Multidisciplinary Pretreatment Approaches to Improve the Bio-methane Production from Lignocellulosic Biomass.

Depleting fossil fuel resources such as crude oil and coal are responsible for greenhouse gas emissions and global warming. Hence, converting biogenic waste such as animal waste and agricultural and industrial residues to biogas (CH4 and CO2) using anaerobic digestion (AD) is a sustainable, renewable, and environmentally friendly way of producing fuel. This nature-derived bioconversion process provides energy security and additional environmental services such as waste management. Furthermore, the liquid and solid waste generated through the AD process could be used as soil amendments to increase fertility. However, natural recalcitrance of biomass pertaining to the intricate network of polysaccharides and lignin, high crystallinity of cellulose, and reduced accessible surface area are some of the major bottlenecks to utilizing these resources as received. Pretreatment helps open up the plant cell wall by disrupting the lignin carbohydrate complex, de-lignifying the biomass, aiding the enzymes to access the polysaccharides due to higher surface area efficiently, and hydrolyze them into simple sugars with the help of bacterial consortium during AD process. This review gives an overview of physical, chemical, biological, and combinatorial pretreatment methods of lignocellulosic substrates and their effect on AD process. Biological pretreatment has emerged as a more desirable pretreatment method in terms of environment safety and efficiency for lignin degradation. Though the higher pretreatment duration has been observed as the most significant challenge that need to be addressed for its adoption on commercial scale. Therefore, research is required to either explore the naturally occurring or prepare the genetically engineered microbes for selective degradation of lignin at faster rates and high tolerance for variation in environment factors. [ABSTRACT FROM AUTHOR]