Bioethanol production from expired cookies and economic analysis for practical application

This work examined the potential of bioethanol production from expired cookies (EC) by the separate hydrolysis and fermentation process. EC was hydrolyzed by glucoamylase with different enzyme addition (3.5 U/g to 140 U/g) to produce the EC hydrolysate. The glucose concentration increased with enzyme addition from 3.5 U/g to 14 U/g and the highest glucose concentration of 21.2 g/L was obtained. The EC hydrolysate was used by Saccharomyces cerevisiae for bioethanol production. The optimal ethanol production obtained from this study was 40.1 g/L in term of economics and efficiency. According to the mass balance, the highest ethanol yield from EC was 0.4 g/g. Techno-economic analysis of the plant with capacity of 5 tons EC/day was also assessed in this study. The total capital cost and annual operation cost were US$540400.7 and US$144543.9/y, respectively. The revenue of the plant was US$390522/y with the sales of 660 t/y ethanol and 412.5 t/y oils. The plant should feed the EC more than 1.04 t/d (334.2 t/y) to avoid the shutdown point. This is the first study to demonstrate the bioethanol production from EC and assess the economic feasibility for industrial application.