Microbial pretreatment of lignocellulosic biomass for enhanced biomethanation and waste management

Biogas obtained from organic remains entails a developed technology and an appreciable methane yield, but its use may not be sustainable. The potential methane yield of various lignocellulose biomass and the operational conditions employed are inherently reviewed. Although of lower methane yields compared to conventional substrates, agricultural biomass is a cheap option. The major challenges encountered during its biogasification are its recalcitrance nature primarily due to the presence of crystalline cellulose and lignin. This necessitates an essential pretreatment step through physical, chemical or biological interventions for enhanced biomethanation potential. Various pretreatment-physical, chemical, and biological-strategies have been developed to overcome the inherent recalcitrance of lignocellulose to anaerobic degradation. Biological pretreatment approach, however, outcompete other pretreatments due to their application in milder conditions, little corrosiveness, and lower byproduct formation. Such pretreatment importantly aids in selectively reducing the lignin content and crystalline nature of the lignocellulosic biomass, which would evidently enhance the hydrolysis and production of monomers for their further anaerobic digestion (AD) for methanation. A variety of applied biological pretreatment strategies comprises microaerobic treatments, ensiling or composting, separation of digestion stages, and pretreatments using various lignocellulolytic fungi alongside. The net energy output through such approaches is substantially more and relatively inexpensive compared to other established chemical and mechanical approaches. The present review highlights the use of biological agents including bacterial, fungal and/or their enzymes which trigger biodegradation of wastes and utilization of lignocellulose for biofuel production. Additionally, the different physical, chemical, and biological pretreatment strategies for biogas yield enhancement are presented.