Extraction of Chitin from Green Crab Shells by Mechanochemistry and Aging

Crustacean shell waste is one of the most important chitin sources for commercial use due to its low price and high availability. The extraction of chitin from this residue relies on two removal steps: one for proteins and another one for minerals. Herein, we report a "solvent-free", one-pot process relying on mechanochemistry and aging to convert crustacean shells into chitin with high yields and low ash content. The extraction was performed on European Green Crabs, one of the world's most damaging invasive species, thus converting a serious environmental threat into a biomaterial opportunity. Successful chitin isolation of Green Crabs was achieved by milling of solid acids (i.e., citric, ascorbic, malic, succinic, and salicylic acid) for 10 to 30 min, while a combination of milling and aging was necessary for aqueous acids (i.e., hydrochloric and acetic acid). Milling, aging times, and shell to acid ratios were optimized, while the process could be scaled to 200 g of shell starting materials. This method required limited chemical and energy inputs, which were quantified by sustainability metrics. The process reported is a more sustainable approach for chitin production over the current industrial methods and has the potential to be extended to other chitin sources (e.g., lobster, shrimp, and insects).