Greenhouse gas emissions reduction

International Maritime Organization (IMO) regulations for greenhouse gas (GHG) emissions reductions from shipping have been adopted as amendments to Annex VI of MARPOL, as shown in the table here.

IMO has also agreed to continue to further develop new requirements which will aim for the total decarbonisation of the shipping activity. The planned next steps and possible years for adoption are shown in the table here.

Amendments effective 1 January 2023

1. EEXI

In simple terms, EEXI is a “design” requirement to mandate slow steaming for all existing ships. The reference for slow steaming is equivalent with the EEDI requirement in 2022, for some ships EEDI Phase 2 for others EEDI Phase 3, as shown here.

The formula (click on formula above to expand the view) for EEXI utilises the same factors and coefficients as those of EEDI.

Compliance is ensured by engine / shaft power limitation (EPL & ShaPoLi) which means, for mechanical controlled engines, a physical mechanical stopper limiting the fuel index. It can be adjusted if full engine power is required but secured/locked by a unique wire seal with a part number and IMO number. The wire seal can only be installed when the OPL stopper is secured in the correct position, as shown here (Source: https://www.man-es.com/docs/default-source/document-sync/man-opl-eexi-overridable-power-limitation-mc-eng.pdf)

For electronically controlled engines, the fuel index is limited by software and access to full power will be possible through a password. Ships need to report each time engine power usage is in excess of what is limited by the EEXI regulation. The mode of compliance and control is documented in the EEXI Technical File.

The compliance is required at the first planned survey (annual, intermediary or special) on and after 1 January 2023. Compliance will be certified by the International Energy Efficiency Certificate.

The three IMO Guidelines, for the calculation of the attained EEXI, application of power limitation and for the survey and certification of compliance, can be viewed below:

• Resolution MEPC.350(78)
• Resolution MEPC.335(76)
• Resolution MEPC.351(78)

2. CII

The CII is aimed at measuring the operational efficiency of ships and, providing a rating of efficiency comparing ships of the same type as defined in the IMO Data Collection System. The efficiency is measured by calculating the total annual amount of CO₂ emissions divided by the ship’s maximum (summer draught) DWT and divided by the total annual distance of voyages of the ship. This formula is known as the Annual Emission Rating (AER). The annual attained AER value is compared with the required CII/AER value. The required CII/AER values for each ship type are decreasing by a number of percentages every year. So far, IMO has agreed to the degree of reduction of the required CII/AER values between 2023 and 2026.

Since ships of same type could have different attained annual CII/AER values because of the operational and environmental conditions, the CII regulation provides a rating system, as shown here. The rating is below and above the required value with plus/minus borders and the results will be as follows:

• ships with annual CII/AER values within categories A - D are compliant with the requirement;
• however, if a ship is rated category D three consecutive years, it needs to present a Plan of Corrective Actions explaining how it will improve efficiency at least to category C;
• when a ship is rated category E, it will also need to present a Plan of Corrective Actions according to which it is aiming to improve efficiency to category C.

Below are the four IMO Guidelines defining the CII, the required values, the CII rating and the boundaries for the rating categories:

• Resolution MEPC.352(78)
• Resolution MEPC.353(78)
• Resolution MEPC.338(76)
• Resolution MEPC.354(78)

IMO has also recognised that the same ships engaged in different types of operations would have a significant variation in the annual attained CII/AER value. For example, a Shuttle Tanker with Dynamic Propulsion system will have an operational profile totally different from the operational profile of tankers of the same DWT engaged only in regular trade/voyages. Similarly, if tankers are also engaged on ship-to-ship (STS) operations, there would be a negative impact on the annual attained CII/AER value. There are also differences between regular oil product tankers and parcel chemical tankers of similar DWT as the IMO DCS makes no distinction between a chemical tanker and an oil tanker. Comparable differences apply to other ship types as well.

Consequently, IMO has approved a number of correction factors which in principle apply to adjust the total fuel consumption for the calculation of the annual attained CII/AER value. These are given in the fifth IMO Guideline for the application of the CII regulation, below:

• Resolution MEPC.355(78)

Since all these references were based statistically using data that has not been through a thorough quality control process and since this is a totally new approach, IMO has decided to include a review clause into the rules for both the EEXI and, particularly, CII application. The review should be conducted before 1 January 2026 (planned to be completed by Spring 2025) and:

• consider adequacy of all CII Guidelines;
• consider degree of annual CII reduction factors for 2027-2030;
• consider strengthened corrective actions if appropriate;
• check the need for enhancement of the enforcement mechanism.

Click here to view the INTERTANKO guidance on Carbon Intensity Indicator (CII) Calculators