Key Insights, Tools, and Future Prospects on Oyster Shell End-of-Life: A Critical Analysis of Sustainable Solutions

Abstract

Oyster farming represents one of the most developed aquaculture activities, producing delicacies unfortunately related to a direct accumulation of waste shells. Facing what is becoming an environmental issue, chemists are currently developing solutions to add value to this wild source of raw material in line with the principles of sustainable chemistry. An argumentative overview of this question is proposed here with a focus on recent data. Starting with a presentation of the environmental impact of oyster farming, existing and promising applications are then classified according to the type of raw materials derived from the oyster shell, namely the natural oyster shell (NOS), the calcined natural oyster shell (CNOS), and biomolecules of the organic matrix extracted from the oyster shell. Their relevance is discussed in regard to their scalability, originality, and sustainability. This review constitutes the first critical compilation on oyster shell applications, with the aim to provide essential elements to better comprehend the recycling of waste oyster shells.

Chemical evidence of rare porphyrins in purple shells of Crassostrea gigas oyster

“…shells is made of an inner iridescent nacreous and an outer prismatic layer often associated with melanins deposition 15,16 , the calcitic shell of C. gigas consists of a prismatic outer layer and a foliated inner layer more or less interrupted by a chalky structure ( Supplementary Fig. S2) 1 . Consequently, we also hypothesized that a deposition of pigments could be associated with the formation of a specific microstructure.…”

“…Pinctada margaritifera ) have been extensively studied compared to their edible cousins (e.g. Crassostrea gigas ) 1 . Prized by gourmets, the aesthetic appeal of shellfish as a gastronomic showcase is arousing growing interest.…”

“…Prized by gourmets, the aesthetic appeal of shellfish as a gastronomic showcase is arousing growing interest. However, the accumulation of wasted shells becomes a real environmental problem, predominantly in oyster farming or tourist areas 1 . At a time when sustainable and intelligent uses of renewable aquatic resources are needed, the transformation of this calcareous by-product into a value-added material is a relevant challenge to be taken up.…”

“…While the use or transformation of calcium carbonate or its organic matrix is the first-line source for recycling edible oyster shell, its colouration is still unwell understood and therefore little valued 1 . Despite the functional roles of shell colours in camouflage, thermoregulation or immunity, the molecular mechanisms related to shell colouration remain poorly documented 2 .…”

“…By combining the identification of shell pigments with corresponding biosynthetic pathways and associated genes, key information on the relation between shell colouration, mineralization or other molecular mechanisms can be obtained as previously reported in marine snails 3 . Therefore, the identification of shell pigments appears to be a possible gateway to the recovery of natural dyes from wasted oyster shells for a broad range of applications in health or material science, helping to contribute to a sustainable future for shellfish farming industry 1 .…”