A comprehensive review of characterization, pretreatment and its applications on different lignocellulosic biomass for bioethanol production

With the draining of petroleum derivatives, expanding natural contamination issues, there has been rising enthusiasm for the examination of lignocellulosic biomass for an alternative fsource of energy. Characterization of various biomass, its intermediate, and products is a need for conversion of any biomass to biofuels. Chemical composition of lignocellulosic biomass is an essential point for developing potent pretreatment technologies to break its rigid structure, conversion of sugar by different enzymes mainly cellulose to glucose and even various microorganisms which can ferment sugars into bioethanol and other value-added green chemicals. In this present review work, the main focus is on the proximate and ultimate analysis of different feedstocks, and altered pretreatment techniques such as physical, chemical, physicochemical, and biological methods for bioethanol production have been addressed, which ultimately will help in overcoming the recalcitrance of lignocellulosic biomass by degrading the lignin fraction, breaking down of lignocellulose components, hydrolysis, and fermentation process. Recently, combined pretreatment is gaining popularity as it is more favorable and profitable for improving chemical yield and process of enzymatic hydrolysis of LBs, but it increases the cost of operation. Acid pretreatment, steam explosion, and hydrothermal processes all together show a comparatively high effect on degrading hemicelluloses fraction. Alkali, oxidative, and organosolv pretreatment are more efficient in removing and degrading of lignin portion. This present study will empower a better idea and knowledge of the available process with the upcoming advanced processes which would help to overcome the limitations and establish technology to facilitate the pretreatment methods to make an authentic concept of biorefinery.