How Fuel System Check Monitoring Will Reduce Risks, Save Time & Money

By Steve Bee – VPS Group Marketing & Strategic Projects Director

Statistically, data indicates that a vessel will suffer between one and two incidences of main engine damage over the course of its operational lifetime. The average damage costs have been estimated at around $650,000 per incident, with even more damaging incidents costing up to $1.2 million per claim. Therefore, it is important to identify the main causes of this damage and understand how it can be prevented.

Prevention of damage is, of course, preferable to cure. Fuel quality and handling issues remain a leading contributor to critical main engine failures. VPS frequently observe that such issues could have been prevented through the implementation of a robust and well-structured fuel management programme onboard vessels.

A common misconception is that a fuel meeting the international marine fuel quality standard, ISO 8217, means it is “fit for purpose”. But this is definitely not the case as even fuels that are “on specification”, at the point of delivery to the vessel, can cause major engine damage if not properly managed post-delivery. ISO 8217 specifies the requirements for petroleum fuels for use in marine diesel engines and boilers, prior to appropriate treatment before use, which means that fuels should then be treated onboard between delivery and being burnt.

Catalysts used in petroleum refining are made of Aluminium Silicates, which over time breakdown. The resulting, coarse, dense fragments composing of aluminium and silicon, eventually reside in the residual portion of the refining stream. Known as “Cat-Fines”, these particles are highly abrasive and can cause severe damage to vessel engine parts.

Major marine engine manufacturers recommend a fuel should contain less than 10-15 mg/kg Aluminium plus Silicon (Al+Si) at the engine inlet. However, assuming a delivered fuel meets the stringent ISO8217:2024 limits of 40-60 mg/kg Al+Si, dependent upon the fuel grade, the fuel treatment plant would have to operate at an efficiency level capable of removing 75%-83% of these highly abrasive particles in order to meet the engine manufacturers’ requirements.

Furthermore, the International Council on Combustion Engines' (CIMAC’s) recommendation regarding fuel quality states “Fuel analysis is the only way to monitor the quality of fuel as delivered at the time and place of custody transfer, before and after the fuel cleaning onboard and at the engine inlet. Regular monitoring of the fuel cleaning plant will provide information, which will help to make decisions about the maintenance cycles of the equipment as well as potential engine problems resulting from malfunctioning or inadequate operation.”

Yet one of the most important, but often overlooked processes, is that of regular Fuel System Checks (FSCs) in order to assess the level of aluminium and silicon catalytic fines within fuel. The presence of “cat-fines” within fuel can be extremely damaging, causing rapid engine-part wear. Monitoring cat-fine levels before they can enter vessel engines, can prevent such damage. Therefore, sending samples for analysis which are taken Before & After purification processes, on a quarterly basis is the most effective way to monitor cat-fine levels. FSCs will also help comply to the engine manufacturers general recommendation of a maximum of 10-15 mg/Kg level of cat-fines in the fuel, entering the engines and assess purifier efficiency.

There are numerous reasons why regular fuel system checks are critical:

• Help identify potential risks & operational issues before major damage occurs.
• Confirm that the system’s flow rate, temperatures, discharge cycles are properly adjusted to handle the specific fuel that is being treated
• Verify that the fuel treatment system is properly maintained
• Reduce operating cost and increase lifecycles of critical components
• Identify presence of unusual components that can enter fuel post- delivery.

Periodic sampling from the fuel treatment system will also identify problems such as water ingress from ballast systems, leaking heating coils and cargo contamination. The last thing anyone wants to see is a purifier working as a pump!

A prime example and case study is highlighted below:

An LPG Tanker bunkered HSFO in Fujairah where its fuel met ISO 8217 specifications. However, after using the bunkered fuel, the Chief Engineer reported the main engine expansion tank low level alarm, with the main engine exhaust gas temperature high on cylinder unit 2 & 4. The vessel commenced a gradual slowdown of the main engine. The Chief Engineer reported the vessel was unable to run the engine due to suspected leaks on the main engine cylinders. The vessel drifted for about 10 hours before dropping anchor off the coast of India.

Upon dismantling the engine, the following findings were made:

The VPS Technical Advisor recommended the vessel submit fuel system samples and upon checking, the results from the system, these indicated that the purifier was in fact only working like a pump.

The screening size of Al+Si on the before engine sample further confirmed why the vessel was having problems, as the physical size of Al+Si particles ranged: 5-45 µm.

The ideal particle size range of cat-fines that can be effectively removed by a marine vessel's purifier system typically falls between 5 to 15 µm. Purifiers are designed to target these smaller particles, as they are the most common size found in heavy fuel oil and can cause significant wear and damage to engine components

If the particle size of catalytic fines is greater than 15 µm, it can pose significant risks to marine engines. Larger particles are more abrasive and can cause severe wear and damage to critical engine components such as cylinder liners, piston rings, and fuel injectors.
 

Potential Issues:

• Increased Wear: Larger cat-fines can embed themselves in softer metal surfaces, leading to accelerated wear and tear
• Engine Efficiency: The presence of larger cat-fines can reduce engine efficiency and increase fuel consumption.
• Maintenance Costs: More frequent and costly maintenance may be required to address the damage caused by these particles.

Mitigation Strategies:

• Enhanced Filtration: Using advanced filtration systems to capture larger particles before they enter the engine
• Regular Monitoring: Continuously monitoring fuel quality and performing regular maintenance to detect and address cat-fines early.
• Fuel Treatment: Employing fuel treatment systems to reduce the concentration of cat-fines in the fuel.

This VPS fact finding was highly appreciated by the vessel Chief Engineer and the ship owner, following their realisation of what was the cause of the problem. They subsequently put in place routine sampling of fuel system check (FSC) samples to prevent the same incident from reoccurring.

As part of the VPS FSC service, each vessel has a monitoring chart checking the cat-fine level upon receipt of the fuel, then the before-purifier level and the after-purifier level. Should any submitted FQT (Manifold) sample show >40mg/Kg Cat-fines, then the vessel will be advised to send an additional sample for Fuel System Check. The before-purifier sample should always have a lower cat-fine level than the manifold sample. Then the after-purifier should always be below 15mg/kg cat-fines, if the purifier is working efficiently.
 

Currently 52% of all samples received by VPS for testing are VLSFOs, with a further 32% being HSFOs. As the two leading fuel grades used in global shipping, they are the two which will and often contain varying levels of cat-fines.

For VLSFOs across Q1-2025, 17% of all samples tested had cat-fine levels between 41-60 mg/Kg, which was slightly lower level than Q4-2024 and full year 2024, at 18%. These levels are high enough to cause concern and would trigger the request for additional FSC samples to be sent for analysis. 

Across 2024 and Q1-25, less than 2% of samples tested exceed the ISO8217 specification limit of 60 mg/Kg.

So, around 19% of VLSFOs delivered in Q1-2025 had cat-fine levels >40mg/Kg. Should the recipient vessels not have effective, efficient, purification of their fuel, then they run the risk that 1 in 5 fuel deliveries could cause engine damage.

For HSFOs across Q1-2025, 12.5% of all samples tested had cat-fine levels between 41-60 mg/Kg, which was lower level than Q4-2024 and full year 2024, at 19% and 20% respectively. These levels are also high enough to cause concern and would trigger the request for additional FSC samples to be sent for analysis.

Again, like VLSFOs, HSFOs across 2024 and Q1-25, showed less than 2% of samples tested exceed the ISO8217 specification limit of 60 mg/Kg.

So, around 13% of HSFOs delivered in Q1-2025 had cat-fine levels >40mg/Kg. Should the recipient vessels not have effective, efficient, purification of their fuel, then they run the risk that 1 in 7 fuel deliveries could cause engine damage.

In summary, Cat-fines found in the residual component of VLSFO and HSFO fuels, are highly corrosive materials, which can cause considerable and costly damages to vessels. Regular monitoring of onboard purifier performance efficiency, as part of a routine preventive maintenance programme, should be a key tool in mitigating such risks.

It is therefore, recommended that a vessel submits “before and after purifier” samples, for each onboard purifier, four times per year. This way the efficiency of the purifiers can be checked and advice provided to ensure optimum efficiency is being achieved and the engine is being protected to the highest level possible.

For further information on how Fuel System Checks (FSCs) can help you protect your vessels from costly breakdowns, damages and repairs, please contact marketing@vpsveritas.com

By Steve Bee – VPS Group Marketing & Strategic Projects Director & Emilian Buksak – VPS Decarbonisation Advisor

On Friday 11th April 2025, the International Maritime Organization (IMO) achieved another important step towards establishing a legally binding framework to reduce greenhouse gas (GHG) emissions from ships globally, aiming for net-zero emissions by or around 2050.

The IMO Net-zero Framework is the first in the world to combine mandatory emissions limits and GHG pricing across an entire industry sector.   Approved by the Marine Environment Protection Committee during its 83rd session (MEPC 83), the measures include a new fuel standard for ships and a global pricing mechanism for emissions.

These measures, set to be formally adopted in October 2025 before entry into force in 2027, will become mandatory for large ocean-going ships over 5,000 gross tonnage, which emit 85% of the total CO2 emissions from international shipping.  This Net-Zero Framework will be included in a new Chapter 5 of MARPOL Annex VI.

With an estimated 900 renewable-fuel-ready vessels expected to be sailing the seas by 2030, it is felt necessary to implement global regulation to deliver renewable fuels at a commercially viable price, as current pricing for “green fuels” is 3-4 times the price of fossil fuels. Such regulations will make it possible for ships to operate on green fuels and also incentivise fuel and energy providers to invest in new production capacity.

Under the draft regulations, ships will be required to comply with: 

1.    Global fuel standard: Ships must reduce, over time, their annual greenhouse gas fuel intensity (GFI) – that is, how much GHG is emitted for each unit of energy used. This is calculated using a well-to-wake basis, meaning total emissions are measured from fuel production through to its use on board.  

2.    Global economic measure: Ships operating above GFI thresholds will need to acquire remedial units to balance their excess emissions, while those using zero or near-zero GHG  fuels or technologies will be eligible for financial rewards for their lower emissions profile.

3.    Two-tier Compliance Targets: Each ship will have to meet both a Base Target and a Direct Compliance Target for its annual GFI. Vessels that stay under the stricter Direct Compliance Target are eligible to earn surplus units, whereas those over the thresholds face a compliance deficit that must be remedied.

4.    Data Collection & Reporting: Operators must calculate and report their attained annual GFI each calendar year, verifying it against their target annual GFI. This includes rigorous recordkeeping and submission to the IMO GFI Registry, which tracks each vessel’s emissions performance and any remedial or surplus units.

5.    IMO Net-Zero Fund Contributions: Ships that exceed their GFI limits are required to make GHG emissions pricing contributions to the new IMO Net-Zero Fund. Collected revenues will be used to reward ships using zero/near-zero fuels, support research and technological innovation in cleaner shipping, and help ensure a just and equitable transition for the maritime sector.

Net-Zero Framework Implementation and Green Balance Mechanism
From 2028 to 2030, ships will be subject to a tiered levy linked to their well-to-wake (WtW) carbon intensity. Based on a 2008 baseline of 93.3 gCO₂eq/MJ (the industry average in 2008), operators will face no charge for fuel emissions at or below approximately 77.44 gCO₂eq/MJ, a moderate levy of $100/mtCO₂eq for emissions between 77.44 and 89.57 gCO₂eq/MJ, and a higher rate of $380/mtCO₂eq for emissions exceeding 89.57 gCO₂eq/MJ. These thresholds and levies align with the overarching goal of driving down overall carbon intensity by a minimum of 4% by 2028 and 17%for direct compliance targets—with further, more stringent reductions taking effect in subsequent years.

Surplus Units and Over-Compliance
A ship’s carbon intensity below the lower threshold (77.44 gCO₂eq/MJ) constitutes “over-compliance,” generating surplus units that can be banked or traded. Conversely, exceeding thresholds will require the purchase of remedial units to cover the compliance deficit.

Sustainable Fuel Certification Scheme (SFCS) and Fuel Lifecycle Label (FLL)
Under the new framework, all fuels must carry a Fuel Lifecycle Label (FLL), which documents their GHG intensity and other sustainability attributes on a well-to-wake basis. These values must be certified by a recognized Sustainable Fuel Certification Scheme (SFCS), ensuring accurate, transparent calculations and preventing any misrepresentation of environmental impact.

Zero or Near-Zero GHG Technologies, Fuels, and Energy Sources
Recognising the importance of incentivising advanced solutions, the regulation sets specific lifecycle emission thresholds for what qualifies as a zero or near-zero GHG (ZNZ) fuel or technology: Initial threshold (valid until 31 December 2034): ZNZ fuels must not exceed 19.0 g CO₂eq/MJ on a well-to-wake basis. Post-2035 Threshold: Starting 1 January 2035, the permissible GHG intensity tightens to no more than 14.0 g CO₂eq/MJ.

Ships adopting fuels and technologies below these thresholds can earn financial rewards through the IMO Net-Zero Fund, effectively offsetting some of the initial costs of transitioning away from conventional fossil fuels. By gradually lowering the allowable GHG intensity, the regulation encourages ongoing innovation, investment, and broader adoption of advanced, low-emission solutions across the global fleet.

Green Balance Mechanism
Central to this approach is the Green Balance Mechanism, which integrates closely with the GFI. In essence, it applies a fee on higher-intensity fossil fuels and allocates those proceeds to green fuels, balancing costs across a diverse energy mix. The greater the well-to-wake emission reductions a fuel delivers, the larger the financial allocation it receives—effectively levelling the playing field and stimulating a shift to sustainable alternatives.

Disbursement of Revenues
All revenues from levies and remedial unit purchases will be directed to the IMO Net-Zero Fund, which will then distribute the funds to:

• Reward low-emission ships
• Support innovation, research, infrastructure, and just-transition initiatives (particularly in developing countries)
• Fund training, technology transfer, and capacity-building aligned with the IMO GHG Strategy
• Mitigate impacts on vulnerable States, such as Small Island Developing States (SIDS) and Least Developed Countries (LDCs)
• By steadily lowering the permissible carbon intensity and introducing financial incentives for clean fuels, the new framework aims not only to reduce overall emissions but also to accelerate the maritime sector’s transition to sustainable energy solutions.

How VPS Can Help
Staying ahead of new regulatory demands isn’t just a matter of compliance—it’s a strategic move that protects both profitability and operational excellence. With industry-leading expertise in low-to-zero carbon fuel testing, advanced emissions measurement technology, and comprehensive decarbonisation software and advisory services, VPS empowers it’s customers to meet and exceed environmental targets, being uniquely positioned to guide customers through every step, ensuring accurate reporting, cost control and ongoing improvement.

1.    Bunker Delivery Note (BDN) Validation & Fuel Testing
Fuel Quality & Lifecycle Analysis: VPS lead the way in marine fuel testing, developing new methodologies to provide key data on all fuel types. The past 4 years have seen major innovations and developments for biofuels and methanol testing and advisory services.

VPS validate the greenhouse gas intensity of customers fuels whether they are fossil or low-to-zero carbon fuels, based on well-to-wake standards. By analysing lifecycle GHG emissions, customers can gain confidence in their compliance numbers and avoid under- or over-reporting.

Accurate Renewable Content Measurement: Through state-of-the-art lab testing and Fuel Lifecycle Label (FLL) verification, VPS confirm the genuine renewable portion of biofuels—helping you pay the correct level of carbon taxation or remedial contributions.

Early Issue Detection: By validating BDNs and testing delivered fuel, VPS services can help prevent engine damage, unplanned downtime, and costly disputes over fuel quality.

2.    Direct Emissions Measurement & Reporting
Advanced Monitoring Systems (e.g., Emsys and ShoreLink): These systems provide real-time emissions data, allowing customers to track their vessel’s GHG Fuel Intensity (GFI) and compliance status in one seamless workflow.

Data Accuracy & Transparency: Automatic digital data transfer ensures vessel emissions records are consistent, easily auditable, and ready for both internal use and external verification.

Timely Remedial Actions: With up-to-the-minute reporting, operators can make course or speed adjustments to keep emissions in check, reducing the likelihood of expensive remedial unit purchases.

3.    Operational Efficiency & Advisory
Fuel Selection & Hybrid Solutions: VPS experts help match the right fuel to each vessel’s operational profile, whether that’s low-carbon or near-zero carbon fuels, blends, or hybrid setups combining LNG and batteries to reduce methane slip. This tailored approach ensures maximum efficiency and a smaller overall GHG footprint.

Power Generation & Predictive Maintenance: VPS advisors optimize power distribution to cut fuel usage and enhance system reliability. By conducting in-depth fuel performance analysis, its possible to detect early engine abnormalities, enabling proactive maintenance that prevents costly repairs and downtime.

SEEMP Updates & Crew Training: VPS provide step-by-step guidance in incorporating new regulations into Ship Energy Efficiency Management Plan (SEEMP). Additionally, we train vessels’ crew on best practices that build a culture of efficiency, helping our customers reduce emissions and comply with evolving GHG limits.

4.    Net-Zero Fund & Market Mechanisms
Remedial & Surplus Units: Understand how to acquire remedial units (if GFI thresholds are exceeded) and capitalise on surplus units or zero-/near-zero fuels to earn financial rewards.

Cost-Benefit Analysis: VPS Advisory team helps the evaluation process when purchasing or trading units is beneficial versus investing in cleaner technologies or optimising operations.

Strategic Positioning: Tap into VPS insights on emerging market mechanisms to stay ahead of future pricing changes and incentives that could shift the competitive landscape.

5.    Long-Term Decarbonisation Roadmaps
Holistic Compliance Planning: Whether preparing for EEXI, CII, or the IMO’s Net-Zero Framework, VPS design future-proof strategies that keep the fleet competitive for the long haul.

Integrated Training & Engagement: From onboard crew training to management briefings, VPS ensures everyone understands the regulations, the rationale behind them, and how to maintain best practices.

Continuous Improvement: VPS advisory goes beyond periodic check-ins; by partnering with our customers regarding ongoing performance reviews, data benchmarking, and the identification of new efficiency measures.

Next Steps
Formal adoption of the IMO Net-Zero Framework is scheduled for October 2025, with entry into force by 2027. However, preparation must start now to avoid last-minute risks, manage costs effectively, and stay ahead of competitors.

If you’d like to assess your vessel’s readiness or explore how to optimize your operations under the new rules, please get in touch with our decarbonisation advisory team at: Emilian.buksak@vpsveritas.com

We’re here to help you convert regulatory pressure into practical advantages—keeping you compliant, cost-effective, and resilient for the future.

Steve Bee – VPS, Group Marketing & Strategic Projects Director

Cashew Nut Shell Liquid - Background

As demand grows from all modes of transportation for low-to-zero carbon fuels, to support efforts in complying and achieving numerous environmental legislation leading to global decarbonisation, many alternative fuel sources are being considered. One of the most common and in demand sources of such fuels, is Fatty Acid Methyl Esters (FAME), as either a 100% fuel-source, or as part of a bio-fossil blend. But with road transportation, aviation and shipping, all seeking to use FAME in their respective biofuels, demand is outweighing supply. Therefore, other bio-materials are being considered as alternatives to FAME.

One such material is Cashew Nut Shell Liquid (CNSL), which is the oil extracted from the shells of the cashew nut. This by-product of the cashew industry is a naturally occurring substituted phenol, which is abundantly available and a waste product, with a lower demand than FAME. The composition, properties and quality of CNSL depend upon the specific manufacturing production process used to extract the oil from the shell. These vary from, mechanical pressing to solvent extraction, vacuum pyrolysis, vacuum distillation or solvent extraction.

The industrial applications where CNSL is a key component are wide ranging and include, the production of polymers, plastics, resins, adhesives, surface coatings, insecticides, fungicides, anti-termite products and even pharmaceutical products.

There are three main components of CNSL, these are Cardanol, (also known as Ginkgol), Cardol and Anacardic Acid:

These substituted phenols tend to exhibit high acid number values (>3mgKOH/g). They also show high iodine values (>300gI2/100g), indicating an elevated level of unsaturation and hence increased degrees of reactivity and instability. Then also, high potassium levels leading to potential post-combustion deposits and corrosion of turbocharger nozzle rings.

As monomers, these chemicals are also prone to polymerisation at temperatures, >200ºC. As a consequence CNSL is potentially a highly reactive, very corrosive material.

However, the levels of acidity and reactivity can be reduced during the production and refining process by converting Cardol and Anacardic Acid to Cardanol. If the CNSL is >98% Cardanol, then the reactivity is significantly reduced.

VPS Testing of CNSL as a Biofuel

Over the past 3 years VPS have tested various CNSL compounds and fuel-blends to assess the potential of CNSL to be a viable biofuel.

Firstly, the use of CNSL blends can significantly reduce HC, CO/CO2 and smoke emissions, although they can raise NOx emissions slightly. However, VPS would advise never to use 100% CNSL as a fuel, as its far too reactive and corrosive. Further advice is to always check with the OEM regarding the compatibility of CNSL-based biodiesel blended products, with their machinery. Traditional marine fuels when blended with CNSL, may reduce the high acid number, reactivity and potassium levels of 100% CNSL, but also increase the energy content, sulphur content, cold-flow and sediment potential issues.

Fuel Combustion Analysis (FCA) of CNSL/Fossil Fuel Blends

In the recent past, VPS have tested CNSL products, blended with marine gas oil (MGO), very low sulphur fuel oils (VLSFO) and high sulphur fuel oils (HSFO). When undertaking fuel combustion analysis (FCA) of CNSL blended at varying percentages with MGO, VLSFO and HSFO, a wide range of results were produced in relation to, estimated cetane number, ignition delay and rate of heat release (ROHR), examples are given in the table below:

The CNSL blends with HSFO which undertook FCA, were particularly poor, with low Estimated Cetane Number (ECN), long Ignition Delay and low ROHR. CNSL blended with VLSFO gave better results, with acceptable ECN, shorter ignition delay and improved ROHR. Blending CNSL with MGO, gave better results than those obtained by HSFO/CNSL and VLSFO/CNSL blends.

Whether the blends were 80/20, 70/30 or 50/50 Fossil/CNSL, the blends using HSFO consistently gave the poorest FCA results. This may be due to a negative interaction between the asphaltenic content of the HSFO and the acidic nature of the CNSL.

Each of the CNSL blends gave poorer FCA results, when compared with the 100% fossil fuels, HSFO, VLSFO, MGO and 100% FAME.

Please note, to VPS knowledge, the above highlighted CNSL blends were not burnt onboard a vessel.

Burning CNSL/Fossil Blends

CNSL-blended fuels with MGO, VLSFO, or HSFO, have shown mixed reactions to vessel operations, where some CNSL-blends have been stored and burnt without issue, whilst, other CNSL-blends have given rise to operational problems such as:

• Fuel sludging
• Fuel injector failure
• Corrosion of engine parts
• Filter clogging
• Fuel system deposits
• Corrosion of turbocharger nozzle rings
• Damage to Selective Catalytic Reactor (SCR) units.

The quality of the CNSL, through its production and refining processes, will of course be significantly influential in relation to the quality of the fuel, but also the quality of the fossil fuel with which it is blended, will also have an influence.

A B100 Case Study

In early 2024, two vessels bunkered a B100 fuel in Flushing. The B100, was assumed to be 100% FAME, however, the first vessel began burning the fuel and experienced significant difficulties with blocked filters, delayed ignition and abnormal exhaust temperatures. Prior to burning the fuel, the second vessel sent samples to VPS for testing and via proprietary GCMS methodology. The fuel was found to consist of 40% FAME, 10% FAME Bottoms and 50% CNSL. So theoretically the fuel was a B100, it just wasn’t the 100% FAME, which had been ordered. This case highlights the need to know your fuel, its components and for biofuels, the need to know if the bio-source is truly sustainable? Having the fuel certified by an independent body such as ISCC, accompanied by independent testing from VPS, will provide the necessary confidence regarding the biofuel.

Potential Contaminating Properties of CNSL

In the final quarter of 2024, a VPS customer experienced numerous operational issues with its vessels when burning VLSFO fuels. These issues included blocked filters, delayed ignition and abnormal exhaust temperatures. On testing the fuel, GCMS analysis detected and identified the presence of 10,000-15,000ppm of CNSL within these fuels.

Up to the end of 2024, CNSL, which is a non-volatile chemical species, could only be detected using high-end, GCMS methodology. As CNSL is now more common within the fuel supply chain, it brings an elevated risk of potential contamination to fossil fuel supplies.

Therefore, VPS has developed a pre-burn, rapid screening technique, which detects and identifies the presence CNSL and other non-volatile organic chemicals. Whereas previously, only volatile organic chemicals could be detected by GCMS-Headspace Screening, this new and unique development of a qualitative GCMS-Headspace chemical screening method makes it possible, within a single analysis, to detect volatile (VOC), semi-volatile (SVOC) and non-volatile (NVOC) components within HSFO and VLSFO fuels. 

Over the upcoming weeks, VPS will be releasing a technical white paper covering the development of this new GCMS-HS Advanced Screening Method, which is now available from every VPS laboratory.

CNSL Summary – Friend or Foe?

CNSL has certainly divided opinion of its applicability to be considered as a bio-component within marine biofuels. Its natural high level of acidity and reactivity, along with its potential to polymerise, certainly raises negative questions. Data would indicate using 100% CNSL as a fuel should be avoided, along with blending CNSL with HSFO fuels. Vessel operational issues, due to the presence of high levels of CNSL have caused fuel system, engine and exhaust damages.

For the purposes of ISO 8217:2024 and all preceding versions, CNSL is not recognised as a standard fuel component. Accordingly, its presence in a marine fuel may be considered a contaminant and potentially classified as off-specification when assessed against the ISO 8217 standard.

However, in instances where CNSL is intentionally used as a blending component and does not fully conform to any of the defined categories within ISO 8217, the fuel may still be deemed acceptable—provided that its characteristics and specification limits are mutually agreed upon by the buyer and seller. In such cases, the fuel shall be classified under an appropriate category defined in ISO 8217, accompanied by any necessary deviations or additional parameters required to adequately characterise the fuel's properties.

It is also worth noting that CNSL production and refining techniques are improving in order to produce a higher quality product. As stated, when the CNSL has a Cardanol content of >98%, with a significant reduction in the presence of Cardol and Anacardic Acid, then the product is a far less reactive component. Therefore, from a fuel purchasers perspective, it will be the choice of the CNSL supplier and the production processes they employ, which will be a significant factor in what is received and the CNSL properties, behaviour and overall quality of the product.

CNSL does require a much higher level of fuel management than other fossil fuel, or biofuel blends. So, whether it is in the development of a fit-for-purpose marine fuel blend, or in damage prevention detection of CNSL as a contaminant within fuels, VPS can provide high level, in-depth, expertise and experience in relation to CNSL-based fuels.

For further information on how VPS can assist and support you regarding CNSL-based marine fuels, please contact marketing@vpsveritas.com

As global market leader in marine fuel testing and bunker quantity surveys, VPS has tested the most marine fuel samples in the market to-date and has witnessed first-hand what new fuels have to offer, and what the expected issues and risks in managing these fuels will be. Based on this data, VPS has launched Marine Fuel Insights.

Marine Fuel Insights is a quarterly subscription-based service, where VPS’ technical expertise is combined with its proprietary database of fuel oil and distillate samples, to derive special insights for its users. Subscribers receive insights on: availability of VLSFO, quality of tested fuels, potential operational issues, fuel performance, operational characteristics, compliance levels.

Stay ahead in the marine fuel industry with Marine Fuel Insights.

2pm Friday 20th June 2025

Riviera Maritime Media Webinar

Presenter: VPS Commercial Director-Europe, John MacKenzie

Register: Lubricants for conventional and emerging marine fuels

Stanley George, VPS Group Scientific & Technical Manager, highlights the effect of FAME contamination on marine engine oils.

Join Senior VPS Management and fellow Expert Panelists at the next Free VPS Seminar, covering key decarbonization topics, including low-to-zero carbon fuel management issues. Registration link: https://forms.gle/dvsfJMaMJsGZgcxn8

VPS, the world’s leading marine fuel testing company, updates their recent findings regarding contaminated marine fuel delivered to vessels in the Port of Singapore.

Following its bunker alerts issued on the 11th and 31st March 2022, VPS can confirm it has now identified 60 vessels that have received High Sulphur Fuel Oil (HSFO) deliveries containing chlorinated hydrocarbons bunkered in the port of Singapore. Each of these deliveries were made from two suppliers and 12 delivery barges, between mid-February to mid-March 2022 and contained chlorinated hydrocarbon contaminants of up to 2,000ppm.

VPS also confirms, no new reports have been received from vessels experiencing, seriously damaging effects due to these bunker fuel contaminations, other than the 14 originally reported in our press release of 31st March.

VPS CEO Malcolm Cooper stated “We have now identified a significant quantity of bunker fuel, 140,170 metric tonnes to be precise, that has been contaminated with chlorinated hydrocarbons. This equates to $120 million at current market value. We would advise our customers to be very aware that this contaminated fuel remains in the supply chain and could potentially be reused or re-blended for use as a bunker fuel. The best mitigating measure to prevent the risk of receiving and using this fuel, is to test at the point of bunkering. However, as shown in this case, standard ISO8217 test methods are not sufficient to detect these contamination events. VPS therefore strongly recommend GCMS screening as the most effective method of detecting chemical contaminants in bunker fuel including chlorinated hydrocarbons.”