SBTi CNZS V2.0, EU ETS Reforms and the New Playbook for SAF Certificates

Sustainable aviation fuel certificates (SAFc) are emerging as an important voluntary-market tool for addressing aviation-related Scope 3 emissions from business travel and freight in a measurable, auditable manner. The Science Based Targets Initiative’s (SBTi) Corporate Net-Zero Standard Version 2.0 (CNZS V2.0), the European Union’s Emissions Trading System (EU ETS), and the ReFuelEU Aviation framework show that voluntary and compliance markets are aligning on sustainable aviation fuel (SAF) and its importance for decarbonizing aviation.

This environment creates both challenges and opportunities for companies. Mandates, data quality standards, and assurance requirements for aviation-related emissions are becoming more stringent. At the same time, SBTi CNZS V2.0 explicitly recognizes market-based mechanisms such as SAFc, including book-and-claim chain-of-custody models, as valid tools for achieving targets in hard-to-abate sectors when physical decarbonization is limited.

This article highlights the importance of SAFc, summarizes recent updates in SBTi CNZS V2.0 and EU ETS proposals for SAF, addresses buyer concerns about claims, supply, and cost, and provides a practical guidance lens for developing credible SAFc strategies.

Why SAFc is coming into focus now

Aviation is among the most difficult sectors to decarbonize, with limited short‑term options beyond efficiency gains. Policymakers and standard setters are increasingly converging on SAF as the primary near‑ to medium‑term lever for reducing commercial aviation life-cycle emissions.

The EU’s ReFuelEU Aviation Regulation requires minimum blends of SAF in fuel supplied at EU airports, starting at 2% in 2025 and increasing to 70% by 2050, with a separate mandate for synthetic fuels. The UK has introduced a similar mandate, while several other jurisdictions globally are exploring their own blending obligations or incentive programs.

In parallel, SBTi CNZS V2.0 introduces an implementation hierarchy that permits the use of energy attribute and commodity certificates, including book-and-claim instruments, to meet Scope 3 targets within defined integrity guardrails. In aviation, unbundled SAF certificates may be used to address emissions in relevant Scope 3 categories, such as business travel and upstream fuel use, where direct physical decarbonization is constrained.

SAFc builds on the goal of compliance programs by supporting further SAF production while being increasingly supported by maturing voluntary standards. For companies working toward aviation-related Scope 3 targets, it is one of the few options that links real, trackable action in the fuel system with an accounting framework recognized by standard setters.

Current SAFc considerations within SBTi CNZS V2.0

Recognition of market instruments and book‑and‑claim

The CNZS V2.0 standard broadens the toolkit available for implementing science‑based targets by formally recognizing market instruments, such as energy attribute certificates (EACs) and commodity certificates, as part of an implementation hierarchy. These instruments may rely on different chain‑of‑custody models, including mass balance and book‑and‑claim, provided they meet a set of guardrails relating to integrity, traceability and impact.

In this framework, SAF certificates are treated as decoupled environmental attributes representing the reduced emissions associated with SAF consumption (as opposed to jet fuel), which can be applied by airlines and corporate buyers to relevant Scope 3 emissions. SBTi clarifies that such instruments are eligible within certain levels of the implementation hierarchy, particularly at the activity‑pool level where emissions sit in shared systems like aviation fuel pools, if they:

• Accurately and conservatively represent the underlying activity and its life‑cycle emissions (representativeness);
• Match the volume and type of activity in the inventory (volume matching);
• Are issued, transferred and retired through secure tracking systems that prevent double counting; and
• Demonstrate a credible system‑level impact, meaning that demand for certificates contributes to increased supply of the low‑carbon commodity.

These conditions are directly relevant to SAFc program design and registry infrastructure, and they shape how buyers should evaluate different SAFc offerings.

Timelines and transition window

CNZS V2.0 is moving from conceptual recognition of market instruments toward concrete implementation rules and timelines. The final standard was approved in June 2026 and becomes effective on 1 February 2027, with new target submissions required to align with V2.0 from 1 February 2028 onward.

The window is now open for SAFc buyers. Procurement decisions can be aligned with the new hierarchy and integrity criteria as the new standard becomes mandatory. Adopters of market-based instruments can use this period to test SAFc procurement and claims, establish internal governance, and gather evidence that their market instruments drive real system-level impact.

Chain‑of‑custody, attributional accounting and claim types

CNZS V2.0 requires market instruments for target implementation to use attributional accounting instead of only consequential, baseline-comparison methods. For SAFc, certificates must include a verified life-cycle emission factor, most commonly gCO2e per megajoule, rather than only stating “tonnes of CO2 avoided” compared to a fossil baseline.

The standard sets higher requirements for data quality, chain-of-custody integrity, and registry design. Certificates must be issued, transferred, and retired in transparent systems, such as registries, that prevent double counting and support legitimate co-claiming across value chains. Buyers should note that not all existing SAFc schemes will qualify automatically; due diligence is required to confirm compliance with CNZS V2.0 integrity standards.

Within this structure, SBTi differentiates between actions that directly contribute to Scope 3 reduction targets, such as SAFc used in aviation, and other market instruments like carbon credits, which are subject to separate recognition and neutralization rules. Companies should position SAFc carefully within their climate performance portfolios as the standard moves toward instrument-to-action matching, for example, using SAFc to address aviation emission footprints.

What changed under the EU Commission’s EU ETS proposal for aviation and SAF?

SAF support broadened across the EEA and extended in time

Alongside ReFuelEU Aviation and existing ETS mechanisms, the European Commission’s 2026 proposal for EU ETS revisions significantly scales up support for SAF within the regulated market. The proposal increases the dedicated SAF support pot from the existing 20 million allowances to a total of 110 million additional allowances, extending support through to 2040.

Under the proposal, SAF support would no longer be limited to fuel uplifted at specific airports. Instead, eligible SAF uplifted anywhere in the European Economic Area could qualify for support, with the benefit distributed proportionally across an airline’s covered ETS emissions. This effectively introduces an ETS‑aligned “book‑and‑claim” style approach, where SAF taken on at one airport contributes to an airline’s overall ETS compliance position across its network.

The proposal extends SAF support past 2030, with allowances available through the end of 2040.

Price differential, fuel types and technology scope

The revised ETS proposal refines how the price differential between SAF and fossil kerosene is used to calculate the allowance incentive. The support levels would vary by fuel type, with higher coverage of the price gap for advanced biofuels and renewable fuels of non‑biological origin (RFNBOs) than for other eligible non‑fossil fuels. Some analyses indicate that advanced biofuels could receive around 50% of the remaining price gap, RFNBOs and green hydrogen around 60%, and the catch‑all category around 30%, with certain categories phasing out after 2029.

The proposal extends support beyond drop‑in liquid fuels to include flights performed with electric and hybrid‑electric aircraft, reflecting the growing role of alternative propulsion technologies in aviation decarbonization.

Since 2021, Vertis Environmental Finance Limited (Vertis) has been part of the STX group. Primarily focused on the compliance markets, Vertis’ Aviation Team supports aircraft operators with their compliance obligations, including accounting for SAF across the ETS, CORSIA and ReFuelEU Aviation frameworks. The team can be contacted here: aviation@vertis.com

Turning Scope 3 aviation challenges into opportunities

Addressing buyer concerns: claims, supply and cost

Historically, many companies have been reluctant to engage with SAF because of three main concerns: uncertainty regarding credible environmental claims, limited availability and the relatively high cost compared to conventional jet fuel.

These concerns are understandable given the market’s ongoing growth, limited supply, and evolving accounting rules. Physical SAF now makes up only a small share of global jet fuel, about 0.6% of total use according to recent studies, even though it is growing each year. The price gap between SAF and fossil kerosene is still large, often two to three times higher, even with government support.

Additionally, many buyers have waited for greater clarity from SBTi and the GHG Protocol on how market‑based mechanisms, including SAFc and other energy attribute certificates, can be used within Scope 3 inventories and target implementation, and for guidance on claims and disclosure. The publication of CNZS V2.0 and ongoing Scope 3 revisions at GHG Protocol provide clearer direction, even as some details are still being refined.

How to Build a Corporate Strategy for SAFc Procurement

With so many moving pieces in flight, hesitation is understandable. However, continuing to wait carries its own risks. As mandates tighten and stakeholders scrutinize aviation‑related emissions more closely, companies that delay engagement with SAFc and other market‑based mechanisms may find themselves constrained later by higher prices, more limited supply options and compressed timelines.

With more than 20 years of experience in voluntary and compliance markets, STX recommends that buyers take a more disciplined, action-oriented approach:

• Clarify their aviation‑related Scope 3 baseline, covering business travel, upstream fuel use and relevant logistics categories.
• Map the structural constraints that limit direct abatement at the activity level (for example, lack of SAF at specific hubs, limited control over airline fuel procurement) and document these to satisfy CNZS V2.0’s requirement to prioritize direct actions where feasible.
• Develop a procurement and claims strategy that integrates SAFc within broader Scope 3 and net‑zero roadmaps, ensuring alignment with both SBTi and evolving GHG Protocol guidance.

The experts at STX can help buyers clear the path to action by translating the standards into practical procurement decisions, structuring contracts that align with both compliance and voluntary expectations and building the documentation and governance needed for credible, auditable claims.

Why voluntary market solutions still matter

Voluntary markets as a bridge and demand signal

Despite the growth of SAF mandates, voluntary market solutions remain critical for scaling SAF in the near term. Mandates such as ReFuelEU create a baseline of demand, but they are not yet sufficient to unlock the full investment needed to decarbonize aviation, particularly given the long lead times and capital intensity of SAF projects.

Voluntary procurement of climate performance assets, such as EACs for electricity and SAFc for aviation, can create additional demand signals beyond minimum compliance, supporting early deployment, learning curves and the scale‑up of production capacity. Historically, voluntary purchases of EACs helped catalyze renewable electricity markets by giving developers revenue certainty and demonstrating corporate appetite for low‑carbon power, even before comprehensive renewable portfolio standards were in place.

SAFc plays a similar role in aviation. By purchasing certificates linked to verified SAF production, corporates can channel finance into SAF projects and signal durable demand, encouraging project developers and airlines to invest in new capacity and supply agreements. This is particularly important in an environment where mandates are still ramping up and where some jurisdictions rely more on incentives than on blending obligations.

Few credible alternatives for aviation Scope 3

For many corporates, aviation‑related Scope 3 emissions from inter‑regional business travel and air freight are difficult to address through traditional levers alone. Options such as reducing travel, switching travel modes or engaging suppliers are important but often insufficient to fully align with science-based trajectories, especially for organizations with global operations and high travel intensity.

Buyers seeking practical and auditable Scope 3 solutions for aviation have limited alternatives that meet both feasibility and integrity thresholds. SAFc is one of the only voluntary‑market instruments that can be:

• Directly linked to verified fuel production;
• Integrated with airlines’ decarbonization strategies;
• Aligned with emerging accounting and reporting standards; and
• Supported by robust chain‑of‑custody and registry infrastructure.

For inter‑regional Scope 3 emissions, voluntary markets are often the only mechanisms that enable buyers to go beyond the baseline of regulatory mandates, especially when their flights span multiple jurisdictions with various policy regimes.