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An Application Programming Interface (API) is a set of rules and protocols that allows different systems to communicate, whether those are software applications, services, platforms or devices. It lets one system request data or trigger an action from another without either side needing to know how the other is built internally. The API acts as a bridge between the client and the server, setting out how requests are made, what information can be exchanged and what responses to expect. In practice, APIs allow separate tools to work together without manual copying between them.
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Book and claim for first-time participants: how an API eases entry
In 2026, global SAF production is expected to reach about 2.4 million tonnes, constituting close to 0.8 per cent of total aviation fuel use, against an understood worldwide aviation fuel demand of around 300 million tonnes1. Since SAF production is also geographically unevenly distributed, availability may not be guaranteed where a given airline or corporate buyer requires it. Book and claim systems help address this mismatch: fuel is supplied and blended where production and infrastructure allow; meanwhile its verified environmental attributes are recorded in a registry as units, transferred to an end buyer and retired. The buyer then can make the corresponding claim without physically accessing the fuel. Availability rather than demand is one of the sustainable aviation fuel (SAF) market’s biggest constraints.
In order for a book and claim system to work, it must possess strong guardrails, such as recognised sustainability certification, traceability from feedstock and production through to the claim, pathway-specific lifecycle emissions data, clear reporting boundaries, independent verification, prevention of double counting and transparent records of retirement and disclosure. Combining different feedstocks, certification schemes, emissions methodologies, registries, contracts and evolving regulations is a complex process, which can make organisations wary, particularly when a claim will come under the scrutiny of auditors, regulators, customers or investors.
An API connection to a registry can streamline the process, letting an organisation participate through systems it already uses rather than building new ones.
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How an API connection helps
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For organisations managing SAF environmental attributes, the volume of transactions grows as more buyers are involved. When handling programs manually, that growth can translate into more data entry, more reconciliation, more resources and more room for error.
An API connection between the Registry and an external platform helps solve this manual work. Inventory recorded in the Registry can be reflected automatically on a connected platform, reducing manual entry. Retirements can be requested in bulk or individually, with each request passed to the Registry to be completed and designated to the named beneficiary.
The practical effect of connected systems is that scale stops adding manual work. As a programme grows, the API connection manages the increasing volume of data transfer instead of the team doing it manually.
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How the RSB Book & Claim Registry keeps claims defensible with API connectivity       Â
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Part of the RSB Book & Claim System, the RSB Book & Claim Registry is a secure digital platform that allows companies to separate the environmental attributes of a physical renewable fuel from the fuel itself and register them as TIECs (Transferable Instruments with Entitlement to Claim ). Each registered unit becomes available to be transferred to a buyer and then retired once, with that retirement recorded.
The value of the RSB Book & Claim Registry is not only that it records units but that it holds the line on integrity: transparent records, a traceable chain from the registered attribute through to the retired claim, and documentation issued by RSB, including a Book & Claim Retirement Statement to support Scope 1 and Scope 3 reduction claims. These are the guardrails that let a claim stand up to an auditor, a regulator or a customer.
An API does not change any of this. The rigour stays where it belongs, in the standard and the Registry, and the API expands access. Connecting to a registry built for scrutiny is what lets an organisation move quickly without trading away the defensibility of its claims.
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What comes next
RSB is releasing an API integration that brings this connectivity to sustainable aviation fuel programmes. Details, and the partner involved, will follow. Watch for the integration with Chooose.
1 Press release: SAF Production Volumes Still Disappointing, IATA, 6 June 2026 — https://www.iata.org/en/pressroom/2026-releases/06-06-saf-production-volumes-still-disappointing/
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