Solid-state Pretreatment Research Articles

Microwave-assisted solid-state pretreatment for fabrication of hemp fibres using ethanolamine at low temperature

Conventional methods faced challenges in pretreating natural cellulose fibres due to their high energy consumption and large wastewater drainage. This research devised an efficient solid-state pretreatment method for pretreating hemp fibres using ethanolamine (ETA) assisted by microwave (MW) heating. This method produced a notable removal rate of lignin (85.4 %) with the highest cellulose content (83.0 %) at a high solid content (30 %) and low temperature (70 °C). Both FT-IR and XRD analyses indicated that the pretreatment did not alter the structure of cellulose within the hemp fibres but increased crystallinity as the CrI increased from 84 % in raw hemp fibre to 89 % in pretreated fibre. As a result, it produced hemp fibres with impressive fineness (4.6 dtex) and breaking strength (3.81 cN/dtex), meeting the requirement of textile fibre. In addition, an improvement in glucose concentration (15.6 %) was observed in enzymatic hydrolysis of the MW pretreated hemp fibres compared to the fibres pretreated without MW. Furthermore, the FT-IR and NMR data confirmed that the amination of lignin occurred even at low temperature, which contributed to the high lignin removal rate. Thus, this study presents a potentially effective energy-saving, and environmentally sustainable solid-state method for pretreating hemp fibres.

Enhanced ethanol production from tree trimmings via microbial consortium pretreatment with selective degradation of lignin

The microbial consortia designedly screened in our lab were used for solid-state pretreatment of tree trimmings to degrade lignin selectively in this work, and the commercial fungal isolate pretreatment was taken in comparison. The results showed that a highly selective degradation of lignin was observed in the tree trimmings pretreated via the microbial consortium DM-1, in which 14.0% of lignin was decomposed and no significant degradation of cellulose was noted within 20 days. Meanwhile, in this trial, shorter fibers and a lower crude fiber crystallinity were found in the tree trimmings after pretreatment. And the pH values of the tree trimmings undergoing biopretreatment in each trial were all kept at around 7.0. In the SSF (simultaneous saccharification and fermentation) process, 20% increment of the ethanol yield was obtained in the trial loaded with DM-1 pretreated tree trimmings compared to the control, in which a higher acid-based buffering capability was also observed. The scanning electron microscope test revealed that after SSF, the DM-1 pretreated tree trimmings had less crude fibers and more void ratios. Herein, it was feasible to produce more ethanol from tree trimmings via solid-state pretreatment by using the microbial consortium DM-1.

Corn silage fungal-based solid-state pretreatment for enhanced biogas production in anaerobic co-digestion with cow manure

The objective of this research was to use white-rot fungus Trametes versicolor for corn silage pretreatment and to investigate the effect of pretreatment on biogas productivity. Semi-continuous pilot-scale experiment, comprised of two experimental phases, was carried out. In the first phase, operational conditions of the full-scale biogas plant were reproduced at pilot-scale. In that phase, the reactor was daily fed with the mixture of cow manure, digestate from industrial postfermentor, corn grits and ensiled corn silage, and the average methane generation rate was 0.167 m3CH4 kgVS−1. In the second phase, corn grits and ensiled corn silage were replaced with corn silage pretreated with T. versicolor, and the average methane generation rate increased up to 0.236 m3CH4 kgVS−1. The results of this study suggest that application of fungal-based solid-state pretreated corn silage has positive effect on pH stability and increase the biogas productivity.

Optimization and kinetic study of biogas production from rice husk through solid-state alkaline pretreatment method

Biogas production of raw and solid-state alkaline pretreated rice husk (RH) was investigated at mesophilic conditions. Three concentrations of sodium hydroxide was used to prepare the samples namely; 1, 3 and 5% at 100 and 120°C. The 3% pretreated RH at 100°C (3N100) produced the highest cumulative biogas of 4705 ml followed by 5% pretreated RH at 120°C sample with a cumulative volume of 4590 ml. The combined severity factor (CSF) showed that a moderate severity treatment was needed to improve biogas production for solid-state pretreated RH. First order kinetic model and the modified Gompertz model were used to evaluate biogas production while Chen and Hashimoto model was used to determine the critical hydraulic retention time (HRTcritical). The biodegradability constants (k0) ranged between 0.5163 to 1.1294 with 3N100 and 5N120 having the highest values of 0.8086 and 1.1294 d−1 respectively. Modified Gompertz model showed there was marginal percentage difference between experimental and predicted biogas production except for 1N100 with percentage difference of 11.57%. The HRTcritical for 3N100 was calculated to be 11.60 days. The optimum conditions for solid-state alkaline pretreatment of RH were 3% concentration of NaOH and reaction temperature of 100°C

Comparison between solid-state and powder-state alkali pretreatment on saccharification and fermentation for bioethanol production from rice straw

ABSTRACTThe efficacy of different concentrations of NaOH (0.25%, 0.50%, 0.75%, and 1.00%) for the pretreatment of rice straw in solid and powder state in enzymatic saccharification and fermentation for the production of bioethanol was evaluated. A greater amount of biomass was recovered through solid-state pretreatment (3.74 g) from 5 g of rice straw. The highest increase in the volume of rice straw powder as a result of swelling was observed with 1.00% NaOH pretreatment (48.07%), which was statistically identical to 0.75% NaOH pretreatment (32.31%). The surface of rice straw was disrupted by the 0.75% NaOH and 1.00% NaOH pretreated samples as observed using field-emission scanning electron microscopy (FE-SEM) and atomic force microscopy (AFM). In Fourier-transform infrared (FT-IR) spectra, absorbance of hydroxyl groups at 1,050 cm−1 due to the OH group of lignin was gradually decreased with the increase of NaOH concentration. The greatest amounts of glucose and ethanol were obtained in 1.00% NaOH solid-state pretreated and powder-state hydrolyzed samples (0.804 g g−1 and 0.379 g g−1, respectively), which was statistically similar to the use of 0.75% NaOH (0.763 g g−1 and 0.358 g g−1, respectively). Thus, solid-state pretreatment with 0.75% NaOH and powder-state hydrolysis appear to be suitable for fermentation and bioethanol production from rice straw.

Effect of ionic liquid weight ratio on pretreatment of bamboo powder prior to enzymatic saccharification

The pretreatment efficiency of weight ratios ranging from 0 to 10 of the ionic liquid, cholinum IL, to bamboo powder was investigated. An IL/biomass ratio of 3g/g was critical to obtain a cellulose saccharification ratio of 80%. At this ratio, the treated bamboo powder remained as a solid. The solid-state pretreatment required a minimum amount of cholinium IL, which could reduce the cost of IL-assisted pretreatment and reduce the amount of wastewater generated in the process.

Enhanced solid-state anaerobic digestion of corn stover by alkaline pretreatment

Alkaline pretreatment was applied to enhance biogas production from corn stover through solid-state anaerobic digestion. Different NaOH loadings (1%, 2.5%, 5.0% and 7.5% (w/w)) were tested for solid-state pretreatment of corn stover. Lignin degradation during pretreatment increased from 9.1% to 46.2% when NaOH concentration increased from 1.0% to 7.5%. The NaOH-pretreated corn stover was digested using effluent of liquid anaerobic digestion as inoculum and nitrogen source. NaOH loading of 1% did not cause significant improvement on biogas yield. The highest biogas yield of 372.4 L/kg VS was obtained with 5% NaOH-pretreated corn stover, which was 37.0% higher than that of the untreated corn stover. However, a higher NaOH loading of 7.5% caused faster production of volatile fatty acids during the hydrolysis and acidogenesis stages, which inhibited the methanogenesis. Simultaneous NaOH treatment and anaerobic digestion did not significantly improve the biogas production ( P > 0.05).