Carbon Intensity Indicator (CII)

A sailing container vessel seen from above A sailing container vessel as seen from above

The Carbon Intensity Indicator (CII) is a new energy efficiency mechanism introduced by the International Maritime Organization (IMO) to measure and reduce the annual operational carbon emissions of ships.

How does the Carbon Intensity Indicator work?

The CII is an index that compares a ship's operational carbon intensity with its attained energy efficiency based on the design index and existing ship characteristics. This indicator is used to assess the operational efficiency of vessels, enabling comparison between ships of similar size or purpose. It also provides guidance for regulators when developing new regulations related to reducing operational carbon intensity. The CII helps track progress towards improving energy efficiency, encouraging vessel owners and operators to meet applicable targets while still meeting their operational needs. This indicator allows stakeholders in the maritime industry to understand how their operations are contributing to greenhouse gas emissions, informing them of how they can improve their existing fleet or design future vessels for improved energy efficiency.

Emissions reduction goal setting

The Carbon Intensity Indicator is a comprehensive rating scheme that measures ships operational carbon intensity, allowing them to set reduction goals. Through using the CII rating system, stakeholders can easily compare their vessels' performance and gauge how their vessels can become more efficient. The annual reduction factor of the CII rating provides a specific rating level based on its cargo and passengers, with a higher number indicating greater efficiency. This rating system helps ship owners decide which design elements have the greatest potential for reducing emissions and which should be improved for maximum efficiency.

How is carbon intensity calculated?

The Carbon Intensity Indicator is used as a measure of operational carbon intensity or the amount of CO2 emitted per nautical mile travelled by a vessel. It takes into account the vessel’s gross tonnage, and passengers/cargo carried and uses EEXI measurements to rate its performance. The CII rating ranges from zero to ten, with zero being the best rating and ten being the worst. A higher CII rating indicates inferior performance levels in terms of emissions and operational efficiency. Major conversions, such as engine upgrades, can greatly reduce a ship's CII rating by lowering emissions per gram of fuel burned during operation. A low CII rating indicates that the ship is operating at an optimal level in terms of emissions output relative to its size and capacity for passengers/cargo. Vessel owners should strive for improved efficiency through major conversion projects when necessary or feasible to achieve their desired performance goals while reducing their environmental impact.