Environmental Ship Index (ESI)
D6. Decarbonization, emissions and alternative fuelsDefinition
Voluntary index used by ports to reward cleaner ships.
The Environmental Ship Index is a voluntary scheme run through the World Ports Climate Action Program that scores a ship on how far its NOx and SOx emissions and CO2 reporting beat the IMO baseline, with bonus points for onshore-power capability. Participating ports give discounted dues to high-scoring ships, rewarding cleaner vessels with lower port costs. It is one of several port-incentive tools, alongside the CleanShipping Index and class environmental notations, that push the existing fleet beyond minimum compliance.