A comparative view

Sometimes overlooked among the energy efficiency measures devised at IMO, the Energy Efficiency Operational Indicator is a highly significant method for gauging a ship’s total carbon emissions by transport work. This article explores the distinct position EEOI occupies as a measure for ship decarbonisation, in the context of IMO’s Energy Efficiency Design Index, the Energy Efficiency Existing Ship Index (EEXI) and the Carbon Intensity Indicator (CII).

By Andreas Symeonidis,
Marketing & Partner Relations Manager at METIS Cyberspace Technology

Energy Efficiency Operational Indicator (EEOI):
As its name suggests, the EEOI is an operational index created from measuring the ratio of a vessel’s CO2 emissions to work done. EEOI is complementary to the EEDI (Energy Efficiency Design Index), which was developed by IMO to capture a ship’s achievable efficiency based on its design characteristics.

EEOI is derived by applying a CO2 conversion factor to the amount/type of fuel a ship needs to carry a given cargo over a given distance (in tonne miles). For benchmarking purposes, EEOI therefore establishes a ship’s operating efficiency based on transport work as reflected by cargo carried.

Carbon Intensity Indicator (CII):

The EEOI therefore offers a way of benchmarking a ship’s carbon intensity by establishing the relationship between its efficiency and CO2 emissions. However, as its mandatory benchmarking tool for assessing CO2 by work done, IMO preferred the CII (Carbon Intensity Indicator). CII ratings are also derived from fuel consumed and a CO2 conversion factor, but in this case the relevant ratio uses distance travelled and cargo capacity. 

IMO – CII Rating Infographic

Based on ship ratings that extend from A to E and to encourage owners and operators to align with IMO decarbonisation trajectories. the CII’s definition uses the ship’s deadweight as a defining parameter, irrespective of whether the ‘work’ is being done by a laden ship or one in ballast.

Comparison of CII and EEOI:

Where CII reflects CO2 emissions in terms of the transport work a ship does by cargo capacity, EEOI refers to the cargo carried during a given voyage. In detail, while EEOI effectively bases its calculation of work on laden ship moves, the CII uses an Annual Efficiency Ratio (AER) which considers ballast and laden moves. By ignoring factors such as deadweight draft ratios, the CII assumes the vessel performs more work than the EEOI calculation.

Repeated per voyage calculations of the EEOI and the CII provide valuable insights into a vessel’s actual efficiency. METIS offers functionality and KPIs to enable accurate measurement of both CII and the EEOI metrics, including detailed documentation covering the factors that affect these metrics, future trend visualization and quantifying the benefit of corrective actions. METIS helps shipping companies to meet regulatory requirements and contribute to a sustainable future for maritime transportation while retaining the commercial value of their assets.

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