Re ECF Project: 2015-06

Project Title: Development of green process technologies to produce chitosan from seafood shell waste

Applicant: Professor HUI Chi Wai, Department of Chemical and Biomolecular Engineering, The Hong Kong University of Science and Technology

Total Approved Grant: $493,552

Duration: 1/4/2016 to 30/9/2017

Project Status/Remarks: Completed

Current chitosan production processes are highly polluting and use and discharge large volumes of contaminated acid, alkali and carbon dioxide gas. The study aims to modify the traditional chitosan production process with a view to developing a new Green Chitosan Production process based on:
(1) recovery of value-added by-products that are currently discarded as waste;
(2) reuse of energy by applying pinch analysis to optimize and recycle energy; and,
(3) recycle and re-use of unreacted raw materials for all the process chemicals involved.

Summary of the Findings/Outcomes:
The research team increased the shrimp shell utility in chitosan production from 15% to 65% by recovering by products from waste streams, such as CO2, Ca(OH)2, and protein, which is traditionally discharged as waste. The shells are first washed and dried at 40°C to remove moisture. Next it is blended and sieved to below 1mm, to reaction efficiency and reduce reaction duration. Methanol with lower boiling point compared to ethanol is used to extract pigments containing astaxanthin for 2 hours at 65°C. The pigments are then recovered via evaporation whereas the methanol can be reused for extraction. The research team found that two times of H+ concentration to the total mineral content is sufficient to complete the demineralization step. A concentration of two times is recommended for a shorter reaction time of one hour. Industrial grade chitosan with DDA >87% can be produced using 20% w/w NaOH at boiling point in just under an hour. This process has also reduced the overall chemicals required by recycling them. Results were disseminated in seminars.