After nine years, a Swedish research program called Marine Paint has served up an eco-friendly antifoulant that is as much cocktail as coating.
And it all began with a doggie drug.
The new coating combines a novel biocide with micro-encapsulated “clever mixtures” that target various fouling organisms.
Marine Paint / Jan-Olof Yxell (left), Karsten Pedersen (right), Roger Lindbolm (bottom)
|A new biocide targets barnacles (top left), a severe fouling problem. By customizing antifouling blends, researchers can strategically target marine bacteria (top right), barnacles and algae (bottom) and a host of other fouling organisms.|
‘Several Thousand Recipes’
Unlike current antifoulants that typically use high doses of one or two “active ingredients” to wipe out a broad spectrum of fouling organisms, Marine Paint uses specifically designed biocide blends that scientists say are far more effective and less damaging.
These strategic blends are contained in “a vast collection of several thousand recipes” that the researchers have developed since 2003, “with different concentrations and combinations of biocides, all equally effective in their antifouling properties, but with estimated 100-fold differences in environmental risk,” the team writes in the project’s detailed Final Report.
From Dogs to Barnacles
Marine Paint is a joint research program of the University of Gothenburg and Chalmers University of Technology. The program, on Sweden’s west coast, began in 2003 when researchers stumbled across the revelation that a veterinary anesthetic called medetomidine proved effective in—of all things—preventing fouling on ship hulls.
The free base form of medetomidine has been trademarked as Selektope by the Swedish company I-Tech AB (a spinoff from the University of Gothenburg). The Marine Paint team says medetomidine has proved highly effective against barnacles, which are considered the toughest fouling organism.
High concentrations of medetomidine can harm fish and other sea creatures, but the team says its paint formulations avoid that level of concentration.
In 2009, the team applied for Europe-wide registration of medetomidine as an antifouling biocide.
Still, the novel agent is not effective against every fouling critter. That’s where the recipes come in.
Balancing Effectiveness and Risk
To tackle other types of fouling (algae, mussels, sea squirts and moss animals), the researchers have developed a concept for producing optimized combinations of different antifouling agents.
“Each biocide in the mixture has a specific activity profile and is efficacious to a known extent against a known subset of fouling organisms,” the team reports.
The idea is to combine the different biocides and adjust the balance to eliminate all types of fouling.
“Acting in concert, the compounds in the mixture completely prevent fouling,” the report says. “The ratios and concentrations of the compounds in the mixture are optimally adjusted, in order to provide full antifouling efficacy but avoid overdosing.”
To produce the recipes, the researchers have developed a model system that weighs a biocide’s effectiveness against its expected environmental risk. The blends are all equally effective but offer different levels of expected risk, the team says.
By micro-encapsulating the biocides, the team has addressed another common problem with current paint systems: the initial burst that leaches excessive amounts of biocides into the water.
By embedding each biocide separately in microcapsules that measure a few micrometers in diameter, scientists have dampened the initial release burst. The separation also helps avoid chemical interactions among the biocides, which facilitates paint formulation, the team says.
|Results from a second round of panel testing in 2011 after four months at sea found heavy fouling on the control panel (A) and only a loose slime layer on the optimized Marine Paint (B).|
Real-world testing of the medetomidine-containing paints began in 2009 and remains underway. Final testing on biodegradation and bioaccumulation is also underway and will complete the environmental risk assessment of medetomidine.
Scientific details of the Marine Paint program will be published later this year.
“To continue with the present environmental impact of biocides originating from marine paints is not a sustainable solution for any of the stakeholders involved,” project chairman Göran Dahlberg writes in the final report. “From the paint producers, the shipping industry and all living organisms in the waters, to all of us who are in need of and depend on healthy seas.”