Process optimization for production of bioethanol from sugarcane bagasse at Wonji Sugar Factory, Ethiopian

Abstract The Ethiopian sugar estates produce large amounts of bagasse annually. An alternative bioethanol energy source is produced through pretreatment and valorization processes. Therefore, this study aimed to optimize pretreatment, hydrolysis and fermentation processes to produce bioethanol from sugarcane bagasse. Different concentrations of alkaline (NaOH) and acid (H2SO4) were used to hydrolyse sugarcane bagasse at different pressures and reaction times, while fermentation experiments were carried out at different incubation temperatures and for different periods at different initial pH values. The pretreatment process was used to extract cellulose, hemicellulose and lignin, whereas hydrolysis was used for reducing sugars, and fermentation was used for ethanol. After the quality test, the collected data were subjected to statistical analysis and model optimization using design expert statistical software version 7.0. The results of the statistical analysis on pretreatment optimization revealed that 2.5% NaOH and 15 psi at 35 minutes resulted in the maximum extraction of cellulose (81.25) with the maximum removal of hemicellulose (8.41) and lignin (6.02%). For pretreated bagasse hydrolysis, 2.05% H2SO4 at 205.92°C within 60 minutes produced a maximum yield of reducing sugars (80.89 g/l), while the maximum yield of ethanol produced under optimized conditions (6 initial pH, 30°C and 71.83 hours of incubation) was 42.98 g/l.