Bivalve mollusc shells are made mainly of CaCO3 (ca 95%), with a small fraction of organic material. If from these shells this mineral is retrieved, they could become a renewable and sustainable “mine” of a “blue” CaCO3. Bivalve mollusc shells, also after the removal of the animal flesh, maintain a certain quantity of organic substances, part in the muscle and part in the shell. Therefore, as the first step of the “blue” CaCO3 production, it is necessary to completely remove organic components, firing shells into an appropriate furnace after washing to remove salts. Successively, they have to be transformed at the form and dimensions specific for each expected product, grinding them by a suitable mill equipment. To maintain the carbon footprint, all the process has to be carried out in an engineered plant designed to operate using a green protocol. The waste resulting from the firing process could be reused further in the building sector, such as additive or admixture in lime mortars.
At the moment, bivalve mollusc shells are not considered a waste that can be re-used, while they can represent a full-fledged renewable secondary raw material. A new regulation, followed at a local and national level, would be propaedeutic for the creation of a not yet existing value chain. In a perspective of circular economy, starting from the recovery of the shells a “blue” CaCO3 can be reached, absolutely renewable and sustainable, in contrast to that mined, which is currently used in every industrial application. No attempt evaluated the use of a shell derived CaCO3 in any industrial fields to date, except building (unsustainable because of the big quantities required) and poultry feed. Possibile high added value applications can be in the production of paper, cosmetics and nutraceutics, plastics, glass, which conversely require limited quantities of CaCO3.