IMO Annex VI Regulations and ESI Baselines

Nitrogen oxides

MARPOL Annex VI limits the NOX emissions of future marine engines. The figure below depicts the emission limits for current and future Tiers. The limit value depends on the rated engine speed above 130 rpm.

Figure: IMO Annex VI NOX Limit Value (g/kWh)

As from 1 January 2011 new engines are required to comply with Tier II values for NOX; however, for the purpose of calculating the ESI NOX score the ESI Working Group has decided to maintain the Tier I levels as a baseline for the next few years.

n < 130 130 ≤ n < 2 000 ≥ 2 000 RPM
Limit Value 17 45*n^-0.2 9.8 g/kWh


Sulphur oxides

In the coming years the lower limits for fuel sulphur content from the revised Annex VI to the MARPOL Convention will come into effect, as shown in the Table below.

Table : MARPOL Annex VI Sulphur Limit % (m/m) in Fuel


Date High Sea (HFO) SOX ECA (MDO/Gasoil)  
2012 3.50 1.00 % S (m/m)
2015 0.10 % S (m/m)
2020* 0.50 % S (m/m)
* Alternative date is 2025, on basis of 2018 review

The baselines for ESI SOX are in line with the limit values set by IMO and that determined by the ESI working group. IMO limit values are in place for fuels that would normally be used at the High Seas and in (S)ECA’s and these will be tightened in accordance with IMO regulations. In addition there is a second baseline for MDO/Gasoil set by the ESI Working Group at 0.5 % sulphur which will be maintained for the next few years.

The limit value of the sulphur content for fuel used at the High Seas (HFO) changed to 3.50 % (m/m) on 1 January 2012; the limit value for fuel used in SOX-ECA (MDO/Gasoil) changes to 0.10 % (m/m) on 1 January 2015.

Consequently the base line for calculation of ESI SOX of HFO is now at 3.50 % and is used for calculation of ESI SOX scores for bunker operations from 1 January 2012. The base line change for MDO/Gasoil will be applied as from 1 January 2015.

Abatement technologies:

In the case of NOX emissions, it should be noted that where IMO approved abatement technologies of primary or secondary nature are applied, their effects have been included in the respective EIAPP certificate(s) issued.
For ESI SOX the equivalent values for an IMO approved exhaust gas cleaning system may be used for calculation purposes.