**2. Lignocellulose biomass (LB)**

LB is a composite, based on intertwined biopolymers on a dry basis, consisting of 35–45% cellulose, 25–30% hemicellulose, and 25–30% lignin [9]. These are classified into four major proportions based on their source, namely, woody biomass, agricultural residues (for example, rice/wheat/barley straws, corn stover, sugarcane bagasse), energy crops (switchgrass, *Miscanthus* and short-rotation hardwood is specifically grown for biofuel production) and a group of cellulosic wastes (for example, municipal solid waste, pulp mill and lumber mill wastes) [10]. Cellulose and hemicellulose are broken down by enzymatic saccharification into simple sugars which are further digested by microorganisms through the anaerobic digestion process to produce bioenergy such as biogas [11]. Nonetheless, the application of LB for the net reduction of CO2 emissions from the transport sector is considered environmentally benign [12]. As a result, pretreatment becomes very important to improve the digestibility of the LB [5, 13]. **Table 1** shows the various chemical compositions of sugarcane bagasse, a lignin-rich residue obtained from the sugar industry.
