Chitin and chitosan, versatile biopolymers widely used in biomedicine, packaging, and wastewater treatment, are traditionally extracted from crustacean waste. However, the growing interest in sustainable resource use has led to increasing exploration of alternative sources such as insect and fungal byproducts. This study addresses current research gaps through a dual approach: (a) a systematic literature review of chitin extraction from crustacean, insect, and fungal wastes, and (b) an experimental evaluation of acid-based demineralization techniques using black soldier fly exuviae as a model insect-derived source. While crustacean-derived chitin remains dominant, insect-based sources are gaining traction despite challenges in scalability and process standardization. Experimentally, hydrochloric acid demonstrated high demineralization efficiency but resulted in lower yields. Greener alternatives such as citric and formic acid showed a more balanced performance, offering higher yield with moderate efficiency. Combining citric acid with reduced concentrations of HCl improved mineral removal and yield, highlighting a promising route toward more sustainable chitin recovery. Overall, this study emphasizes the need for greener methodologies and consistent sustainability assessments to support circular bioeconomy strategies in chitin extraction.