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Bunker Fuel

VPS tackles stability issues of various bunker fuels and advises precautionary measures

Steve Bee of VPS highlights the different fuel management approaches required to avoid instability and de-stablization of marine fossil fuels and biofuels.

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Steve Bee, Group Marketing and Strategic Projects Director of marine fuels testing company VPS, on Tuesday (22 July) highlighted the different fuel management approaches required to avoid instability and de-stablization of marine fossil fuels and biofuels:

Today’s ships can carry a number of different marine fuel types, from High Sulphur Fuel Oils (HSFOs), to Very Low Sulphur Fuel Oils (VLSFOs), Marine Gas Oils (MGOs), Ultra Low Sulphur Fuel Oils (ULSFOs), Biofuels, LNG and Methanol. Each of these fuels have varying degrees of stability, or instability, which can be triggered by numerous causes and effects.

However, to mitigate the risks of de-stabilsation, a range of fuel management approaches can be applied to marine fuels. This paper aims to cover the more common fuels, their associated stability issues and how to monitor and potentially overcome them.

High Sulphur Fuel Oil (HSFO) & Very Low Sulphur Fuel Oil (VLSFO)

Today, residual fuel is often referred to as HSFO, whereas VLSFO is a blended fuel of mainly distillates and residual fuels, which results in a usually less stable fuel than HSFO. Yet VLSFOs are still prone to certain similar stability concerns as its 100% residual counterpart and hence the associated test parameters.

Residual fuel, is comprised of process residues where the fractions did not boil during refining. These fuels contain asphaltenes, usually between 3-10%, which are the organic part of the crude oil, or residual oil, that is not soluble in straight chain solvents, eg pentane, heptane.

Asphaltenes exist as a colloidal suspension stabilized by resin molecules (aromatic ring systems) in the oil. The stability of asphaltic dispersions depends on the ratio of resin to asphaltene molecules.

The determination of the quantity of resin is important in estimating the potential damage created by asphaltenes. Asphaltene precipitates as a result of pressure drop, temperature, acids, mixing of incompatible oils, chemical contaminants, or other conditions and/or materials that break the stability of the asphaltic dispersion. This is the sludge witnessed when marine fuels de-stabilize.

The ability to retain asphaltenes within the fuel solution is known as the “Stability Reserve” of the fuel.

Bulk residual fuel stored for long periods can become unstable, where the asphaltene content can precipitate out of solution causing the formation of sludge. This has the potential to block filters and pipes, leaving tanks with an unpumpable residue. The ‘fuel break up’ is dependent on the nature of the liquid hydrocarbons in which the asphaltenes are suspended. If the medium is aromatic then they will remain in suspension. If it’s paraffinic, the asphaltenes may have a propensity to coalesce into sludge. Once a fuel has chemically broken down there is no way to satisfactorily reverse the process. Precipitated asphaltene cannot be redissolved.

Industry best practice is to avoid mixing fuels. Arbitrary comingling can lead to incompatibility problems and a loss of stability in the resultant blend. For example, when a heavy fuel oil with a high asphaltene content is mixed with a low-gravity distillate with a predominance of paraffinic aliphatic hydrocarbons, the stability reserve can be depleted and asphaltenes can flocculate and precipitate as sludge.

Compatibility problems must be treated as a critical concern, as they can lead to fuel starvation in diesel generators, potentially resulting in power loss. Incompatibility may cause fuel system paralysis and the subsequent clean-up is often both complex and time-consuming. There is a very simple, indicative test which can be carried out to highlight a fuels compatibility, the ASTM D4740 “spot test” . Here a blend composed of representative volumes of the sample fuel and the blend stock is heated and homogenized. A drop of the blend is put on a test paper and heated to 100°C. After 1 hour, the test paper is removed from the oven and the resultant spot is examined for evidence of precipitation and rated for compatibility against D4740 reference spots.

To provide valued information regarding a residual fuel’s stability there are a series of laboratory tests to further assess stability:

Total Sediment Potential (TSP)

The measurement of sediment involves filtering the oil through a filtration medium under vacuum. The mass of sediment is reported as a percentage by mass. The test provides an indication of the stability of the fuel as asphaltenes precipitate out forming sludge, blocking filters and choking purifiers. For residual fuels, TSP involves ageing the oil at 100ºC for 24 hours. So far in 2025, 1% of all HSFO off-specifications are related to TSP, whilst 3% of all VSLFO off-specifications are related to the same parameter. 

Total Sediment Accelerated (TSA): (Chemical Aging) A sample of the fuel is heated to achieve a viscosity of approximately 50Cst. After 10 minutes, a measured amount of hexadecane is added and the sample is placed in an ageing bath at 100ºC for one hour. The sample is shaken vigorously prior to passing through a filter paper. The result of the test is reported to the nearest 0.01% m/m and is expressed as Total Sediment Accelerated (TSA). The agreed limit for both TSP and TSA is 0.10% m/m. A fuel that falls below this limit should be viewed as thermally stable and able to homogenously maintain asphaltenic phase suspension.

Total Sediment Existent (TSE): A fuel sample is heated to 100ºC and passed through a filter paper. The amount of dry sludge retained on the filter paper correlates with the amount of sludge that is likely to be separated by an on-board centrifuge.

Separability Number, or Reserve Stability Number (RSN) is a complimentary test to the hot filtration stability methods of TSP, TSA, TSE. Using this method, the fuel is mixed with toluene which is aromatic and keeps the asphaltenes in solution. If the sample has poor stability reserve, then asphaltenes will precipitate when Heptane is added- which is naphthenic. As asphaltenes fall out of solution the transmittance through the sample increases resulting in a measure of the separability number.

Separability Number is an excellent accompaniment to the routine hot filtration methods. It can identify potentially troublesome fuels (unstable) even when the HFT method is indicating a low sediment content. Conversely, it may indicate that a high sediment fuel is in fact quite stable and unlikely to form sludge. This information in combination, is extremely useful from an operational perspective, as it will indicate in advance if and what mitigation steps are appropriate.

Note: The full article on ‘How stable is your marine fuel?’ can be viewed here.  

 

Photo credit: VPS
Published: 23 July, 2025

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Methanol

World Fuel and partners complete first green methanol bunkering of car carrier in Shanghai

Operation involved the delivery of approximately 2,800 MT of green methanol to “Arctic Tern” via a ship-to-ship transfer using SIPG Energy’s dedicated methanol bunkering vessel “M/V Hai Gang Zhi Yuan”.
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July 22, 2026

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World Fuel and partners complete first green methanol bunkering of car carrier in Shanghai

Marine fuel provider World Fuel on Tuesday (21 July) said it successfully completed the first green methanol bunkering of M/V Arctic Tern, with EUKOR Car Carriers and SIPG Energy at the Port of Shanghai. 

Arctic Tern is the first vessel in the new Shaper Class series of car carriers. 

The operation involved the delivery of approximately 2,800 MT of green methanol to Arctic Tern via a ship-to-ship transfer using SIPG Energy’s dedicated methanol bunkering vessel M/V Hai Gang Zhi Yuan, the largest vessel of its kind in operation. 

The bunkering operation was carried out at Haitong Terminal, Waigaoqiao Port Area, Shanghai Port, with cargo handling operations conducted simultaneously during bunkering.

This marks EUKOR Car Carriers’ first green methanol operation and the first time Arctic Tern has bunkered methanol since its delivery on 9 July. The operation marked the first bunkering at Shanghai Port of green methanol produced locally in Shanghai for an international PCTC operator. 

It also demonstrated the city’s integrated green methanol value chain, spanning local production, storage and bunkering, and established a replicable “Shanghai Model” for green methanol supply.

World Fuel arranged the supply and delivery of the fuel on behalf of EUKOR Car Carriers, working with SIPG Energy as the physical supplier at the Port of Shanghai.

The green methanol supplied was produced from municipal solid waste, ISCC-EU certified, and had a carbon intensity value below 25 gCO₂e/MJ.

Arctic Tern is the first of fourteen Shaper Class vessels ordered by Wallenius Wilhelmsen. With a capacity of 9,300 car equivalent units and methanol dual-fuel capability, the vessel will be operated by EUKOR Car Carriers, jointly owned by Wallenius Wilhelmsen and Hyundai Motor Group. Following her first green methanol bunkering, Arctic Tern will continue her maiden voyage from Asia to Europe.

Xavier Leroi, COO Shipping Services at Wallenius Wilhelmsen and CEO of EUKOR Car Carriers, said: “Completing Arctic Tern’s first green methanol bunkering shortly after delivery is a significant milestone towards our decarbonisation ambition for both EUKOR Car Carriers and Wallenius Wilhelmsen. It demonstrates how investments in next-generation vessel technology and fuel flexibility are being translated into real-world operations. 

“This achievement reflects the strong collaboration between all parties involved. Together, we have shown how partnerships across the maritime value chain can help make lower-emission fuels available and operationally viable at scale.”

Mark Tamsitt, SVP Global Marine Sales at World Fuel, said, “The first bunkering event with a new fuel is a significant moment for any shipowner, and our role is to make it as seamless as possible. By connecting EUKOR Car Carriers with SIPG Energy’s proven green methanol capability at the Port of Shanghai, we were able to deliver on reliable supply, fuel quality, and safe processes. As more of our customers bring methanol dual-fuel tonnage into service, we are committed to being the partner that makes these kinds of operations routine.”

Mr. Zhang Da, General Manager of SIPG Energy, said, “Welcoming Arctic Tern to the Port of Shanghai for her first green methanol bunkering demonstrates the strength and maturity of our supply capability. Building on our well-established methanol ship-to-ship bunkering services for container vessels, we have already extended such services to pure car and truck carriers (PCTCs). This bunkering sets a new record for the largest single SIMOPs green methanol bunkering for PCTCs in China, marking another step in building Shanghai’s position as a global green energy hub for international shipping.”

This operation follows Wallenius Wilhelmsen’s announcement on 9 July that Arctic Tern would complete her first methanol bunkering shortly after delivery. The vessel entered service on routes between Asia and Europe immediately following handover from China Merchants Jinling Shipyard in Nanjing.

 

Photo credit: World Fuel
Published: 22 July, 2026

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Ammonia

HPA and MB Energy develop safety concept for STS ammonia bunkering

HPA says the Port of Hamburg will become “bunker ready” for ammonia, laying the groundwork for safe and reliable ammonia bunkering in the future.
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July 22, 2026

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HPA and MB Energy develop safety concept for STS ammonia bunkering

The Hamburg Port Authority (HPA) and integrated energy company MB Energy on Tuesday (21 July) said they have completed a comprehensive risk analysis and developed a dedicated safety concept for ship-to-ship ammonia bunkering.

MB Energy said the analysis lays the groundwork for the safe introduction of ammonia as a future marine fuel.

“With our planned ammonia import terminal in Hamburg-Blumensand, MB Energy intends to provide the reliable land side supply infrastructure needed to support this transition across northern German ports,” it said in a social media post. 

Mabanaft Group was renamed to MB Energy last year and merged over 50 existing brands under one identity. 

Separately, HPA said the Port of Hamburg will become “bunker ready” for ammonia, laying the groundwork for safe and reliable ammonia bunkering in the future.

“The focus is in particular on container ships, cruise ships as well as RoRo and ConRo (Container/RoRo) ships,” it said. 

“We expect ammonia to establish itself as an alternative marine marine fuel in the coming years. With our preparatory work, we are already creating the conditions to welcome the first ammonia-powered ships in Hamburg and to bunker them safely.:

HPA added that the import terminal for ammonia planned by MB Energy from 2029 will make a decisive contribution to ensuring the reliable availability of ammonia as a bunker fuel in northern German ports in the long term. 

“The use of an ammonia bunker barge is considered a possible addition to the landside infrastructure to enable ship bunkering in the port and beyond in the future,” it said.

Related: Mabanaft Group renames as MB Energy, merging over 50 brands under one identity

 

Photo credit: Hamburg Port Authority
Published: 22 July, 2026

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Bunker Fuel

Alkagesta highlights key insights of Malta bunkering market in 2026

Darren Lee Axisa discusses the key trends influencing Malta’s bunkering market and the factors that will determine Malta’s long-term competitiveness as a regional bunkering hub.
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July 22, 2026

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Alkagesta highlights key insights of Malta bunkering market in 2026

In an article published on Alkagesta Market Insights, Darren Lee Axisa, Malta Country Manager of Alkagesta, on Monday (20 July) discussed the key trends influencing Malta’s bunkering market and the factors that will determine Malta’s long-term competitiveness as a regional bunkering hub: 

Malta’s bunkering and energy market is moving through a period of structural adjustment. The disruptions that defined the first half of 2026 have accelerated shifts in product demand, terminal strategy, and the competitive dynamics of one of the Mediterranean’s most strategically positioned bunkering hubs. For Alkagesta, whose storage footprint on the island approaches 300,000 cubic metres, the period has tested operational flexibility while reinforcing the value of diversified infrastructure access.

A Market Shifting in Two Directions

Malta’s broader economy has remained resilient — GDP growth reached 3.9% in Q1 2026 — but the bunkering market has undergone a significant product mix shift, the roots of which predate the current geopolitical disruption.

The Mediterranean Emission Control Area, which came into force on 1 May 2025, triggered an immediate and measurable realignment in fuel demand across the region. VPS data covering the first six months post-ECA implementation shows that across the top ten Mediterranean bunkering ports, VLSFO volumes fell 23%, MGO more than doubled, ULSFO quadrupled, and biofuels increased fivefold. In Valletta specifically, the shift was even more pronounced: VLSFO dropped 57% from 111,641 mt to 47,732 mt, while MGO volumes more than tripled from 33,299 mt to 103,445 mt, and ULSFO rose from 2,821 mt to 34,535 mt over the same period.

This structural rotation has been further accelerated by the broader regulatory environment. FuelEU Maritime and EU ETS requirements are pushing shipowners toward cleaner, verifiable fuel options at every port call — a direction Alkagesta had already positioned itself ahead of, having been among the first movers in the Mediterranean to support the transition to 0.1% sulphur fuel oil following the ECA’s introduction.

Layered on top of this regulatory shift has been a period of reduced terminal capacity affecting bunkering market availability across the island. Fuel oil volumes dropped roughly 35% year-on-year between January and May 2026, falling from approximately 382,000 mt in 2025 to 247,000 mt. DMA demand moved sharply in the opposite direction, rising from around 150,000 mt in January to April 2025 to 247,000 mt over the same period in 2026 — a trend consistent with both the ECA-driven product mix shift and the disruption to heavier fuel availability during the constrained period.

Note: The full article can be read here. 

 

Photo credit: Alkagesta
Published: 22 July, 2026

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