Lloyd’s Register Fuel Oil Bunkering Analysis and Advisory Service (FOBAS) on Tuesday (29 April) released a bulletin regarding testing of fuel samples from different vessels, which bunkered in Istanbul, that have reported problems with fuel injection equipment seemingly caused by a substance sticking and seizing the jerk type fuel pumps:

In recent days, FOBAS has tested fuel samples from different vessels that have reported problems with fuel injection equipment seemingly caused by a substance sticking and seizing the jerk type fuel pumps. These vessels bunkered fuel in March and April this year from Istanbul.

These fuels have been further investigated with extended chemical analysis showing a number of chemical species present with some at very high levels.

Various chemicals were found including 4-Cumyl Phenol and Cyclohexane Diol at high levels. Resin acids and Acrylates were also identified along with unusually high levels of DCPD (Dicyclopentadiene), Indene and trace levels of Tetrachloroethylene.

Not all these chemicals may be contributing to the problems, but they are in a pattern seen in some problem fuels from Antwerp and Rotterdam in 2024 and a number of problem fuels from Houston in 2023 and 2018. Some of these chemicals can polymerise and are used in the manufacture of resins and plastics and may be reacting together under the heat and pressure of the fuel injection system.

These fuels were found to be on-spec based on standard routine analysis. However, there are some particular parameters of note. Viscosity was low at around 40cSt, acid numbers were high (1.50 – 2.50mgKOH/g) and all fuels were VLSFO with sulphur content <0.50%. This low viscosity and high acid number pattern aligns with other contaminated fuels seen in Houston in 2023).

We would suggest that if you have bunkered in the last 2-3 months in Istanbul to be particularly cautious with the use of the fuel. In particular if the fuel has a low viscosity, around 50cSt or lower, high acid number >1.00mgKOH/g or high sediments, we would suggest to discuss further testing options as this problematic fuel may not be isolated to only two vessels.

It should also be noted and suppliers reminded that any fuel purchased against the ISO8217 standard must meet the general requirements of clause 5 as well as limits in the characteristics tables. Clause 5 includes the statement that the fuel should be a “homogeneous blend of hydrocarbons derived from petroleum refining” and be free from any substance or chemical waste that “jeopardizes the safety of the ship or adversely affects the performance of the machinery”.

Photo credit: Hans Reniers on Unsplash
Published: 30 April, 2025

Steve Bee, Group Marketing and Strategic Projects Director of marine fuels testing company VPS on Thursday (24 April) highlighted the potential and the pitfalls of Cashew Nut Shell Liquid (CNSL) in marine biofuels in view of the maritime industry turning to CNSL as an alternative low carbon bio-option for Fatty Acid Methyl Esters (FAME):

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 it is 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.

Note: The full article on CNSL can be viewed here.

Photo credit: VPS
Published: 25 April, 2025

Steve Bee, Group Marketing and Strategic Projects Director, and Emilian Buksak, Decarbonisation Advisor of marine fuels testing company VPS, on Wednesday (16 April) broke down what the newly approved IMO net-zero framework means for ship operators and how VPS can support compliance through fuel testing, emissions measurement, and strategic advisory:

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: 

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.  

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.

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.

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.

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.

Note: The full article, including on how VPS can support compliance through fuel testing, emissions measurement, and strategic advisory, can be found here. 

Related: IMO MPEC 83 approves net-zero regulations for global shipping

Photo credit: VPS
Published: 17 April, 2025