News

Reduced biofouling for increased energy efficiency

19 November 2015

Even though barnacles and other marine organisms are tiny creatures, they can have severe negative impact on the environment as well as businesses today.

Associate Professor Lena Granhag, Chalmers University of Technology, is currently conducting research that will lead to improved environment and competitiveness for the maritime sector. Her interest lays in research on biofouling, and reduced biofouling that will lead to increased energy efficiency.

- Biofouling, the growth of marine organisms on ship hulls, creates friction on the ship. If you reduce biofouling you get less friction and you therefore needs to use less fuel, which leads to less emissions of carbon dioxide. Research on naval ships from US shows that soft fouling, for example seaweed, leads to about 16 % friction increase and hard fouling, such as barnacles, up to 59 % friction increase, Lena Granhag says.

In 2008 the IMO International Convention on the Control of Harmful Anti-fouling Systems on Ships was adopted, which banned Tributyltin (TBT) - a toxic substance that previously was used in bottom paint. Today, there are a few things that ship owners can do in order to avoid biofouling. Since TBT was banned, most vessels today use copper based paint and hull cleaning. During the hull cleaning, some of the copper is removed – something that is not good for the environment. Further, the removal of copper will make the paint less effective. Lena Granhag´s research aims to attack the problem by searching for the best ways to clean the hull. Research about the importance of swimming speed and fouling release of barnacles and algae has also been conducted.

- The research for instance suggests that roughness on the hull can be important for reducing barnacles since they prefer a smooth surface, Lena Granhag says.
Another problem with biofouling is the transfer of invasive aquatic species. Ships can introduce invasive species either with ballast water or as hull fouling. The IMO Ballast Water Management Convention will when in force regulate ballast water introductions. Lena Granhag argues that it is likely that also harder regulations for hull introductions will be adopted in the future since approximately half of the invasive species introduced by shipping derive from the hull.

- To date we are not sure if hull cleaning leads to release of viable invasive species to the environment, Lena Granhag says.

In a current research project the ship hull fouling is characterized and friction-measurements will be conducted in lab together with modelling of friction from fouling of different roughness.

Planned future research involves development of hard non-toxic paint made for cleaning, optimisation of water jet cleaning and collection of removed (potentially harmful) organisms as well as remotely operated vehicles for monitoring and hull inspection.