Cost-effective process development for sericin recovery from silk degumming wastewater

Sericin is a silk protein gum that draws attention due to recovery opportunity from textile effluents since it has anti-bacterial, anti-cancer, anti-UV and moisture absorption properties. This study investigates the development of a cost-effective process for the recovery of sericin from silk degumming effluents that would contribute to closing the technical and economical gaps in the field of resource recovery. The cost of sericin recovery was initially calculated by evaluation of capital and operational costs based on pilot and lab-scale tests. Eight alternatives from A1 to A8, covering combinations of pre-treatment (flocculation/sedimentation), volume reduction (nanofiltration-NF), solidification (ethanol precipitation + centrifugation) and drying (lyophilization, spray drying or oven drying) steps were considered to find the optimum recovery cost that would be competitive with the commercial price of sericin. Total costs were estimated to be between €140,000 and €2,600,000 for a plant lifetime of 15 years. The unit cost of recovered sericin was estimated to vary significantly from €89 to €1300 per kg. Alternatives A6 (pre-treatment + NF + oven drying), A7 (pre-treatment + oven drying), and A8 (pre-treatment + NF) enable competitiveness with market prices. For these alternatives, staff and energy expenditures were the main cost items. The payback period can be reduced from 15 years to 5 years by increasing the unit price of recovered sericin by 5%–30%. The developed cost-effective process would form a novel basis for a circular business model for the recovery of sericin as well as other resources such as nutrients, water, and energy.