Marine biofouling can be defined as the colonisation of man-made surfaces in seawater by microscopic and macroscopic organisms. This phenomenon can result in great loss of function and effectiveness both for cruising ships and for static constructions. Of special concern is the negative effects of hard foulers such as barnacles, which cause:
- increased drag resistance resulting in up to 40% increases fuel consumption
- disruption of the corrosion protective layer of marine vessels and constructions
Current antifouling technologies are based either on release of biocides or on low-adhesion coatings, e.g. silicone based coatings. Present biocide-based strategies are based on a continuous exposure of biocides at the film/water interface and consequently release into the environment if the antifouling efficacy is to be maintained.
Existing biocide-based solutions are not regarded as sustainable. Low adhesion coatings suffer from drawbacks of low durability and associated high material and maintenance costs. Therefore, there is currently no sustainable and cost-efficient solution available on the market today to minimize the costly and environmentally important problem of marine biofouling of marine vessels and constructions.
A novel method will be elaborated in order to deal with hard fouler such as barnacles. This approach is not based on the exposure and release of biocide into the water. Instead it is based on the direct contact between biocide residing inside a coating and fouling organisms such as the barnacles.
The technical challenge is to find the optimal combination of biocide/coating matrix in order to completely eliminate the release of biocides. Expected impacts of the project are: lower fuel consumption, lower dispersion of biocide, reduced maintenance cost and longer life time (economical aspects) together with, reduced accumulation in the system of biocides and CO2 and reduced alien species transportation by ships.
Environmentally friendly antifouling paint
The colonisation of a ship's hull by marine organisms is termed biofouling. So-called hard foulers, such as barnacles, are of particular concern as they can increase drag on a ship, resulting in up to 40 % increased fuel consumption.
Current antifouling technologies are based on the release of biocides or on low-adhesion coatings. Biocides such as copper oxide are based on continuous exposure, which can have long-term ecological effects and so cannot be considered as sustainable. Low-adhesion coatings suffer from lack of durability and associated high material and maintenance costs.
The http://www.leaf-antifouling.eu (LEAF) (Low emission antifouling coatings based on the novel discovered post settlement penetration triggered antifouling) project was established to develop and demonstrate a new antifouling technology based on neither biocide emission nor low adhesion. Researchers are working on a new approach in which the antifouling effect occurs when the barnacle penetrates the paint. The biocide is only needed in low concentrations and the coating in which it is held can last for years.
The LEAF project has developed new methods for measuring biocide leaching rates and for characterization of antifouling paint formulations, set up a number of different assays for testing of biocide efficacy. Furthermore, the project is conducting a sustainability assessment of the LEAF coatings. Field testing of different LEAF formulations is currently under way in widely different fouling conditions in the North Atlantic, English Channel, Mediterranean and Brazilian coastal waters. Encouraging results have been achieved for the first set of biocides and paint formulations at all the field sites.
The innovative character of LEAF is that it provides significant operational benefits: As it is not based on continuous biocide emission and erosion of the paint, it enables longer service life and maintenance cycles. The low amount of biocide required to achieve antifouling efficacy also has environmental benefits. The effectiveness of LEAF, even with water-based paints, will remove the need for solvents and reduce emissions from volatile organic compounds (VOCs). The removal of solvents and VOCs will allow safe indoor working during poor weather, thereby enabling European shipyards to compete more effectively. Methods developed through the LEAF project will also help future research into the next generation of environmentally friendly antifouling coatings.