Ternary ionic liquid-water pretreatment systems of an agave bagasse and municipal solid waste blend.
BACKGROUND
Pretreatment 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.


RESULTS
Both 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 and1H-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.


CONCLUSIONS
Our 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).
Department of Chemical Engineering, Universidad Autónoma de Nayarit, Tepic, Mexico.
Jose A
JA
Perez-Pimienta
Department of Chemical Engineering and Conn Center for Renewable Energy Research, University of Louisville, Louisville, KY USA.|Biological Systems and Engineering Division, Lawrence Berkeley National Laboratory, Joint BioEnergy Institute, 5885 Hollis Street, Emeryville, CA 94608 USA.
Noppadon
N
Sathitsuksanoh
Biological and Chemical Processing Department, Idaho National Laboratory, Idaho Falls, ID USA.
Vicki S
VS
Thompson
Biological Systems and Engineering Division, Lawrence Berkeley National Laboratory, Joint BioEnergy Institute, 5885 Hollis Street, Emeryville, CA 94608 USA.|Biological and Engineering Sciences Center, Sandia National Laboratories, Livermore, CA USA.
Kim
K
Tran
Department of Biotechnology and Bioengineering, CINVESTAV-IPN, Ciudad de México, Mexico.
Teresa
T
Ponce-Noyola
Energy Nanomaterials Department, Sandia National Laboratories, Livermore, CA USA.
Vitalie
V
Stavila
Biological Systems and Engineering Division, Lawrence Berkeley National Laboratory, Joint BioEnergy Institute, 5885 Hollis Street, Emeryville, CA 94608 USA.|Biological and Engineering Sciences Center, Sandia National Laboratories, Livermore, CA USA.
Seema
S
Singh
Biological Systems and Engineering Division, Lawrence Berkeley National Laboratory, Joint BioEnergy Institute, 5885 Hollis Street, Emeryville, CA 94608 USA.|Biological and Engineering Sciences Center, Sandia National Laboratories, Livermore, CA USA.
Blake A
BA
Simmons
Agave bagasse; Biomass blend; Biomass pretreatment; IL recycling; Ionic liquid; Municipal solid waste; Ternary system