Shells from aquaculture: a valuable biomaterial, not a nuisance waste product

Abstract Mollusc aquaculture is advocated as a highly sustainable food source and may play an important role in future food security globally. With production increasing worldwide, it is timely to appraise all aspects of aquaculture when considering its expanding role as a food source. In this regard, one regularly overlooked aspect of mollusc aquaculture is waste generation: namely the production of calcareous shells. Shells from the aquaculture industry are widely regarded as a nuisance waste product, yet at the same time, calcium carbonate is mined in the form of limestone and viewed as a valuable commodity. In a time of increased awareness of the need for a circular economy, the aquaculture and seafood industry should consider shells as a valuable biomaterial that can be reused for both environmental and economic benefit. This review discusses the current waste shell issue and identifies large‐scale shell applications that are already in place. Further, it highlights proposed applications that have the potential to be scaled up to address the problem of waste shell accumulations and reduce our reliance on environmentally damaging incineration and landfill disposal. Of the plethora of shell valorisation techniques proposed in the scientific literature, this review will focus only on those that can incorporate large‐scale shell utilisation, and do not require high‐energy processing, and are thus; simple, sustainable and potentially economically viable. Further, this review questions whether, in many cases, shells can provide more inherent value being returned to the marine environment rather than being used in land‐based applications.