Recognised exclusions let operators deduct fuel+distance for voyages that burn fuel without corresponding commercial work.
Formula
$$ I_\text{attained}^\text{adj} = \frac{\text{CO}_2^\text{total} - \text{CO}_2^\text{excl}}{(\text{Distance}^\text{total} - \text{Distance}^\text{excl}) \cdot \text{Capacity}} $$
Symbol legend
| Symbol | Meaning | Unit | Source |
|---|---|---|---|
| $I_\text{attained}^\text{adj}$ | Adjusted Attained CII | g CO₂ / (dwt·nm) | result |
| $\text{CO}_2^\text{total}$ | Raw total CO₂ for the year | t | DCS |
| $\text{CO}_2^\text{excl}$ | CO₂ emitted during excluded voyages | t | voyage log |
| $\text{Distance}^\text{total}$ | Raw distance | nm | DCS |
| $\text{Distance}^\text{excl}$ | Distance excluded | nm | voyage log |
| $Capacity$ | DWT or GT per ship type | - | MEPC.337(76) |
Exclusion categories
- Ice navigation - logbook + ice chart.
- Search-and-rescue (SAR) - coast-guard confirmation.
- Safety / CSR-avoidance distance.
- STS ship-to-ship transfers.
- Cargo heating (product tankers).
- Shuttle-tanker DP at FPSO.
Sources
- IMO MEPC.355(78) - 2022 voyage adjustments guidelines.