Pretreatment of Lignocellulosic Biomass with 1-Ethyl-3-methylimidazolium Acetate for Its Eventual Valorization by Anaerobic Digestion

Abstract

This study assessed the breakdown of lignocellulosic biomass (LB) with the ionic liquid (IL) 1-ethyl-3-methylimidazolium acetate ([Emim][Ac]) as a pretreatment to increase the methane yield. The pretreatment was conducted for wheat straw (WS), barley straw (BS), and grape stem (GS) at 120 °C for 120 min, using several LB to [Emim][Ac] ratios (1:1, 1:3, and 1:5 w/w). Pretreatment significantly disrupted the lignocellulose matrix of each biomass into soluble sugars. GS showed the highest sugar yield, which was followed by WS, while BS was slightly hydrolyzed (175.3 ± 2.3, 158.2 ± 5.2, and 51.1 ± 3.1 mg glucose g–1 biomass, respectively). Likewise, the pretreatment significantly reduced the cellulose crystallinity index (CrI) of the resulting solid fractions of GS and WS by 15% and 9%, respectively, but slightly affected the CrI of BS (5%). Thus, BMP tests were only carried out for raw and hydrothermally and [Emim][Ac] (1:5) pretreated GS and WS. The untreated GS and WS showed similar methane yields to those achieved for the solid fraction obtained after pretreatment with an LB to [Emim][Ac] ratio of 1:5 (219 ± 10 and 368 ± 1 mL CH4 g–1 VS, respectively). The methane production of the solid plus liquid fraction obtained after IL pretreatment increased by 1.61- and 1.34-fold compared to the raw GS and WS, respectively.

Effect of alkaline pretreatment on the characteristics of barley straw and modeling of methane production via codigestion of pretreated straw with sewage sludge

“…The decomposition rates were very low and became negligible after this stage. Similar results were found by the authors (Marin-Batista et al 2021;Siddiqi et al 2022). The TGA curves indicated that there was less degradation residue (char) from the pretreated straw than from the untreated straw.…”

“…The maximum peaks in the DTG profiles for the different samples occurred in this stage and were detected in the temperature range 300 to 320 °C due to exothermic reactions of the cellulose. Moreover, the peaks for the pretreated samples were greater than those for the untreated samples, which was explained by the increased cellulose proportion after pretreatment, similar to the findings of Marin-Batista et al (2021).…”

Enzymatic Valorization of Lignocellulosic Biomass—The Influence of Deep Eutectic Solvents and Ionic Liquids on the Activity of Cellulolytic Enzymes

“…[Cl]), were studied [37][38][39][40]. To reflect the environment of the enzymatic hydrolysis of biomass pretreated with ILs, we have added 10% v/v of ILs to the reaction mixture.…”

“…Since a much higher glucose yield was obtained in the presence of 24 mg (19 U) of cellulase from A. niger, we decided to use the amounts of all biocatalysts that correspond to the same activity (19 U) for further studies. ), were studied [37][38][39][40]. To reflect the environment of the enzymatic hydrolysis of biomass pretreated with ILs, we have added 10% v/v of ILs to the reaction mixture.…”