mean you can just blend some types with current Jet A up to 50%, and just put it straight in the platform.“
There are some current limits on amounts and proportions, usually at or near 50%, largely around the requirement for certain aromatics within the fuel for efficient and predictable engine function. It should be said, however, that SAF production is by no means anywhere near approaching this level.
Challenges include three key linked factors: pricing, policy and scaleup
Quite simply, SAFs are more expensive than traditional fuels today. At the same time, the pricing externalities of fuel-based emissions — in other words, the cost to the planet of the carbon that aircraft produce — are not fully or even mostly included in airline operations or ticket prices.
That’s an uncomfortable truth for aviation, which has largely resisted carbon pricing, as early potential runners and riders in the sustainable fuels market begin to scale up.
“One of the really important things,” Poole says, “is to get governments to create the regulatory and policy environment that is going to be used to enable that scale-up. SAFs are more expensive than current Jet-A: it’s not going to be a classic market driver that drives the scale-up, it’s going to have to be policy-created.”
At the same time, the definition of sustainable fuels — and the eligibility of certain technologies — could use some attention as well.
LanzaTech’s Freya Burton explains: “we’re taking a waste carbon source, be it gases, or be it landfill, and we’re using that as a feedstock. Today, that doesn’t qualify for any tax credits, it doesn’t qualify under the renewable transport fuel obligation in the UK, it’s uncertain how it qualifies in the renewable energy directive in Europe.”
The impact, she says, is that “you don’t know if you’re actually going to have a market to sell that fuel, because it’s not eligible… if we could have the certainty that these things qualify, you could probably double all the commitments that are out there today.”
But beyond that, a key factor at present is that the scale-up will be beyond the traditional government investment timescales: five or ten years, through the next election or two. And since generating these sorts of lower-carbon fuels at scale will require infrastructure, it’s also about ensuring that the rest of the process — power generation, concrete or other structures, transportation, and so on — is also operating as cleanly as possible.
That’s true in the inherent digitalisation of fuel production as well.
“We will firstly need to have a much more integrated system — to understand how things are being produced, and to have a lot more transparency around the whole energy system, particularly for the CO2 emissions, and how everything interlinks,” Poole explains.
Blockchain is certainly an option for tracking the environmental credentials of feedstocks, production, transportation and distribution, but there’s a point at which ensuring the carbon footprint of the data processing doesn’t negate gains in the actual fuels. But with the growth of cryptography-based currencies in particular, awareness is growing around the environmental impact of the processing power needed to run them.
Work is ongoing around data governance, usage, movement, control and sharing, while policies to ensure ethical and trustworthy use of artificial intelligence, especially around the carbon chain of custody, will also need to be agreed and implemented.
These are big questions, and solving them will require much effort — but they will need to be solved in order for the promised gains from sustainable aviation fuels to be realised.
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We’re discussing this in the Yocova Challenges area – In your opinion, what directives – if any – could be put in place to enable the scaling up of the next generation of sustainable aviation fuel?
Article published 29th April 2021
Written by John Walton
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