Measured Exhaust Data Alongside Fuel-Based Estimates: What Method D Means for Shipping’s Carbon Reporting

Jan Mattsson, chairman of Everimpact, argues in a Splash247 opinion piece (17 September 2026) that shipping should complement calculated emissions with direct, continuous measurement at the source. Everimpact sells onboard emissions measurement systems. He says estimates remain necessary for standardised accounting but are no longer sufficient for effective management. In his view, carbon now affects operating costs, vessel performance, customer relationships, investment decisions and access to finance.

Most maritime emissions are determined from fuel consumption using prescribed emission factors. Under the EU MRV Regulation, Method A uses bunker delivery notes and periodic tank stocktakes. Method B uses tank readings taken daily at sea and at every bunkering. Method C uses fuel-flow meters and can provide consumption data in real time. All three, Mattsson notes, calculate emissions from fuel use rather than measuring what leaves the exhaust after combustion.

Direct measurement is designated Method D, one of the four permitted monitoring methods. It works by multiplying exhaust gas concentration by exhaust flow. The company must state the device calibration and uncertainty in its monitoring plan, which is assessed by an accredited verifier. Under the EU Emissions Trading System, shipping companies must surrender allowances for each tonne of verified emissions within scope.

That scope matters for this readership. The EU MRV and the ETS for shipping apply to ships of 5,000 GT and above that carry passengers or cargo for commercial purposes. Most yachts fall below that threshold.

Mattsson says that where fuel-based assumptions produce a figure higher than actual post-combustion emissions, verified direct measurement could reduce the allowances required. He adds that sensors can link exhaust readings to speed, load, route, weather, currents and engine settings. That data could help operators assess slow steaming, route optimisation, engine tuning, hull and propeller condition, and fuel quality.

He also proposes a measured baseline before any intervention, followed by comparable data afterwards, to test whether an investment delivered the expected reduction. He stresses that calculation methodologies will remain necessary, and that direct measurement should be seen as complementary rather than a wholesale replacement.

A claim to test, not accept

The argument rests on a real distinction. Calculated figures inherit the assumptions behind fuel records, fuel characteristics and the emission factor chosen, while a measured figure observes the exhaust. That difference matters most where carbon carries a direct cost.

The possible allowance saving deserves caution. Mattsson says verified measurement could lower the allowances required only where assumptions overstate actual emissions. The reverse case is not addressed, and a measured figure could equally confirm or exceed the estimate. Operators should treat any saving as a hypothesis to test within their monitoring plan, not as a budget line.

The commentary comes from the chairman of a company that sells measurement equipment, so the commercial interest should be kept in view. The regulatory basis, however, can be checked independently: Method D already exists within the EU framework, with verification attached.

There is also a limit the argument does not address. An exhaust sensor reads the carbon dioxide leaving the stack and cannot tell biogenic carbon from fossil carbon. The regulation’s default factor for HVO is 3.115 g CO2 per gram of fuel, against 3.206 for marine gasoil. Under the ETS, the biomass fraction of a fuel meeting EU sustainability criteria carries a zero CO2 emission factor. The benefit of a renewable fuel is established through certification, not at the funnel.

Decisions it could inform

For technical managers, the most practical value may be in capital allocation. A measured baseline and a comparable post-intervention dataset could give owners firmer evidence when weighing engine modifications, hull coatings, propeller work or wind assistance. That evidence would help a captain or manager defend spending to owners, financiers and charterers, because it rests on performance on the vessel’s own routes rather than on manufacturer projections alone.

For charter operators, the same data may strengthen customer reporting and sustainability-linked finance discussions. Mattsson’s point that credibility lies in showing how a number was produced is the right test for any ESG claim. An auditable chain from sensor to verified report would be harder to challenge than an aggregated estimate.

What may follow

Adoption will probably depend on whether the cost of installation, monitoring-plan work and verification is outweighed by the operational and carbon-cost benefits. The regulation already allows methods to be combined once a verifier has assessed the combination, and it requires companies using more than one method to compare the results. It will be worth watching how large the gap proves where fleets run measured and calculated figures in parallel. If the gaps are material, scrutiny of fuel-based assumptions may grow. If they are small, the case would rest mainly on operational insight rather than allowance savings.