Handling of the use of biofuels on ships

Biofuels are renewable fuels produced from biological organisms (biomass) in which the primary raw materials used are vegetable oils. Biofuels do not emit sulphur oxides (SOx) during combustion; moreover, they are generally considered to be carbon neutral because the amount of carbon dioxide (CO2) they do emit during combustion tends to be absorbed by source plants, etc. during their growing stage. In addition, biofuel usage can also be advantageous when used as a drop-in marine fuel (depending on fuel type) because modifications of existing marine diesel engines converted over to biofuel use are typically not required.


For these reasons, the number of biofuel trials being held has been increasing in recent years; this, in turn, has led to a corresponding increase in the number of inquiries received related to biofuel usage. Since these inquiries tend to be about various matters and not just general information requests, we have prepared the following questions and answers for your reference in order to better support safe and proper operation when using biofuels on ships.

For better understanding of the use of biofuels on ships

No. Question Answer
1 What type of biofuels are usually used?

For marine use, currently main candidate biofuels are of the following three types.

① SVO(Straight Vegetable Oil) ② FAME(Fatty Acid Methyl Ester) ③ HVO(Hydrotreated Vegetable Oil)
Manufacturing method Oils extracted from rapeseeds, palms or soybeans Produced by transesterification of vegetable oils, waste cooking oils or animal fats Purified from fats or vegetable oils by a hydrotreating method
CO2 emission reduction and cost Superior to FAME and HVO Inferior to SVO Inferior to SVO and FAME
Usage characteristics Although the quality varies depending on the raw materials, it is a fuel that requires heating due to its higher kinematic viscosity and flow point compared to light oil, and it also requires consideration of oxidation stability. It has the same features as SVO, but its kinematic viscosity is equivalent to MGO. It can be used alone or by mixing with conventional marine fuels.
2 Are there any IMO statutory requirements regarding CO2 emission accounting when using biofuels?

Biofuels do emit CO2 when burned, but they are, for the most part, considered to actually generate zero CO2 emissions (i.e. they are carbon neutral) because the CO2 that is released into the atmosphere is eventually absorbed by plants, etc. during their growing stage . However, regarding the consideration of the GHG emission reduction effect (conversion factor in IMO EEDI and EEXI as well as emission factor in IMO DCS and CII) from ships using biofuels, a procedure for evaluating the CO2 reduction effect of biofuel in life cycle accounting is currently being developed by the IMO. We will provide updates on IMO progress in developing this procedure as such information becomes available to us.

3 What IMO statutory requirements are applicable to the use of biofuels?

In addition to the requirements applicable to conventional petroleum-based fuel oils (e.g. flash point requirements of SOLAS, sulphur content requirements of MARPOL Annex VI, etc.), Reg. 18.3.2 of MARPOL Annex VI, which are related to the quality of fuel oils derived by methods other than petroleum refining, are applicable.
More specifically, Reg. stipulates that fuel oil derived by methods other than petroleum refining shall not cause an engine to exceed the applicable NOx emission limit. Therefore, it is necessary to demonstrate that NOx emissions of onboard diesel engines do not exceed the applicable NOx emission limit due to the use of the biofuel.

4 Are there any special procedures necessary for the use of biofuels? 

Prior to use of a biofuel, it is necessary to technically demonstrate that NOx emissions of diesel engines do not exceed the applicable NOx emission limits due to use of the biofuel on the basis of NOx measurement data on test-beds or on board and/or other technical literature. Therefore, we believe that the cooperation of engine manufacturers and biofuel suppliers is essential. For a ship registered with ClassNK, we will, in principle, examine the technical validity of such a demonstration and provide necessary feedback. However, considering the fact that the current MARPOL Annex VI and NOx Technical Code do NOT envisage use of biofuel and that NO specific NOx certification procedures or requirements intended for the use of biofuel are stipulated, instructions from the Flag State Administration are also to be followed as necessary. In the meantime, in the case of the temporary use of a biofuel on a trial basis rather than on a permanent basis, it may be possible to obtain a temporary exemption from the Flag State Administration. Reg. 3.2 of MARPOL Annex VI stipulates the provisions of an exemption to conduct trials for emission reduction technology research; such an exemption request, therefore, may be an option to consider.

5 Are NOx emissions required to be remeasured during the use of biofuel?

If it can be obviously confirmed, based on existing measurement data or literature, that use of a biofuel will not cause relevant engines to exceed the applicable NOx emission limits, NOx re-measurement is not necessarily essential. However, the NOx emissions of existing diesel engines are generally measured for the use of DM grade distillate oil only; the NOx emission characteristics of biofuels, therefore, are not always crystal clear. If a demonstration with biofuel based on existing measurement data or literature is either impossible or very difficult, we believe it necessary to conduct NOx re-measurement with the biofuel for the purpose of obtaining the measurement data needed to demonstrate compliance. Such re-measurements can be conducted either on test-beds or on board on the condition that the engines are identical to those installed on board the ship intending to use the biofuel; in other words, such measurements are acceptable if carried out on any ship where engines with the identical specifications are installed. It is noted that any remeasurements shall, in principle, comply with the requirements of the NOx Technical Code. Thus, if a diesel engine with identical specifications is not available or if it is not possible to conduct re-measurements fully complying with the requirements of NOx Technical Code, additional technical justification will be necessary for demonstrating NOx emission compliance.
In the case of temporary use on a trial basis, our understanding is that necessary conditions such as NOx remeasurement should be confirmed with the Flag State Administration.

6 Do engine Technical Files need to be amended with respect to the use of biofuels?

If limitations related to the acceptable fuel oil type are described in the existing Technical Files, it may be necessary to amend such descriptions. However, in general, we understand that the necessity of amendments to Technical File is subject to the instructions of the Flag State Administration. For example, if the Flag State Administration issues an official acceptance letter for the use of biofuel, the amendment of the Technical File may not be required.

7 What are the classification requirements applicable to the use of biofuels?

In principle, the suitability of biofuel use in the engine is to be confirmed in accordance with B2.3.1-5(5), Part B of Guidance for the Survey and Construction of Steel Ships.

8 What precautions should be taken when using biofuels?

FAME is a fuel in which various issues may arise over time; so, it is important to take appropriate countermeasures and use the biofuel up as soon as possible.

Possible issue

Recommended countermeasure

Microorganisms such as bacteria are contained in the vegetable oils and tend to grow in the water which is generated in the storage tanks. Suppress the growth of microorganisms by the periodic removal of water in the tanks or heating tanks.
A larger number of carbon molecules and a lower liquidity at low temperatures in comparison to diesel fuels (MGO) may cause transport failure of fuels and the clogging of filters due to the wax formation at low temperatures. Pay attention to the temperature of during storage and transfer, and regularly inspect and clean the strainers or filters.
Due to its high detergency, deposits on the inner surface of the tanks or pipes may peel off at the change-over process and cause clogging of the filters. Mitigate the risk by washing tanks and pipes before changing-over fuels.
Due to its low oxidation stability and longer storage time in anks, more organic acid and sludges may be generated by oxidative deterioration. This may cause the clogging of filters, corrosion of metal components and damage to sliding components. Add antioxidants to prevent deterioration.
A high permeability to rubber may causing the swelling of rubber components. Confirm the durability of the components.
9 What is the procedure for conducting biofuel trial?

In general, the following (1) through (3) are required.

(1) Request a temporary exemption from NOx emission compliance from the Flag State Administration.
(2) Consult with the engine and fuel supply systems manufacturer about the suitability of the biofuel.
(3) In principle, confirm the suitability of the biofuel on the vessel in the presence of a ClassNK surveyor.
10 Contact

For any questions about biofuels, please contact:

Machinery Department, Administration Center Annex, Head Office
Address: 3-3 Kioi-cho, Chiyoda-ku, Tokyo 102-0094, Japan
Tel.: +81-3-5226-2022