Promising Unconventional Pretreatments for Lignocellulosic Biomass.

Lignocellulosic biomass represents a huge potential for energy production. However, it is relatively an unemployed source for biofuel and biogas production due to the difficulties obtained in the digestibility of the lignocellulosic materials and the inaccessibility of the polymers to the enzymes for degradation. The authors thus review some of the unconventional technologies that have been freshly developed (since a decade and a half) for lignocellulosic biomass pretreatment so as to break the lignin seal, liberate cellulose from the plant cell wall matrix, disrupt and reduce the crystallinity of the cellulose, increase the porosity of the biomass, and achieve desired fractionation. As a result, the cellulose will be rendered more accessible to enzymes for rapid and efficient hydrolysis and this will enhance biogas or biofuel production. The various components of lignocelluloses are initially described. The various technologies that exist for pretreatment of lignocellulosic materials are then classified into physical, physicochemical, chemical, and biological pretreatments. For physical pretreatment, microwave irradiation, ultrasound irradiation, and pulsed electric field are reviewed. For physicochemical pretreatment, ammonia fiber explosion, supercritical carbon dioxide explosion, and steam explosion are discussed. For chemical pretreatment, ammonia recycled percolation, organosolv process, and oxidative processes such as ozonolysis and wet oxidation are reviewed. Finally, biological pretreatment consists of microbial and enzymatic treatment. For each of these aforementioned technologies, the effects on biofuel and biogas production from different biomass are described and discussed with the aid of past studies. [ABSTRACT FROM PUBLISHER]