Organisms,
such as algae and barnacles, sticking to the lower structure of ships
are increasing the required propulsive power. It is estimated that
ships’ fuel consumption could be reduced by up to forty percent by
removing those organisms. Erosive systems containing biocides are mainly
used for this purpose. However, the use of eco-friendly alternatives
such as silicon based fouling release coatings, nearly all enhanced with
an oil additive, have increased lately. Researchers at GE Global
Research Center in the U.S. have shown that organisms react differently
to the various silicone fouling release coatings, and coating type
crossed with oil type is very important when it comes to establishing an
organism’s attachment strength magnitude.
However,
there is a need for improved eco-friendly alternatives and researchers
are working on solutions. For example, scientists at the University of
Gothenburg in Sweden have developed what they call a “low emission”
approach where avermectins, a class of antibiotics, are included. Only
very small amounts are released, since the substances in the coating are
tightly associated with the binding matrix agent. The scientists found
that 1mg avermectin/gr coating very effectively hindered adult barnacles
from colonization, but a similar coating did not disturb barnacle
larvae. The reason is that the barnacles first encounter the avermectin
when they try to stick tighter to the surface and the avermectin then
make them detach. This principle was named post settlement inhibition
(PSI) because this coating only seems to influence adult barnacle
growth.
Another
innovation that neither involves toxic substances currently used nor
nanoparticles, has been developed by researchers connected to the
European Commission-funded project AMBIO (Advanced Nanostructured
Surfaces for the Control of Biofouling). Their coating technology that
can replace the toxic biocides technology is instead based on
nano-pattering. Molecules within their innovative paint will arrange
themselves in a chequeboard pattern were hydrophobic nanosized points
are combined with hydrophilic nanosized points. This texture makes it
very hard for algae and barnacles to hold on to the surface and the
water’s friction will remove them.
Although
a coating alternative that do not release any toxic substances into the
environment appears to be the safest choice, the AMBIO coating
technology will first be studied extensively in a real world setting to
make sure it has the right properties, for example that it can last five
years on ships, before it can become commercially available.
