WHAT IS BIOFOULING?
The biofouling or biological fouling is the accumulation of different types of microorganisms, algae, plants and animals on the wetted surfaces of vessels. The variety among biofouling organisms is highly diverse and extends far beyond the attachment of barnacles and seaweeds. According to some estimates, over 1,700 species comprising over 4,000 organisms are responsible for biofouling. Biofouling is divided into microfouling, a biofilm formation and bacterial adhesion, and macrofouling of larger organisms. Organisms are also classified as hard or soft-fouling types. From calcareous fouling of barnacles, encrusting molluscs, tube worms, mussels and other organisms to non-calcareous fouling organisms like seaweed, hydroids, algae and biofilm slime.
WHY IS IT IMPORTANT?
The buildup of biofouling on marine vessels significantly impacts on navigation. The accumulation of biofoulers on hulls can increase both the hydrodynamic volume of a vessel and the hydrodynamic friction, leading to increased drag of up to 60% and decreased speeds by up to 10%, which can require up to a 40% increase in fuel to compensate. With fuel typically comprising up to half of the marine transport costs, the methods to keep the hull clean and prevent the buildup of biofouling, are estimated to save the shipping industry around $60 billion per year. Moreover, increased fuel use due to biofouling contributes to adverse environmental effects and is predicted to increase emissions of carbon dioxide and sulfur dioxide between 38 and 72% by 2020.
THE GLOBAL IMPACT ON ENVIRONMENT
Harmful emissions go hand in hand with fuel consumption. Avoiding the extra fuel required to overcome the hull friction caused by fouling, contributes in reducing the worldwide emission of greenhouse gases, carbon dioxide (CO2) nitrous oxides (NOx), sulfur oxides (SOx), particulate matter (PM) and other atmospheric pollutants. Just to make it clear, the 16 biggest container ships
sulfur oxide pollution
the cars in the world. But the impact is much more important because there are more than 50,000 ships in the world’s merchant fleets.
THE INVASIVE NONINDIGENOUS SPECIES
Fouling introduces invasive nonindigenous species (NIS) but trying to limit the spread by applying highly toxic antifouling coatings is a poor solution, the gains are outweighed by the damage done by the chemicals. Furthermore, it is not very effective, there is evidence that they contribute to the creation of a sort of super-NIS which are resistant to biocides and better armed to take over a new marine environment than the local species they displace. To really prevent the spread of NIS, ships must sail with a completely clean hull. They will not pick up fouling while en route and therefore if they sail with a clean hull, they will arrive with a clean hull. This would require thorough cleaning before the ship sails, not a 25% or 75% job.