by Emissions from copper-based antifouling paints are a well-known environmental problem. Up to 40 percent of copper inputs to the Baltic Sea come from antifouling paints on ships and pleasure craft. According to a new study from Chalmers University of Technology, Sweden, this is completely unnecessary. When researchers compared copper-based antifouling paint with biocide-free silicone-based paint, they found that the eco-friendly alternative was the best at keeping fouling at bay.
“This means that we now have a great opportunity to drastically reduce the release of heavy metals into our sensitive sea. This is the first independent scientific study to show that silicone paint is more effective than copper-based paint in the Baltic Sea region,” says Maria Lagerström, researcher in marine environmental science at Chalmers.
Together with colleagues from the University of Gothenburg, the Swedish Environmental Institute IVL and Chalmers, Maria Lagerström investigated whether biocide-free silicone paints on boat and pleasure craft hulls are a viable alternative to copper-based primers for combat encrustations. The study was carried out over a year at three sites in the Baltic Sea and Skagerrak region and the results have been published in the scientific journal Marine Pollution Bulletin.
Environmentally friendly paints are rarely used.
The use of copper in antifouling paints is a known and widespread environmental problem for aquatic plants and organisms in the Baltic Sea. The heavy metal does not degrade in the environment and therefore it is common for water, sediment and soil in marinas, ports and shipyards to become contaminated and exceed environmental reference values for copper. An earlier study by Chalmers shows that antifouling paints account for up to 40 percent of total copper inputs to the Baltic Sea.
“As the Baltic Sea is an inland sea, the exchange of water takes between 25 and 30 years. This means that the heavy metal remains for a long time. Therefore, it is important to be aware of the substances we release”, says Maria Lagerström.
Despite the negative impact of heavy metals on the marine environment, the market for antifouling paints for boats and pleasure craft is completely dominated by copper-based paints. The market share of silicone-based paints for the maritime transport sector was 1% in 2009 and increased to 10% in 2014. For the recreational boating sector, it is estimated that the proportion of boats painted with paint silicone is significantly less. And although there are more environmentally friendly options on the market, the change seems to be difficult to achieve.
“Both the shipbuilding industry and the recreational boating sector have one thing in common: they are very traditional. People like to use the products they are used to, and they are also skeptical about whether non-toxic alternative solutions really work”, says Maria Lagerström.
Effective even over a longer period of time
Although the study of the different antifouling paints was completed after twelve months, it was found that the results persist over time.
“In fact, we left our test panels at one of the test sites. These have been under the surface for over two years. We can see that the silicone paint still works well, and more importantly, it works better than the copper paint,” says Maria Lagerström.
More about research and antifouling paints
- The scientific article ‘Are silicone antifouling coatings a viable and environmentally sustainable alternative to biocidal antifouling coatings in the Baltic Sea region?‘ has been published in the Marine Pollution Bulletin magazine.
- The studio is led by Maria Lagerström, Anna-Lisa Wrange, Dinis Reis Oliveira, Lena Granhag, Ann I. Larsson and Erik Ytreberg. The researchers are based at Chalmers University of Technology, the University of Gothenburg and the IVL Swedish Environmental Institute.
- Traditional antifouling paints inhibit fouling by continuously leaching out copper and/or other toxic substances that are poisonous to marine organisms. In the case of silicone paints, it is their smooth surface properties that make it difficult for fouling to adhere to the hull. The paints are also self-cleaning, meaning any dirt that has managed to stick to it is removed as the hull moves through the water.
- Silicone paint is based on the substance silicone, which is produced using silicone oxide extracted from sand. The scientific article’s collection of ecotoxicological studies shows that silicone paints are significantly less harmful to the environment than copper paints. But some silicone paints contain highly fluorinated substances, known as PFAS, which are highly resistant to biodegradation in the environment. However, the silicone paint tested in the study did not contain fluoride.
- The research was mainly funded by the Swedish Transport Administration, under the Swedish Lighthouse Maritime Competence Center and the Sustainable Transport project.
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