They signal a concrete climate impact. Overstatement creates a credibility problem.
Overly direct formulations such as delivered emission-free when the underlying logic is more limited.
First the methodology, then the scope of the statement, then the limitations.
Precise language protects trust and avoids later corrections.
Emission avoidance claims are based on a comparison: the actual greenhouse gas output of an activity is set against a hypothetical reference scenario. The difference is reported as “avoided emissions”. The devil lies in the details of the reference scenario.
In shipping, the most common method is the well-to-wake comparison. When a vessel bunkers e-methanol instead of conventional VLSFO, the greenhouse gas emissions of both fuels are compared across the entire life cycle — from production through transport to combustion on board. Only when all stages are included is the comparison complete.
The difficulty begins with the system boundary. If only tank-to-wake is considered, the emission reduction from methanol appears smaller, since methanol does release CO2 during combustion — the advantage lies primarily in production from renewable sources (well-to-tank). Communicating only part of the chain distorts the picture.
Further methodological pitfalls include allocation in multi-output processes (when a production process yields additional products alongside the fuel), temporal attribution (when was the green electricity for electrolysis generated?) and the question of additionality (would the emission reduction have occurred without the specific measure?). Each of these questions can materially alter the stated avoidance value.
Most avoidance claims reach the end customer through sustainability reports, Scope 3 surveys or customer-specific emission statements. In the process, they pass through several hands: the fuel producer provides the base values, the carrier aggregates them per voyage or per TEU, and the customer integrates them into their own climate balance.
At each step, information is lost or simplified. A carrier communicating “30 % less CO2 per TEU” must clarify: 30 % less than what? Than the fleet average of the previous year? Than the average industry emission? Than a specific reference fuel? Without this specification, the figure is valueless — or worse: misleading.
For customer communication, a standardised data sheet per shipment or period is advisable, containing the following elements: fuel type and source, calculation method (well-to-wake or tank-to-wake), reference scenario, absolute and specific emission values and the certification scheme. Carriers who establish this standard early create trust and substantially reduce later clarification effort.
Several recent cases demonstrate how quickly imprecise claims escalate. NGOs such as Transport & Environment have repeatedly criticised carriers whose sustainability communications created the impression that certain routes were “emission-free”, even though the underlying methodology was based on accounting attribution or book-and-claim.
The lesson is clear: the regulatory environment — particularly the EU Green Claims Directive, which obliges companies to substantiate environmental claims scientifically — will further narrow the scope for vague formulations. Operators who invest today in clean methodology and transparent communication are better prepared for future requirements than those relying on imprecise language.
A robust claim follows four principles. First: methodology first — before any figure is cited, the calculation basis must be disclosed. Second: define the system boundary clearly — well-to-wake, tank-to-wake or another delineation, stated explicitly.
Third: name the reference scenario — what is the comparison against? Fourth: communicate limitations honestly — what the claim does not cover is as important as what it states. An operator who consistently applies these four principles builds a communication foundation that withstands critical scrutiny.
Many avoidance claims leave the building without anyone outside the marketing or sustainability team having tested the underlying numbers. A workable sign-off process assigns at least three checkpoints. First, the technical or fuel team confirms the calculation method and the source of the base data — was the well-to-wake figure supplied by the fuel producer, a certification scheme, or an internal estimate? Second, legal or compliance reviews the wording against the applicable claims rules, checking that comparative statements name their reference point and that absolute figures are distinguished from specific ones. Third, a senior sign-off — someone not involved in drafting the claim — reads it as an outsider would, asking whether an average customer could reconstruct the calculation from the published text alone.
Where a claim will appear in a sustainability report, an annual filing or investor communication, this three-step review should be documented, not just performed informally. A short record of who approved which wording, and on what basis, becomes valuable if a claim is later challenged by a customer, a journalist or a regulator. Companies that skip this step tend to discover the gap only once a claim is already public and difficult to withdraw without reputational cost.
A claim becomes considerably harder to challenge once it rests on documentation that a third party can check independently. This means keeping the calculation itself — not only the final percentage — on file: the fuel batch data, the reference scenario chosen, and the assumptions behind allocation and temporal attribution. Where a certification scheme is involved, the underlying certificate and chain-of-custody documentation should be retrievable for the period the claim covers, not only at the time it was made.
Independent verification, where a classification society, an auditor or a certification body reviews the calculation against its underlying data, adds a further layer of credibility. It does not eliminate methodological choices — someone still has to decide on the system boundary — but it confirms that the stated numbers follow from the declared method rather than from a more favourable alternative calculation quietly substituted afterwards. Operators who build this audit trail as a matter of routine, rather than reconstructing it under pressure after a challenge, find that responding to customer or NGO scrutiny becomes a matter of retrieving a file rather than defending a decision made months earlier.