Biofuels

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 may be applicable to the use of biofuels?

Use of biofuels can be subject to requirements for quality of fuel oils of Reg. 18.3 of MARPOL Annex VI in addition to requirements applicable to conventional petroleum-based fuel oils (e.g. flash point requirements of SOLAS, sulphur content requirements of Reg. 14, MARPOL Annex VI, etc.).
Regarding the application of Reg. 18.3, MARPOL Annex VI, fuel oil derived by petroleum refining shall be subject to the Reg. 18.3.1. Meanwhile, Reg. 18.3.2 of MARPOL Annex VI shall be applicable to fuel oil derived by methods other than petroleum refining.
For biofuels, application of Reg. 18.3.1 or 18.3.2 of MARPOL Annex VI depends on the terms such as blend ratio of biofuels and modification/adjustment of engine.

(*Please note that this item may be altered since this is made based on informal information obtained from participants from ClassNK and Working Papers developed during MEPC 78.)

4 What biofuels does Reg. 18.3.2.2 “fuel oil...shall not cause an engine to exceed the applicable NOx emission limit...” apply to?

With regard to the use of biofuels, Unified Interpretation (UI), which clarifies the application of Reg. 18.3.1 and 18.3.2 of MARPOL Annex VI, is approved at MEPC 78. The outline of UI is as below.


1. A fuel oil which is a blend of not more than 30% by volume of biofuel should meet the requirements of Reg. 18.3.1 of MARPOL Annex VI. (i.e. Such a fuel oil is not be subject to the Reg. 18.3.2.2 “fuel oil...shall not cause an engine to exceed the applicable NOx emission limit...”.)

2. A fuel oil which is a blend of more than 30% by volume of biofuel should meet the requirements of Reg. 18.3.2 of MARPOL Annex VI. For application of the Reg. 18.3.2.2 “fuel oil...shall not cause an engine to exceed the applicable NOx emission limit...”, it should be interpreted that:

    (i) Where a marine diesel engine can operate on a biofuel or a biofuel blend without changes to its NOx critical components or settings/operating values outside those as given by that engine’s approved Technical File, such a fuel oil should be permitted to use without having to undertake the assessment as given by the Reg. 18.3.2.2.

    (ii) Where a marine diesel engine can operate on a biofuel or a biofuel blend with changes to its NOx critical components or settings/operating values outside those as given by that engine’s approved Technical File, such a fuel oil shall be required to undertake the assessment as given by the Reg. 18.3.2.2. For the assessment, onboard simplified measurement method according to 6.3 of the NTC 2008 is available. Also, as applicable to possible deviations when undertaking measurements on board, an allowance of 10% of the applicable limit may be accepted.

(*Please note that this item may be altered since this is made based on informal information obtained from participants from ClassNK and Working Papers developed during MEPC 78.)

5 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.
6 What are the recommendations for using biofuels?

Prior to using biofuels, it is recommended to consult with the engine and fuel supply system manufacturer about the suitability of biofuel and the necessity of modifications/adjustments for equipment.

7 Contact

For any questions about biofuels, please contact:

NIPPON KAIJI KYOKAI (ClassNK)
Machinery Department, Administration Center Annex, Head Office
Address: 3-3 Kioi-cho, Chiyoda-ku, Tokyo 102-0094, Japan
Tel.: +81-3-5226-2022
Email: mcd@classnk.or.jp