Published: 21 December 2021

Members are reminded that new International Maritime Organisation (IMO) legislation under MARPOL Annex VI is due to become applicable in just one year, with the new regulations requiring various measures and preparations to be undertaken in advance.

As part of the IMO’s drive to cut greenhouse gases from shipping, on  17 June 2021 the IMO agreed new legislation under MARPOL Annex VI as a near term measure to reduce carbon dioxide (CO2) emissions from vessels. The first target being a reduction of greenhouse gases from shipping by 40% by 2030, compared to 2008 levels, and a 70% reduction by 2050.

The new regulations enter into force on 1 November 2022 and the requirements will require compliance from 1 January 2023.

Two new measures are being introduced covering almost all existing vessels that have to comply with MARPOL Annex VI, addressing technical and operational issues in relation to emissions.


The requirement to have an Energy Efficiency Existing Ship Index (EEXI) applies to all vessels over 400GT subject to MARPOL Annex VI, with a few exceptions, such as drilling rigs, non-powered vessels and some icebreakers.

A vessel’s EEXI will need to be determined by calculation and compared to a mandatory required limit for that vessel type. If the attained EEXI is above the required EEXI, then measures will be required to ensure compliance.

A vessel’s emissions per ton and mile are calculated based on main engine power, fuel consumption of the main engine and generators and a conversion factor to CO2 mass, divided by the transport work of the vessel, which is dependent on a vessel’s deadweight and speed in relation to the power of the main engine. EEXI is dependent on vessel design, rather than on any variable operational matters.

The calculation of the required versus attained EEXI is contained in a technical file which needs to be approved by either the flag state or a Recognised Organisation and thereafter is carried on the vessel.

After the regulations enter into force on 1 January 2023, at the first survey for the International Air Pollution Prevention Certificate, whether the survey is an annual, intermediate or renewal survey, the attained EEXI shall be independently verified by the vessel’s flag state, or a Recognised Organisation, and a new International Energy Efficiency Certificate issued.


The Carbon Intensity Indicator (CII) is a measure of how efficiently a vessel transports cargo or passengers. It is measured in grams of CO2 emitted per the vessel’s deadweight and nautical mile.

An enhanced Shipboard Energy Efficiency Management Plan will need to be developed, including a plan for achieving a compliant CII, and approved by the vessel’s flag state or a Recognised Organisation.

The CII is applicable to vessels of 5,000 GT and above, with a few exceptions as noted above. Vessels will be required to annually determine their Operational Carbon Intensity Indicator (CII) from fuel oil data collection system information. The CII will then need to be documented and checked against the required annual CII and the vessel will be given a descending rating of A to E. A vessel rated D for three consecutive years, or any vessel rated E, would have to submit a corrective action plan detailing how they will achieve a rating of C or above. The rating will be recorded in the vessel’s Ship Energy Efficiency Management Plan. Ports and flag states are encouraged to provide incentives to those vessels achieving the highest ratings.

The level of each CO2 limit (A to E) will incrementally decrease until 2030, becoming ever more stringent, encouraging shipowners to find new ways to comply, and most probably hastening the scrapping of older more inefficient tonnage.


There are numerous options which can be considered in order to reduce a vessel’s CO2 emissions, including the following:

  • Reducing operating speed when on passage.
  • Overridable main engine power reduction / limitation. Override of the main engine limiter is only permitted for securing the safety of the vessel, for example if there is heavy weather on a lee shore or for the saving of life at sea, and any such non-compliance has to be noted in the onboard management manual. It is anticipated that this will be the most popular measure employed, as it is relatively easily achieved.
  • Engine optimisation, for example, the removal of one turbocharger, where two are fitted.
  • Installation of energy efficient devices, such as an enhanced propeller, wake equalising ducts, an air bubble lubrication system and propeller boss cap fins.
  • Alternative additional propulsion technology, such as from wind powered Flettner rotors.
  • Use of alternative low or zero carbon fuels, for example bio–LNG, ammonia and hydrogen, which will become more viable as technology improves and the availability of such fuels increases.
  • Installation of a shaft generator.

Members requiring any further guidance are advised to contact the loss prevention department.