Organosolv Fractionation of Softwood Biomass for Biofuel and Biorefinery Applications

Abstract

Softwoods represent a significant fraction of the available lignocellulosic biomass for conversion into a variety of bio-based products. Its inherent recalcitrance, however, makes its successful utilization an ongoing challenge. In the current work the research efforts for the fractionation and utilization of softwood biomass with the organosolv process are reviewed. A short introduction into the specific challenges of softwood utilization, the development of the biorefinery concept, as well as the initial efforts for the development of organosolv as a pulping method is also provided for better understanding of the related research framework. The effect of organosolv pretreatment at various conditions, in the fractionation efficiency of wood components, enzymatic hydrolysis and bioethanol production yields is then discussed. Specific attention is given in the effect of the pretreated biomass properties such as residual lignin on enzymatic hydrolysis. Finally, the valorization of organosolv lignin via the production of biofuels, chemicals, and materials is also described.

Pretreatment of Corn Stover Using Organosolv with Hydrogen Peroxide for Effective Enzymatic Saccharification

“…Due to its high carbohydrate content, lignocellulosic biomass can be a good source of fermentable sugar for biofuel production [1]. In the bioconversion process of lignocellulosic biomass into biofuel such as fuel ethanol, pretreatment is essential and commonly performed to crack the lignin structure and loosen the crystalline structure of cellulose.…”

“…It is known that chemical pretreatments modify the cellulose structure and crystallinity of lignocellulosic biomass, e.g., cellulose is modified to cellulose III during ammonia pretreatment, whereas organosolv pretreatment generally does not significantly modify the cellulose structure, but it depolymerizes the cellulose and removes amorphous lignin and hemicellulose, resulting in the change of crystallinity [5]. The modification of these structures is the main factor affecting the economics of the bioethanol production process, and much research has been carried out worldwide to develop the processes [1,6].…”

“…Among them, hemicellulose has covalent linkages with lignin forming lignin carbohydrate complexes and association with cellulose, which play an important role in hindering enzymatic hydrolysis of cellulose [6]. Modification of biomass structure and chemical composition through chemical pretreatment can be a major factor affecting the enzymatic saccharification of cellulose, and there have been many research efforts to develop an effective pretreatment method [1,7]. The organosolv pretreatment method is similar to the organosolv pulping process, but the extent of lignin removal in organosolv pretreatment is not as high as the organosolv pulping process.…”

Catalytic Processes from Biomass-Derived Hexoses and Pentoses: A Recent Literature Overview

“…Lignocellulosic material can undergo different types of pretreatment to release its components, including fractionation by thermochemical and physical methods, and biological or organosolv and other chemical procedures. Among such components are lignin, hemicellulose and cellulose, the latter being the major component, circa 45% [19][20][21].…”

“…Xylose, together with mannose, a pentose and a hexose, are the main components of hemicelluloses originating from wood. For example, in softwoods, the xylan share ranges between 3 and 8% w/w dry solid (DS), while mannans are present in a higher percentage-from 10 up to 13% w/w DS, with an overall content in hemicelluloses from 25 to 35% w/w DS [19]. Hardwoods are richer in hemicellulose fraction (24-40%), while grasses and leaves can contain as much as 85% w/w DS of hemicelluloses, with xylan-and xylose-related polymers the main component of the hemicellulosic fraction in this case [69].…”