VLSFO is not one CO₂ factor: the bunker delivery note decides
The same 0.50 % sulphur fuel can count as 3.114 or 3.151 tonnes of CO₂ per tonne burned, depending on the grade written on the BDN.
In brief
- Bunker delivery note
- MARPOL Annex VI, regulation 18
- Sulphur limit outside ECAs
- 0.50 % since 1 Jan 2020, regulation 14
- Diesel and gas oil, ISO 8217 DMX to DMB
- 3.206 t CO₂ per tonne of fuel
- Light fuel oil, RMA to RMD
- 3.151 t CO₂ per tonne of fuel
- Heavy fuel oil, RME to RMK
- 3.114 t CO₂ per tonne of fuel
- Where these factors apply
- IMO DCS and the CII; the EU MRV regulation uses the same values
Why the name is not enough
“VLSFO” describes sulphur, not grade. A 0.50 % fuel can be delivered as a light residual grade such as RMD 80 or as a heavy one such as RMG 380. IMO gives each class its own CO₂ factor, and the class follows the ISO 8217 grade on the bunker delivery note.
A worked example
1,000 t as RMG 3801,000 × 3.114 = 3,114 t CO₂
1,000 t as RMD 801,000 × 3.151 = 3,151 t CO₂
Difference37 t CO₂ for the same tonnage of fuel
Across a fleet and a year, that difference reaches the CII and, on EU and EEA voyages, the allowance bill.
Where it goes wrong
A system that applies one factor to everything called VLSFO will be wrong for part of the fleet’s fuel. The fix is to take the factor from each delivery’s grade and carry it with that fuel until it is burned.
What to check
- The ISO 8217 grade on every bunker delivery note since 1 Jan 2026.
- That each bunker delivery keeps its own factor until it is consumed.
- How consumption is assigned when deliveries of different grades share a tank.
Our reading at 8 Oct 2026, for planning. Not legal advice; the authority’s current text decides.
Sources
- MARPOL Annex VI, regulations 14 and 18
- IMO guidelines on the method of calculation of the attained EEDI: CO₂ conversion factors
- Regulation (EU) 2015/757, Annex I