Replenishment oilers, fleet tankers, sealift ships. Exempt from IMO regulation (Article 3.3 of MARPOL) but most navies now track CO₂ per steaming day as an internal metric - NATO Green Defence Framework.
Formula
$$ \text{CO}2^\text{year} = \sum_j F_j \cdot C{f,j} $$
$$ \text{Intensity} = \frac{\text{CO}2^\text{year}}{d\text{steam}} $$
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) |
| $Bench (Steaming days / year)$ | operational benchmark | d | operations log |
| $d_\text{op}$ | Operating days | d | operations log |
NATO Green Defence tracks fleet fuel-intensity but does not enforce MARPOL carbon. USN’s Great Green Fleet demonstrated 50 % biofuel underway; RFA and others trial GTL and HVO.
Sources
- NATO - Green Defence Framework.
- IMO MEPC.364(79) - Cf conversion factors.