Ports may differentiate their port dues on the basis of environmental criteria. In Sweden, for example, 20-25 of the bigger ports have differentiated their port dues based on the sulphur content of the fuel used and NOx emissions from the onboard engines. In addition to the port dues, Swedish fairway dues are also differentiated on the basis of NOx and SOx emission levels.
Environmental Ship Index
As part of its promotion of sustainable shipping, IAPH has developed the Environmental Ship Index (ESI). Ships fuelled by LNG generally achieve a high ESI score. Around the world, over 50 ports typically provide 5-10% discounts on harbour dues or another financial incentive, contributing to a positive business case for operators. Over 2,300 ships have been registered to qualify for port discounts and/or incentives.