Over 7 million tonnes of mollusc shells are discarded by the seafood industry every year. These shells consist of over 90% calcium carbonate. Crushed shells can reduce soil acidity in agriculture or be fed to egg-laying hens as a calcium supplement. However calcium carbonate is also a common ingredient in the production of cement that is one of the largest sources of harmful CO2 emissions. Currently the majority of the cement industry’s calcium carbonate is coming from ecologically harmful and unsustainable limestone mining. Researchers at the University of Brighton’s School of Architecture and Design, in partnership with specialist material consultants Local Works Studio, are working on an EU-funded INTERREG SB&WRC research project looking at the potentials of sourcing waste material flows local to construction sites to provide material for insulation and rain screen cladding of social housing developments.
One of the projects has the University of Brighton team partnering with restaurants recycling oyster shells into beautiful tiles suitable to hang on the outside of buildings. One restaurant, ‘English’s of Brighton’, who throw away over 50,000 oyster shells annually, have donated shells to the project. Local Works Studio fire some shells to 900°C to create ‘quick lime’ and mix it with unfired crushed oyster shells forming an aggregate. Pressing the mixture into silicone castes there is a natural chemical reaction when water is added to the mix creating some heat. This hydraulic reaction is similar to concrete ‘curing’. After about 3 weeks the tiles are hard enough to hang on a building. Ben from Local Works states that “We’re working on 50kg of oyster per m2 of hung tile. Traditional clay tiles are 78kg/m2.” So not only we are working with waste material, but the manufacturing process is more efficient that the current system.
Last updated on the 16-10-2018 by Sylvain Bosquet