Harbour tugs and escort tugs - short, high-power bursts at berthing, long idle periods on station. Outside CII scope; per-job or per-operating-hour intensity.
Formula
$$ \text{CO}_2^\text{year} = \sum_j F_j \cdot C_{f,j} $$$$ \\text{Intensity} = \\frac{\\text{CO}_2 \\cdot 1000}{N_\\text{jobs}} $$Symbol legend
| Symbol | Meaning | Unit | Source |
|---|---|---|---|
| $F_j$ | Mass of fuel $j$ | t | bunker log |
| $C_{f,j}$ | CO₂ factor | t CO₂ / t fuel | MEPC.364(79) |
| $Bench (Jobs / year)$ | operational benchmark | – | operations log |
| $d_\text{op}$ | Operating days | d | operations log |
Battery-electric tugs (Damen Sea Axe-E, Svitzer Elektra) now live-operate in Rotterdam, Singapore and Oslo. Per-job emissions drop to the grid-side only - 0 at berth for purely electric.
Sources
- ITS - International Tug & Salvage sustainability.
- IMO MEPC.364(79) - Cf conversion factors.