Effect of alkaline and alkaline-photocatalytic pretreatment on characteristics and biogas production of rice straw.

To overcome recalcitrant nature and investigate enhancement of biogas production of rice straw (RS), it was subjected to pretreatment under mild conditions. Alkaline pretreatment using sodium hydroxide (NaOH), photocatalytic pretreatment utilizing titania nanoparticles (TiO2 NPs) and alkaline-photocatalytic pretreatment was used to disrupt the lignocellulose complex. As compared to raw RS, maximum biogas and methane enhancement due to alkaline pretreatment was observed for 1.5% w/v NaOH pretreated RS which was 50 and 71% respectively. Photocatalytic pretreatment of RS at 0.25 g/L TiO2 increased biogas and methane yield by 30 and 36% respectively. However, maximum biogas and methane enhancement was observed for alkaline-photocatalytic pretreatment at 1.5% w/v NaOH-0.25 g/L TiO2 which was 74 and 122% respectively. Comparatively high enhancements were observed during alkaline-photocatalytic combined pretreatment due to increased cellulose and decreased lignin content. Moreover, the experimental data obtained from the experiments were validated using a non-linear kinetic model.