Ionic liquid pretreatment of stinging nettle stems and giant miscanthus for bioethanol production

Abstract

Production of ethanol from lignocellulosic biomass is considered the most promising proposition for developing a sustainable and carbon–neutral energy system. The use of renewable raw materials and variability of lignocellulosic feedstock generating hexose and pentose sugars also brings advantages of the most abundant, sustainable and non-food competitive biomass. Great attention is now paid to agricultural wastes and overgrowing plants as an alternative to fast-growing energetic crops. The presented study explores the use of stinging nettle stems, which have not been treated as a source of bioethanol. Apart from being considered a weed, stinging nettle is used in pharmacy or cosmetics, yet its stems are always a non-edible waste. Therefore, the aim was to evaluate the effectiveness of pretreatment using imidazolium- and ammonium-based ionic liquids, enzymatic hydrolysis, fermentation of stinging nettle stems, and comparison of such a process with giant miscanthus. Raw and ionic liquid-pretreated feedstocks of stinging nettle and miscanthus were subjected to compositional analysis and scanning electron microscopy to determine the pretreatment effect. Next, the same conditions of enzymatic hydrolysis and fermentation were applied to both crops to explore the stinging nettle stems potential in the area of bioethanol production. The study showed that the pretreatment of both stinging nettle and miscanthus with imidazolium acetates allowed for increased availability of the critical lignocellulosic fraction. The use of 1-butyl-3-methylimidazolium acetate in the pretreatment of stinging nettle allowed to obtain very high ethanol concentrations of 7.3 g L−1, with 7.0 g L−1 achieved for miscanthus. Results similar for both plants were obtained for 1-ethyl-3-buthylimidazolium acetate. Moreover, in the case of ammonium ionic liquids, even though they have comparable potential to dissolve cellulose, it was impossible to depolymerize lignocellulose and extract lignin. Furthermore, they did not improve the efficiency of the hydrolysis process, which in turn led to low alcohol concentration. Overall, from the presented results, it can be assumed that the stinging nettle stems are a very promising bioenergy crop.

Biomass-derived 2-methyltetrahydrofuran platform: a focus on precious and non-precious metal-based catalysts for the biorefinery

“…8,9 Biomass pretreatment methods have evolved over the years, with physical, chemical, and biological processes having been improved upon. [10][11][12][13] The hydrothermal pretreatment method is one of the convenient approaches that is in accordance with green chemistry guidelines because it can be carried out devoid of harsh chemicals and can be implemented for large-scale biomass pretreatment. 14 After pretreatment, useful biofuels like tetrahydrofuran (THF), 2-methyltetrahydrofuran (MTHF), 2-methylfuran (2-MF), dimethylfurans (DMF), pentanediols, bioethanol, and biodiesel can be produced from the available sugars.…”

Multiscale molecular simulations for the solvation of lignin in ionic liquids

“…Smuga-Kogut et al . 47 , 48 have developed the ML models for predicting bioethanol yields from lignocellulosic biomass with the use of ionic liquid pretreatments. These models are developed with a small set of data points; however, to develop a robust ML model for lignin and biomass conversion, a vast number of databases are needed.…”