Biofuel testing essential as cruise lines lead shipping’s green transition

As shipping increases its use of biofuels to meet stricter emissions regulations, CM Technologies (CMT) is urging shipowners to adopt rigorous monitoring practices to mitigate the risks posed by biodiesel blends.

While these fuels are seen as a key pathway to decarbonization, their chemical make-up presents new operational challenges.

“The push for biofuels is transforming marine fuel strategies,” said David Fuhlbrügge, CMT’s co-managing director. “But with that shift comes the need for greater diligence. Operators must actively monitor fuel quality to prevent issues that could compromise engine efficiency, reliability, and compliance.”

The IMO’s emissions targets and the latest ISO 8217:2024 fuel standards have cleared the way for higher biofuel content in marine fuels, with blends ranging from 10% biodiesel to 100% pure FAME (Fatty Acid Methyl Ester). However, without proper oversight, biofuels can lead to fuel instability, corrosion, and mechanical wear, driving up maintenance costs and increasing operational risks.

For instance, DNV research has found the solvent-like nature of biofuels can dislodge tank residues, clogging filters and separators. The higher acidity in biofuels also risks increased corrosion, making lubrication adjustments essential. Higher BN (base number) lubricants will be required to neutralize acids and protect components from excessive wear. Biofuels also absorb more water, which fosters microbial growth and fuel degradation.

The latest CIMAC advisory also highlights concern over high FAME content, particularly with regards to fuel stability and long-term storage.

“Research has reinforced the need for biofuel users to regularly monitor fuel and engine performance,” said Fuhlbrügge. “Biofuels do offer sustainability benefits, but without the right monitoring and management, they can result in long-term engine damage, significant downtime and costs. Marine engines designed for conventional fuels will require operational adjustments to handle high biofuel concentrations, while fuel heating and purification systems should also be optimized for biofuel properties.”

CMT has seen a surge of interest for its test kits from the cruise industry, indicating the sector’s preference for the fuel as a way of meeting sustainability goals.

“When different fuels are blended onboard, the risk of fuel instability and compatibility issues increases, so it is important ship managers and crews continue to test and monitor this fuel regularly,” Fuhlbrügge said. “The low energy density of some biofuels could also mean more fuel is required to maintain voyage range. This will certainly impact bunkering strategies and procurement planning, making compatibility testing essential when mixing biofuels with conventional fuels. Otherwise fuel and lube oil inconsistencies could be missed leading to unexpected cruise itinerary cancellations.”

With feedstock variability and different blending methods, CMT advises shipowners to implement strict testing protocols for viscosity, stability, and water content analysis. These checks help validate biofuel batches before use, preventing unexpected performance issues.

“With tightening fuel standards and alternative fuels becoming mainstream, shipowners must adopt systematic fuel monitoring to safeguard engine reliability and regulatory compliance,” said Fuhlbrügge.

The testing regime CMT recommends involves comprehensive initial fuel analysis, regular periodic testing, and continuous monitoring of critical performance parameters. Its biofuel test kits provide operators with precise, actionable insights that go beyond traditional fuel assessment methodologies.

“It's not simply about reducing carbon emissions, it's about understanding the complex chemical interactions happening within engine systems when we introduce higher biofuel percentages."

The main biofuels for marine diesel engines are:

1️: Fatty Acid Methyl Esters (FAME) – Biodiesel. This is the most common biofuel in shipping, often blended with fossil fuels (e.g., B10, B20, B30). Derived from vegetable oils, animal fats, or recycled cooking oil, challenges include higher acidity, water absorption, microbial growth, fuel stability issues.

2️. Hydrotreated Vegetable Oil (HVO) – Renewable Diesel.  Produced through hydrotreatment of vegetable oils and fats. This has better stability and compatibility than FAME, as it lacks oxygen molecules. Can be used as a drop-in fuel without blending (e.g., 100% HVO).

3️. Bio-LNG (Liquefied Biomethane). Produced from biogas (e.g., landfill gas, agricultural waste). Works in LNG-powered ships, offering low-carbon emissions. Requires specialized storage tanks and engine modifications.

4️. Bio-methanol. Derived from renewable biomass (e.g., forestry residues, municipal waste). Can be used in methanol-ready marine engines. Lower emissions but corrosive, requiring modified fuel systems.

5. Bio-ethanol. Similar to bio-methanol but less common in shipping. Primarily used in smaller marine engines. Energy content lower than fossil fuels, requiring more fuel per voyage.

6️. Pyrolysis Oils & Bio-Crude. Derived from biomass (wood, agricultural waste, algae). Can be refined into marine-compatible fuels but not yet widely adopted.