A fragmented registry landscape, unresolved ESG reporting questions, and a persistent gap between intent and integrity – can the voluntary SAF market build the trust it needs to scale?
This is the second article in a three-part series. You can view the first article here: Beyond regulation: navigating the global voluntary market for SAF
The voluntary Sustainable Aviation Fuel (SAF) market is, at its core, a market built on trust. When a corporate buyer purchases a SAF credit, they are not receiving a bucket of fuel with their business trip, they are receiving a promise: that a specific volume of lower-carbon fuel was produced and delivered, that its emissions savings are real and verified, and that no one else has claimed those same savings. In a market that operates largely on paper or digitally, the integrity of that promise is everything.
That promise is currently under strain. Accounting standards for SAF vary across jurisdictions and registries. The sustainability criteria applied to qualifying fuels sometimes differ between platforms (from very strict, to bare minimum). Definitions of ‘additionality’ (i.e., the assurance that a voluntary purchase delivers a benefit beyond what would have occurred anyway) remain contested. Double-counting risks persist in a registry landscape that remains stubbornly siloed. And, critically, the formal ESG[1] reporting frameworks that corporate buyers depend on – the GHG Protocol and the Science Based Targets initiative (SBTi) Corporate Net-Zero Standard – have yet to fully embrace voluntary SAF credits as legitimate instruments for Scope 3[2] emissions reductions. For many potential buyers, this ambiguity has been a dealbreaker: without recognition from these frameworks, their SAF credits would only have the reporting value of an expensive carbon offset.
The good news is that this picture is slowly changing. Recent updates from SBTi appear to signal a meaningful shift, explicitly allowing the use of Environmental Attribute Certificates (EACs) for Scope 3 targets, provided they adhere to rigorous integrity principles, and only as a transitional solution. If this direction holds, it would represent a significant moment for the voluntary SAF market. But GHG Protocol acceptance remains outstanding, and the broader question of whether the market’s accounting infrastructure is robust enough to support these frameworks has not yet been answered. To understand why, it is worth tracing how we got here.
From Spreadsheets to Standards: The Evolution of SAF Accounting
Looking back just five or six years, voluntary SAF accounting was essentially borrowed clothing. The frameworks governing early transactions were adapted from bulk biofuel trading conventions (HVO, renewable diesel) and steered by sustainability and supply chain professionals from that same traditional biofuel world. Producers led; airlines followed. For most carriers, SAF was still a peripheral topic with thin internal expertise and limited strategic priority, leaving the producers who understood the mechanics largely free to set the terms.
This did not mean the market was entirely without structure. Pioneers including SkyNRG, KLM, Roundtable on Sustainable Biomaterials (RSB), and World Energy were already pushing for the first ‘book-and-claim’ transactions for corporate clients, recognizing early on that physical co-mingling of SAF with conventional jet fuel made traceability impractical at scale. Book-and-claim, a chain of custody model in which the environmental attributes of SAF are separated from the physical fuel and traded independently as certificates, was broadly recognized as the only viable mechanism for scaling voluntary demand. Yet major players including Neste and Shell initially showed resistance. Both preferred the physical traceability of the ‘mass balance’ model[3], which they viewed as more defensible under GHG Protocol and SBTi guidelines. The tension between these two approaches pragmatic-scale versus traceable-integrity, would continue to define the market for years to come.
Early voluntary transactions, involving corporate buyers such as Microsoft, Boston Consulting Group, and Coldplay, were instrumental in providing the market with its initial commercial traction. But each SAF supplier basically operated its own bespoke product definition and audit protocol. There were no common guidelines for additionality, unit sizing, sustainability verification, or third-party assurance.
The Constitutional Convention: WEF Clean Skies for Tomorrow
This pioneering theoretical groundwork around SAF credits and the first wave of transactions eventually found a broader home in the World Economic Forum’s Clean Skies for Tomorrow (WEF CST) workstream on SAF credits. This initiative functioned as the industry’s constitutional convention, bringing together competitors, regulators, and first mover clients to define the fundamental DNA of a SAF credit. The rationale was straightforward: standardization allows buyers to purchase with confidence, while rigorous accounting prevents low-quality claims from endangering the market’s credibility.
The WEF CST framework established consensus-based definitions for SAF credit unit sizing (one metric ton of neat SAF), lifecycle GHG accounting methodologies, and integrity principles designed to ensure that SAF certificates represent real, verifiable climate benefits while preventing double-counting. It was, by any measure, a significant achievement of cross-industry cooperation.
Yet the framework also made a consequential compromise. While explicitly disqualifying mandated volumes, such as those produced under EU blending mandates or CORSIA, from SAF credit issuance, it adopted a permissive stance toward market-based incentives such as the U.S. Renewable Fuel Standard (RFS) or North American state, provincial, or federal low-carbon fuel (LCF) programs. The WEF CST guidance allows producers to monetize these compliance credits on top of SAF credit sales to voluntary buyers.
Critics argue that this “stacking” arrangement lacks a rigorous defense against double-claiming. And that’s a fair question. Under the WEF CST framework, a producer can sell an LCFS credit to a compliance buyer, helping that party offset its own regulated emissions obligations, while simultaneously selling a SAF credit to a voluntary corporate buyer claiming additional atmospheric benefit. The result risks being a zero-sum transaction: the voluntary investment may simply be subsidizing a volume that was already delivering value within a compliance system, with no net gain in atmospheric benefit. This vulnerability in standard SAF accounting practices remains one of the most significant unresolved integrity questions in the voluntary market.
A Proliferation of SAF programs and SAF registries
Parallel to the WEF CST standardization effort, a wave of SAF registries and programs emerged, each attempting to operationalize the book-and-claim process in slightly different ways. The Sustainable Aviation Buyers Alliance (SABA), a partnership between EDF, RMI, and major corporations, developed a collective procurement model for SAF credits. RMI collaborated with the Energy Web Foundation to build the SAFc registry, an independent, non-profit, blockchain-based platform designed to create, trade, and retire SAF attributes while enforcing sustainability standards and preventing double counting. In parallel, RSB operated its own established book-and-claim registry, offering similar functionality with a longer track record.
Meanwhile, industry giants pursued their own paths. Shell launched the Avelia registry, a blockchain-based platform designed to track SAF attributes within a physical supply chain framework – though exclusively for Shell-traded volumes. Neste, together with ISCC,[4] pursued a stricter interpretation of mass balance and additionality – one that excluded LCF and RFS credits from the accounting framework. This led to the development of the ISCC Credit Transfer System, which functions as both a registry and an accounting standard.
In the business aviation sector, 4AIR’s Assure registry established itself as the go-to platform for that market segment. 123Carbon offers an ambitious, sophisticated, multi-modal blockchain-based system extending beyond aviation to include marine and road fuels. Commercial platforms such as CHOOOSE and SQUAKE have built strong transactional experiences for airlines and travel management companies, excelling at inventory management and user experience, though often providing less public transparency on their underlying accounting methodologies. IATA developed its own registry – the Civil Aviation Decarbonization Organization, or CADO system – engineered through the lens of the airline operator.
What this adds up to is a crowded and fragmented landscape. The key registries – RSB, RMI, ISCC, IATA, Avelia, and others – each apply distinct accounting guidelines and rarely interoperate. Some maintain public retirement or redemption tables that allow external verification of claims; others remain opaque about the final status of a retired credit. Most were engineered for a specific primary user group: the IATA registry is built around the needs of airline operators while ISCC, RMI, and RSB place heavier emphasis on corporate Scope 3 reporting. By optimizing for one constituency, each platform tends to underserve the others.
The practical consequences are tangible. Airlines, producers, traders, and corporate buyers are effectively forced to maintain subscriptions across multiple registries, multiplying costs and increasing manual overhead. While blockchain-based solutions prevent double-claiming and -spending within one platform, the risk of a single SAF volume being claimed across more than one platform is still technically persistent.
Toward Interoperability: Slow Progress on a Necessary Path
The need for further alignment – whether through enhanced standardization, interoperability, or eventual registry consolidation – is widely acknowledged. Progress, however, remains slow. Groups such as the Book & Claim Interoperability Working Group have yet to produce significant breakthroughs. A recent announcement from IATA, 123Carbon, and Assure suggests movement toward interoperability, but the technical scope remains vague, and these three players do not represent the largest registries by SAF transaction volume.
Potential structural solutions would include a meta-registry database – a neutral layer that aggregates issuance and retirement data across platforms – or a ‘clearing house’ model in which registries perform double-blinded cross-checks before validating a credit. Fully functional interoperability would also allow credits to be transferred between registries to enable market players to consolidate their entire credit inventory into a single platform of their choosing, materially reducing the administrative and auditing burden.
The SAF market is not the first voluntary environmental market to navigate this fragmentation and process of evolution towards common standards and practices. Renewable Energy Certificates (RECs), basically book-and-claim for renewable electricity, went through a similar registry proliferation phase before regulatory pressure and corporate buyer demands gradually forced consolidation and eventual GHG Protocol recognition. The voluntary carbon market took a bumpier road: weak verification practices and inconsistent standards ultimately produced a public credibility crisis when investigative reporting exposed inflated and double-counted claims, requiring the creation of independent oversight bodies to restore market confidence. Both trajectories hold a clear lesson for SAF: fragmentation can be resolved, but it may take time, external pressure, and collaborative effort. What should be prevented at all costs is a credibility crisis that would hurt the reputation of the SAF industry as a whole.
An End-to-End SAF Accounting and Inventory Management Vision
Looking beyond the voluntary SAF credit market to further examine the regulatory market, there is a broader operational need that the registry debate often obscures: comprehensive SAF inventory management. Airlines and producers need to digitally trace every volume of fuel from feedstock collection to production facility to aircraft wing-tip. This is not merely a voluntary market aspiration; it is a regulatory necessity, as frameworks such as RefuelEU, CORSIA, RFS, LCFS, and the EU Emissions Trading System impose their own reporting requirements on SAF volumes.
Several platforms are positioning themselves to fill this operational gap. Avelia, CHOOOSE, and 4AIR’s Assure have built inventory management capabilities alongside their registry functions. Fuel management software providers like Skymetrix (with 123Carbon) are adding SAF tracking and automated regulatory reporting as extensions to systems airlines already operate, and many aspire to eventually interact and integrate directly with the EU Union Database for biofuels.
The industry’s endpoint would be a fully integrated digital tracking system that covers both regulatory and voluntary SAF across all chain-of-custody models, eliminating the reliance on error-prone spreadsheets and fragmented paper trails. That endpoint would benefit every participant in the value chain and would, crucially, provide the level of watertight credibility that the ultimate beneficiaries of the resulting emission reduction, airlines, freight forwarders, business and private customers require.
Conclusion
The structural progress of the past five years in voluntary SAF accounting is real. The WEF CST framework provided a common vocabulary. Multiple registries have introduced transparency where spreadsheets once prevailed. SBTi appears to be moving in a direction that will give voluntary SAF credits a legitimate reporting role. But gaps remain between registries, accounting standards, and what the market claims versus what ESG frameworks will formally recognize.
For now, buyers and sellers alike should approach the voluntary SAF market with clear eyes: understanding not just what a SAF credit claims to deliver, but which registry issued it, under which accounting standard, with what additionality definition, and against what sustainability criteria. In a market where the “truth” is still being negotiated, those details are the difference between a credible investment and an expensive gesture.
Up Next in the Series
In Part 3, we will move from the technicalities of SAF accounting to a raw reality check of the voluntary market. We’ll examine why Scope 3 claims are proving so difficult to sell, how airlines and SAF producers are navigating the mismatch between producer “push” and buyer “pull,” and how a new generation of intermediaries is helping corporate customers find their footing while the final verdict from SBTi and the GHG Protocol remains pending.
About the Author
Hugo Boiten is the Managing Director of SAF Planet and a Senior Associate at Stillwater.
SAF Planet is a specialized platform and intermediary dedicated to navigating the complexities of the voluntary Sustainable Aviation Fuel (SAF) market. By bridging the gap between fuel producers, airlines, and corporate SAF buyers, SAF Planet provides custom and tailored solutions to its clients and partners. With a focus on credibility, deep market insight, and rigorous adherence to SAF accounting standards, Hugo and his team help organizations reach their emission reduction and SAF use targets.
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