WHILE a wide availability of alternatives such as hydrogen and ammonia are still some way off, biofuels do not require major modifications to existing marine diesel engines and their auxiliary systems.

In response to biofuels’ attention, ClassNK has published a technical guide to support their safe use on ships, outlining biofuels’ characteristics, potential issues arising from their differences from conventional petroleum fuels, and precautions for biofuels’ safe use, such as measures to protect machinery and deal with sludge.

The guide also covers the stipulations and interpretations for biofuels under latest NOx and GHG reduction regulations and offers a future vision for biofuels.

Biofuels are said to be carbon neutral renewable fuels because they are produced from biological organisms (biomass) based on plants. The total amount of CO2 absorbed during plant growth may offset the amount emitted during combustion.

Based on this understanding, biofuels can be a potent element to reduce net GHG emissions, especially for existing ships.

The biofuels experience

Since 2020, ClassNK has received many enquiries about the use of biofuels. In short- and mid-term onboard trials involving biofuels, no significant issues were reported in the period to December 2023. However, risks associated with long-term use remain uncertain.

Three main types of biofuels are covered in the technical guide: Straight Vegetable Oil (SVO), extracted from soyabeans, rapeseed or palm or used cooking oil; Fatty Acid Methyl Ester (FAME) or Ethyl Ester (FAEE), produced by esterification of SVO with methanol (ethanol); and Hydrotreated Vegetable Oil (HVO), produced by hydrogenation of SVO.

While quality standards have been developed for HVO and FAME, there are no equivalent standards for SVO. However, SVO is generally the lowest cost among these fuels due to the raw feedstock used, followed — respectively — by FAME and HVO.

In some cases, FAME provides a favourable balance in quality and price, and ClassNK notes it was also maritime’s most widely used biofuel in 2023. However, due to its low price and low GHG emissions during production, SVO may become more widely used; HVO use may possibly increase because of its lower risk.

Understanding characteristics and precautions associated with using the three types is critical to fuel selection.

For example, while HVO has properties similar to distillate oils, SVO and FAME characteristic are different. The latter two can also be subject to oxidisation or may dissolve deposits — known as a cleaning effect.

SVO itself and distillate oils do not usually cause oil-resistant rubbers, such as NBR, to distend (or swell) due to insufficient interaction between rubbers and oils. In contrast, FAME, as well as the lower fatty acids generated through deterioration of either SVO or FAME, can cause NBR swelling due to their properties. In consequence, it is recommended that FAME and SVO are used with high-resistant rubbers, such as fluorine rubbers.

Interviews with shipping companies confirmed that biofuels’ use continued without issues in cases where oils were consumed before long-term storage — usually within three months. Measures put in place to support biofuels’ use included regular circulation and heating, and more frequent checking of FO filters.

ClassNK Transition Support Services

ClassNK has developed “ClassNK Transition Support Services” to meet customers’ potential challenges managing GHG emissions.

The menu includes ClassNK ZETA (Zero Emission Transition Accelerator), a tool for managing GHG emissions already used on more than 5,000 ships in 2023. ClassNK ZETA monitors GHG emissions and CII ratings of individual ships and fleets, also offering functionality to simulate the impact on emissions of slow steaming, energy-saving devices or switching fuels.

If the data for biofuels consumption is reported using the ClassNK MRV Portal, GHG emissions are automatically calculated.

ClassNK ZETA also allows users to display GHG emissions for ships and fleets operating within the EU-ETS, and to manage their emission allowances. ClassNK plans to introduce functions for the FuelEU Maritime Regulation in 2025.

Furthermore, the service covers the certification which aligns with international biofuels certification schemes and verifies that emissions reductions are being achieved through biofuel used, providing clients with a one-stop solution.

The “Technical Guide for Using Biofuels” is available to download via “Guidelines” on ClassNK’s My Page after registration or follow this link: www.classnk.or.jp/account/en/Rules_Guidance/ssl/guidelines.aspx