As of 1 July 2017, the Environmental Ship Index (ESI) will also start evaluating performance in the field of CO2. To date, only the environmental performance of ships on emissions of air pollution (NOx and SOx) were assessed. This makes the index the first sustainable quality mark in international shipping that includes the performance and, more particularly, the reduction in CO2 in its assessment.

Port of Rotterdam: Environmental Ship Index will also evaluate CO2 performance, the first one with a quality mark in shipping

The index does this based on historical data already included in the index. The ESI compares the fuel consumption and the nautical miles travelled in the past three years (e.g. 2013, 2014, 2015) to that of the following year (2016). If relatively less fuel has been consumed - in other words, if sailing was more efficient - then less CO2 has been emitted. ESI has chosen for this method because it is actually very difficult to measure CO2 emissions.

Environmental Ship Index

The ESI is a score that is issued at the request of ship owners as of 1 January 2011. Ships that score high on the Environmental Ship Index receive a premium from the participating ports and other organisations that reward sustainable shipping. As of 1 April 2017, the index comprised 5497 ships and 50 bonus providers.

ESI Discount

In the port of Rotterdam, sustainable seagoing vessels are rewarded. Vessels that score high on the Environmental Ship Index (ESI) receive a discount on seaport dues already paid. The ESI is an international benchmark for emissions from seagoing vessels. Vessels that perform better than the legal norm will be rewarded a 10% discount on the gross tonnage part of the port dues. Since 01-01-2015, the discount is doubled when vessels also have low NOx emissions. Low NOx emissions are achieved by using LNG as fuel or large catalysts. The discount for clean vessels is in line with the policy of the Port of Rotterdam Authority on sustainable port development.


At the end of each quarter the Port of Rotterdam Authority will determine which vessels are eligible for the ESI discount. Applicable condition: at the actual time of arrival (ATA) in Rotterdam the vessel must have an ESI score of 31 points or more.

The discount applies to each call in the quarter concerned, with a maximum of 20 calls per single ship per quarter. The discount will be doubled if the ship also has an individual ESI-NOx score of 31.0 or more. When the ESI score is adjusted by the International Association of Ports and Harbours (IAPH) to below 31.0 points, or the ship is granted the status ‘inactive’, all paid out ESI discounts need to be repaid within four weeks upon first request.

For questions about the calculation of the ESI score, please contact the ESI Office of the International Association of Ports and Harbours.

Automatic confirmation

The agency of the relevant vessels will automatically receive a confirmation after each quarter. Applying for the ESI discount to the Port of Rotterdam Authority is not required. The discount will be remitted to the relevant agency. The IAPH always keeps an up-to-date list of vessels that qualify for the ESI discount.

Source: Port of Rotterdam