Exploring the functional properties and utilisation potential of mollusca shell by-products through an interdisciplinary approach

Abstract

Molluscan shellfish aquaculture contributes to 42.6% of global aquaculture production. With a continued increase in shellfish production, disposal of shell waste during processing is emerging as an environmental and financial concern. Whilst major commercial species such as Crassostrea spp. has been extensively investigated on usage of its shell, with information that are crucial for valorisation, e.g. safety and crystal polymorphs, evaluated. There is currently little understanding of utilisation opportunities of shell in several uprising Australian commercially harvested species including Akoya Oyster (Pinctada fucata), Roe’s Abalone (Haliotis roei) and Greenlip Abalone (Haliotis levigata), making it challenging to identify ideal usages based on evidence-based information. Therefore, in this study, an interdisciplinary approach was employed to characterise the shells, and thereafter suggest some potential utilisation opportunities. This characterisation included crude mineral content, elemental profiling and food safety evaluation. As well, physical, chemical, and thermal stability of the shell products was assessed. TGA result suggests that all shells investigated have high thermal stability, suggesting the possibility of utilisation as a functional filler in engineering applications. Subsequent FTIR, SEM and XRD analyses identified that CaCO3 was the main compositions with up to 77.6% of it found to be aragonite. The spectacular high aragonite content compared to well-investigated Crassostrea spp. suggested an opportunity for the utilisation of refined abalone shell as a source of biomedical engineering due to its potent biocompatibility. Additionally, safety evaluations on whole shell also outlined that all investigated samples were safe when utilised as a crude calcium supplement for populations > 11 years old, which could be another viable options of utilisation. This article could underpin abalone and akoya industries actions to fully utilise existing waste streams to achieve a more sustainable future.