The Maritime Emissions Compliance Stack: How CII, FuelEU and EU ETS Fit Together

Three regimes, one tonne of fuel

A decade ago a fleet's emissions obligation was a single annual report. Today the same tonne of fuel, burned on the same voyage, is measured by three separate regimes, each with its own methodology, its own geographic boundary and its own deadline. CII rates the vessel's operational carbon intensity. FuelEU Maritime prices the greenhouse-gas intensity of the energy used on board. EU ETS puts a price on the CO2 itself. None of them was designed to line up with the others.

The consequence is not that compliance is harder. It is that compliance is no longer one task. An operator now reconciles three numbers drawn from the same source data but answering to different rules, and a decision that improves one can leave another untouched. Slow steaming helps the CII rating and cuts the ETS bill, but it does nothing for FuelEU intensity if the fuel itself has not changed.

CII: a rating that travels with the vessel

The Carbon Intensity Indicator is an IMO measure under MARPOL Annex VI. It divides a vessel's annual CO2 emissions by its transport work and assigns a rating from A to E against a reference line that tightens every year to 2030. A D or E rating is not a fine. It is a commercial signal a charterer can read, and it follows the vessel into the next negotiation.

The criticism is worth stating plainly: the metric rewards deadweight-distance, so a vessel that sails further in ballast can rate better than one doing more useful work. Operators manage the methodology they have, not the one they would have designed.

FuelEU Maritime: intensity, not tonnage

FuelEU Maritime, Regulation (EU) 2023/1805, in force from January 2025, prices the well-to-wake greenhouse-gas intensity of the energy a ship uses, against a 2020 baseline that steps down on a fixed schedule. It is fuel-led, not distance-led. That moves the decision off the bunker manager's desk and onto the voyage plan and the charter party. Pooling, banking and borrowing can move the penalty around, but the benefit sits at the vessel and contract level, not the fleet level where operators instinctively look.

EU ETS: a price on the carbon

EU ETS extended to shipping in January 2024, under Directive (EU) 2023/959, phasing in to full surrender by 2026. For voyages between EEA ports it covers all emissions; for voyages into or out of the EEA, half. The shipping company surrenders allowances for the prior year, and where the charter party is silent on who carries that cost, it lands by default rather than by agreement.

The boundaries and calendars do not match

This is where the stack bites. CII runs on the full calendar year of global operations. FuelEU applies well-to-wake intensity to the EU scope. EU ETS prices CO2 on the EU scope with a phase-in. The clocks differ too: the MRV emissions report falls due on 31 March, EU ETS allowances are surrendered in September, and CII ratings settle early in the year. An operator managing all three is reconciling different scopes against different deadlines, from data captured the same way for each.

It all rests on the noon report

The one thing the three regimes share is their input. Every rating, intensity figure and allowance calculation traces back to the same noon-report and sensor data. When that data is rounded, inconsistent or unvalidated, the error propagates into all three, and it surfaces months later when a verifier or a charterer questions a number nobody can reconstruct. Underneath three regimes sits one problem, and it is a data-quality problem.

What it means for the operator

The job is no longer to comply with a rule. It is to see the three numbers early enough to act on them, on data clean enough to defend. That is a forecasting and data-discipline problem before it is a software one. The regimes will keep tightening to 2030 and beyond. The fleets that manage them well are the ones that already treat the noon report as the evidence document it has quietly become.