Hydrogen and sustainable fuels

This category covers sustainable aviation fuel, hydrogen and the fuel cell systems built around it. The tanks and plumbing on the aircraft are under fuel systems, and the engine is under propulsion. What is bought here is a commodity with a specification, a delivery chain and a claim attached, and buyers get into trouble on the third one.

The fuel is a specification before it is a product

An aircraft engine is certificated against standards that assume an approved fuel, and an engine applicant must also meet the fuel venting and exhaust emission requirements that sit alongside them.^1,2 In practice that means the operative question to a fuel supplier is not "is it sustainable". It is: which specification does this batch meet, at what blend ratio, and who certifies the batch. Ask for the certificate of analysis, ask what the blend limit is for the engines you operate, and ask what the engine manufacturer's published position is on that fuel at that ratio. For military and government work the specifications are published documents with a status and a date, searchable in the government's own standardization register, and quoting against a superseded revision is a common error.⁴

Infrastructure decides whether you can actually take delivery

Ask where the fuel is produced, how it reaches your airport, and who blends it. Ask whether the blending happens at the refinery, at the terminal or into the airport hydrant system, and who holds the fuel quality responsibility at each handoff. Ask what happens when your uplift exceeds the supply available that month. For hydrogen the same questions get harder: ask about the state it arrives in, the storage on site, boil-off, the refuelling equipment and who owns it, and what the turnaround time becomes. Ask what the contingency is when the supply does not arrive, because the aircraft still has to fly.

The claim is a separate product

Environmental attributes are traded separately from molecules, and a buyer should know which they are purchasing. Ask whether you are buying physical fuel, a book-and-claim attribute, or both. Ask who registers the claim, who retires it, and what documentation you receive. Ask how the emissions reduction was calculated and against which methodology, and get that in writing before you put a figure in an annual report. The FAA's Energy Division publishes its work on new fuels, including testing and evaluation and analysis of economics, environmental benefits and supply, which is a reasonable place to calibrate what a claim is worth.³

Where the public record can be checked

Fuel specifications, engine emission standards and government fuel documents are all published.^1,4 They prove what a fuel must meet and what an engine was certificated against. They do not prove that a particular cargo met the specification on the day it was loaded, which is what a certificate of analysis and a chain of custody are for. Ask for both, per batch, and keep them.

Questions that sort suppliers

Ask which specification and blend ratio the offer is for. Ask for a certificate of analysis from a recent batch. Ask what the delivered volume was last quarter, and to which airports. Ask what the contract says when supply fails.