Emissions from copper-based antifouling paints are a known environmental problem. As much as 40 percent of the copper that ends up in the Baltic Sea comes from anti-fouling paints used on ships and recreational craft. According to a new study from Chalmers University of Technology, Sweden, this isn’t necessary at all. When the researchers compared copper-based anti-fouling paint to biocide-free silicone-based paint, they found that the environmentally friendly alternative was the best for keeping fouling at bay.
“This means we now have a tremendous opportunity to drastically reduce the release of the heavy metal 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, marine environmental sciences researcher 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 the hulls of ships and recreational craft are a viable alternative to copper-based bottom paints to prevent fouling. The study was conducted over a year at three sites in the Baltic Sea region and the Skagerrak 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, so it is common for water, sediment and soil in marinas, harbors and shipyards to be contaminated and exceed environmental guidelines for copper. An earlier study by Chalmers shows that anti-fouling paints account for as much as 40 percent of the total copper supply to the Baltic Sea.
‘Because the Baltic Sea is an inland sea, it takes 25 to 30 years for the water to be exchanged. This means that the heavy metal stays put for a very long time. It is therefore important to be aware of the substances we release,’ says Maria Lagerström.
Despite the negative impact of heavy metals on the marine environment, the antifouling paint market for ships and recreational craft is completely dominated by copper-based paints. The market share of silicone-based marine paints was 1 percent in 2009 and rose to 10 percent in 2014. For the pleasure craft sector, the proportion of boats painted with silicone paint is estimated to be considerably lower. And while there are more eco-friendly options on the market, change seems hard to come by.
‘Both shipbuilding and pleasure craft 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, the results proved to be sustained over time.
‘We did indeed leave our test panels at one of the test locations. These have now been under the surface for more than two years. We see that the silicone paint still works well and, more importantly, works better than the copper paint,’ says Maria Lagerström.
More about the research and antifouling paints
- The scientific article ‘Are antifouling silicone coatings a viable and environmentally sustainable alternative to biocidal antifouling coatings in the Baltic Sea area?‘ is published in the journal Marine Pollution Bulletin.
- The study is led by Maria Lagerström, Anna-Lisa Wrange, Dinis Reis Oliveira, Lena Granhag, Ann I. Larsson and Erik Ytreberg. The researchers work at Chalmers University of Technology, the University of Gothenburg and the Swedish Environmental Institute IVL.
- Traditional antifouling paints inhibit fouling by continuously leaching copper and/or other toxins that are toxic to marine organisms. With silicone paints, it is precisely the smooth surface properties that make it difficult for fouling to adhere to the hull. The paints are also self-cleaning, meaning any fouling that has managed to adhere is removed as the hull moves through the water.
- Silicone paint is based on the substance silicone, which is produced with silicone oxide extracted from sand. The scientific paper’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 was fluorine-free.
- The research was mainly funded by the Swedish Transport Administration, in the framework of the Lighthouse Swedish Maritime Competence Center and the Sustainable Shipping project.
Material supplied by Chalmers University of Technology. Note: Content is editable for style and length.