Barnacles, algae, and mussels love attaching themselves to ship hulls. This biofouling increases drag, fuel consumption, and greenhouse gas emissions. Antifouling paints prevent this — but at a significant environmental cost.
A Toxic History
Tributyltin (TBT), once the most effective antifouling agent, caused devastating environmental damage. It was found to cause imposex in sea snails — females developing male reproductive organs — at concentrations as low as 1 nanogram per litre. Entire populations of dog whelks were wiped out near busy shipping lanes.
TBT was globally banned by the International Maritime Organisation in 2008, but its legacy persists. TBT remains in harbour sediments, continuing to leach into the water column decades later.
Current Alternatives
Today's antifouling paints typically use copper-based biocides. While less acutely toxic than TBT, copper accumulates in harbour sediments and is toxic to many marine organisms at elevated concentrations. Some marinas now exceed copper environmental quality standards.
Booster biocides — additional chemicals like Irgarol, diuron, and zinc pyrithione — are added to enhance effectiveness. Several of these are now flagged as CECs, with emerging evidence of environmental harm.
The Innovation Challenge
The shipping industry needs solutions that prevent biofouling without poisoning the sea. Promising alternatives include:
- **Foul-release coatings** — ultra-smooth silicone surfaces that organisms can't grip
- **Biomimetic surfaces** — textures inspired by shark skin or dolphin skin
- **UV-based systems** — LED arrays that prevent settlement
- **Ultrasonic devices** — sound waves that deter organisms
The Bigger Picture
Biofouling isn't just an environmental issue — it's a biosecurity one. Organisms attached to hulls can be transported across oceans, introducing invasive species to new environments. Finding effective, non-toxic antifouling solutions addresses multiple challenges simultaneously.
This article is part of the CONTRAST project, funded by the European Union under Horizon Europe. Views expressed are those of the author(s) only.