Background, objectives and basic definitions
The EEOI guidelines can be used to establish a consistent approach for the voluntary use of an EEOI, which will assist ship-owners, ship operators and parties concerned in the evaluation of the performance of their fleet with regard to CO2 emissions. As the amount of CO2 emitted from a ship is directly related to its actual fuel consumption, the EEOI can also provide useful information on a ship’s performance with regard to its operational fuel efficiency. The objective of the IMO guidelines is to provide the users with assistance in the process of establishing a mechanism to achieve the limitation or reduction of GHG emissions from ships in operation (MariEMS 2017).
To help with consistent estimation of EEOI, the following definitions are provided in the EEOI guidelines:
Fuel consumption: Fuel consumption is defined as all fuels consumed at sea and in port or for a voyage or period in question (e.g., a day), by main, auxiliary engines, boilers and incinerators.
Distance sailed: Distance sailed means the actual distance sailed in nautical miles (deck log-book data) for the voyage or period in question.
Ship and cargo types: The EEOI guidelines are applicable for all ships performing transport work. The types of cargo are generic and include but not limited to: all gas, liquid and solid bulk cargo, general cargo, containerized cargo, heavy lifts, frozen and chilled goods, timber and forest products, cargo carried on freight vehicles, cars and freight vehicles on Ro-Ro, ferries and passengers (for passenger and Ro-Pax passenger ships).
Cargo mass carried or work done: In general, cargo mass carried or work done is expressed as follows:
- For dry cargo carriers, liquid tankers, gas tankers, ro-ro cargo ships and general cargo ships, metric tonnes (t) of the cargo carried should be used;
- For containerships carrying solely containers, number of containers (TEU) or metric tons (t) of the total mass of cargo and containers should be used;
- For ships carrying a combination of containers and other cargoes, a TEU mass of 10 t could be applied for loaded TEUs and 2 t for empty TEUs; and
- For passenger ships, including Ro-Pax passenger ships, number of passengers or gross tonnage of the ship should be used;
It should be generally noted that for specific cases, the choice of cargo definition should fit the purpose of energy management and may vary from one company to the other (MariEMS 2017).