Organosolv pretreatment: an in-depth purview of mechanics of the system

Abstract

The concept of biorefinery has been advancing globally and organosolv pretreatment strategy has seen an upsurge in research due to its efficiency in removing the recalcitrant lignin and dissolution of cellulose. The high-performance organosolv system uses green solvents and its reusability contributes concurrently to the biorefinery sector and sustainability. The major advantage of the current system involves the continuous removal of lignin to enhance cellulose accessibility, thereby easing the later biorefinery steps, which were immensely restricted due to the recalcitrant lignin. The current system process can be further explored and enhanced via the amalgamation of new technologies, which is still a work in progress. Thus, the current review summarizes organosolv pretreatment and the range of solvents used, along with a detailed mechanistic approach that results in efficient pretreatment of LCB. The latest developments for designing high-performance pretreatment systems, their pitfalls, and advanced assessments such as Life Cycle Assessment along with Techno-Economic Assessment have also been deliberated to allow an insight into its diverse potential applicability towards a sustainable future.

Keywords: Cellulose; Lignin; Lignocellulose biomass; Organic solvent; Pretreatment.

Fig. 1

Diagrammatical representation of the chemical structures of different components in lignocellulose

Fig. 2

Different types of organic solvents used in the organosolv process and their 3-D conformers. (The 3-D conformers have been freely accessed from https://pubchem.ncbi.nlm.nih.gov/)

Fig. 3

Diagrammatical representation of the mechanistic action of organosolv pretreatment on lignocellulosic biomass

Fig. 4

Diagram demonstrating the reaction mechanism of alcohols with lignocellulosic biomass

Fig. 5

Diagrammatic representation of reaction mechanism of organic acids with lignocellulosic biomass

Fig. 6

Pictorial representation of the organosolv system and the different assistance methods available currently