Exploration of water-recycled cassava bioethanol production integrated with anaerobic digestion treatment

Abstract

Due to the limited success of discharge target-hitting treatment in coping with environmental pollution from the alcohol industry, our attention was directed towards the distillery spent (DS) wash recycle in a cleaner bioethanol production by integrating anaerobic digestion treatment with conventional fermentation. An anaerobic digestion effluent from an alcohol waste water treatment plant is applicable for single use in ethanol fermentation. With further experimental estimate, the recycle of DS treated by a sole thermophilic up flow anaerobic sludge blanket (UASB) treatment was adverse to ethanol fermentation, resulting in a gradual increase of the residual total sugar from 1.2% at batch 1 to 8.0% at batch 5 after 48 h. With a combination of the thermophilic and mesophilic UASB treatment, the thirteenbatch fermentation recycling its DS achieved ~10.5% of ethanol production and > 90% of starch utilization after 48 h, which was comparable to that using tap water. This revealed a potential of the anaerobic digestion treatment in water-saving and emission reduction for bioethanol industry.

Key words: Anaerobic digestion, cassava, cleaner bioethanol production, distillery spent wash, thermophilic and mesophilic up flow anaerobic sludge blanket, recycle and reuse.