The SAFc Registry — operated by RMI and the Environmental Defense Fund — surpassed 500,000 metric tonnes of CO₂e abated in February 2026, representing 164,000 metric tonnes of physical SAF tracked across its platform since launch in 2023. That milestone makes book-and-claim the fastest-scaling accounting mechanism in sustainable aviation fuel markets. It also makes the questions surrounding it more urgent than ever: Does the system actually drive new SAF production? Can it survive the feedstock fraud crisis? And will regulators and corporate auditors continue to accept it?

How Book-and-Claim Actually Works

Aviation uses three chain-of-custody models for SAF. Physical segregation keeps certified fuel molecules separated from conventional jet fuel throughout the supply chain — maximum traceability, minimum flexibility. Mass balance tracks sustainable attributes proportionally across a connected system. Book-and-claim goes further: it fully decouples environmental benefits from physical fuel molecules.

The mechanism operates in three stages. First, a SAF producer books certified fuel into a registry, where a lifecycle assessment determines the GHG reduction and a Book & Claim Unit (BCU) or SAF Certificate (SAFc) is issued. Second, that certificate can be bought, sold, and transferred between parties. Third, an end-user — an airline or corporate buyer — purchases and retires the certificate, permanently claiming the environmental benefit. Once retired, a certificate cannot be reused.

The critical feature: no physical SAF needs to move between the producer and the claimant. A corporate buyer in London can retire a certificate for SAF produced at a refinery in Louisiana without that fuel ever touching a European airport. Proponents argue this is identical to how renewable electricity certificates work under Scope 2 of the GHG Protocol. Critics call it “crypto SAF.”

The Registry Ecosystem: RSB, SAFc, OPIS, and the Interoperability Agreement

Three major registries dominate the book-and-claim landscape in 2026. The RSB Book & Claim Registry, operated by the Roundtable on Sustainable Biomaterials, is the longest-established — sustainability-first, global in scope, and the basis for much of the ICAO and EU regulatory architecture. Its Manual v3.0, published in April 2023, sets out additionality tracking and double-counting prevention protocols.

The SAFc Registry, backed by RMI, EDF, and the Sustainable Aviation Buyers Alliance (SABA), launched in 2023 with a focus on corporate buyers and digital auditability. It is the registry behind the 500,000-tonne milestone. The OPIS SAF Certificate Platform, operated by Argus Media, serves a complementary role in price discovery and secondary trading.

Critically, RSB, OPIS, and ReSAF have signed an interoperability agreement to prevent double-counting and enable certificate transfers between systems — a structural step toward a unified, credible ecosystem.

Who’s Using Book-and-Claim — and Why

Microsoft has been the anchor tenant of SAF book-and-claim since 2021, partnering with United Airlines and Air BP in the first RSB-certified pilot programme. That evolved into a 10-year deal with World Energy for SAF certificates and founding-partner status in SkyNRG’s Project Runway book-and-claim platform, launched in 2024.

Dell Technologies illustrates the core use case directly. As Laura Clifford, Dell’s representative, stated: book-and-claim is “useful because SAF is not available to uplift where our aircraft are based.” That is the mechanism’s fundamental value proposition — enabling SAF participation where physical supply does not yet exist.

The most significant demand signal comes from the SABA consortium: 20 corporate customers, four fuel providers, and three airlines collectively purchasing 50 million gallons of SAF certificates, representing approximately 500,000 tonnes of CO₂e reduction. This is not niche experimentation; it is structured corporate procurement at scale.

Book-and-claim is only as credible as its feedstock verification — and right now, verification relies on auditing paperwork, not testing fuel. That is the gap the industry must close before a major fraud scandal closes it for them.

The Three Credibility Threats

1. Additionality Doubt

Does book-and-claim drive new SAF production, or does it monetise fuel that would have been produced anyway? IATA projects just 2.4 million tonnes of SAF in 2026 — 0.8% of global jet fuel — with many plants operating well below capacity. If a producer is already manufacturing SAF to meet a ReFuelEU blending mandate, issuing a book-and-claim certificate for that same fuel does not create additional environmental benefit. The RSB defines additionality as “the capacity of increased demand for SAF unlocked by book & claim to result in increased production,” but enforcing that definition in practice remains an open problem.

2. Feedstock Fraud — The Achilles Heel

Used cooking oil (UCO) accounts for over one-third of European biofuel consumption, and Europe imports more than 95% of its UCO from third countries. The fraud vector is straightforward: virgin palm oil, prohibited under EU sustainability rules, is mislabelled as UCO to command premium feedstock prices. Chemical similarity makes laboratory detection extremely difficult; verification relies overwhelmingly on paperwork audits.

This is not a theoretical risk. The US EPA launched formal audits of biofuel producers’ UCO supply chains in August 2024. A December 2025 Journalismfund Europe investigation documented mislabelling of Malaysian palm oil as UCO in Repsol’s Spanish supply chain. Transport & Environment’s assessment is blunt: “Verification typically relies on auditing paperwork and records along the supply chain, rather than actually testing the biofuel product.”

The implication for book-and-claim is existential. If the feedstock underlying a certificate is fraudulent, the entire emissions reduction claim collapses.

3. Geographic Disconnect

A corporate buyer in San Francisco can claim SAF produced in Singapore and burned at a regional hub, while their own aircraft uses conventional jet fuel. The environmental benefit is real in aggregate — total aviation CO₂ emissions are reduced — but critics argue this resembles the speculative dynamics of early carbon offset markets. The practical risk is reputational: corporates are uncertain whether book-and-claim claims will survive rigorous net-zero audits under evolving SBTi and GHG Protocol guidance.

Physical SAF vs. Book-and-Claim: The Trade-offs

Physical uplift offers direct fuel-to-flight traceability and higher perceived credibility, but is more expensive, constrained by blending infrastructure, and unavailable at most airports globally. Book-and-claim offers global reach, lower cost, and high scalability — but depends entirely on registry integrity and upstream certification quality. Both will coexist; the question is whether the credibility gap between them can be managed.

How CORSIA and ReFuelEU Treat Book-and-Claim

Under ICAO’s CORSIA, book-and-claim is explicitly eligible. SAF must be certified through approved mechanisms — RSB ICAO CORSIA, ISCC CORSIA, or equivalent — and meet lifecycle GHG reduction thresholds of approximately 10%. ICAO’s 60th DGCA meeting in February 2025 included a dedicated session on promoting regional adoption, recognising book-and-claim as a key enabler for SAF in emerging markets.

The European picture is more complicated. ReFuelEU Aviation mandates increasing SAF blending but book-and-claim implementation details remain unresolved — including whether EU book-and-claim SAF must be EU-sourced or globally sourced, and how to prevent regulatory gaming between compliance and voluntary markets.

The Reform Agenda

Feedstock verification is the most urgent priority. The reform argument is that paperwork-based auditing must give way to physical and chemical testing — including isotopic analysis capable of distinguishing virgin from used oils. The ISCC–OMV–Airbus collaboration is one of the most prominent efforts to strengthen verification procedures across registries.

Additionality tiers would differentiate certificates by the degree to which they drive new production. A tiered model might classify Tier 1 as demand-driven production beyond mandates, Tier 2 as demand supporting existing capacity, and Tier 3 as compliance SAF already required by regulation.

Unified global standards are in development. ISO working groups are drafting international book-and-claim specifications, targeting 2026–2027 for finalisation. The CoSAFA initiative, launched in May 2023, has published unified procedures for SAF environmental attribute transactions, including immutable tracking IDs.

GHG accounting alignment remains unfinished. Full recognition under the GHG Protocol and Science Based Targets initiative (SBTi) is essential for corporate confidence, but guidance is still evolving.

Key Takeaways

• Book-and-claim works — but conditionally. The 500,000-tonne SAFc milestone proves the registry infrastructure is functional and corporate demand is real. The mechanism solves a genuine problem: enabling SAF participation in regions without production infrastructure.
• Feedstock fraud is the existential risk. UCO mislabelling is documented, ongoing, and exploits the same paperwork-based verification that book-and-claim registries rely on upstream. One major scandal could collapse market confidence overnight.
• Additionality needs enforcement, not just definition. Without tiered tracking that distinguishes voluntary demand from mandated compliance, book-and-claim risks becoming a premium accounting layer over production that would have happened regardless.
• Reform proposals are appropriate but unimplemented. Isotopic feedstock testing, additionality tiers, ISO standards, and independent governance are all on the table. The gap is between consensus and codification — and the window for proactive reform is narrowing as the market scales.
• Book-and-claim is a transitional mechanism, not an end state. The question is whether it can maintain credibility long enough to serve its bridging function — or whether it becomes aviation’s version of the carbon offset credibility crisis.