Loss of efficiency, deviation from design parameters, increase of unscheduled maintenance (i.e. unscheduled drydock) or reduction of day rates (i.e. offshore industry) are only a few. In addition to business issues, there are environmental impacts and compliance with local regulations.
But is biofouling all about organisms attaching to surfaces? Yes and no: biofouling may contain micro and macro organisms (microfouling and macrofouling). Macrofouling is what most people see since it is how invasive species such as mussels, crabs and barnacles are carried from one place to another all over the world.
However, microfouling is equally important. Not only does it create the perfect conditions for macrofouling to appear but it also creates specific chemical environments on metallic surfaces that accelerate corrosion. Accelerated corrosion may occur as the result of corrosive metabolic products such as sulphides, ammonia, organic acids, or mineral acids. And as if corrosion is not bad enough, biofouling on seawater surfaces means reduction in thermal performance, acceleration of microbiologically influenced corrosion, loss of production and increase in the maintenance cost of heat exchanger equipment.
Not surprisingly then, a recent study focused on ways of removing biofouling film that adheres to heat exchangers cooled by seawater, using agents such as environmentally harmless non-oxidising biocides and quarternary ammonium compounds (QACs) – a subject I covered during my recent PhD. The results of the study show that these biocides represent an efficient alternative way to eliminate mature biofilms stuck to the surfaces of the heat exchanger’s tube. So, in terms of the efficiency of these exchangers and the environmentally responsible use of new biocides, it represents an acceptable alternative.
Biofouling is challenging because it combines very diverse fields of expertise, from chemical (chemical composition of the biocides, internal composition of the biofouling or composition of extrapolimer substances) to mechanical (heat exchanging equipment, pumps head loss) or environmental (effluent impact, eco-toxicological tests), to name just a few.
And it has an equally diverse spread in the marine industry. Ballast water management (invasive species), energy efficiency (added hull resistance and loss of heat exchanger efficiency), vessel’s operational expenses and environmental compliance are all linked in one way or another to biofouling.
The marine industry may not be as heavily affected as the offshore or land-based industries, where assets remain static for prolonged periods. In such cases, economic losses are quite significant: when a contract is finished, the equipment is moved from one location to another and it is not uncommon for the floating part to be fully colonised and deep cleaning and (sometimes) drydocking is required. Having said that, ships may also stay static for long periods of time and most of us have seen what a hull looks like after only a few weeks at anchor, especially in warmer waters.
I think there are plenty of good reasons why biofouling should climb higher in the agenda of the shipping industry. Quite apart from environmental and regulatory implications, it affects business performance too.