Pretreated Straw Research Articles

Influence of the Conditions of Alkaline Pretreatment of Vegetable Raw Material before Hydrolysis in a Rotor Pulsation Device on the Cellulose Conversion

Introduction. The growing global energy demand, limited fossil fuel resources, and increasing greenhouse gasemissions highlight the need for expanded use of renewable energy sources, particularly biomass.Problem Statement. A significant drawback in the production of bioethanol is its high cost, primarily due tothe presence of hemicellulose and lignin.Purpose. This study aims to determine the effect of treating an alkaline suspension of wheat straw in a rotary pulsation device on the degree of cellulose conversion during enzymatic hydrolysis, a critical step in the productionof fuel ethanol.Materials and Methods. The raw material is pre-crushed wheat straw. The experiments have been conductedwith the use of a rotary pulsation device in an experimental plant.Results. It has been found that the combined physical effects of the discrete pulse energy input method andreduced straw particle size significantly increase the lignin extraction, from 40.0% at an average particle size of2—1 mm to 62.0% at an average particle size of 0.4—0.1 mm. Additionally, the treatment of an alkaline suspension of wheat straw at 90 оC for one hour, at alkali concentrations ranging from 1 to 4% (wt./wt.), results in anincrease in the cellulose conversion during enzymatic hydrolysis from 38% to 65.8%. Additionally, a corresponding decrease in the lignin content, from 17.1% to 3.16% has been reported.Conclusions. Increasing alkali concentration during the alkaline pretreatment of wheat straw using the discrete-pulse energy input method in a rotary pulsation device enhances the rate of cellulose conversion duringsubsequent enzymatic hydrolysis.

Enhancing Enzymatic Hydrolysis of Rice Straw by Acid-Assisted Mechanocatalytic Depolymerization Pretreatment

The inherent complexity of cellulose, hemicellulose, and lignin contributes to the recalcitrance of lignocellulosic biomass, resulting in a low conversion efficiency and high cost of bioethanol conversion. Pretreatment methods that disrupt the plant cell structure of lignocellulose, such as straw, can significantly enhance the conversion efficiency. In this study, we utilized an acid-assisted mechanocatalytic depolymerization technique to pretreat rice straw, and the results demonstrated a significant disruption of the cellulose structure of the straw. Compared to the untreated straw, the particle size of pretreated straw reduced from 279 μm to 11.8 μm, the crystallinity of cellulose decreased from 43.05% to 22.71%, the specific surface area increased by 177%, and the surface oxygen-to-carbon ratio (O/C) ratio was enhanced by 75%. The changes in microstructure enabled the pretreated straw to achieve a total sugar yield of over 95% within 12 h of enzymatic hydrolysis, significantly superior to the 36.24% yield from untreated straw, the 45.20% yield from acid impregnated straw, and the 73.25% yield from ball milled straw. Consequently, acid-assisted mechanocatalytic depolymerization emerges as a highly effective pretreatment strategy to enhance both the enzymatic hydrolysis and the overall conversion efficiency of rice straw.

Delignification characteristics of rice straw pretreatment combining biogas slurry immersion with freeze–thaw

Delignification characteristics of rice straw pretreatment combining biogas slurry immersion with freeze–thaw

High-efficient synthesis of straw-derived carbon quantum dots for facilitating methanogenic performance in high-load co-digestion of food waste and excess sludge

Anaerobic digestion (AD), as a crucial technology for organic waste resource recovery, faces the challenge of low efficiency in converting high-load organic substance into biogas. In this study, high-load AD system with food waste and excess sludge as co-substrates was constructed. The effect and mechanism of carbon quantum dots (CQD) derived from straw in promoting the performance of AD systems have been studied. The oxidation pretreatment of straw with H2O2 and acetic acid increased the yield of hydrothermal synthesis CQD to approximately 40%. The effect of different CQD on CH4 yield performance was further explored. The cumulative CH4 yield performance of the fermenter was improved after adding CQD. The CQD synthesized from pretreated straw and the nitrogen-doped CQD synthesized using Chlorella as the nitrogen source showed competitive promotion performance, increasing cumulative CH4 yield by 17.71% and 8.87%, respectively. These CQD can effectively accelerate the degradation of dissolved organic matter and thus improve the CH4 yield performance, with the most significant effect of CQD synthesized from pretreated straw. Electrochemical analysis and the correlation analysis between microorganisms and performance parameters showed that these CQD established an electron conductive network to enhance the electron transfer of the system. This well conductive conditions enriched hydrogenotrophic methanogenic (Methanosarcina), electroactive bacteria (Clostridium_sensu_stricto_1), and hydrolytic-acidifying bacteria (norank_f__Bacteroidetes_vadinHA17). This study significantly enhanced the yield of straw-derived CQD through green methods, and deeply revealed the potential promoting mechanisms of biomass-derived CQD by investigating the correlation between system performance and microorganisms in high-load AD systems

Rearing of Black Soldier Fly Larvae with Corn Straw and the Assistance of Gut Microorganisms in Digesting Corn Straw.

Corn straw is considered a renewable biomass energy source, and its unreasonable disposal leads to resource waste and environmental pollution. Black soldier fly (Hermetia illucens L.) larvae (BSFL) facilitate the bioconversion of various types of organic wastes. In this study, we found that 88% of BSFL survived, and 37.4% of corn straw was digested after 14 days of feeding with corn straw. Contrary to expectations, the pretreatment of corn straw with alkaline hydrogen peroxide did not promote its digestion but rather reduced the growth and survival rates of BSFL. Acinetobacter, Dysgonomonas, and unclassified Enterobacteriaceae were the abundant genera in the BSFL gut fed with corn straw. Compared with the standard diet, the relative abundances of carbohydrate metabolism genes, such as the gene abundances of β-glucosidase and α-glucosidase, were higher with corn straw as the substrate. These results suggested that the gut microbial community could regulate suitable and functional microorganisms in response to the substrates. Furthermore, four cellulase-producing strains, namely Klebsiella pneumoniae, Proteus mirabilis, Klebsiella oxytoca, and Providencia rettgeri, were isolated from the guts of corn straw BSFL. These four strains helped increase the conversion rates of corn straw, the weights of BSFL, and survival rates. In summary, we reared BSFL with corn straw and discovered the functions of gut microorganisms in adapting to the substrates. We also isolated four cellulase-producing strains from the BSFL guts and declared the benefits of BSFL digesting corn straw.

Synergistic effect of biological pre-treatment on co digestion of rice straw and sewage sludge: Process optimization and microbial interactions

The increasing demand for renewable energy sources has prompted a search for innovative and efficient approaches for biogas production. This study investigates the potential of achieving sustainable biogas production through a synergistic combination of biological pre-treatment and co-digestion of rice straw (RS) and sewage sludge (SS). The goal is to enhance the overall methane yield, mitigate substrate limitations, and optimize the biogas production process. In this study, rice straw and sewage sludge were anaerobically co-digested in ratios of 100:0, 70:30, 50:50, 30:70, and 30:70. It was observed that the co-digestion ratio of 70:30 is optimal to achieve maximum methane yield of 0.3 L CH4/(g VS added). Biological pre-treatment with five different organisms Sphingobium sp., Paenibacillus sp., Microbacterium sp., Pseudomonas sp., and Stenotrophomonas sp. was also examined for RS and co-digested with SS at the optimized ratio to improve the degradability of RS. This pre-treatment strategy is anticipated to enhance the accessibility of microorganisms to substrates and accelerate the rates of hydrolysis. The biological pre-treatment resulted in a 20–23% improvement in methane yield compared to untreated substrates. Metagenomic studies revealed the dominance of Bacteroidetes, Firmicutes, and Proteobacteria, which are capable of utilizing lignocellulosic biomass and ultimately converting it to methane. The acetoclastic methanogensis is the major methane generating pathway which is supported by the complete dominance of genus Methanosaeta.

Disintegration of lignocellulosic material through visible light SiO2/g-C3N4 photocatalyst for biogas generation

This study presents the synthesis of g-C3N4 and the fabrication of SiO2/g-C3N4 via the hydrothermal polycondensation method, serving as a highly efficient visible light activated photocatalyst for enhancing anaerobic digestion and biogas production from rice straw through pretreatment at various time intervals. The efficacy of the pretreatment was evaluated using a range of analytical techniques, including XRD, FTIR, FESEM, EDX, and UV–vis analysis. The results showcased a remarkable 81 % reduction in silica content compared to untreated rice straw, along with a significant 121 % increase in biogas production. The study demonstrate that the 7-h treatment duration facilitates the highest silica reduction and biogas yield. These findings underscore the immense potential of SiO2/g-C3N4 as a promising catalyst for rice straw pretreatment, thereby leading to enhanced biogas production during anaerobic digestion.

Electro-driven deep eutectic solvent pretreatment of wheat straw with enhancive component fractionation and hydrogen evolution at room temperature

Electro-driven deep eutectic solvent pretreatment of wheat straw with enhancive component fractionation and hydrogen evolution at room temperature

Nanocellulose separation from barley straw via ultrasound-assisted choline chloride – Formic acid deep eutectic solvent pretreatment and high-intensity ultrasonication

The present study aims at investigating the application of ultrasound assisted choline chloride (ChCl) – formic acid (FA) deep eutectic solvent (DES) pretreatment of Barley straw. In addition, the efficiency of a wet grinding followed by high intensity ultrasound (HIUS) treatment for production of cellulose nanofibers (CNF) has been evaluated. The DES (using ChCl: FA at 1:9 M ratio) treatment at 45 kHz ultrasound frequency and 3 h of treatment duration resulted in 84.68 ± 1.02 % and 82.96 ± 0.79 % of lignin and hemicellulose solubilisation, respectively. The purification of DES treated solid residue resulted in cellulose with more than 90 % purity. Further, 10 min of wet grinding followed by 40 min of HIUS treatment resulted in more than 80 % nano-fibrillation efficiency. The produced CNF had diameters less than 100 nm in number size distribution and type I cellulose structure. This study confirmed that the developed process offers a sustainable method for producing nanocellulose from agricultural waste.

Composted maize straw under fungi inoculation reduces soil N2O emissions and mitigates the microbial N limitation in a wheat upland

Enhancement of microbial assimilation of inorganic nitrogen (N) by straw addition is believed to be an effective pathway to improve farmland N cycling. However, the effectiveness of differently pretreated straws on soil N2O emissions and soil N-acquiring enzyme activities remains unclear. In this study, a pot experiment with four treatments (I, no addition, CK; II, respective addition of maize straw, S; III, composted maize straw under no fungi inoculation, SC; and IV, composted maize straw under fungi inoculation, SCPA) at the same quantity of carbon (C) input was conducted under the same amount of inorganic N fertilization. Results showed that the seasonal cumulative N2O emissions following the SCPA treatment were the lowest at 4.03 kg N ha−1, representing a significant reduction of 19 % compared with the CK treatment. The S and SC treatments had no significant effects on N2O emissions. The decrease of soil N2O emissions following the SCPA treatment was mainly attributed to the increase of microbial N assimilation and the increased abundance of functional genes related to N2O reductase. The SCPA treatment significantly decreased soil alkaline phosphatase (ALP) activity and increased leucine aminopeptidase (LAP) activity at the basal fertilization, while increased soil ALP and LAP activity, decreased soil N-Acetyl-β-D-Glucosidase (NAG) activity at harvest. Compared with the CK treatment, the S, SC, and SCPA treatment significantly increased soil β-glucosidase (β-GC) activity at harvest. The decrease in the (NAG+LAP)/ALP ratio following the SCPA treatment indicated that the composted maize straw under fungi inoculation alleviated microbial N limitation at harvest. Moreover, PICRUSt analysis also suggested that the SCPA treatment increased the abundance of bacterial genes associated with N assimilation and N2O reduction, whereas the S and SC treatment did not significantly affect the abundance of N2O reduction genes compared with the CK treatment. Our results suggest that the composted maize straw under fungi inoculation would reduce the risk of N2O emissions and effectively mitigate the microbial N limitation in dryland wheat system.

Quantitative recovery and regeneration of basic deep eutectic solvent for biomass treatment with industrialized membrane-based strategy

As a new type of ionic liquids, basic deep eutectic solvents have been reported as emerging medium for biorefinery, extraction, catalysis and so on. Quantitative recovery with recycling of basic DES was important for the scale utilization of biomass and the environmental conservation. An electrodialysis-based method was designed for divisionally regenerating basic DES choline chloride-monoethanol amine (ChCl-MEA) after pretreatment of wheat straw. Influence of primary process parameters on recovery of ChCl-MEA was studied and recovery economy of ChCl-MEA was analyzed. Recovery ratio of ChCl and MEA varied within 89.2 %-96.0 % and 93.3 %-97.9 %. Energy consumption of ChCl-MEA recovery changed within 4.2–29.4 kW·h/kg. Transport rate of basic DES ChCl-MEA altered in the range of 12.2–464.7 mmol/(m2·min). Process economy analysis proved that recovery cost of basic DES ChCl-MEA was less than 7 % (0.81–7.07 $/kg) of DES purchase cost. Insight brought by this study indicated a technically feasible and economical approach for basic DES recycling after biomass pretreatment.

Pretreated wheat straw blended with coffee husk biomass resources for the generation of biogas energy

Wheat straw and coffee husk are agricultural residues that may be successfully exploited for energy generation through anaerobic digestion. Improper handling of biogas-producing facilities can result in methane emissions, a potent greenhouse gas that may outweigh some environmental benefits. As a result, the environmental pollution issue raising exponentially, the usage of organic wastes becomes today's scenario to overcome the environmental issue. The quest for alternative energy supplies, especially those extracted from renewable materials like biomass is sparked by rising global energy demand and the gradual decline of oil reserves. In this study, two experiments are focused on the combined impact of co-digestion and thermal pretreatment of wheat straw blended with coffee husk biomass. Wheat straw and coffee husk wastes were analysed and used as biogas sources to generate energy. The volatile solid which was pretreated at 160°C temperature, 3% concentration of sulphuric acid, resulted in 30 minutes of cooking time by using biogas. The biomass system yielded is biogas and biomethane, with 764 and 460 mL/g. The biogas energy generated could be used to replace fossil fuels for a variety of purposes, reducing emissions and promoting the country's long-term sustainability. Furthermore, the experimental data obtained from both experiments are validated.

Supercritical CO2 as effective wheat straw pretreatment for subsequent mild fractionation strategies

The efficient utilization of lignocellulosic biomass in biorefineries is pivotal for the transition to a carbon–neutral society, emphasizing the need for environmentally friendly fractionation techniques. While the extensive use of chemicals in biorefinery operations can yield favorable quantities of specific biomass components, adopting less chemically intense conditions is crucial for holistic methodologies that preserve the inherent potential of all biomass constituents. This study comprehensively investigates the use of supercritical carbon dioxide (sc-CO2) as a green pretreatment to improve subsequent mild fractionation on wheat straw. Sc-CO2 at 300 bars, 100 °C and 70% moisture was found to have minimal impact on the chemical composition and the lignin structure, while there were significant morphological changes as heightened surface area and reduced density. Apart from increasing enzymatic saccharification efficiency, the treatment notably enhanced subsequent mild delignification through alkaline and flow-through organosolv extractions. The combination of the pretreatments enhances the lignin solubilization yields from 49 to 79% for alkaline and 74 to 91% for organosolv extractions, while retaining a high β-O-4 conservation of 49 and 59 linkages per 100 aromatic units, respectively. Additionally, the combined use of sc-CO2 with mild dilute acid pretreatment improved xylose solubilization from 59 to 76 % and enzymatic saccharification from 53 to 90%, albeit with increased lignin condensation. In summary, this study demonstrates the potential of sc-CO2 pretreatment as a versatile tool for biomass valorization within the evolving bioeconomy, by combining enhanced extraction yields with minimal lignin structural impact. Our work thereby highlights the promise of the use of sc-CO2 to contribute to the overall economic potential of improved biorefinery processes.

Green Extraction of Reed Lignin: The Effect of the Deep Eutectic Solvent Composition on the UV-Shielding and Antioxidant Properties of Lignin.

Lignin, the second most abundant natural polymer, is a by-product of the biorefinery and pulp and paper industries. This study was undertaken to evaluate the properties and estimate the prospects of using lignin as a by-product of the pretreatment of common reed straw (Phragmites australis) with deep eutectic solvents (DESs) of various compositions: choline chloride/oxalic acid (ChCl/OA), choline chloride/lactic acid (ChCl/LA), and choline chloride/monoethanol amine (ChCl/EA). The lignin samples, hereinafter referred to as Lig-OA, Lig-LA, and Lig-EA, were obtained as by-products after optimizing the conditions of reed straw pretreatment with DESs in order to improve the efficiency of subsequent enzymatic hydrolysis. The lignin was studied using gel penetration chromatography, UV-vis, ATR-FTIR, and 1H and 13C NMR spectroscopy; its antioxidant activity was assessed, and the UV-shielding properties of lignin/polyvinyl alcohol composite films were estimated. The DES composition had a significant impact on the structure and properties of the extracted lignin. The lignin's ability to scavenge ABTS+• and DPPH• radicals, as well as the efficiency of UV radiation shielding, decreased as follows: Lig-OA > Lig-LA > Lig-EA. The PVA/Lig-OA and PVA/Lig-LA films with a lignin content of 4% of the weight of PVA block UV radiation in the UVA range by 96% and 87%, respectively, and completely block UV radiation in the UVB range.

Unlocking the potential of oat straw: Efficient pretreatment methods for enhanced glucose production

The excellent physical and chemical properties of deep eutectic solvents, especially the ability of some of them to dissolve biomass, make them broadly applicable in biomass pretreatment. In this study, oat straw was pretreated with deep eutectic solvents composed of choline chloride and an acid (formic, lactic, or oxalic acid). The highest reducing sugar yield was obtained for the formic acid/choline chloride mixture. Using a pretreatment temperature of 110 °C, a reaction time of 2 h, and a solid-liquid ratio of 1:20, the reducing sugar yield obtained by cellulase hydrolysis was 23.5%, the degradation rate of cellulose reached 76.9%, and hemicellulose was completely degraded. The pretreated oat straw was then analyzed by scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction. The changes in its crystallinity and lignin content compared to the untreated specimen were determined. A preliminary mechanism for the pretreatment of oat straw with formic acid/choline chloride was revealed. The study could provide an opportunity to expand the application in biochemicals or biological feed processes.

Catalyst‐free pretreatment of raw wheat straw by atmospheric‐pressure pulsed air discharge for enhancement of sugar production

AbstractThis study presents atmospheric‐pressure plasma as a novel catalyst‐free pretreatment method for raw wheat straw (RWS) biomass. The work explores the effects of processing parameters, such as milled particle size, moisture content of RWS, and plasma generations, on pretreatment efficiency. To understand the mechanisms behind the enhanced pretreatment efficiency, various analysis techniques were used to analyze the physical and chemical properties of RWS before and after pretreatment. The analysis reveals that plasma pretreatment significantly damages the surface smoothness of RWS and enhances the decomposition of lignocellulosic structures. These effects are primarily attributed to the reactive species generated by the pulsed discharge, rather than the accompanying UV radiation, acidification, or heating actions during plasma pretreatment.

Biocalorimetry-aided monitoring of fungal pretreatment of lignocellulosic agricultural residues

The present study aimed to investigate whether and how non-invasive biocalorimetric measurements could serve for process monitoring of fungal pretreatment during solid-state fermentation (SSF) of lignocellulosic agricultural residues such as wheat straw. Seven filamentous fungi representing different lignocellulose decay types were employed. Water-soluble sugars being immediately available after fungal pretreatment and those becoming water-extractable after enzymatic digestion of pretreated wheat straw with hydrolysing (hemi)cellulases were considered to constitute the total bioaccessible sugar fraction. The latter was used to indicate the success of pretreatments and linked to corresponding species-specific metabolic heat yield coefficients (YQ/X) derived from metabolic heat flux measurements during fungal wheat straw colonisation. An YQ/X range of about 120 to 140 kJ/g was seemingly optimal for pretreatment upon consideration of all investigated fungi and application of a non-linear Gaussian fitting model. Upon exclusion from analysis of the brown-rot basidiomycete Gloeophyllum trabeum, which differs from all other here investigated fungi in employing extracellular Fenton chemistry for lignocellulose decomposition, a linear relationship where amounts of total bioaccessible sugars were suggested to increase with increasing YQ/X values was obtained. It remains to be elucidated whether an YQ/X range being optimal for fungal pretreatment could firmly be established, or if the sugar accessibility for post-treatment generally increases with increasing YQ/X values as long as “conventional” enzymatic, i.e. (hemi)cellulase-based, lignocellulose decomposition mechanisms are operative. In any case, metabolic heat measurement–derived parameters such as YQ/X values may become very valuable tools supporting the assessment of the suitability of different fungal species for pretreatment of lignocellulosic substrates.Key points• Biocalorimetry was used to monitor wheat straw pretreatment with seven filamentous fungi.• Metabolic heat yield coefficients (YQ/X) seem to indicate pretreatment success.• YQ/X values may support the selection of suitable fungal strains for pretreatment.

Reduction of inhibitory effect of lignin via degradation and improvement of anaerobic digestion performance of maize straw by oxidative pretreatment with Fe2+-activated persulfate

The stable aromatic structure of lignin is one of the factors that limit the utilization of maize straw. In this study, pretreatment with Fe2+/persulfate (PS) was used to remove lignin while reducing the contents of lignin derivatives produced in the pretreatment. In comparison with the original straw, the lignin and hemicellulose contents of the pretreated straw were reduced to 54.58 % and 72.91 %, respectively. In the Fourier transform infrared spectrum, the characteristic peaks of both syringyl and guaiacyl units were significantly weaker after pretreatment with Fe2+/PS, which indicated that the pretreatment destroyed the structure of lignin. The pretreatment products were examined by gas chromatography–mass spectrometry, and the results indicated that the present pretreatment method reduced the contents of soluble inhibitors produced from lignin. After pretreatment, only levulinic acid, 4-hydroxybenzaldehyde, vanillin, 4-hydroxybenzoic acid, xylose, coumaric acid, and 4-coumaric acid were produce, whereas more than 20 soluble inhibitors are known to be produced from lignin. In anaerobic fermentation experiments, in comparison with the control group, the pretreated group exhibited higher gas production (an increase of 18.09 %) and a significantly higher methane content. This indicates that pretreatment with Fe2+/PS can improve the efficiency of the resource utilization of maize straw by degrading lignin.

Enhanced production of lactic acid from pretreated rice straw using co-cultivation of Bacillus licheniformis and Bacillus sonorenesis.

Lactic acid (LA) production from sugar mixture derived from lignocellulosic rice straw employing co- culture system of thermotolerant and inhibitor tolerant Bacillus licheniformis DGB and Bacillus sonorenesis DGS15 was carried out. In minimal media, both the strains of Bacillus DGB and DGS15 worked together by efficiently utilising glucose and xylose respectively. Response Surface Methodology (RSM) was used for optimisation of pretreatment of rice straw to achieve maximum yield of 50.852g/L total reducing sugar (TRS) from 100 gm of rice straw biomass. Pretreatment of rice straw resulted in its delignification, as confirmed by FTIR spectroscopy, since the peak at 1668cm-1 disappeared due to removal of lignin and scanning electron microscopy (SEM) revealed disruption in structural and morphological features. Crystallinity index (CrI) of treated rice straw increased by 15.54% in comparison to native biomass. DGB and DGS15 individually yielded 0.64g/g and 0.82g/g lactic acid respectively, where as their co-cultivation led to effective utilisation of bothglucose and xylose within 15h (70%) and complete utilisation in 48h, producing 49.75g/L LA with a yield of 0.98g/g and productivity of 1.036g/L/h, andresulting in reduction in fermentation time. Separate hydrolysis of rice straw and co-fermentation (SHCF) of hydrolysates by Bacillus spp. enhanced the production of lactic acid, can circumvent challenges in biorefining of lignocellulosic biomass.

Effects of nanobubble water on digestate soaking hydrolysis of rice straw

This study investigated the performance of combined nanobubble water (NW) and digestate in the soaking hydrolysis process. Two types of NW (CO2NW and O2NW) with digestate were used to soak rice straw for 1, 2, 3, 5, and 7 days. During soaking process, the volatile fatty acids (VFA) concentration in the treatment with O2NW and digestate for 3 days (O2NW-3 d) reached 7179.5 mg-HAc/L. Moreover, the highest specific methane yield (SMY) obtained in this treatment could reach 336.7 NmL/gVS. Although the addition of NW did not significantly increase SMY from digestate soaking, NW could accelerate the rate of methane production and reduce digestion time of T80. The enrichment of Enterobacter in the soaking process was observed when using CO2NW and O2NW as soaking solutions which played important roles in VFA production. This study provides a new insight into environment-friendly enhanced crop straw pretreatment, combining NW and digestate soaking hydrolysis.