Towards a sustainable and blue economy: unlocking the potential of biogenic CaCO3 from mussel shells.

Global seafood industry reached an all-time record of 214 million tonnes (MT) in 2020 but the world’s consumption of aquatic foods will continue to rise together with the population. Seafood production is forecast to grow another 14% by 2030 and of the total production molluscs comprised about 17 MT/year [1]. Europe is the second worldwide bivalve producer and Italy remains in the top ten of the world producers (Fao-Fishstat). Considering that discarded shells represent more than half of the fish-product mass in the ocean, with high disposal costs and considerable environmental impacts, a proper valorization of its residues would decrease the ocean contamination and improve the sustainable management of marine resources by obtaining high value-added products. In line with the blue-economy concept, we are exploring the potential of seafood waste as a valuable raw material to be biorefined, to obtain CaCO3-based products for advanced applications. Mussel shells are a renewable source of biogenic CaCO3, containing up to 99% of calcite and aragonite (the two main polymorphs of calcium carbonate) and an organic matrix acting as a glue [2]. Calcium carbonate is currently obtained in an unsustainable way by mineral extraction from rocks and is an extremely versatile compound, used in a wide range of applications (in paper, plastics, paint industries, in the production of food supplements, toothpastes and baking powders, in waste treatment, animal feed and building materials). Improving an existing protocol [2], this contribution explores the intriguing properties of a peculiar form of calcium carbonate, known as “soft calcite”, obtained from Mediterranean mussel shells by controlled dissolution of the aragonite component. This material proved to possess a high specific surface, as shown by morphological analyses, resulting in interesting adsorption capability toward organic emerging pollutants, such as tetracycline. Further studies are needed to identify interesting new applications such as adsorption of other pollutants (hormones, drugs) or as a substitute for other high impact and non-renewable materials.