Microbial pretreatment of lignocellulosic biomass for enhanced biomethanation and waste management

Abstract

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.

Biorefinery done right

“…Numerous approaches have been considered in order to produce methane, either relying on thermochemical processes such as gasification [35] or pyrolysis [36], or even biological processes. In the latter, biomass is pretreated with microorganisms [23] or enzymes [37] to generate a substrate that could be digested by methane producing microorganisms more easily. réSolve Énergie has also investigated a complementary approach allowing the production of biogas from lignin.…”

“…hemicellulose has also been considered for the production of value-added products such as xylitol through the reduction of the c5 carbonyl structure, or through selective oxidation to organic acids (such as lactic acid), or even through acidinduced dehydration towards furfural [22]. Pentose, although not easily assimilated by classical yeasts, remains a sugar source that can be utilized to produce lower-level products such as methane through biomethanation [23]. however, it would be difficult to motivate establishing a fully industrial setup only for the utilization of hemicellulose, and they should be combined with other sources or carbon residues in order to boost the nitrogen and phosphorus demand of the biomethane-producing microorganisms.…”

A review on strategies to optimize metabolic stages of anaerobic digestion of municipal solid wastes towards enhanced resources recovery

“…Microorganisms which are responsible for hydrolysis release extracellular enzymes which cause the transformation to occur [30]. The hydrolysis of complex organic compounds such as lignocelluloses materials is very slow and is the rate-limiting step during the AD process [31][32][33].…”

“…Some of the advantages of microbial pre-treatments include less corrosiveness and formation of less harmful products due to the absence of chemicals [62]. However, microbial pretreatment processes are very slow and require several specific enzymes because of the heterogeneous composition of OFMSW [30,59].…”

Enzymatic Hydrolysis of Two-way Pretreated Sawdust of <i>Eucalyptus globulus</i> and <i>Cupressus lusitanica</i>

“…Waste lignocelluloses, though largely underutilized, are the most abundant potential source for different industrial uses (Mishra et al, 2018). One of these is the requirement of fermentable sugars for large scale biofuel productions.…”