Pretreatment Of Lignocellulosic Biomass Research Articles

Production of Industrially Important Cellulases and Pectinases using Lignocellulosic Biomass

Cellulases and pectinases are the two main industrially important enzymes that find significant applications in food, feed, pharmaceutical, textile and environmental sectors. In the present study, Trichoderma asperellum S14 was used for enzymes production in liquid state fermentation and for enzymatic hydrolysis of lignocellulosic biomass. Prior to liquid state fermentation, Trichoderma asperellum S14 was qualitatively screened for the pectinolytic and cellulytic activity by using plate assay method. Alkaline pretreatment (1% NaOH) was used for the pretreatment of lignocellulosic biomasses including; wheat bran, wheat straw, rice straw, rice husk and sugarcane bagasse. Maximum cellulase activity of 4.3 U/mL was observed at pH 4.8 and 30ºC after 72 hours of incubation from Trichoderma asperellum S14 using alkali pretreated sugarcane bagasse as a substrate. While, maximum pectinase activity 9.2 U/mL obtained at pH 4.8 and 30ºC after 72 hours of incubation from Trichoderma asperellum S14 using alkali pretreated wheat bran. Enzymatic hydrolysis was also performed using crude enzymes extract at 50ºC for 72 hours. Maximum hydrolysis (70%) was observed in case of pretreated sugarcane bagasse using Trichoderma asperellum S14 as fungal source for enzyme production. Lignocellulosic biomasses are considered as the best feedstock used in second generation biofuel production because of their renewable resources as well as inexpensive and environment friendly nature. Present study shows the potential of Trichoderma asperellum S14 to degrade variety of lignocellulosic biomass efficiently and could be used to hydrolyze complex lignocellulosic materials towards the production of second generation biofuel.

Comparative Analysis on Microwave and Pressure Cooker Pre-Treatment of Lignocellulosic Biomass in Glucose Production via Fungal Treatment

Oil Palm Empty Fruit Bunch (OPEFB) is lignocellulosic biomass waste generated from palm oil processing industries. Due to its significant compositions of cellulose, hemicellulose, and lignin, OPEFB can be further utilized and converted into value-added chemical products which can be used as alternative energy. Hence, the focus of this research is to analyze the effect of microwave pre-treatment (MP) and pressure cooker pre-treatment (PCP) parameters on OPEFB lignin reduction. The treated OPEFB was directly processed using two serial fungal treatment processes. The first fungal treatment process (FT-1) was to maximize the OPEFB lignin removal while the second fungal treatment process (FT-2) was to maximize the glucose production. Combination of microbes such as Phanerochaete chrysosporium, Trichoderma harzianum, Aspergillus niger, and Tricodherma viride was used for both fungal treatment processes. The OPEFB passing 25-mesh screening was used as raw materials. The raw materials mixed with 0.05 w/w NaOH pellets and water to achieve a concentration ratio of 3/50 (w/v) were pre-treated with either MP or PCP. Subsequently, the slurry produced from the pre-treatment process was introduced to FT-1 (P. chrysosporium for 5 days) and finally to FT-2 (T. harzianum, A. niger and T. viride for 4 days). The compositions of lignin, cellulose, hemicellulose, and glucose were analyzed at each process transition and the end of the whole process. It was observed that PCP (60 mins) was the best pre-treatment process with 39.23%-w of lignin removed. On the other hand, combination of MP (150 watts, 60 mins) was followed with FT-1 removed 66.67%-w of lignin. Only around 38.37%-w of lignin was removed when using the whole process, e.g., MP (150 watts, 60 mins), FT-1, and FT-2. The highest composition of glucose, ca. 131.02%-w, was obtained when 40-min PCP followed with FT-1 and FT-2 was applied. The obtained results exhibited that large lignin removal did not necessarily promote high glucose yield in the final product as observed in the 60-min PCP, e.g., P. chrysosporium consumed not only lignin but also presumably hemicellulose and cellulose.

Production of carotenoids from aromatics and pretreated lignocellulosic biomass by Novosphingobium aromaticivorans.

There is economic and environmental interest in generating commodity chemicals from renewable resources, such as lignocellulosic biomass, that can substitute for chemicals derived from fossil fuels. The bacterium Novosphingobium aromaticivorans is a promising microbial platform for producing commodity chemicals from lignocellulosic biomass because it can produce these from compounds in pretreated lignocellulosic biomass, which many industrial microbial catalysts cannot metabolize. Here, we show that N. aromaticivorans can be engineered to produce several valuable carotenoids. We also show that engineered N. aromaticivorans strains can produce these lipophilic chemicals concurrently with the extracellular commodity chemical 2-pyrone-4,6-dicarboxylic acid when grown in a complex liquor obtained from alkaline pretreated lignocellulosic biomass. Concurrent microbial production of valuable intra- and extracellular products can increase the economic value generated from the conversion of lignocellulosic biomass-derived compounds into commodity chemicals and facilitate the separation of water- and membrane-soluble products.

Production of cellooligosaccharides from oil palm bunch in bio-based choline chloride deep eutectic solvents and MALDI-TOF MS analysis of COS mixture

Lignocellulosic biomass pretreatment and cellulose dissolution are principal challenges for its conversion to high-value chemicals, materials and fuels. This work focused on production of soluble cellooligosaccharides (COS) from palm bunch for future use as nutraceutical supplement to enhance human's immune and digestive systems. Deep eutectic solvents (DESs) have been found as eco-friendly, renewable and promising solvents selective for lignin and hemicellulose removal from biomass. Additionally, the investigation of most suitable DES for both cellulose dissolution and subsequently cleavage of cellulose to COS is crucial. In the study, palm empty fruit bunch (EFB) was pretreated in different DES for screening of most favorable cellulose inter- and intra-molecular structural dissolution in a combination with beta,1–4 glycosidic bond cleavage by elevated reaction temperature for COS production. ChCl/urea was found to be the most promising DES for dissolving 76.83% of EFB constituents. The highest COS production yield at 90.1%w/w based on treated EFB fraction (74.7% COS yield based on cellulose in native EFB) was achieved in ChCl/urea DES from cellulose fraction extracted from EFB at 240 °C for 20 min. The study additionally provided insightful characterization and elucidation of COS molecular structure using 2D-HSQC and MALDI-TOF/MS techniques. MALDI-TOF/MS was a promising and rapid technique for simultaneously qualitative and quantitative analysis of COS at different degrees of polymerization in COS product.

Lignocellulosic biomass pretreatment: Industrial oriented high-solid twin-screw extrusion method to improve biogas production from forestry biomass resources

Forestry lignocellulosic waste is an important, largely untapped source of biomass for producing clean energy. In this study, a high-solids twin-screw extrusion approach is developed as a novel pretreatment method to effectively increase the biogas production rate to better fit commercial requirements. Multiple screw designs are progressively introduced with increasingly intensified mechanical shear. The experiments also looked at the impact of feed solids content and several cost-effective processing aids along with these screw designs. Various characterization methods were used to relate the physical state of the biomass based on its specific surface area and volatile fraction, to the rate of biomethane generation possible from a 14- and 31-day biomethane potential test. An increase in biomethane production over this period by up to 190% was possible with the optimal screw design compared to a benchmark sample. This is a promising finding for the industrialization of biomethane production from forestry lignocellulosic biomass.

Microfluidic reactor designed for time-lapsed imaging of pretreatment and enzymatic hydrolysis of lignocellulosic biomass

The effect of tissue-specific biochemical heterogeneities of lignocellulosic biomass on biomass deconstruction is best understood through confocal laser scanning microscopy (CLSM) combined with immunohistochemistry. However, this process can be challenging, given the fragility of plant materials, and is generally not able to observe changes in the same section of biomass during both pretreatment and enzymatic hydrolysis. To overcome this challenge, a custom polydimethylsiloxane (PDMS) microfluidic imaging reactor was constructed using standard photolithographic techniques. As proof of concept, CLSM was performed on 60 μm-thick corn stem sections during pretreatment and enzymatic hydrolysis using the imaging reactor. Based on the fluorescence images, the less lignified parenchyma cell walls were more susceptible to pretreatment than the lignin-rich vascular bundles. During enzymatic hydrolysis, the highly lignified protoxylem cell wall was the most resistant, remaining unhydrolyzed even after 48 h. Therefore, imaging thin whole biomass sections was useful to obtain tissue-specific changes during biomass deconstruction.

Characterization of β-glucosidases from Meridianimaribacter sp. CL38

The production of second-generation biofuel requires a huge amount of freshwater. It is estimated that at least three gal of freshwater is used to produce one gal of biofuel. The replacement of freshwater with seawater serves as a potential alternative in biofuel generation. Therefore, salt-tolerant enzymes play an important role in saccharification and fermentation process. Halophilic β-glucosidase is one of the key enzymes for the process. In this study, the β-glucosidase of halophile Meridianimaribacter sp. CL38 isolated from mangrove soil was characterized. Strain CL38 achieved maximum production of β-glucosidase at 12th hour of growth. The β-glucosidase showed highest activity at 2% (w/v) NaCl while highly stable at salt concentration ranging from 1-2% (w/v) (more than 96% of relative activity). Its β-glucosidase activity remained active in the presence of 5mM Mn2+, Mg2+, Ca2+ ions, and 1% (v/v) Tween-20 and Tween-80. The draft genome sequence of strain CL38 was retrieved from GenBank database and submitted to dbCAN meta server for CAZymes annotation. Strain CL38 harbors 44 GHs and GH3 are annotated as β-glucosidases. The β-glucosidases of Meridianimaribacter flavus (99.61%) and Mesoflavibacter sabulilitoris (97.44%) showed the closest identity with Bgl3a and Bgl3b protein sequences from strain CL38, respectively. Glycoside hydrolase family 3 domain was identified in both enzymes via InterPro scan server. The presence of signal peptides indicated that both enzymes were secreted extracellularly. Five motifs were identified in Bgl3a and Bgl3b, with the active site (nucleophile) found at Asp296 and Asp297, respectively. Collectively, these β-glucosidases could be potentially used in the biofuel production, in particular the lignocellulosic biomass pretreatment process. This is the first attempt to characterize the β-glucosidase in genus Meridianimaribacter as so far none of the lignocellulolytic enzymes from this genus were characterized.

Isolation of xylose-utilizing yeasts from oil palm waste for xylitol and ethanol production

The energy crisis triggers the use of energy sources that are renewable, such as biomass made from lignocellulosic materials, to produce various chemical compounds for food ingredients and biofuel. The efficient conversion of lignocellulosic biomass into products with added value involves the activity of microorganisms, such as yeasts. For the conversion, microorganisms must be able to use various sugars in lignocellulosic biomass, including pentose sugars, especially xylose. This study aims to isolate xylose-utilizing yeasts and analyze their fermentation activity to produce xylitol and ethanol, as well as their ability to grow in liquid hydrolysate produced from pretreated lignocellulosic biomass. Nineteen yeast isolates could grow on solid and liquid media using solely xylose as a carbon source. All isolates can grow in a xylose medium with incubation at 30 °C, 37 °C, 42 °C, and 45 °C. Six isolates, namely SLI (1), SL3, SL6, SL7, R5, and OPT4B, were chosen based on their considerable growth and high xylose consumption rate in a medium with 50 g/L xylose with incubation at 30 °C for 48 h. Four isolates tested, namely SLI (1), SL6, SL7, and R5, can produce xylitol in media containing xylose carbon sources. The concentration of xylitol produced was determined using high-pressure liquid chromatography (HPLC), and the results ranged from 5.0 to 6.0 g/L. Five isolates tested, namely SLI (1), SL6, SL3, R5, and OPT4B, can produce ethanol. The ethanol content produced was determined using gas chromatography (GC), with concentrations ranging from 0.85 to 1.34 g/L. Three isolates, namely SL1(1), R5, and SL6, were able to produce xylitol and ethanol from xylose as carbon sources and were also able to grow on liquid hydrolyzate from pretreated oil palm trunk waste with the subcritical water method. The three isolates were further analyzed using the 18S rDNA sequence to identify the species and confirm their phylogenetic position. Identification based on DNA sequence analysis revealed that isolates SL1(1) and R5 were Pichia kudriavzevii, while isolate SL6 was Candida xylopsoci. The yeast strains isolated from this study could potentially be used for the bioconversion process of lignocellulosic biomass waste to produce value-added derivative products.Graphical

Changes in various lignocellulose biomasses structure after microwave-assisted hydrotropic pretreatment

Effective pretreatment of lignocellulosic biomass combined with delignification is a condition for effective enzymatic hydrolysis of cellulose, which is of key significance for the efficiency of the process of production of cellulosic ethanol. Becoming aware of the full range of changes in the structure of lignocellulose as a result of biomass pretreatment is important in view of the necessity to optimise the process of technological production of bioethanol. Our research was aimed at a comprehensive analysis of changes in structure of pine chip (softwood), beech chip (hardwood) and wheat straw (non-wood) biomasses resulting from a newly developed pretreatment method combining the use of hydrotrope in the form of sodium cumene sulfonate and microwave radiation. The performed analyses of the biomass composition indicate a high effectiveness of the proposed pretreatment method in the area of biomass delignification and hemicellulose removal. An effective removal of amorphous substances, i.e. lignin and hemicellulose, led to an increase in the crystallinity of pine chip biomass to 55%, and beech chips and wheat straw biomasses to 61%.

Alkaline-thermal and mild ultrasonic pretreatments for improving biomethane yields: Impact on structural properties of chestnut shells

The high fiber content of chestnut shells (CS) makes biomethane production inefficient when using the anaerobic digestion (AD) method. Therefore, this study has evaluated for the first time the combined effect of alkaline-thermal (AT) and mild ultrasonic (US) pretreatments prior to the AD of CS. The cumulative biomethane yields (CMY) of untreated and pretreated (4% NaOH + 100 °C thermal + US) CS were 79.10 ± 7.9 and 266.9 ± 9.3 mL CH4/g VS, respectively. The effects of the pretreatment of lignocellulosic biomass at different intensities were interpreted according to amounts of lignocellulosic solubilization, soluble chemical oxygen demand/total chemical oxygen demand, and scanning electron microscope images. Solubilization of the lignin from CS with pretreatments varied between 44.5 and 65.6% w/w. The use of AT pretreatments, together with US pretreatments, successfully increased the solubility of lignocellulosic compounds compared to the first case, whilst CMYs showed a positive correlation with lignocellulosic solubilization amounts. After pretreatments, total volatile fatty acid (VFA) concentrations were measured in the anaerobic process, from which the highest VFA was measured to be 1555 ± 108 mg HAc L-1, well below the appropriate value for AD (≤8000 mg HAc L-1). After pretreatments, the CMYs were successfully simulated by the modified Gompertz and Logistic model (R2 = 0.942–0.984). This study presents a promising strategy in the sense that the biomethane yield of CS containing large amounts of fiber can be significantly increased by combined AT and mild US pretreatment methods.

Bioethanol production from alkali-pretreated rice straw: effects on fermentation yield, structural characterization, and ethanol analysis.

Current ethanol production technology has a dire need for efficient conversion of lignocellulosic biomass to fermentable sugars. The conversion requires pretreatment of the biomass, one of the most expensive steps, and thus it is quite necessary to identify the most cost-effective and high-efficiency conversion method. In this study, rice straw (RS) biomass was pretreated using 4% NaOH alkali, soaked for 4 h, and autoclaved for 30min. The structural and morphological changes were examined using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and scanning electron microscopy (SEM) analysis in both native and alkali-treated RS. The FTIR analysis revealed that native RS contains a considerable amount of lignin that was removed after the pretreatment process. The XRD pattern of the RS revealed an increasing crystallite size of the pretreated lignocellulosic biomass. The study of SEM clearly showed the distorted structure and surface porosity after the pretreatment process. Enzymatic hydrolysis efficiency was checked by comparing the commercial enzymes and microbial hydrolysis extracted from a fungal isolate. The best-reducing sugar yield obtained was 0.62g/L, achieved at optimized conditions from the commercial enzymes. Fermentation efficiency was checked using the yeast isolate Saccharomyces cerevisiae in both the native and pretreated substrate, and the highest ethanol concentration (21.45%) was achieved using 20% w/v biomass loading, enzyme loading (2:1:1), and fermentation for a week at 30°C and pH 4.5. This concentration was higher than that of the untreated RS (3.67%). The ethanol thus produced was further checked for analysis by the 1H and 13C nuclear magnetic resonance (NMR) methods.

Machine learning prediction of delignification and lignin structure regulation of deep eutectic solvents pretreatment processes

Prediction of the pretreatment efficiency of lignocellulosic biomass with ternary deep eutectic solvents (DES) containing Lewis acids by machine learning (ML). Principal component analysis, partial least square method, spearman correlation matrix, random forest, extreme gradient boosting and deep neural network were used to elucidate the correlation between 77 variables and the mechanism of lignin depolymerization. The effects of raw material composition, reaction conditions, physicochemical properties of DES and structural parameters in lignin on 9 target variables including β-O-4 bond, β-β bond, β-5 bond, weight average molecular weight, number average molecular weight, polydispersity index, ratio of syringyl units to guaiacyl units, content of phenolic hydroxyl groups and delignification were analyzed. Multivariate analysis showed that temperature, polarity related parameters of HBD and acidity of Lewis acids contributed significantly to the degree of lignin depolymerization. The types and fracture mechanisms of the bonds between different structural units of lignin can be determined by the analysis of structural parameters. XGBoost model has the best performance among all the ML models, and the R square of the test sets for the target variables is above 0.76. Feature importance analysis showed that structural parameters significantly affected the pretreatment effect. The physical and chemical parameters of HBD, such as dipole moment, Log P and surface tension should be paid attention to in the design of DES. The study of the weak intermolecular forces in the lignin and DES systems is beneficial to reveal the mechanism of the pretreatment process. This study provides novel insights into the structural regulation and high-value utilization of lignin in the process of DES pretreatment of lignocellulosic biomass.

Life-cycle assessment as a prospection stage for the biochemical methane potential of pretreated lignocellulosic biomass

The goal of neutrality in greenhouse gas emissions has intensified the search for renewable fuels. However, it is crucial to ensure sustainability of new technologies before proposing their implementation. This study proposes the use of life-cycle assessment (LCA) as an intermediary tool to identify critical hotspots in the exploration of hydrothermal pretreatment of lignocellulosic biomass, followed by biochemical methane potential assessment. Brewer s spent grain (BSG) was investigated, and laboratory-scale results were applied in an attributional assessment model with business-as-usual serving as the baseline. The LCA revealed that assumptions made in the lab could pose limitations. In Brazil, the two-stage co-digestion of pretreated hydrothermal BSG showed promising prospects, with a reduction to a new value of −54 kg CO2-eq Ton−1 BSG compared to 90 kg CO2-eq Ton−1 BSG in the business-as-usual scenario. Within the top ten global beer producing countries, only Brazil and Spain demonstrated potential for exploring this proposal.

Effects of various acid catalysts in dimethyl isosorbide/water co-solvent system for lignocellulosic biomass pretreatment

Novel organosolv pretreatments of biomass using biobased green solvents have attracted increasing attention to realize sustainable biorefinery. We have demonstrated that the feasibility of dimethyl isosorbide/water co-solvent in fractionating lignocellulosic biomass (Eucalyptus) for multiple products under a mild condition (120 °C, 60 min). To take a further step towards revealing the effects of catalysts, we explored various Brønsted (e.g., H2SO4, HCl, and p-TsOH), Lewis acid catalysts (e.g., AlCl3 and FeCl3) and their combinations in this co-solvent system. An interesting finding was that the delignification efficiency of AlCl3 was lower than that of H2SO4 (69.9% vs 91.2%), while the cellulose conversion efficiency of the pretreated pulp was similar (∼80%). It is hypothesized that the presence of Al3+ could inhibit the binding of lignin to cellulase, which was supported by the quantum chemistry calculations. Results revealed the presence of cation− π interactions between Al3+ and lignin with interaction energy (ΔE) was 1022.04 kJ/mol and 1003.04 kJ/mol for S and G type of lignin, respectively. In addition, the pretreatment with H2SO4 -AlCl3 co-catalyst could achieve a high lignin removal efficiency of 93.0% and almost complete enzymatic hydrolysis of obtained cellulose pulp (∼100%). This research demonstrated that the co-catalyst strategy effectively improved the overall performance of the solvent-based biorefinery.

Effectiveness of using physical pretreatment of lignocellulosic biomass

Effectiveness of using physical pretreatment of lignocellulosic biomass

Effect of natural deep eutectic solvents on properties of micro crystalline cellulose isolated from kenaf fibre

Natural deep eutectic solvents have gained popularity due to their environmentally benign, recyclable, and reusable properties. They can be used many times without losingtheir effectiveness. Therefore, natural deep eutectic solvents used as effective reagent for lignocellulosic biomass pre-treatment for lignin removal. In this work, the natural deep eutectic solvents (i.e., Lactic Acid: Choline Chloride) is used to treat the kenaf fibre biomass with a molar ratio of 2:1 and then microcrystalline cellulose was obtained through acid hydrolysis. The analytical analysis of kenaf microcrystalline cellulose was investigated through Infrared fourier transform spectroscopy, X-ray Diffraction, thermogravimetric analysis, particle size distribution analysis, and scanning electron microscopy. The fourier transform infrared spectroscopy analysis result showed that the maximum proportion of lignin and partial hemicellulose from kenaf fibre were removed during natural deep eutectic solvents pre-treatment. Kenaf microcrystalline cellulose X-ray diffraction results revealed higher crystallinity at 78° compared to other peaks. The thermal analysis shows the kenaf microcrystalline cellulose thermal stability , making it suitable material for more desirable application in many areas. We concluded from obtained results that microcrystalline cellulose extracted with natural deep eutectic solvent pre-treated kenaf fibre can be used in various cellulosic material development in the future for the food packaging, tissue culture, paper, automotive, biomedical, and pharmaceutical applications.

Draft genome sequence of Hahella sp. CR1 and its ability in producing cellulases for saccharifying agricultural biomass.

Hahella is a genus that has not been well-studied, with only two identified species. The potential of this genus to produce cellulases is yet to be fully explored. The present study isolated Hahella sp. CR1 from mangrove soil in Tanjung Piai National Park, Malaysia, and performed whole genome sequencing (WGS) using NovaSeq 6000. The final assembled genome consists of 62 contigs, 7,106,771bp, a GC ratio of 53.5%, and encoded for 6,397 genes. The CR1 strain exhibited the highest similarity with Hahella sp. HN01 compared to other available genomes, where the ANI, dDDH, AAI, and POCP were 97.04%, 75.2%, 97.95%, and 91.0%, respectively. In addition, the CAZymes analysis identified 88 GTs, 54 GHs, 11 CEs, 7 AAs, 2 PLs, and 48 CBMs in the genome of strain CR1. Among these proteins, 11 are related to cellulose degradation. The cellulases produced from strain CR1 were characterized and demonstrated optimal activity at 60 ℃, pH 7.0, and 15% (w/v) sodium chloride. The enzyme was activated by K+, Fe2+, Mg2+, Co2+, and Tween 40. Furthermore, cellulases from strain CR1 improved the saccharification efficiency of a commercial cellulase blend on the tested agricultural wastes, including empty fruit bunch, coconut husk, and sugarcane bagasse. This study provides new insights into the cellulases produced by strain CR1 and their potential to be used in lignocellulosic biomass pre-treatment.

Suppression of Lignin Repolymerisation to Enhance Cellulose Bioconversion and Lignin Valorisation - A Review.

The recent discovery that the prevention of lignin repolymerisation/condensation in lignocellulosic biomass pretreatment can both enhance the bioconversion of cellulose and the quality of the obtained lignin, has brought a lignocellulose biorefinery closer to reality. In this work, the development of this approach and the last advancements are reviewed. The review reveals the successful implementation for a wide range of lignocellulosic substrates including softwood, hardwood, and agricultural residues. As well, it is shown that the approach can enhance various pretreatment technologies, including steam, acid and organosolv processes. Recent developments involve the discovery of new and greener additives which prevent lignin repolymerisation, the implementation of cellulose saccharification at industrially realistic conditions and high-yield fermentation. In addition, first applications of the lignin obtained in these processes are reviewed, showcasing its enhanced quality for functionalisation and use in polymers, as well as for its depolymerisation to aromatic monomers. The recent progresses bring closer the prospect of a biorefinery that can valorise all fractions of lignocellulosic biomass.

Exploration of the interaction mechanism of lignocellulosic hybrid systems based on deep eutectic solvents

The interactions of three deep eutectic solvents (DES) choline chloride-glycerol (ChCl-GLY), ChCl-lactic acid (ChCl-LA) and ChCl-urea (ChCl-U) with cellulose-hemicellulose and cellulose-lignin hybrid systems were investigated using the simulated computational approach. Aiming to simulate DES pretreatment of real lignocellulosic biomass in nature. DES pretreatment could disrupt the original hydrogen bonding network structure among the lignocellulosic components and reconstruct the new DES-lignocellulosic hydrogen bonding network structure. ChCl-U had the highest intensity of action on the hybrid systems, removing 78.3% of the hydrogen bonds between cellulose-4-O-methyl Gluconic acid xylan (cellulose-Gxyl) and 68.4% of the hydrogen bonds between cellulose-Veratrylglycerol-b-guaiacyl ether (cellulose-VG), respectively. The increase of urea content facilitated the interaction between DES and lignocellulosic blend system. Finally, the addition of appropriate water (DES:H2O = 1:5) and DES formed the new DES-water hydrogen bonding network structure more favorable for the interaction of DES with lignocellulose.

Insight into lignocellulosic biomass torrefaction kinetics with case study of pinewood sawdust torrefaction

Torrefaction, as a promising pretreatment of lignocellulosic biomass, can upgrade its physicochemical properties and thermochemical conversion performance. The kinetics of lignocellulosic biomass torrefaction is fundamental for elucidating its reaction mechanism and optimizing its process. Although some kinetic models have been studied to describe the kinetic characteristics of lignocellulosic biomass torrefaction, a systematical analysis of the kinetic models is still missing. In this study, the derivation, numerical calculations, parametric studies and characteristics of those kinetic models for lignocellulosic biomass torrefaction were comprehensively studied. The reaction order model, two-step model and distributed activation energy model (DAEM) for lignocellulosic biomass torrefaction were used to analyze the experimental kinetic data of pinewood sawdust torrefaction at three different final torrefaction temperatures of 523, 548 and 573 K. The results show that (i) the reaction order model cannot provide accurate fit to the experimental kinetic data of pinewood sawdust torrefaction; (ii) the two-step model can provide the best fit but it contains too many parameters and involves intermediate reactions making it difficult to apply; (iii) the DAEM can describe the kinetic behaviors of pinewood sawdust torrefaction with adequate accuracy and reflect the reactivity distribution of thermal decomposition reactions involving in pinewood sawdust torrefaction.