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A. R. Abouelela et al.
include mitigating land-use changes associated with use of edible biomass and contributing to rural economic development [4]. In addition, the use of lignocellulose
biomass as a platform for renewable chemicals and materials production is experiencing a renaissance due to the increasing demand to decarbonize the chemical
industry [5].
Lignocellulose is the material that makes up the cell walls of woody plants and it is
composed of three biopolymers: cellulose (35–50%), hemicellulose (30–40%), and
lignin (10–30%). These three polymers are arranged in a three-dimensional structure
that has naturally evolved to resist degradation and deconstruction, which is essential
to maintain the plant’s structural integrity. Unfortunately for us, the increased structural complexity of lignocellulose makes it highly recalcitrant to mild chemical or
biological modification [6]. Therefore, the use of lignocellulose biomass as a viable
feedstock in a biorefinery requires integrating an additional processing step called
“pretreatment” [7]. The main objective of a pretreatment process is to effectively
deconstruct the rigid lignocellulose structure to facilitate its subsequent processing of fuels, chemicals, and materials. For bioethanol production, the deconstruction
effect improves the enzymatic hydrolysis of the carbohydrate polymers to their sugar
monomers. For biochemicals and materials production, pretreatment is fundamentally important to effectively isolate each biopolymer from the lignocellulose matrix
for subsequent upgrading and transformation to value-added products [8].
Although lignocellulosic materials are abundant and relatively cheap, the addition
of a pretreatment process was projected to be the most capital-intensive step in a
biorefinery facility. In fact, for bioethanol production, the cost of pretreatment was
estimated to be higher than the enzymatic hydrolysis and fermentation cost combined
[9]. Evaluating various pretreatment technologies has, therefore, become a major
research field with an objective to find a low-cost technology that can penetrate the
market and expedite industry learning. The mission became far more challenging
recently due to the significant drop in oil prices, reduced energy security concerns,
as well as the wide implementation of new shale oil and gas extraction technologies
(e.g., hydraulic fracturing and horizontal drilling) [10].
Several lignocellulose pretreatment methods are under various degrees of development today, including steam explosion [11], ammonia fiber expansion (AFEX) [12],
dilute acid [13], hot water [14], and Organosolv [15]. Ionic liquid (IL)-based pretreatment is one of the recent approaches introduced in the biomass pretreatment field. ILs
have shown exciting potential to be used as solvents for the lignocellulosic biomass
processing due to their outstanding capability to dissolve [16], fractionate [17], or
convert lignocellulose biopolymers to higher value-added chemicals [18]. As these
fields continue to grow, questions related to the economic justification and technical
challenges of using ILs on a large-scale become more and more pressing. This is especially true in spite of the overwhelming popularity of ILs in academia; ILs-based processes are still very limited with only a few current industrial applications [19]. The
most successful example of an industrial process using ILs is the BASIL™ process
introduced by BASF in 2002. In this process, the ionic liquid 1-methylimidazolium
chloride ([C 1 im][Cl]) is produced in situ by using 1-methylimidazole as an HCl
scavenger during the production of diethylphenylphosphonite. The use of an ionic
A. R. Abouelela et al.
include mitigating land-use changes associated with use of edible biomass and contributing to rural economic development [4]. In addition, the use of lignocellulose
biomass as a platform for renewable chemicals and materials production is experiencing a renaissance due to the increasing demand to decarbonize the chemical
industry [5].
Lignocellulose is the material that makes up the cell walls of woody plants and it is
composed of three biopolymers: cellulose (35–50%), hemicellulose (30–40%), and
lignin (10–30%). These three polymers are arranged in a three-dimensional structure
that has naturally evolved to resist degradation and deconstruction, which is essential
to maintain the plant’s structural integrity. Unfortunately for us, the increased structural complexity of lignocellulose makes it highly recalcitrant to mild chemical or
biological modification [6]. Therefore, the use of lignocellulose biomass as a viable
feedstock in a biorefinery requires integrating an additional processing step called
“pretreatment” [7]. The main objective of a pretreatment process is to effectively
deconstruct the rigid lignocellulose structure to facilitate its subsequent processing of fuels, chemicals, and materials. For bioethanol production, the deconstruction
effect improves the enzymatic hydrolysis of the carbohydrate polymers to their sugar
monomers. For biochemicals and materials production, pretreatment is fundamentally important to effectively isolate each biopolymer from the lignocellulose matrix
for subsequent upgrading and transformation to value-added products [8].
Although lignocellulosic materials are abundant and relatively cheap, the addition
of a pretreatment process was projected to be the most capital-intensive step in a
biorefinery facility. In fact, for bioethanol production, the cost of pretreatment was
estimated to be higher than the enzymatic hydrolysis and fermentation cost combined
[9]. Evaluating various pretreatment technologies has, therefore, become a major
research field with an objective to find a low-cost technology that can penetrate the
market and expedite industry learning. The mission became far more challenging
recently due to the significant drop in oil prices, reduced energy security concerns,
as well as the wide implementation of new shale oil and gas extraction technologies
(e.g., hydraulic fracturing and horizontal drilling) [10].
Several lignocellulose pretreatment methods are under various degrees of development today, including steam explosion [11], ammonia fiber expansion (AFEX) [12],
dilute acid [13], hot water [14], and Organosolv [15]. Ionic liquid (IL)-based pretreatment is one of the recent approaches introduced in the biomass pretreatment field. ILs
have shown exciting potential to be used as solvents for the lignocellulosic biomass
processing due to their outstanding capability to dissolve [16], fractionate [17], or
convert lignocellulose biopolymers to higher value-added chemicals [18]. As these
fields continue to grow, questions related to the economic justification and technical
challenges of using ILs on a large-scale become more and more pressing. This is especially true in spite of the overwhelming popularity of ILs in academia; ILs-based processes are still very limited with only a few current industrial applications [19]. The
most successful example of an industrial process using ILs is the BASIL™ process
introduced by BASF in 2002. In this process, the ionic liquid 1-methylimidazolium
chloride ([C 1 im][Cl]) is produced in situ by using 1-methylimidazole as an HCl
scavenger during the production of diethylphenylphosphonite. The use of an ionic