Book and claim for sustainable aviation fuel is an accounting system that separates the fuel’s environmental benefit from the physical fuel itself, so a buyer anywhere in the world can purchase and retire a certificate for the carbon reduction even if the fuel is burned at an airport thousands of miles away. A producer injects SAF into a shared airport fuel supply, the quantified greenhouse gas savings are issued as a digital certificate on a registry, and a buyer purchases that certificate, claims the reduction against its own emissions, and retires it permanently so no one else can use the same tonne. The model exists because shipping specialized fuel to every airport is neither practical nor affordable, and it works only when the registry, documentation, and reporting framework all line up.
How the System Actually Works
The core idea is to treat the molecules and the environmental benefit as two separate products. A SAF producer blends fuel into a shared airport fuel system, where it gets burned by whatever aircraft happens to refuel there. At the same time, the quantified carbon reduction from that fuel batch is registered as a digital unit on a dedicated registry. One Book and Claim Unit, or BCU, currently equals one tonne of certified SAF.1Roundtable on Sustainable Biomaterials. RSB Book and Claim Registry Rulebook
The certificate then moves electronically from the producer’s registry account to a buyer’s account. That buyer might be an airline claiming a Scope 1 reduction or a corporation offsetting its business travel under Scope 3. The final step is retirement: the buyer permanently cancels the certificate, removing it from circulation so the same tonne of SAF cannot be claimed twice.1Roundtable on Sustainable Biomaterials. RSB Book and Claim Registry Rulebook
One rule sits underneath everything: environmental attributes cannot be created in a registry until after proof of delivery of the blended SAF into a common fuel infrastructure, or direct proof of combustion. You cannot generate certificates for fuel that has not actually been produced and delivered.2International Air Transport Association. IATA Sustainable Aviation Fuel SAF Accounting and Reporting Methodology
The Roundtable on Sustainable Biomaterials operates the most established book and claim registry for SAF, though other systems including the CADO SAF Registry also exist.
How It Differs From Mass Balance
Book and claim is not the only chain-of-custody model for SAF, and the difference matters because regulators treat the two differently. Under mass balance, sustainable and conventional feedstocks are physically mixed and the environmental attributes are allocated proportionally: if 30 percent of the input was certified sustainable, 30 percent of the output earns certification. The attributes stay attached to the physical product as it moves through the supply chain.3Alternative Fuels Data Center. Sustainable Aviation Fuel
Under book and claim, that connection is severed entirely. The environmental attributes become standalone certificates sold to any buyer, regardless of whether that buyer ever touches the physical fuel. The tradeoff is geographic flexibility on one side and heightened scrutiny on the other. Fully decoupling attributes from molecules makes verification harder, which is why registry design and third-party certification carry so much weight in this model.
What Documentation Stands Behind a Valid Certificate
Before a certificate can be issued, the fuel behind it needs a solid paper trail. The foundational document is the Proof of Sustainability, which the fuel producer or an authorized blender generates for each batch. It identifies the feedstock, such as used cooking oil, animal fats, or municipal solid waste.4Roundtable on Sustainable Biomaterials. RSB Sustainability Certification
The Proof of Sustainability must also include lifecycle greenhouse gas emission values, measured in grams of CO2 equivalent per megajoule. Those values capture the full carbon footprint of the fuel, from feedstock cultivation or collection through processing and delivery, and they determine the certificate’s value because the emissions reduction is calculated against a fossil fuel baseline of roughly 90 grams of CO2 equivalent per megajoule.4Roundtable on Sustainable Biomaterials. RSB Sustainability Certification
Volume records matter just as much. The amount of physical fuel injected into the supply chain is verified through meter readings, shipping manifests, or blending documentation, and the registry will not issue more certificates than the verified volume supports. Verification also confirms that the feedstock does not compete with food crops or contribute to deforestation, and that the fuel meets minimum carbon reduction thresholds. Under most certification schemes this means at least a 50 percent reduction compared to fossil jet fuel, with some frameworks requiring 60 percent or more for fuels produced after certain dates.4Roundtable on Sustainable Biomaterials. RSB Sustainability Certification
The fuel itself also has to meet ASTM D7566, the technical standard for aviation turbine fuel containing synthesized hydrocarbons.5ASTM International. ASTM D7566-24 – Standard Specification for Aviation Turbine Fuel Containing Synthesized Hydrocarbons Without both the documentation and the technical qualification, no legitimate registry will issue a certificate, and any downstream carbon reduction claim is auditably hollow.
Who Can Claim What: Scope 1 and Scope 3
One of the most misunderstood aspects of SAF book and claim is who gets to claim what. A single batch of SAF can legitimately generate both a Scope 1 claim for the airline that burned the fuel and a Scope 3 claim for a corporate customer whose employees flew on that airline. This is not double counting. The airline reduces its direct combustion emissions under Scope 1, while the corporate customer reduces the indirect emissions in its value chain under Scope 3.6International Air Transport Association. SAF Accounting Based on Robust Chain-of-Custody Approaches
In a typical transaction, BCUs are transferred to the airline or transport operator, which claims the Scope 1 reduction. The operator can then assign the corresponding Scope 3 attribute to a specific corporate customer. Both attributes should be linked to the same batch of fuel in the registry, creating a transparent chain from production to final claim.2International Air Transport Association. IATA Sustainable Aviation Fuel SAF Accounting and Reporting Methodology
This dual-scope structure is what makes SAF certificates attractive to corporations with net-zero commitments. Business travel often represents a large share of corporate Scope 3 emissions, and buying SAF certificates is one of the few available levers for reducing it.
How Registries Prevent Double Counting
Double counting is the central integrity risk in any certificate-based system. IATA’s framework identifies three distinct ways it can happen. Double claiming occurs when the same batch’s emission reduction is counted more than once under the same scope. Double issuance occurs when more than one certificate is generated from the same physical batch across different registries. Double usage occurs when the same certificate is retired in two different registries.6International Air Transport Association. SAF Accounting Based on Robust Chain-of-Custody Approaches
Registries counter these risks in several ways. Each batch of fuel receives a unique identification number that can be tracked across systems. Interoperability between registries allows cross-checking so the same batch cannot generate certificates in more than one place. And retirement is designed to be permanent and irreversible: once a certificate is cancelled, it cannot be reinstated or transferred. A master registry, or a network of interoperating registries, is considered essential to making this work at global scale.6International Air Transport Association. SAF Accounting Based on Robust Chain-of-Custody Approaches
Independent third-party audits reinforce these safeguards. Auditors review physical fuel records alongside digital registry entries to verify that the volume of certificates issued does not exceed the volume of fuel actually produced and delivered. Discrepancies can disqualify the certificates.
Which Regulators Accept Book and Claim
Several overlapping regulatory frameworks shape how book and claim operates, and they do not all treat the model the same way. Before buying certificates, you need to know which framework governs the obligation you are trying to satisfy.
CORSIA
The Carbon Offsetting and Reduction Scheme for International Aviation is ICAO’s global framework for managing aviation emissions. It recognizes SAF as a compliance tool but does not fully embrace pure book and claim. Sustainability attributes are not entirely decoupled from the fuel; they remain linked to purchasing and blending records. ICAO’s Committee on Aviation Environmental Protection continues studying different SAF accounting methodologies and their compatibility with CORSIA, so the rules here are still evolving. CORSIA requires a minimum 10 percent lifecycle greenhouse gas reduction compared to conventional jet fuel, with fuel compliance certified by approved Sustainability Certification Schemes.7ICAO. CORSIA Sustainability Criteria
ReFuelEU Aviation
The European Union takes a stricter approach. For compliance purposes, SAF claimed under ReFuelEU must be physically supplied to the European market. Book and claim is only permitted for fuels actually delivered to European airports, meaning a company cannot purchase certificates for SAF blended at a facility in Asia and use them to satisfy EU mandates. Non-compliance penalties for fuel suppliers must be at least twice the price difference between the alternative fuel and conventional jet fuel, multiplied by the shortfall volume. Using 2024 reference prices, that works out to roughly €2,700 per tonne for biofuels and €14,000 per tonne for synthetic e-kerosene.
The Corporate Reporting Trap
This is where many companies get tripped up. The two most influential corporate emissions reporting standards do not currently endorse book and claim for Scope 3 accounting, and ignoring that gap creates real audit risk.
The Greenhouse Gas Protocol, the most widely used framework for corporate carbon accounting, does not include market-based approaches like book and claim for calculating Scope 1 or Scope 3 emissions. Its current Corporate Standard and Scope 3 Standard have no mechanism for it. The GHG Protocol has surveyed stakeholders about expanding market-based accounting to Scope 3, and SAF was a frequently cited use case, but as of 2026 the standards have not been updated to allow it.8Greenhouse Gas Protocol. Market-based Accounting Approaches Survey Draft Summary Report
The Science Based Targets initiative has similarly signaled that chain-of-custody models should flow down the value chain rather than across it, which constrains how BCUs can be applied. A company purchasing BCUs may be able to reference them in a voluntary sustainability report or a press release but may not be able to use them to reduce its reported Scope 3 number under GHG Protocol-aligned frameworks.
This gap between what the SAF industry is building and what corporate reporting standards currently accept is the single biggest practical risk for buyers. Before committing significant capital to SAF certificates, verify whether the reporting framework your company uses will actually recognize the claim. IATA recommends a purchase-based emissions calculation for SAF regardless of chain-of-custody model and encourages airlines to reference registry excerpts in their sustainability reports.2International Air Transport Association. IATA Sustainable Aviation Fuel SAF Accounting and Reporting Methodology That recommendation does not override the GHG Protocol’s current rules.
Enforcement Exposure
Making a SAF-based carbon reduction claim that cannot withstand scrutiny is not just an embarrassment. Regulatory enforcement around environmental marketing has tightened, and SAF claims are not exempt.
In the United States, the Federal Trade Commission’s Green Guides set the baseline for what counts as a deceptive environmental claim. State attorneys general have brought actions under state consumer protection and deceptive advertising statutes against companies whose climate claims did not match their practices. The FTC, SEC, and DOJ have increased scrutiny of carbon credit-related claims. No landmark SAF-specific enforcement action has set a clear precedent yet, but the legal infrastructure to challenge misleading book and claim assertions already exists.
In the EU, ReFuelEU Aviation’s penalty structure is explicit: fuel suppliers who fall short of mandated SAF blending volumes face fines calibrated at a minimum of twice the cost differential between the alternative fuel and conventional jet fuel, multiplied by the shortfall.
The most common way companies expose themselves is by claiming SAF-based reductions under a reporting standard that does not accept book and claim. Reporting a lower Scope 3 number in a GHG Protocol-aligned disclosure based solely on retired BCUs is the kind of discrepancy that auditors and regulators notice. The safer approach is to disclose SAF certificate purchases separately from the formal emissions inventory, making clear what framework the claim relies on and what the certificates represent.
How U.S. Tax Policy Shapes Certificate Pricing
Tax credits flow to the fuel producer, not the certificate buyer, but they shape the price you pay for a BCU. The original SAF-specific blender’s tax credit under Section 40B of the Internal Revenue Code offered a base credit of $1.25 per gallon for fuel achieving at least a 50 percent lifecycle greenhouse gas reduction, plus an additional $0.01 per gallon for each percentage point beyond 50 percent, up to a maximum of $1.75 per gallon. That credit expired on December 31, 2024.9Alternative Fuels Data Center. Sustainable Aviation Fuel SAF Tax Credit
The Section 45Z Clean Fuel Production Credit was designed as the successor, covering a broader range of clean fuels including SAF. The One, Big, Beautiful Bill enacted in 2025 eliminated the special increased credit rate for sustainable aviation fuel produced after December 31, 2025. SAF producers can still qualify for the general Section 45Z credit, but the enhanced SAF-specific amount no longer applies. The credit depends on emissions rate tables published annually by the Treasury Department, and producers must obtain certification from a qualified certifier attesting to production volumes and lifecycle emissions.10Federal Register. Section 45Z Clean Fuel Production Credit A smaller tax incentive means higher production costs, which means pricier certificates for corporate buyers.