Integrated alkaline-solid/liquid separation-thermal multiple-step pretreatment of lignocellulosic biomass for biogas production enhancement

Multiple-step pretreatment showed the benefits of improved biomass fractionation, maximized cellulose/hemicelluloses utilization, and enhanced anaerobic digestion performance. This study proposed a pretreatment concept, the integrated alkaline-solid/liquid separation-thermal multiple-step pretreatment (AK-SL-TP), to pretreat spent mushroom substrate (SMS), Napier grass (NP), rice straw (RS), and rice husk (RH) for enhancing anaerobic digestion performance. The integrated alkaline-solid/liquid separation pretreatment (AK-SL) was also compared to evaluate the effect of integrated thermal pretreatment in AK-SL-TP. The pretreatment effect toward enzymatic hydrolysis was also assessed. Multiple pretreatment (AK-SL-TP) showed better performance in terms of biogas production, in which biogas yield was 485 L/kg-VS for SMS, 660 L/kg-VS for NP, 564 L/kg-VS for RS and 101 L/kg-VS for RH, respectively. A linear relationship between biogas production and released glucose/total sugar (glucose and xylose) was observed, with regression coefficient (R2) in the range of 0.88-0.92, indicating enzymatic hydrolysis performance could serve as one promising index for evaluating biogas production.