CII and biofuels

Are biofuels accepted as means of improving a vessel’s CII rating?


ABS Regulatory News - MARPOL Annex VI - Biofuels as Marine Fuels.pdf (630.9 KB)


Hello Queseanians!

Following the 80th session of the Marine Environment Protection Committee (MEPC 80) in July 2023, the International Maritime Organisation (IMO) has published interim guidance on the calculations of the conversion factor (Cf) for marine biofuels blends.

  • Biofuels must be certified by a sustainability certification scheme to be considered “sustainable”. Examples of such schemes include the International Sustainability and Carbon Certification (ISCC) and the Roundtable on Sustainable Biomaterials (RSB).
  • These biofuels must achieve a minimum well-to-wake greenhouse gas (GHG) emissions reduction of 65% compared to fossil MGO emissions of 94 gCO2e/MJ. Essentially, their emissions intensity should not exceed 33 gCO2e/MJ.
  • To determine the carbon factor (Cf) value for a biofuel, multiply its well-to-wake GHG emissions (expressed in gCO2eq/MJ) stated on the sustainability certificate by the lower calorific value (LCV) of the fuel (expressed in MJ/g). This calculation is necessary for the regulations 26, 27, and 28 of MARPOL Annex VI.
  • For blends of biofuels, the Cf value should be calculated based on the weighted average of the Cf values for each fuel type, considering their respective energy proportions.
  • If a biofuel is not certified as “sustainable” or fails to meet the well-to-wake emission factor criterion, it should be assigned a Cf value equal to that of the equivalent fossil fuel type.

For example, if a ship receives 500MT of VLSFO grade B30 biofuel, with the biofuel component stated as 147MT FAME.

Certified by either ISCC or RSB, the sustainability documentation will indicate the FAME component and the Emissions Intensity (EI). If EI is less than 33 gCO2e/MJ, then the fuel can be considered “sustainable” for the purposes of the circular and the FAME Cf value is calculated as EI x LCV.

Let’s assume that the EI is equal to 18.5 g CO2e/MJ and the Lower Calorific Value (LCV) of 37.5 MJ/kg, then the FAME Cf value is calculated as EI x LCV = 18.5 x 0.0375 = 0.694 t-CO2/t-fuel.

According to the EEDI Guidelines (MEPC.364(79)), the VLSFO residual blend component falls into the category of RMD80, corresponding to “Light Fuel Oil.” It has an assigned Cf value of 3.151 t-CO2/t-fuel and an LCV of 41.2 MJ/kg.

The CF value for a blend should be determined based on the weighted average of the energy contents of its components, rather than just by considering their weights. This means considering the energy content of each component when calculating the overall CF value for the entire fuel as it is delivered. The Cf values are expressed in terms of tonnes of CO2 per tonne of fuel and are specified with a precision of three decimal places.

Emissions Intensity (EI) LCV (MJ/kg) Fuel (kg) Energy (MJ) Energy Fraction CF (t-CO2/tfuel) CF blend (t-CO2/tfuel)
FAME 18.5 37.5 147,000 5,512,500 0.275 0.694 0.194
VLSFO 41.2 353,000 14,543,600 0.725 3.151 2.284
Total 500,000 20,056,100 2.478

The sustainability documentation received with this fuel should be retained on board in the same way as the Bunker Delivery Note – Regulation 18.6 of MARPOL Annex VI.

Calculation of Cf of biofuel blend.xlsx (11.6 KB)

MEPC.1-Circ.905 - Interim Guidance On The Use Of Biofuels Under Regulations 26, 27 And 28 Of Marpol Annex Vi.pdf (94.4 KB)


In the Directive (EU) 2018/2001 of the European Parliament and of the Council is stated that CO2 emissions in use of biofuels and bioliquids is zero.

For biofuels and bioliquids which are certified as sustainable according to EC-recognized voluntary certification schemes the CO2 emission factor can be considered as zero. Thus, for blends the Cf is calculated based on the weighted average of the emission factors for the respective fuels.

From the above, I understand that for the IMO DCS the Cf of such fuels won’t be regarded as zero but as the value of the well-to-wake GHG emissions of the fuel.

So, the reporting for the EU MRV and the IMO DCS in the case of biofuels will be different.