Energy Efficiency Operational Indicator (EEOI) introduction

EEOI is one element of the IMO regulatory framework that is intended to act as an “energy efficiency performance indicator” during the operational phase of the ship and be used to monitor overall ship energy efficiency performance. The purpose of EEOI, according to IMO guidelines, is to establish a consistent approach for measuring a ship’s energy efficiency for each voyage or over a certain period of time. The EEOI is expected to assist ship-owners and ship operators in the evaluation of the operational performance of their fleet.

EEOI, similar to EEDI, represents the amount of CO2 emissions from a ship per unit of cargo-mile transport service (with a unit of gCO2 /tonne.mile). However as against the EEDI that is defined for one operating point of a ship, EEOI represents the actual CO2 emission from combustion of all types of fuels on board a ship during each voyage, which is calculated by multiplying total fuel consumption for each type of fuel (distillate fuel, refined fuel or LNG, etc.) with the respective emission factor of each fuel. The performed transport work is calculated by multiplying the actual mass of cargo and the corresponding actual distance in nautical mile travelled by the vessel. At this stage, IMO has developed the EEOI to encourage ship-owners and ship operators to use it on a voluntary basis and to collect information on the outcome and experiences in applying it (MariEMS 2017).