Sustainable Aviation Fuels: Part 1: What is SAF?

June 09, 2022

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by Gaulthier Blangez* (Time to Fly and Advanced Biofuels USA) Advanced Biofuels USA, in collaboration with Time to Fly, is proud to publish a guide to sustainable aviation fuels (SAF) for a general audience, for corporations working on ESG (environment, social and governance) efforts, as well as for potential investors.

This project started when we realized the gap between amount of understanding the general public has about SAF and the important potential it holds to mitigate climate change. SAF usage is key to adapting to the climate crisis we are all facing as individuals, communities, companies or institutions.

We believe that the first step for a technology to spread is to make it easy to understand. That’s even more the case for aviation: an industry which is hard to defossilize while being massively used by a large spectrum of consumers.

Therefore, this four-part guide is built around the idea of making something that could be perfect for a curious teenager to understand. Though, while key concepts are all depicted in one place and simply explained, we added a technical layer to match the needs of professionals who need to understand, quickly, what SAF is about.

It answers key questions and shines light on key topics: What is SAF? Why use SAF? The Economics of SAF. The Politics of SAF.

This first installment focuses on the ways that SAF is made and explains the international framework and assessment for SAF development from a variety of processes (pathways) using a multitude of feedstocks.

Future installments will highlight why and how SAF is used and will explore some related policy and economic issues.

Background

I was born in a generation raised in the aftermath of Norwegian Prime Minister Gro Harlem Brundtland’s pledge for “our common future”.. I learned how central the notion of “sustainable development” is, as did all the people of my age.

Nevertheless, I also experienced how crucial aviation was as a way to bring together spread-apart families, overseas students, or as means to reach multiple cultures, and to provide crucial services such as medical evacuations or humanitarian help. Therefore, I believe that sobriety and innovation should be seen as complementary. Our work with this guide goes in that direction.

PART 1

The first part of this four-part presentation is about the definition of SAF. Meaning that you’ll get to learn how primary feedstock is transformed into SAF and how the final product is approved for usage.

Beyond the semantical questions raised by this topic such as “What’s the correct word for this production pathway?” or “Should we talk about SAF as a plural?” are the core concepts: technical certification, production pathways and dedicated feedstock.

And there we have our starting point: SAF is jet-fuel without the fuel. Well, almost without the fuel, so far. Confused? Let me guide you through that statement.

First, “SAF is jet-fuel”. It means that SAF has the same chemistry properties as jet-fuel (and in most cases to jet A1 specifically). Therefore, using SAF should be transparent in a jet A1-oriented ecosystem. Think of it as blending water with water: [SPOILER] The end result would probably be water.

It opens up the field of what is possible: since SAF is "drop-in" jet fuel, it can be distributed with jet fuel and there’s no need for a new supply chain. In a world where what pollutes less is what isn’t produced, we’re holding to something here. But it goes even further: since SAF is jet fuel, it can be used in the very same engines as jet fuel. So the supply line isn’t the only thing that doesn’t need to be replaced or upgraded: SAF has been compatible with aircrafts for as long as jet A1 has been.

Second, “almost without the fuel“. This sentence refers to the SAF blending. And this is the point where I could lose you so I’ll clarify one or two things. By talking about SAF as a concept, I could be talking about one of two kinds of SAF: the neat SAF and the blended SAF and hear me out because this is crucial to your understanding.

Neat SAF is the renewable part of the blended SAF while the end product, blended SAF, is a blend of neat SAF and petroleum jet A1. The maximum proportion of neat SAF that can be blended with jet A1 is called the max blending ratio. Studies are ongoing to raise the max blending ratio to the 100% SAF target.

Well, we just described in two points what the technical certification is: it is the certification that the usage of a specific production pathway would allow to obtain SAF, which is the same as jet A1 for all the reasons previously cited. In addition, the certification is valid for a given max blending ratio. Therefore each production pathway is linked to its specific max blend ratio.

Discover more about what SAF is, about the variety of production pathways and the feedstocks for each of them in this presentation.

Next time, we will explain why SAF makes sense in the aviation industry's quest for sustainability. READ MORE Download presentation

*Gaulthier Blangez has a Masters degree in Energy and Environment Economics from the French Institute of Petroleum and New Energies and works as a sustainable aviation fuels consultant with Time to Fly, a firm which guides actors in the aviation world with their operational management.