Enviromental Ship
Index (ESI)

The standard tool used by the world’s ports to reward and incentivise shipowners meeting and exceeding IMO emissions standards

Established back in 2011 and first introduced by the International Association of Ports and Harbors (IAPH) in 2013, the Environmental Ship Index (ESI) is a voluntary tool which currently includes a formula-based evaluation of vessels’ nitrogen oxide (NOx) and sulphur oxide (SOx) emissions. The calculation also rewards vessels  equipped to use available onshore power and which demonstrate fuel efficiency improvements over time, reducing carbon dioxide (CO2) and particulate matter (PM) emissions.

The ESI vessel register now accounts for over 7,000 oceangoing vessels, with over 50 incentive providers having signed up since its foundation 8 years ago. The Index contains over half of the world’s container vessels, with tankers (gas, chemical and oil) accounting for 28% of the total ships registered.

How the Index works

Through ESI, ports and other interested parties can promote ships to use cleaner engines and fuels and with preferential treatment offered either through discounts on port dues, bonuses or other benefits commensurate with the level of cleanliness. Score ranges from 0 for a ship meeting environmental performance regulations in force to 100 for a ship which emits no SOX and no NOX and reports or monitors data to establish its energy efficiency; in other words a ship with a score of 0 points is actually in conformity with the applicable requirements and the ship with 100 points is amongst the best-performing vessels currently at sea today.

Plans to extend the scope of the ESI

The members of the Environmental Ship Index Working Group have now decided to expand the scope of emissions included in the index due to the significant changes in international legislation. In particular, work will focus on incentivising the reduction in carbon dioxide emissions given the IMO Marine Environment Protection Committee (MEPC) target to cut the shipping sector’s overall CO2 output by 50 percent by 2050.