Marine biofouling is the natural accumulation of microorganisms, plants, algae or small animals on submerged or wet surfaces. Left unchecked, biofouling increases hull surface roughness, fuel consumption and greenhouse gas emissions.
Increased roughness presented by a heavily fouled ship hull can result in powering penalties of up to 86% at cruising speed; even relatively light fouling by diatom ‘slimes’ can generate a 10–16% penalty. Without effective antifouling (AF) measures, vessel performance, fuel consumption (and therefore greenhouse gas emissions) are negatively affected.
Bio-fouled vessel hulls from around the world can introduce non-indigenous marine organisms which may contaminate marine waters and compete with native species. It is estimated that 75% of introduced marine species have established in Australian waters as a result of biofouling on marine vessels.
Owners of marine vessels spend considerable time and money to mitigate the effects of fouling on vessel performance and biosecurity.
Anti-foul paints and coatings provide protection against corrosion and contain biocides that slow bio-fouling. The toxicity of these biocides and their negative effect on the marine environment is well documented.
Anti-fouling agents such as tributyltin oxide (TBT) have been historically used on ships and recreational boats to prevent biofouling. TBT slowly leaches out of coatings into the marine environment where it is highly toxic toward non-target organisms. After it led to the collapse of local populations of organisms, TBT was effectively banned globally.
Today, although the biocides used are less toxic there is still growing concern that they can also contaminate and damage marine eco-systems. Further, the cost of anti-foul coating application and maintenance can be very high. Typical costs of hull treatment during a drydocking can range from thousands to several million dollars depending on vessel size and the type of coating system applied.
Rob Van Merkestein
Business Manager – Bioactive Materials
“Marine biofouling control is similar in many ways to pest and disease control in agriculture – both rely on toxic or biocidal chemicals and both are under regulatory pressure.
The marine coating program aims to develop non-toxic bioactive additives that improve the effectiveness and durability of antifoul coatings to meet operational and environmental requirements. Results from our initial studies in Australia indicate our materials are compatible with common formulations and their inclusion coincides with significantly reduced biofouling. This, and the interest by coating manufacturers undertaking their own studies at various locations around world, is very encouraging.”