As with most industries at present, shipping’s need to reduce its emissions is accelerating. One of the key contributors to the world’s carbon footprint, and one whose footprint is particularly hard to abate, the industry is steaming ahead to find viable solutions to minimise its impact on the climate, and to do so while remaining commercially and operationally efficient. Notwithstanding the ESG goals of individual businesses, the backdrop of societal pressure is augmented by regulatory bodies increasing the environmental requirements of shipping — such as those from the IMO.

The International Maritime Organisation (IMO) is a United Nations agency which regulates shipping from safety matters, to security, to, as stated, environmental concerns. The IMO’s GHG emissions reduction targets state that shipping must reduce its CO2 emissions by at least 40% by 2030.

Now, with less than a decade to meet this target, maritime must address all routes to decarbonisation, most especially those which remain hidden contributors.

How hard biofouling has become a significant contributing player

Hard biofouling, caused by organisms such as the barnacle, creates some of the highest levels of hydrodynamic drag on a vessel hull, and is thought to add around 110 million tons of excess carbon emissions annually across the maritime industry — presenting direct combat with shipping’s drive to achieve IMO-2030.

Indeed, 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. Simplified, hard fouling can significantly increase the fuel consumption of a vessel, and consequently its emissions.

While the presence of biofouling is a very real challenge, exact figures around its frequency can be difficult to obtain. However, there is some understanding of the cost impact of a fouled hull. A 2020 study conducted by I-Tech and independent marine coatings consultant, Safinah Group, released figures estimating that hard biofouling adds some US$6 billion to shipping’s annual bunker bill, largely as a result of these fuel consumption rates.

And if hard biofouling isn’t addressed by the global fleet now, these sums could increase. The past 12+ months has seen an unprecedented level of vessel downtime, otherwise known as ‘idling’, as the world has grappled with the pandemic and its lasting effects. Prime real estate for species such as barnacles, vessels which have been left idle are more likely to be impacted by the biofouling issue, in part due to lack of frequent and high-speed movement, and in part due to lack of upkeep.

Yet it isn’t only complete downtime which results in increased instances of hard fouling. According to I-Tech and Safinah Group, observations across all ship types revealed that the frequency of hard fouling was relatively higher on the lower activity vessels. In fact, 45% of lower activity vessels surveyed suffered from hard fouling coverage of > 10% compared to just 27% of higher activity vessels.

Of course, time spent idle or in low activity is compounded by the phenomenon of rising water temperatures, caused by global warming, creating a prime environment for biofouling, particularly in areas already deemed ‘hotspots’ or ‘red zones’ for the likes of barnacles and other types of biofouling.

Niche areas: further hidden spots

Although the data is difficult to obtain, niche areas, such as boot tops, sea chests, propellers and gratings could account for as much as 10%[1] of the total underwater hull surface of the global shipping fleet — a not insignificant figure. I-Tech and Safinah Group’s study found that at least 95% of the global commercial fleet had heavily fouled niche areas, increasing the risks associated not only with the operational efficacy of the vessel — niche area fouling can significantly impact the technical abilities of a vessel — but its biosecurity too, as a vector for invasive species.

According to the IMO, several studies have determined that vessel biofouling has been a comparable, if not more significant factor, than untreated ballast water for the introduction of invasive aquatic species. In some parts of the world, evidence suggests that 70-80% of invasive species introductions have occurred through biofouling. Consequently, we cannot ignore these parts of the hull’s submerged structure when it comes to biofouling. And there is an increasing amount of regionally focused legislation that aims to preserve local marine ecosystems.

With the prospect of widespread new legislation on the horizon, all operators and owners will need to be proactive to ensure they fall on the right side of any rules concerning hull fouling and ecosystem preservation. But why does biofouling occur so commonly in niche areas in the first instance?

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.

However, oftentimes the challenge starts before this, when application occurs. Niche areas are notoriously difficult to access, and can be dangerous to maintain. Comparatively, these areas sometimes do not receive proper attention in surface preparation and coating coverage.

Changes to how coatings are applied and which coatings are chosen is key to tackling niche area fouling. Even the best antifouling coatings will not give satisfying results if the application is not completed properly. Often niche areas do not get the attention they deserve. The surface preparation should be done with the same level of quality as the rest of the hull and also the application quality should be done on the same level, including film thickness measuring.

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.

How to mitigate the risk of biofouling

More generally in the fight against biofouling, a key area to examine is the idle period guarantee for coatings. Most antifouling agents added to marine coatings will only offer idle day period guarantees of between 14-21 days. However, given the unexpected static periods we’ve seen so far, owners need to be considering whether this works for them, especially if they are going to be frequenting the expanding ‘biofouling hotspots’. Some owners could be benefiting from idle guarantees of 30 days, which is found in antifouling systems containing relatively unique barnacle antifouling agents such as Selektope®.

Active antifouling agent Selektope® works by repelling the organism, rather than killing it. Selektope® is designed to cope with even the toughest fouling conditions, such as long idling periods in high-risk areas for biofouling. However, atypical of most biocides, Selektope® delivers efficacy in nano molar concentrations, achieving the same effect as competitor biocides but in significantly lower quantities, reducing overall biocidal load. 

[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. Biol Invasions 19, 1745–1759 (2017). https://doi.org/10.1007/s10530-017-1386-4

I-Tech is a biotechnology company that has developed the product Selektope®, an active agent that prevents barnacle attachment on submerged surfaces such as ships and boat hulls, but also other marine installations. By increasing the resistance to barnacle growth in marine paint systems (e.g. antifouling coatings), fuel and maintenance costs are reduced. I-Tech has obtained the necessary regulatory approvals for Selektope® and has several of the world’s largest manufacturers of marine antifouling coatings as customers. For more information go to www.i-tech.se