Environmental Ship Index (ESI)
A large number of the world’s key ports have committed themselves to reducing the port-related GHG. This commitment is called the World Port Climate Initiative (WPCI). One aspect of this initiative is to give incentives to ships that visit such ports as a way of reducing port-related emissions.
One of the projects within WPCI is the development of an Environmental Ship Index (ESI). The ESI identifies seagoing ships that perform better in reducing air emissions than the levels required by the IMO MARPOL Annex VI. The ESI evaluates the amount of nitrogen oxide (NOx), sulphur oxide (SOx) that is released by a ship and includes a reporting scheme on the GHG emission of the ship.
The ESI aims to identify cleaner ships in a general way. The index is intended to be used by ports to reward ships when they participate in the scheme for promoting clean shipping. Also, WPCI encourages the shippers and ship owners to use the index as their own promotional instrument. ESI is a voluntary scheme designed to improve the environmental performance of sea going vessels. It can be applied to all types of seagoing ships. It is easy to calculate and simple in its approach.
ESI relies on various formulas for the calculation of various parts for NOx, SOx and CO2. It additionally awards a bonus for the presence of OPS. The ESI Score ranges from zero for a ship that meets the IMO environmental regulations that is already in force and 100 for a ship that emits no SOx and no NOx and reports or monitors its energy efficiency. In other words, a ship with a score of 0 point is actually in full compliance with the applicable regulations while a ship with 100 points has zero air emissions. In reality, the best performing ships currently score at around 40 points (MariEMS 2017).