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ributyltin (TBT), a biocidal anti-fouling coating (AFC), set the bar for 40 years, and coatings using TBT were viewed as tough and long-lasting. TBT

was introduced in the 1960’s in ‘self-polishing’ coatings which allowed gradual surface leeching, revealing fresh active TBT. As the industry got used to an era of smooth hulls, ship designers were even able to specify less powerful engines. TBT however was environmentally dangerous.

It was discovered to cause, amongst other things, imposex (the development of male characteristics in females) in crustaceans. High concentrations were found in sediment, especially surrounding ports. Concern over broad damage to marine ecology led to an international ban, which came into full effect in 2008. Now, as most ships have completed at least

one drydocking with substitute coatings, no replacement has achieved the general acceptance of the shipping industry. Faced with spiraling fuel prices, ship operators are increasingly desperate to find a replacement which will match its effectiveness.

FOULING COSTS Fuel costs are a major headache for ship operators. An average cargo vessel might consume 100 tons of bunker fuel for a days steaming, at over $600 per ton. Fouling, ranging from light slime to crustacean growth, adds between 5% and 40% to those fuel bills. According to a recent formula produced for the US Naval Academy, at today’s bunker prices the effects of slime (the lightest form of fouling) potentially costs the shipping industry 44 million extra tonnes of bunker fuel, costing $28.6 billion in additional fuel costs. That much extra

fuel creates an extra 134 million tonnes of CO2 emissions every year. Such an increase in greenhouse gas emissions

means that, for once, green campaigners and Big Business see eye to eye on the need to find a hull coating which cuts fuel consumption. At the same time however, regulators are moving towards ever tighter restrictions on biocidal components in hull coatings. Cuprous oxides, the most commonly used replacement, are in the spotlight and there is a serious possibility that they will eventually follow tin onto the banned list. Different coating approaches are now

competing for market dominance, but no clear concensus has yet emerged on the way forward. There are, broadly, three main contenders: active antifouling coatings (AFCs) containing substitute biocides such as copper, slick silicone or fuoropolymer coatings (foul-release coatings, or FRCs) which are hard for marine life to attach to, and inert Hard cleanable coatings which are tough enough to allow for regular in-water removal of fouling by scrubbing with diver- operated machines. With the market in flux, we present a round-up of current approaches.

INDUSTRY ATTITUDES Sister magazines Drydock and PCE conducted a survey of attitudes to the currently available coatings within the shipping industry. Responses left no doubt that TBT is still regarded as the gold standard for hull coating performance, and is as yet unmatched. In our survey, owners and operators were

asked to rate different types of hull coatings for effectiveness. TBT scored three to one as ‘very effective’ over current anti-fouling coatings, which were also out-scored by Silicone-based and hard coatings. The most important factors wanted by the industry from hull coatings were: to reduce fuel consumption (92.5%); to protect hull from corrosion (82.9%); and to not need replacement every few years (82%). 57% of those surveyed had not heard of a

current coating which they felt offered a long- term solution to fuel penalties cased by fouling. Those who had were evenly split between current biocidal coatings, silicone FRCs, and Hard coatings.

MORE COMPLEX ISSUES Management of fouling raises complex problems. Besides pressure to reduce fuel bills, and pressure to reduce greenhouse gas emissions, there are increasing restrictions to prevent the spread of water-borne invasive species from port to port. Underwater cleaning of hulls (and thus avoiding the large expense of drydocking) is the simplest way to achieve a smooth hull, but since it releases contaminants into the water that is now banned in most ports (with the exception of ships having Hard coatings). Environmental pressures also include concern

about both copper and the newer biocidal agents in anti-fouling, and about oils released by silicone or fluoropolymer coatings which may interfere with the development of fish embryos. Copper based coatings usually also contain additional ‘booster’ biocides, as do many of the silicone- based FRCs.

LEGISLATIVE DIRECTION Even some manufacturers of copper-based antifouling coating privately foresee an eventual ban of active antifouling agents, and legislators in some key shipping markets are moving in this direction. At the recent Green Shipping Technology

Conference in Hamburg, the EU Commissions DG

for Climate Action Heiko Kunst reported that CO2 emissions have increased 2-5% since 1990, and they are now targeting a 2% reduction, heading towards a total of 50mt of CO2

by 2030. The

EU Commission is expecting to issue a draft on biofouling by the end of the year. Addressing the threat of invasive species,

California is moving to a 5% tolerance of fouling before docking is allowed, based on ship hull inspection reports, and Australian and New Zealand regulators are moving towards tighter


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