The bio-fouling guidelines currently under development by the International Maritime Organisation (IMO) will establish an expanded regime for hull cleaning and associated record keeping that will be as important for work boats as it will be for the world's cargo carrying fleet because speed and fuel efficiency will not be the only purpose for such work.
Bio-fouling on ship's hulls and other floating structures is estimated to be responsible for up to 87 percent of recorded marine species invasions and the issue was officially introduced to the IMO in 2007.
New Zealand is leading the development of the guidelines which are anticipated to be ready for acceptance in 2010.
Although New Zealand's maritime industry shows a high awareness and concern for the problem, invasions are still occurring there. The Mediterranean fan worm (Sabella spallanzanii), already introduced into Australian waters about ten years ago, has recently been found in the Port of Christchurch and a US$2.53 million elimination programme is underway.
Part of the problem with bio-fouling is that even well-maintained hulls can pose an invasive species risk. A US study published this year found that less than one percent of the hull area of 21 in-service containerships was colonised but that biodiversity in those areas was high. One vessel had 20 different species, concentrated mostly on more protected and heterogeneous niche areas including the rudder, stern tubes and intake gratings.
The guidelines, as currently drafted, call for an effective bio-fouling management system covering ships' hulls and associated niche areas. In-water and dry-docking procedures include where and when owner inspections should be made, record keeping and guidance on enforcement and monitoring by port states.
The guidelines are anticipated to lead to the increased frequency and duration of dry-docking and/or in-water cleaning as more time will probably be required to clean niche areas and different coatings may be required on different parts of a vessel.
Care will need to be taken to ensure that the position of docking blocks and supports does not leave unprotected spots on the hull.
According to Dr Rob Hilliard, Managing Consultant for InterMarine Consulting of Australia, a hull clean for ships operating between 15 and 23 knots primarily aims to reduce drag. It focuses on algal beards along the waterline and the hard fouling that projects from the plating of shaded hull undersides.
Cleaning for bio-fouling involves checking areas such as behind anode blocks, inside stud recesses, behind rope guard plates, on and around rudder posts and rudder-tab slots, strop holes and eyes, mouths of apertures, and inside hull openings such as thruster tunnels.
Attention should also be directed at the internal seawater circuits including sea chests, sea strainers, strainer boxes, coffer pipes, manifolds and fire fighting pump apertures.
There is a concern within industry that a heightened awareness of the issues resulting from the publishing of the guidelines might lead coastal states to take unilateral actions to prohibit cleaning activities in their waters.
This has been the case with the IMO ballast water convention which aims to stop the spread of invasive species carried in the ballast tanks of merchant vessels.
Modification to existing hull-cleaning facilities and practices may be required to ensure residues are not released to the marine environment. New technologies are required to achieve this in-water and Dr Grant Hopkins, Senior Scientist with the Cawthron Institute in New Zealand, is developing a two-diver-operated rotating brush system coupled with suction and collection capabilities.
So far, whilst the machine is well over 80 percent successful, diver error, persistent fouling and inaccessible niche areas pose significant challenges.
Tim Wilkins, Regional Manager for Asia-Pacific at INTERTANKO and Secretary to the organisation's environment committee, has been involved in the development of the new guidelines and he believes that INTERTANKO members undertake regular hull maintenance, typically every three to six months.
This brings measurable improvements in fuel efficiency, but there are concerns amongst owners regarding changes resulting from a concern for invasive species.
"In the draft guidelines, there is a distinction between micro and macro fouling and that's what we put in there because we felt that micro-fouling, which is the slime layer, wasn't necessarily high risk and, in fact, it is very difficult to maintain," Mr Wilkins said.
"You would have to get a diver down to clean your hull every three to five weeks if you wanted to keep the slime layer off. We feel the focus of coastal states should be on the high risk in terms of invasive species, and that is the hard or macro-fouling."
Even minimal fouling may be enough to enable a range of organisms to colonise a hull, Dr Richard Piola, a marine scientist with the Cawthron Institute said.
"It doesn't have to be something big. Even thin slime or algal layers might be enough to disrupt or inhibit the effective release of biocides from anti-fouling coatings."
Copper-based anti-fouling is generally considered to be less effective than the now banned TBT-based paints and Dr Piola said that several groups of organisms have shown a significant tolerance for copper.
These groups have also been associated with invasive species introductions from hull fouling. Their tolerance for the high levels of copper found in areas such as ports may further assist in their establishment once transported.
While silicone-based fouling release coatings may not contain such biocides, they still carry the potential for introducing species if used incorrectly, said Dr Piola. Some research has shown that removal of up to 90 percent of attaching organisms is directly dependent on the speed of the vessel, meaning that some fouling release coatings require speeds of over 20 knots to be completely effective.
Once the guidelines are introduced next year, there may be a call to make them mandatory via an IMO convention. These conventions typically relate to commercial vessels 400GT and over.
In the longer term, vessel design modifications may be introduced to simplify hull surfaces for the improved application of coatings and the ease of subsequent cleaning. "I would see the effect on hull form being more influenced by the almost inevitable green house gas (GHG) indexing of ships than the bio-fouling," said Captain Graham Greensmith, lead specialist, external affairs, for classification society Lloyd's Register.
"But there is a link, of course, as a clean hull means a more efficient ship and therefore less GHG emissions."
Given the recent slow-down in new building orders there may be little incentive for incorporating bio-fouling initiatives into vessel design at present. A more immediate concern is the potential bio-fouling risk of laid up vessels. When the record number of vessels and barges currently idling around Singapore and Malaysia start to move again, fouling may need to be considered from both a fuel efficiency and a bio-fouling perspective.
Wendy Laursen
Source: R Hillard, InterMarine Consulting
