Scrap tyres for marine construction: environmental impact

Scrap tyres have been widely used around the world to construct artificial reefs to promote fisheries and, to a lesser extent, in coastal projects such as breakwaters. They are a popular construction material being readily available at no cost, are durable and have large void spaces. These latter features are a disadvantage in land disposal. the fact that these underwater tyre structures are successfully colonised by encrusting marine organisms and fish species has been taken as proof of their suitability. The main negative impact of the use of tyres is the washing ashore of loose tyres from poorly constructed structures after storms, which as led to a ban on their use in many states in the USA. There appears to be little published information about the environmental impact of tyres in the marine environment. Laboratory leaching studies with tyres have detected the release of zinc, benzothiazoles and a range of polycyclic aromatic hydrocarbons. In 1998 an experimental scrap tyre artificial reef was constructed in Poole Bay to provide data on the environmental impact of the material. Colonisation is being monitored in comparison to that on concrete control modules deployed at the same time. Samples of the marine organisms growing on the reef have been analysed for heavy metals and organic compounds. Results from this study after 1 year of deployment show no conclusive evidence for update of tyre dereived heavy metal and organic compounds by the reef organisms. The possibilities of using scrap tyres in marine construction projects and the political barriers to their use are discussed.