Ternary ionic liquid\u2013water pretreatment systems of an agave bagasse and municipal solid waste blend

Noppadon Sathitsuksanoh,Vitalie Stavila,Seema Singh,Kim Tran,Teresa Ponce-Noyola,Blake A. Simmons,Jose A. Perez-Pimienta,Vicki S. Thompson

doi:10.1186/s13068-017-0758-4

Abstract

BackgroundPretreatment is necessary to reduce biomass recalcitrance and enhance the efficiency of enzymatic saccharification for biofuel production. Ionic liquid (IL) pretreatment has gained a significant interest as a pretreatment process that can reduce cellulose crystallinity and remove lignin, key factors that govern enzyme accessibility. There are several challenges that need to be addressed for IL pretreatment to become viable for commercialization, including IL cost and recyclability. In addition, it is unclear whether ILs can maintain process performance when utilizing low-cost, low-quality biomass feedstocks such as the paper fraction of municipal solid waste (MSW), which are readily available in high quantities. One approach to potentially reduce IL cost is to use a blend of ILs at different concentrations in aqueous mixtures. Herein, we describe 14 IL-water systems with mixtures of 1-ethyl-3-ethylimidazolium acetate ([C2C1Im][OAc]), 1-butyl-3-ethylimidazolium acetate ([C4C1Im][OAc]), and water that were used to pretreat MSW blended with agave bagasse (AGB). The detailed analysis of IL recycling in terms of sugar yields of pretreated biomass and IL stability was examined.ResultsBoth biomass types (AGB and MSW) were efficiently disrupted by IL pretreatment. The pretreatment efficiency of [C2C1Im][OAc] and [C4C1Im][OAc] decreased when mixed with water above 40%. The AGB/MSW (1:1) blend demonstrated a glucan conversion of 94.1 and 83.0% using IL systems with ~10 and ~40% water content, respectively. Chemical structures of fresh ILs and recycle ILs presented strong similarities observed by FTIR and 1H-NMR spectroscopy. The glucan and xylan hydrolysis yields obtained from recycled IL exhibited a slight decrease in pretreatment efficiency (less than 10% in terms of hydrolysis yields compared to that of fresh IL), and a decrease in cellulose crystallinity was observed.ConclusionsOur results demonstrated that mixing ILs such as [C2C1Im][OAc] and [C4C1Im][OAc] and blending the paper fraction of MSW with agricultural residues, such as AGB, may contribute to lower the production costs while maintaining high sugar yields. Recycled IL-water mixtures provided comparable results to that of fresh ILs. Both of these results offer the potential of reducing the production costs of sugars and biofuels at biorefineries as compared to more conventional IL conversion technologies.Graphical abstractSchematic of ionic liquid (IL) pretreatment of agave bagasse (AB) and paper-rich fraction of municipal solid waste (MSW)

Highlights

Pretreatment is necessary to reduce biomass recalcitrance and enhance the efficiency of enzymatic saccharification for biofuel production
To provide lower cost biorefinery feedstock inputs, municipal solid waste (MSW) have been used as a blending agent in different feedstocks using Ionic liquid (IL) pretreatment with advantageous features such as year-round availability, reduce landfill disposal and meet biorefinery overall quality specifications [9]
For the untreated AGB, a 31.3% glucan, 15.4% xylan, and 21.6% lignin compositional profile measured is comparable to other agave bagasses from the Tequilana species, but relatively

Summary

Introduction

Pretreatment is necessary to reduce biomass recalcitrance and enhance the efficiency of enzymatic saccharification for biofuel production. There are several challenges that need to be addressed for IL pretreatment to become viable for commercialization, including IL cost and recyclability It is unclear whether ILs can maintain process performance when utiliz‐ ing low-cost, low-quality biomass feedstocks such as the paper fraction of municipal solid waste (MSW), which are readily available in high quantities. Numerous studies have shown that imidazolium-based ionic liquids (ILs) are attractive as green solvents for biomass pretreatment due to several traits, including high cellulose solubility, low vapor pressure, chemical and thermal stability, non-flammability, and phase behavior. These ILs are relatively benign to the environment when compared to pretreatments that use acids, bases, and/or organic solvents. Ionic liquids have been used in the dissolution and partial delignification of corn stover, switchgrass, agave bagasse, softwood, hardwood, and municipal solid waste (MSW) [6,7,8,9,10,11]

Objectives

Methods

Results

Conclusion