Valorization of biomaterials from calcifying marine organism waste

Marine aquaculture and fishery industries produce millions of tonnes of waste every year. According to FAO, global fish production reached about 179 million tonnes in 2018 and the 70 wt% of the processed seafood was discharged as waste. This waste is often just dumped in the sea or disposed in landfill in developing countries while in developed countries their disposal can be costly. Shells, in particular, represent the main marine waste but they also harbour useful chemicals such as chitin, protein and calcium carbonate. So, turning cast off shells into new materials, applying the concept of a circular economy, would benefit both the environment and the economy. Mussel shells, for example, are mainly built up of single crystals of calcite and aragonite in an external and an internal layer, respectively. The recovery of these biomineral building units offers the possibility to overcome the synthetic difficulties in replicating the ability of organisms to act as crystal shapers and morphology modifiers. Mollusk shells are a massive source of biogenic calcium carbonate (bCC) that can potentially substitute ground and precipitated calcium carbonate. These materials can be used as filler in polymeric matrices after a surface coating with hydrophobic molecules. bCC may also be transformed into a new added-value material such as apatite with cytocompatible and osteoinductive properties for biomedical applications or it may be converted into nano-crystalline and amorphous calcium carbonate for applications that span from medical to material science. bCC can also be extracted from crab and shrimp shells individually or in combination with other molecules such as proteins and chitin for potential applications as dye adsorbents. Therefore, this thesis aimed to valorise seafood wastes from different calcifying marine organisms by recovering the biomaterials they are composed of and using them for different applications exploiting their unique features as biominerals.