Life cycle assessment of sericin recovery from silk degumming wastewaters

Sericin is a silk protein discarded with silk degumming wastewater. Life cycle assessment of sericin recovery from silk degumming wastewater was conducted considering two scenarios; base scenario (no recovery), and sericin recovery with membrane hybrid processes. Base scenario consists of silk degumming and treatment of degumming wastewater. The recovery scenario consists of sericin recovery with the process train; silk degumming, sedimentation, nanofiltration (NF), precipitation and lyophilization. Spray drying was also considered as an alternative to the precipitation and lyophilization. The system boundary was set as cradle to grave and the functional unit was selected as 1 kg of sericin. The recovery scenarios had much higher environmental impacts as compared to the base scenario. In terms of kg CO2 equivalence, the impact of the recovery scenarios on climate change (global warming effect) was found to be approximately 2000–2650 times higher than the base scenario. In recovery scenario, endpoint impact score for climate change was as high as 50%, followed by natural resources (34%) and human health impacts (15%). The use of centrifugation + lyophilization option was found to cause 40%–50% more impacts compared to the spray drying option. The highest impact was for the nonrenewable energy impact category, followed by the global warming category. NF and sericin degumming were the processes with highest environmental impacts.