Mollusc shells are viewed by the aquaculture and seafood industries as ‘nuisance waste’ and largely disposed of in landfills. Not only is this an expensive and ecologically harmful practice, it is a colossal waste of potentially useful bio-material.
Over 7 million tonnes of mollusc shells are discarded each year as unwanted waste however the Royal Belgian Institute of Natural Sciences are looking at environmentally and economically sustainable options for these bio-materials.
One of the most exciting applications proposed is the use of discarded shells to restore damaged oyster reefs and cultivate the growth of new oysters. The restoration of these reefs requires little money and effort, but can have huge ecological advantages.
Mollusc shells consist of over 95% calcium carbonate, which is used in many agricultural and engineering applications. Crushed shells can be spread on farmer’s fields to control soil acidity or fed to egg-laying hens as a calcium supplement. Calcium carbonate is also a common ingredient in cement mix and has found additional use in effectively treating wastewater. Unfortunately, the vast majority of the world’s calcium carbonate comes from ecologically harmful and unsustainable limestone mining.
Reusing shell waste is a perfect example of a circular economy, particularly as shells are a valuable bio-material, not only does it improve the sustainability of the aquaculture industry moving forwards, but it can also provide secondary economic benefits to shellfish growers and processors as well