Ethanolic ammonia pretreatment for efficient biogas production from sugarcane bagasse

Sugarcane bagasse (SCB), as an abundant lignocellulosic waste, was subjected to ethanolic ammonia pretreatment followed by anaerobic digestion to produce biogas. Ammonia pretreatment was performed with 10% v/v aqueous ammonia solution at 50 and 70 degrees C for 12 and 24 h. Furthermore, the effect of addition of ethanol to the pretreatment mixture at different concentrations (5, 25, and 50% v/v) was investigated. Two scenarios for biogas production from SCB were considered and compared in terms of equivalent gasoline production per unit mass of biomass: (1) biogas production from the pretreatment separated solid and liquid fractions, and (2) biogas production from the whole pretreatment slurry. The highest methane yield of 298.0, 248.6, and 299.3 ml/g VS (volatile solids) were attained from the liquid fraction, solid fraction, and the whole slurry of pretreatment at 70 degrees C, respectively. Whereas, methane yield from untreated SCB was only 105.6 ml/g VS. Generally, the methane production yield by pretreatments at 70 degrees C was more than those at 50 degrees C. The maximum equivalent gasoline from each ton of SCB for scenarios 1 and 2 were 172 and 182 L, respectively, obtained after pretreatment at 70 degrees C for 12 h with 10% ammonia + 50% ethanol, whereas it was 103 L from untreated SCB.