Smooth sailing

LNG as a marine fuel has, for the last 50+ years, been cited as a reliable fuel choice for shipping’s efforts towards a more sustainable future. Not only is the infrastructure already scaling up for synthetic and bio-LNG, but given its cost and operational abilities, the fuel’s popularity — both in terms of use and in investment — is accelerating.

However, while fuel choice is a vital piece to the decarbonisation puzzle, external factors play a significant role in ensuring shipping is steadily moving towards the 2030, 2040, and 2050 regulations set out by the International Maritime Organization (IMO). One such factor: hard biofouling.

Hard biofouling, caused by organisms such as the barnacle, creates some of the highest levels of hydrodynamic drag on a vessel hull, not only compromising the speed, efficiency, and profitability goals of a vessel, but more so its emissions reductions objectives. In fact, hard biofouling is thought to add approximately 110 million tpy of excess carbon emissions across the maritime industry as a result of a lack of understanding and ineffective antifouling technology.

To put this into perspective, a 2011 study conducted by Michael P. Schultz states that a navy vessel with 10% barnacle fouling requires 36% more power to maintain the same speed. And that impact certainly can ripple through the commercial waves. A 2020 study conducted by I-Tech and independent marine coatings consultant Safinah Group, estimated that hard biofouling adds approximately US$6 billion to shipping’s annual bunker bill.

For LNG-fuelled vessels, and LNG carriers, biofouling can reduce the environmental and cost benefits of the fuels. The reasons for this are manifold, not only in regard to the immediate — such as increasing emissions and cost — but in the long-term. Recent months have seen an influx of LNG new-builds, and if these vessels are going to remain operationally effective beyond 2030, the impact of fouling on this emerging fleet must be taken seriously.

So, what are the effects of biofouling on a ship, and more importantly, how can the LNG industry mitigate the risks associated?

Biofouling on LNG carriers and LNGfuelled vessels

Antifouling coatings are a crucial aspect of ensuring the ongoing security and efficiency of any vessel, including when it comes to the LNG sector. Indeed, the majority of LNG-fuelled new-builds or dual-fuelled vessels — as well as LNG carriers themselves — are constructed in shipyards in the Asia regions, such as in Japan and South Korea. With their warmer waters comes the emergence of hard fouling hotspots: areas which have a higher propensity for attracting and retaining barnacles.

Of course, the more recent expansion of LNG infrastructure in Singapore should also be considered. The increase of LNG bunkering licenses means more and more vessels are wading into hotspots. Warmer water plus ineffective coatings equal a

Dr Markus Hoffmann, I-Tech AB, Sweden, discusses the impact and cost of barnacles and why they matter to LNG’s success as a marine fuel.

greater risk of hard fouling and biofouling for bunkering vessels. Exacerbated by the effects of climate change, warmer water can prove detrimental to a vessel, particularly when it comes to lower activity vessels.

For new-builds, this point is particularly poignant. Due to the complexity of the vessels being constructed, LNG newbuilds can be idle in water for significantly longer, remaining static for as long as 12 - 18 months at any one time. Comparatively, even when in operation, vessels with lower activity levels are more likely to be impacted by biofouling and hard fouling to a greater degree.

The aforementioned 2019 study from I-Tech and Safinah Group cited that the frequency of hard fouling was relatively higher on the lower activity vessels — regardless of ship type — with some 45% of lower activity vessels surveyed suffering from hard fouling coverage of >10% compared to just 27% of higher activity vessels.

With all this in mind, effective antifouling coatings have never been so crucial in the efforts to reduce emissions (as the benefits of LNG fuel indicates) and protect a vessel’s operations and cost impact. This includes exercising coatings best practice — more details are outlined next — during the build, retrofit, and service upkeep of a vessel, not just as it is taking to the waters.

Biofouling’s hidden home

Hard biofouling may have a physical and tangible impact — and its effect clearly notable — but there is another aspect to biofouling which remains hidden and is not immediately obvious: niche areas.

Niche areas of a vessel are those operational components largely internal to a ship, rather than the smooth hull area. This includes boot tops, sea chests, gratings, and dry dock support strips, and although data is difficult to obtain, niche areas could account for as much as 10% of the total underwater hull surface of the global shipping fleet.1 So, what specifically is the significance here?

I-Tech and Safinah Group’s study found that at least 95% of the global commercial fleet has heavily fouled niche areas. For one, this increases the risks of poor vessel operations, as the accumulation of barnacles in niche area cavities and infestation on grates can cause significant maintenance problems with mission critical equipment. For example, fouling build-up in a sea chest can impact the functioning of the box coolers, a vessel’s water-cooling system. When box coolers are fouled, heat exchange is reduced and either the temperature is not lowered sufficiently, or more energy will be needed to obtain the target temperature.

Also, if the water inlets which are covered by grates on the hull surface are clogged, heat exchange can be reduced. In a worst-case scenario, extreme barnacle infestation on their inlet grates can lead to total failure of the box cooler system.

Niche areas have restricted water flow, limiting the action of biocidal coatings which require a flow of water to remove the top layer of coating. This means a thick leach layer of depleted biocides forms, preventing the proper action of the antifouling coating. Similarly, these areas are frequently susceptible to greater turbulence, compromising the coating more so than easier, smooth hull areas.

But when application occurs across a vessel, oftentimes niche areas do not receive the attention they require and can prove challenging to access, and therefore clean and coat, primarily due to their complex and unsmooth surfaces — unlike the hull of a vessel, which can be simply coated to an effective degree.

At the same time, the fouling control solutions used for the hull might not be the ideal choice for niche areas. Fouling control solutions should be used which work under the different hydrodynamic conditions in the niche areas. This can be higher polishing paints which have been designed to work at lower vessel speeds and for longer idling periods. Alternatively, the biocide release rate can be increased to have a similar biofouling prevention effect.

Biosecurity and the threat to ecosystems is another distinguishing element, as niche areas can prove an ideal vector for invasive species. In some parts of the world, evidence suggests that 70 - 80% of invasive species introductions have occurred through biofouling. Consequently, these parts of the hull’s submerged structure cannot be ignored when it comes to biofouling.

What can be done?

Ultimately, if shipping is to successfully decarbonise its operations, and do so in the coming decades, operators and owners must prioritise the protection of their investments. For LNG-fuelled ships and LNG carriers alike, that includes effective and long-term protection against hard fouling and biofouling in general, not only for the efficiency of the vessel, but for its emissions reduction efforts also.

Primarily, the best course of action is adopting a coating with an effective antifouling agent and ensuring correct and thorough application. This is never so apparent as in niche areas. Greater attention to niche area coating is vital given its complex and oftentimes dangerous surface areas — and of course, its propensity for invasive species transfer.

However, the antifouling coating needed for smooth hull areas might not be the optimum choice for niche areas, namely due to the increased impact of waves and turbulence on these areas, in turn compromising the quality of coatings. Therefore, a high polishing rate in coatings will support high performance and low-water flow conditions. Greater time and attention should also be paid to coating when a ship is under construction or in dry dock.

Due to the increasing use of LNG around the world, including in a variety of environmental landscapes, LNG carriers and fuelled ships are adaptive to dynamic conditions. This reinforces the need for effective antifouling coatings. Selektope® is an active antifouling agent which, when added to paints and coatings, repels barnacles and other forms of biofouling. Due to its high concentrate, only a minimal amount of Selektope is required to deliver high quality antifouling technology, reducing the biocidal load of the agent and achieving the same effect as competitor biocides but in significantly lower quantities.

With the right antifouling technology, in-the-know implementation, and ongoing care, all vessel types can mitigate the risks associated with hard fouling and biofouling, leaving LNG carriers and LNG-fuelled vessels to continue efforts towards reducing harmful GHG emissions.

References

1. MOSER, C.S., WIER, T.P., FIRST, M.R. et al. ‘Quantifying the extent of niche areas in the global fleet of commercial ships: the potential for “super-hot spots” of biofouling’, Biological Invasions,

Vol. 19, (2017), pp.1745 - 1759.