A critical review of cast-off crab shell recycling from the perspective of functional and versatile biomaterials.

Shellfish cultivation is an expanding economic activity worldwide. However, the rapid development of crab farming and processing result in a large number of crab shells (CS). Utilizing CS could not only benefit the environment and economy but also promote the sustainable development of aquaculture. In this work, it reviews and analyzes recent attempts in CS recycling, including extracting chitin and its derivatives, for use as adsorbent and flocculant and for preparing polymer composites and catalysts, as well as medical applications. The challenges in these utilizations are discussed, and future research directions are proposed as well. Extracting chitin and its derivates, for use as adsorbent and flocculant, are recent major recycling approaches. Preparing polymer composites and carbon materials has gained more and more attentions. Biotechnology is an alternative method for extracting chitin and its derivates from CS, and high-efficiency desalted and deproteinized bacteria need to be screened. Immobilizing the CS-based adsorbents is the key of treating wastewater in continuous systems. Using CS as a biofiller to prepare polymer composites is promising, and surface modification to improve the interfacial compatibility between CS-based fillers and matrix needs to be further studied.