Assessment of Pretreatment Strategies for Valorization of Lignocellulosic Biomass: Path Forwarding Towards Lignocellulosic Biorefinery

The continuous depletion of fossil resources, energy-crisis, and environmental pollution has become the main drivers for the transition of linear petroleum-refinery to a sustainable biorefinery. Lignocellulosic biomass (LCB) remains the most abundant underutilized renewable biomaterial on our earth that offers a sustainable production of various value-added products like biofuels and other platform chemicals. However, presence of impenetrable lignin sheath along with highly crystalline structure of holocellulose barricades its commercial utilization. In this context, a suitable pretreatment method is mandatory to reduce the recalcitrance of the LCB material. Pretreatment capabilities derived from the extraordinary conditions for its effectiveness in laboratories and even at industrial scale for conversion of LCB are limited. In order to make these LCB bioconversion processes economically viable, more research is needed to focus on developing biorefinery approach. In current scenario, a pretreatment method that can fractionate the variety of LCB to produce lignin free carbohydrates with negligible waste biomass generation is of utmost need. Therefore, to promote the emerging technologies, the present review summarizes the recent advances in the most advanced pretreatment technologies being utilized for the LCB based biorefinery. Pros and cons associated with various pretreatment methods have been critically reviewed. Further, efforts have been made to create a better understanding of the already researched pretreatment technologies to facilitate the future research direction to realize the idea of biorefinery an actuality.