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Environmental Ship Index (ESI)

Voluntary NOx, SOx, CO₂ and OPS performance index used by 50+ ports worldwide to award port-fee rebates. Score 0–100; most ports offer rebates above 30 and premium rebates above 50.

PortIndexESI

Engine NOx performance

ME NOx reduction below Tier II baseline%100 = Tier III (80 % under Tier II).AE NOx reduction below Tier II baseline%

Fuel sulphur

Actual sulphur content used% m/mBelow 0.10 (ECA) drives most SOx score.

CO₂ + OPS

CO₂ bonus (EEDI over-performance)pointsComputed as 100 × fraction below Required EEDI; capped 20.Shore power capability

NOx subscore

15.7/50

SOx subscore

24.0/30

CO₂ subscore

5.0/20

OPS bonus

0points

ESI total

44.8/100

Standard rebate band

Formula, assumptions, and limits

$$\text{ESI} = 0.35 \cdot \text{NO}_x^\text{avg} + 30 \cdot (1 - s/0.5) + \text{EEDI bonus} + \text{OPS bonus}$$

World Ports Climate Initiative formula; full weighting has been revised twice since 2011. Scores are certified quarterly by the operator; ports check the ESI website for each call.

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