The Carbon Intensity Indicator (CII) measures a ship’s energy efficiency in grams of CO₂ per cargo-carrying capacity and nautical mile, forming a key part of IMO’s decarbonization strategy. From 2024, vessels are assigned annual ratings from A to E based on verified operational performance, with thresholds tightening towards 2030. Normec Verifavia provides accredited CII verification, ensuring accuracy, compliance, and credibility in line with IMO requirements.
Resolution MEPC.328(76) adopted at MEPC 76 in June 2021, entered into force on 1 November 2022 and introduced amendments to MARPOL Annex VI with new requirements for:
CII is the operational carbon intensity Indicator expressed in grams of CO₂ per deadweight-nautical mile and it is a measure of vessel efficiency of CO₂ emitted in transporting cargo or passengers. The CII and CII rating scheme will apply to all Cargo and Cruise ships of 5000 gross tonnage and above, that is, the ships that are already subject to the requirements of the IMO Data Collection System (IMO DCS).
The annual operational CII achieved or attained CII will be required to be documented and verified against the required annual operational CII. This will enable the Flag state to determine the operational CII rating, the rating will be given on a scale from A to E, A being the better-performing vessels.
What does it mean for ship operators?
It has been mandatory for Ships to collect and report additional fuel oil consumption data in a calendar year.
The additional data includes:
This data is then verified by an approved Verifier; they will additionally have to calculate the attained CII of each ship. Based on the attained and required CII, a CII rating will be given to a ship.
The required CII is calculated using 2019 as a baseline and a reduction factor will be applied every year from 2019 onwards, this means the ship will have to continuously perform better each year to stay compliant or to maintain a preferred rating. Assuming a ship is rated as C in the year 2021 and not able to sustain the rating, the rating will decrease if the operator does not continuously improve the operational performance of their ships.
Required CII rating is calculated using the CII reference lines for each ship type and a reduction factor is applied every year.
Administrations, port authorities, and other stakeholders, as appropriate will be encouraged to provide incentives to better-rated ships. For ships operating continuously for three years at Level “D” or for one year at Level “E”, an improvement plan will have to be submitted and implemented, which outlines improvement to the vessel’s efficiency to a moderate level rating “C” or above.
The methodology for calculation of CII also includes voyage and fuel corrections for some ship types to compensate for the adverse conditions, cargo operations, and nature of trade. These corrections shall be monitored as per the MEPC guidelines.
MEPC.355(78) 2022 Interim guidelines on correction factors and voyage adjustments for CII calculations (CII guidelines, G5).
Shipping companies submit their IMO DCS fuel oil consumption reports along with the achieved Carbon Intensity Indicator (CII) value to Normec Verifavia.
Normec Verifavia verifies the accuracy of submitted data, including fuel oil consumption, distance travelled, and CII value. The CII rating is confirmed based on this verified data.
After successful verification, Normec Verifavia submits a formal recommendation to the relevant flag state authority.
Based on the recommendation and verified CII rating, the flag state issues the official Statement of Compliance.
For ships operating continuously for three years at Level “D” or for one year at level “E”, a Corrective action plan will have to be included in SEEMP III and implemented, which outlines improvement to the vessel’s efficiency to a moderate level rating “C” or above. The ship should apply for SEEMP III approval before they can get the SOC for above cases.
The Carbon Intensity Indicator (CII) is determined through distinct methods. Two examples of such CIIs, utilizing different metrics, are the Annual Efficiency Ratio (AER) and capacity gross ton distance (cgDist). AER, measured as emissions per deadweight-ton mile, is applied for cargo weight, while cgDist, calculated as emissions per gross ton-mile, is utilized for cargo types emphasizing volume
The first annual CII rating will be assigned in 2024, based on verified data from the 2023 calendar year.
In case of transfer of the ship from one company to another (irrespective of change in Administration), the former company should get the partial data (for the operated period) verified by the relevant Administration or any organization duly authorized by it and transfer the verified data with the supporting documents to the receiving company within one month after the date of transfer.
BoG used as fuel comes from both heel and cargo. Nitrogen mass must be subtracted from LNG consumption since it does not generate CO₂, using CTMS certificates or real-time gas chromatograph data. Supporting certificates/reports must be submitted for verification of annual fuel use and CII.
The amendments to the 2021 Guidelines on the Operational Carbon Intensity Reduction Factors (CII Reduction Factors Guidelines, G3), adopted through IMO Resolution MEPC.400(83), set the required annual reduction factors relative to the 2019 reference line as follows:
| Year | Reduction Factor relative to 2019 |
|---|---|
| 2023 | 5% |
| 2024 | 7% |
| 2025 | 9% |
| 2026 | 11% |
| 2027 | 13.625% |
| 2028 | 16.250% |
| 2029 | 18.875% |
| 2030 | 21.500% |
