Solubilization of Lignocellulosic Biomass Using Pretreatments for Enhanced Methane Production during Anaerobic Digestion of Manure

Abstract

Pretreatment of dairy manure can disrupt the lignocellulosic structure and produce higher levels of soluble sugars, which can be effectively utilized by anaerobic microbes to produce methane (CH4). Biochemical methane potential (BMP) tests were performed for dairy manure substrates to evaluate the effectiveness of four different pretreatment methods: acid, alkaline, sulfite pretreatment to overcome recalcitrance of lignocellulose (SPORL), and alkaline hydrogen peroxide (AHP). SPORL treatment produced the highest CH4 yield (353 mL CH4/g-VS) followed by alkaline, acid, and AHP treatments with 311, 264, and 261 mL CH4/g-VS, respectively. In comparison, untreated raw manure yielded only 166 mL CH4/g-VS. Effective pretreatments allowed reduction of cellulose/hemicellulose fractions and an increase in soluble sugars, suggesting solubilization of carbohydrates within the manure fiber matrix. Enhanced anaerobic digestibility also caused a moderate increase in orthophosphate levels in the digestate. Pretreatment may be a promising strategy for efficient manure management by enhancing both biogas production and nutrient recovery.