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The research on hardwood lignin is quite limited for lignin-based adhesives due to its heterogeneity and chemical complexity compared with those of softwood and non-wood lignin. Herein, a novel approach of producing entirely bio-based and nontoxic wood adhesives by self-crosslinking of industrial hardwood kraft lignin (HKL) is presented to replace formaldehyde-based resin adhesives. The key issues of converting HKL to bio-wood adhesive are their low reactivity for crosslinking capacity and high heterogeneity. For this, HKL extracted from industrial black liquor was acetone fractionated to reduce its heterogeneity, resulting in acetone-soluble HKL (AS-HKL) and acetone-insoluble HKL (AI-HKL), which were then glyoxylated to facilitate crosslinking and form a three-dimensional network structure. Lignin samples were analyzed by gel permeation chromatography (GPC), Fourier transform infrared (FTIR), X-ray photoelectron spectroscopy (XPS), 31P nuclear magnetic resonance (31P NMR), solid state 13C cross-polarization/magic angle spinning (13C CP/MAS) NMR, differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). The adhesive strength of lignin-based adhesives was evaluated by determining the tensile shear strength of plywood. In this current research the chemical structure changes especially the crosslinked structure and adhesion performance were investigated. Results showed that the self-crosslinking was successfully formed by ether bonds formation between glyoxalated lignin. Also, the self-crosslinked acetone insoluble hardwood kraft lignin fractionation (AI-HKL) showed the best adhesion performance. FTIR, XPS and 13C CP/MAS NMR spectra revealed new peaks and ether bonds in the glyoxylated lignin. Therefore, these results indicate a successful self-crosslinking of the hardwood kraft lignin after acetone fractionation and glyoxalation for adhesives via network formation. The glyoxalated AI-HKL (AI-HKL–GLY) exhibited the highest viscosity and provided the best plywood adhesion strength (0.8 MPa) among the adhesives, and showed a good potential as wood adhesives. Thus, the results suggest that the self-crosslinking of hardwood kraft lignin after a proper fractionation and glyoxalation is a promising approach of developing lignin-based bio-adhesives for wood bonding. [Display omitted] • Totally green adhesives were developed by self-crosslinking of fractionated and glyoxalated hardwood kraft lignin. • Self-crosslinking was successfully formed by ether bonds between the glyoxalated lignin. • The self-crosslinked lignin showed better thermal stability than the control. • The self-crosslinked lignin from acetone insoluble fraction showed the best adhesion in plywood. [ABSTRACT FROM AUTHOR]

Renewable resources such as wood are an important candidate towards the replacement of fossil-based materials with bio-based materials. Lignin, comprising up to 40% of woody biomass, has shown great potential in the preparation of nanoparticles (LNPs), which can be used in diverse material applications. Typically, LNPs are prepared from technical lignins, deriving from pulping processes. Their formation is thought to be driven by the hydroxyl content and molecular weight of lignin. However, other equally important parameters are the monolignol composition and the concentration of lignin used. In this study, we used native-like lignin fractions from hardwood and softwood to investigate the impact of lignin structure on LNP formation. We identified a synergistic effect between π-π stacking and hydroxyl group content in nanoparticle formation. Our LNPs exhibited different morphologies, including compact, collapsed spheres, and 'snowman' aggregates. The results described herein provide an in-depth perspective on the formation and structure-property relationship of LNPs from native-like lignin fractions. With this study we aim to promote biorefinery concepts, in which the lignin structure is preserved during extraction. • Lignin was extracted from softwood and hardwood using a green and mild protocol. • Native-like lignin populations were used for nanoparticle preparation. • Lignin nanoparticles were prepared with the anti-solvent precipitation method. • Properties of lignin populations were correlated to nanoparticle morphology. [ABSTRACT FROM AUTHOR]

In this study, the efficient extraction of lignin from wood meal using a deep eutectic system (DESys) was explored, and the obtained lignin was characterized. The impact of various factors, such as the type of DESys components, extraction time, temperature, water content, and solid-liquid ratio, on the lignin extraction process was systematically investigated. The results indicated that a DESys with a carboxylic acid as the HBD provided the highest lignin extraction efficiency. The obtained lignin was characterized in terms of its molecular weight distribution, elemental composition, functional groups, crystalline structure, and thermal stability. The results showed that the lignin obtained by DESys-based extraction had similar properties to lignin extracted using traditional method. Additionally, the study examined the utilization of the residue left after lignin extraction for the adsorption of cationic pollutants, such as the cationic dye neutral red (NR). The residue was found to contain carboxyl groups, which enabled it to adsorb NR efficiently. The kinetic and thermodynamic models suggested that the adsorption was a chemisorption process. Furthermore, the residue showed selective adsorption for cationic dye over anionic dye. This selectivity was attributed to interactions between the residue's functional groups and the cationic dye molecule. Overall, this study provided a sustainable and comprehensive approach to lignin extraction from lignocellulosic biomass using DESys. It also demonstrated the potential of using the residue from the extraction process for the removal of cationic pollutants from wastewater, showcasing a multi-faceted approach to the valorization of lignocellulosic materials. [Display omitted] • DESys was formed by directly combining HBA and HBD with wood meal. • Lignin extraction yield was significantly improved. • Physicochemical properties of the extracted lignin were preserved. • The extracted lignin residue was utilized for highly efficient neutral red adsorption. [ABSTRACT FROM AUTHOR]

Although dye-decolourising peroxidases (DyPs) are well-known for lignin degradation, a comprehensive understanding of their mechanism remains unclear. Therefore, studying the mechanism of lignin degradation by DyPs is necessary for industrial applications and enzyme engineering. In this study, a dye-decolourising peroxidase (CsDyP) gene from C. serinivorans was heterologously expressed and studied for its lignin degradation potential. Molecular docking analysis predicted the binding of 2, 2-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), veratryl alcohol (VA), 2, 6-dimethylphenol (2, 6- DMP), guaiacol (GUA), and lignin to the substrate-binding pocket of CsDyP. Evaluation of the enzymatic properties showed that CsDyP requires pH 4.0 and 30 °C for optimal activity and has a high affinity for ABTS. In addition, CsDyP is stable over a wide range of temperatures and pH and can tolerate 5.0 mM organic solvents. Low NaCl concentrations promoted CsDyP activity. Further, CsDyP significantly reduced the chemical oxygen demand decolourised alkali lignin (AL) and milled wood lignin (MWL). CsDyP targets the β-O-4, C O, and C C bonds linking lignin's G, S, and H units to depolymerize and produce aromatic compounds. Overall, this study delivers valuable insights into the lignin degradation mechanism of CsDyP, which can benefit its industrial applications and lignin valorization. [ABSTRACT FROM AUTHOR]

As a wood containing many ordered cell cavities and blood vessels, eucalyptus is an ideal precursor material in preparing hierarchical porous carbon electrodes for Zn-air batteries. However, insufficient micro-mesoporous and minor active sites inhibit the application of wood-directly derived carbon materials in Zn-air batteries. Hence, a simple and cost-effective formic acid pretreatment method was proposed to prepare nitrogen-doped bulk phase catalysts with abundant micro-mesoporous and enough high active sites from eucalyptus. Formic acid pretreatment selectively removed part of lignin and hemicelluloses, thus generating abundant nanopores and contributing to the introduction of more nitrogen active sites. Moreover, the obtained bulk carbon had high mechanical strength and wonderful electrical conductivity, containing cross-linked networks and natural ion transport channels. Benefiting from the above advantages, the bulk carbon catalyst could be directly used as self-supported cathode, and the resulting Zn-air batteries achieved a long cycle life of more than 300 h. This work provides a simple and feasible method for the development of biomass-derived hierarchical bulk-phase porous carbons for energy-related applications. • Hierarchical porous nitrogen doped bulk carbon derived from eucalyptus by formic acid pretreatment. • The bulk carbon with a large number of nanopores has high mechanical strength and high electrical conductivity. • A high number density of graphite N and pyridine N is introduced in carbon lead to favorable ORR activity. • The Zn-air battery with bulk FA-CN achieves a long cycle life of more than 300 h at 10 mA cm−2. [ABSTRACT FROM AUTHOR]

[Display omitted] • An integrated and eco-friendly biorefinery was proposed. • XOS, glucose and the residual lignin were obtained with high yield. • Genetically modified poplar was a potential feedstock for biorefinery. • The LPC-CSE has higher oxygen content and specific capacitance. • The LPC supercapacitor exhibits an excellent cycling performance. In this work, a green and robust pretreatment which integrated acetic acid-catalyzed hydrothermal and wet mechanical pretreatment, was developed to efficiently produce high yield (up to 40.12%) of xylooligosaccharides and digestible substrates from Caffeoyl Shikimate Esterase down-regulated and control poplar wood. Subsequently, superhigh yield (more than 95%) of glucose and residual lignin were obtained after a moderate enzymatic hydrolysis. The residual lignin fraction exhibited a well-preserved β- O -4 linkages (42.06/100Ar) and high S/G ratio (6.42). Subsequently, lignin-derived porous carbon was successfully synthesized, and it exhibited a high specific capacitance of 273.8 F g−1 at 1.0 A g−1 and long cycling stability (remained 98.5% after 10,000 cycles at 5.0 A g−1) compared to control poplar wood, demonstrating that special advantage of this genetically-modified poplar in this integrated process. This work developed an energy-saving and eco-friendly pretreatment technology as a waste-free route for converting different lignocellulosic biomass to multiple products. [ABSTRACT FROM AUTHOR]

This study evaluated the solubility of low-processed wood fibers produced from a low temperature acid hydrotropic fractionation (AHF) in an ionic liquid (IL) 1,5-diazabicyclo[4.3.0]non-5-enium acetate (DBNH[OAc]. Unbleached wood fibers produced from AHF using p -Toluenesulfonic acid (p -TsOH) with or without post-treatments with lignin and hemicelluloses content up to 15% and 25%, respectively, were dissolved directly into the IL DBNH[OAc]. Post-AHF treatments using dilute alkaline and glycerol swelled the cellulose and partially removed residual lignin resulting in improved dissolution. Semi-quantitative 2D HSQC NMR analyses revealed that the undissolved wood fiber residues were enriched with G units and condensed S units (S cond), demonstrating, as expected, that G units and condensed lignin substructures have a negative effect on dissolution in DBNH[OAc]. Therefore, AHF with rapid fractionation at low temperatures offers a promising advantage over existing high temperature pulp dissolving fiber (PDF) processes in terms of reducing energy input, lowering lignin content as well as reducing lignin condensation for producing man-made cellulosic fibers (MMCF). [ABSTRACT FROM AUTHOR]

Abstract Lignin is a by-product of paper and pulp production resulting from extraction of cellulose, the world's most abundant natural polymer. In this study, we manufactured polypropylene (PP)/PP-grafted maleic anhydride (PP-g-MAH)/glass fiber (GF)/lignin composites via reactive extrusion process for value-addition of lignin, often discarded as wood waste. To enhance adhesion in composites at interphases, diisocyanate was added in-situ during the extrusion process, leading to chemical primary bonding. Structure-property relationship of PP/PP-g-MAH/GF/lignin composites revealed two different reinforcement mechanisms that were supported by FT-IR, TGA, hardness, tensile, flexural, and impact tests, SEM, and density. Up to 7.5 wt% of isocyanate loading, linear urethane bonding was formed; further addition of isocyanate resulted in evolution of chemical crosslinking via allophanate bonding. [ABSTRACT FROM AUTHOR]

Graphical abstract Abstract Wood is the main source of lignin in the world. This generic term "Lignin" describes a large group of aromatic biopolymers, i.e. the second most abundant class of biopolymers on Earth. It accounts for approximately 30% of wood weight while conferring rigidity and antimicrobial properties to wood. Since lignin is combined with cellulose and hemicellulose in biomass, this will constitute a limiting factor in the bioconversion of wood into pulp or second-generation biofuels through the biochemical pathway. These processes generate a huge quantity of lignin as by-products, mainly used as fuels for energy savings. Recently, alternative routes towards lignin's valorization were emphasized (e.g. as bio-based resins, adhesives, or composites), but they strongly depend on lignin's chemical structure, also dependent on fractionation process. Therefore, this review aims to summarize the strong interplay between extraction processes, resource supply, and recent uses of lignin into bio-based materials. [ABSTRACT FROM AUTHOR]

Abstract 3D graphene (or graphene-like porous carbon) is prepared from precursor lignin separated and purified from alkaline pulp black liquor. The lignin is pretreated using rapid freeze-dry technique for the porous, soft and dispersive microstructure. A special temperature control program is designed to keep the porous structure of lignin particles in the carbonization and graphitization process, avoiding agglomeration. The 3D graphene from lignin consist of curve graphene sheets in dimensions around dozen micrometers, which merge each other with clear dihedral angle and form wood-ear like architecture, different from fullerene like carbon crystals. The porous carbon is characterized and analyzed with FTIR, Raman, XRD, SEM, TEM, XPS, and SSA. A possible chemical mechanism in the synthesis of 3D graphene from lignin precursor is proposed. The aromatic groups and alkane fragments in lignin are decomposed during pyrolysis under high temperature, then the benzene rings compose the graphene sheets, and the sp3 free carbon atoms join the graphene sheets with chemical bonds along the framework of lignin polymer, forming the self-supporting and self-constructing 3D graphene, or porous carbon. Graphical abstract Unlabelled Image Highlights • Lignin is separated from alkaline pulp black liquor, and reshaped into a porous form using liquid-nitrogen freezing method. • Graphene-like porous carbon has wood-ear like architecture consisting of curve graphene sheets. • 3D graphene was analyzed by using SEM, TEM, XPS, XRD, FTIR, Raman and surface area analysis. • A possible chemical mechanism in the synthesis of 3D graphene from lignin precursor is proposed. [ABSTRACT FROM AUTHOR]

Magnetic porous carbon materials as peroxymonosulfate (PMS) activators for sulfadiazine degradation were derived from metal-organic frameworks (MOFs) grown in-situ on the cellulose of wood through the one-step pyrolysis method. The cellulose was obtained by treating wood powder with sodium chlorite to remove lignin, and Fe-MOFs (MIL-101(Fe)) nanoparticles were in-situ grown on the cellulose through hydrothermal reaction. The delignification of wood effectively enhanced the in-situ growth of MIL-101(Fe) on the wood tracheid skeleton, increased the specific surface area of magnetic porous carbon material (Fe@PC-50) after pyrolysis, and improved the performance of Fe@PC-50 as a PMS activator for the degradation of sulfadiazine. With the presence of 0.04 g L−1 Fe@PC-50 and 0.12 g L−1 PMS, the degradation percentage of sulfadiazine (20 mg L−1) could reach 100 % within 15 min, indicating excellent catalytic activity. Quenching tests and electron paramagnetic resonance (EPR) indicated that both free and non-free radicals played important roles in PMS activation. X-ray photoelectron spectroscopy (XPS) suggested that Fe0 and Fe 3 C were the possible important active sites for sulfadiazine degradation. This work offered an effective method to synthesize PMS activators from biomass/MOF materials for water treatment. [Display omitted] [ABSTRACT FROM AUTHOR]

The depolymerization of lignin into dicarboxylic acids (DCA) by the Fenton oxidation process is a promising approach to valorising lignin. However, Fenton oxidation is challenging due to the demand for acidic reaction conditions and homogeneous Fe2+ catalysts, which cannot be recovered. Herein, we fabricated a biochar-based solid-acid catalyst (SBC) from the pyrolysis of rice straw biomass followed by H 2 SO 4 treatment. This novel catalyst achieved an enhanced catalytic performance in the activation of H 2 O 2 under circumneutral pH, visible-light irradiation and Fe-free conditions. Under optimum conditions, a cumulative yield of 40.1 μ mol. g c a t − 1 . h − 1 of malonic, maleic, fumaric, succinic and gallic acid was obtained using 40 mM H 2 O 2 , 1 g/L catalyst loading and 4 h reaction time, which is comparable to yields reported in the literature under elevated temperatures and pressures. The activity of SBC stems from the synergy of oxygenated surface functional groups and persistent free radicals (PFRs), which can chemisorb and subsequently activate H 2 O 2 and dissolved O 2 to yield •OH and 1O 2. Addition of NaN 3 scavenger for 1O 2 enhanced the cumulative DCA yields to 282.4 μ mol. g c a t − 1 .h−1, suggesting that 1O 2 is the main reactive oxygen species in the reaction. Finally, the SBC catalysts remained stable at the said reaction conditions and could be recycled without significant deactivation. After five cycles, the lignin conversion and cumulative DCA yields decreased by 19.7% and 23% respectively. These results show that Fe-free, visible-light Fenton-like catalytic oxidation of lignin with acid-modified biochars is a promising way to produce high-value platform chemicals. [Display omitted] • Catalytic metal-free Fenton-like oxidation of alkali lignin was studied. • Carbonaceous solid acid catalysts were produced from pyrolysis of rice straw biomass. • Persistent free radicals on biochars could act as electron donors to activate H 2 O 2 into.•OH and •O 2 −. • Acetonitrile-water mixture was the best solvent for the reaction. • Malonic, malic and succinic acid were the major dicarboxylic acid products from the reaction. [ABSTRACT FROM AUTHOR]

• Degree of cellulose crystallinity during natural weathering periods can specify the performance of wood. • A kinetic study on surface photo-degradation determine the service time of wood materials in exterior uses. • Thermal treatment can delay color change of wood due to upgraded lignin and crystalline structure of cellulose. • Thermal treatment improved the hydrophobicity and crystallinity index of wood. • Natural weathering changed wettability and morphological properties of the wood surface. The hygroscopic behavior of wood-based materials is undoubtedly influential on the material surfaces exposed to climatic conditions. The paper aims to kinetically investigate the photo-degradation and surface characteristics of thermally-treated spruce wood at 185 °C and un-treated (reference) sample through 2 years of natural weathering. Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR) spectroscopy and X-ray diffraction (XRD) were employed to investigate the chemical changes occurred in lignin and crystalline structure of cellulose as a function of outdoor exposure. Detailed measurements of morphological and surface changes were evaluated during exposing periods. Surface wettability and roughness as well as cracks were increased for all samples due to weathering as the exposure time extended. Prominently, the color changes (ΔE) and photo-chemical reactions were found to be negligible in short-time weathering thanks to thermal modification. In the long–term exposing, more OH-bonds caused by lignin leaching out resulted in presence of cracks and the affinity for water on reference sample. Degree of crystallinity significantly decreased by 12.7% in thermally treated wood and 18.3% in reference sample after long-term weathering while, the crystallinity index of thermally-treated wood increased to 4.7% in 6-month weathering. Hence, the amorphous structures and chromophores groups appeared on the reference wood at a faster and more intense rate during exposing time. Thermal treatment delayed photo-yellowing as well as color change of wood due to up-graded lignin and cellulose crystallinity through a photo-stable structure. Accordingly, kinetic studies ascertained the service-time of wood products in exterior uses. [ABSTRACT FROM AUTHOR]

The structure and properties of lignin can vary depending on the type of lignocellulosic biomass it comes from and the separation techniques used, and also affects its suitability for different applications. In this work, the structure and properties of lignin isolated from moso bamboo, wheat straw, and poplar wood by different treatment processes were compared. Results show that deep eutectic solvent (DES) extracted lignin exhibits well-preserved structures (including β-O-4, β–β, and β-5 linkages), a low molecular weight (M n = 2300–3200 g/mol), and relatively homogeneous lignin fragments (1.93 < PDI < 2.33) compared to dealkaline lignin (DL) and milled wood lignin (MWL). Besides, lignin samples extracted by DES have a regular nanostructure, higher carbon residue content (>40 %), and excellent antioxidant properties (the free radical scavenging index >20). Among the three types of biomass, the structural destruction of lignin in straw is the most obvious, which is due to the degradation of β-O-4 and β-β linkages during DES treatment. These findings can contribute to a better understanding of the structural changes that occur in various treatment processes from different lignocellulosic biomass, and help maximize the targeted development of their applications based on the characteristics of lignin. [Display omitted] • Different lignins were prepared from various biomass by different processes. • Various lignin structural and property characteristics were elaborately analyzed. • DESs isolated lignin showed nanostructures structure and antioxidant properties. • Various processes provided a wide vision for better use of lignin in future biorefineries. [ABSTRACT FROM AUTHOR]

[Display omitted] • Review on biomass-based materials in the field of oil/water separation. • Cellulose, lignin, chitosan and wood has great application potential in oil/water separation. • The challenges and perspectives in biomass-based materials oil/water separation development are proposed. The ever-increasing amount of oily wastewater from industries poses a serious threat to the ecological environment and human health, and separation of oil and water remains a worldwide challenge. Because there is a requirement to develop green, efficient and low-cost oil/water separation materials, biomass materials, including cellulose, lignin, chitosan, and wood, are widely used in oil/water adsorption and separation because of their unique spatial structure and abundant active functional groups. In this review, the current design and fabrication process of biomass-based adsorption/separation materials for oi/water separation applications are summarized and highlighted. We focus on the oil/water separation performance and material design concept of the biomass membrane, biomass aerogel, and biomass carbon aerogel from the oil/water separation mechanism and the physical morphology of oil/water separation materials. Furthermore, we propose new future directions for the functional improvement and structural design direction of new biomass-based oil/water separation materials based on the characteristics of biomass. [ABSTRACT FROM AUTHOR]

The mechanical activation of the mixture of aspen wood – high silica zeolite catalysts increases the wood thermal conversion in supercritical ethanol and rises the yield of liquid products. TH-HSZ-30 with Si/Al = . Zeolite catalysts allow to fractionate the mechanically activated wood in supercritical ethanol at 270 °C on solid lignocellulose and on soluble products from hemicelluloses, presented by furfural, 5-hydroxymethylfurfural, levulinic acid and ethyl esters. The elevated temperature (350 °C) decreases the yield of liquid products due to the intensification of secondary reactions of their transformation to gases and chars. The possible mechanism of wood catalytic conversion to bio-liquids in supercritical ethanol is discussed. [ABSTRACT FROM AUTHOR]

The purpose of this study is to investigate the potential use of torrefied biomass of the genus Pinus, in the form of wood bark (CC), chips (CV) and wood pellets (PP), as substitutes for metallurgical coke to reduce the high CO 2 emissions from the use of metallurgical coke in blast furnaces. Thermogravimetric analysis were used to optimize the torrefaction temperature (250 °C or 290 °C), residence time (30 or 60 min) under inert atmosphere. All of the torrefied biomasses were analyzed to determine physical and chemical characteristics (proximate analyses, ultimate analyses, higher calorific value (HHV), Fourier transform infrared spectroscopy (FTIR) and ss -NMR. The composition of condensable and non-condensable gases formed during torrefaction process were also measured. The results showed that the two most promising biomasses were CV and PP torrefied at a temperature of 290 °C at a residence time of 30 min. The kinetics of torrefaction was analyzed by solid state ss -NMR characterization of the torrefied biomass at different time reactions and temperature (250–290 °C) under inert atmosphere, and followed a pseudo-first order kinetic model. The kinetics of evolution of ss -NMR signals related to C-1 of cellulose; C-4 of cellulose in ordered cellulose; C-4 of cellulose in disordered/amorphous cellulose; C-6 of cellulose, and carbon atoms of methoxyl groups in lignins, at different temperatures were used to estimate the activation energy, and values in the range 11–25 kJ mol−1 were obtained. • Brazilian biomasses proved were efficiently torrefied at 250–290 °C and 30–60 min. • Kinetics of torrefaction was measured from ss- NMR analysis for the first time. • Aliphatic ketones and hydrogen are the main gaseous products from torrefaction of biomass with high lignin content. [ABSTRACT FROM AUTHOR]

This work aimed to develop a phosphorous-based biorefinery process for obtaining phosphorylated lignocellulosic fractions in a one-pot protocol from coconut fiber. Natural coconut fiber (NCF) was mixed with 85 % m/m H 3 PO 4 at 70 °C for 1 h to yield the modified coconut fiber (MCF), aqueous phase (AP), and coconut fiber lignin (CFL). MCF was characterized by its TAPPI, FTIR, SEM, EDX, TGA, WCA, and P content. AP was characterized regarding its pH, conductivity, glucose, furfural, HMF, total sugars and ASL contents. CFL structure was evaluated by FTIR, 1H, 31P and 1H-13C HSQC NMR, TGA and P content and was compared to that of milled wood lignin (MWL). It was observed that MCF and CFL were phosphorylated during the pulping (0.54 and 0.23 % wt., respectively), while AP has shown high sugar levels, low inhibitor content, and some remaining phosphorous. The phosphorylation of MCF and CFL also showed an enhancement of their thermal and thermo-oxidative properties. The results show that a platform of functional materials such as biosorbents, biofuels, flame retardants, and biocomposites can be created through an eco-friendly, simple, fast, and novel biorefinery process. • A simple, fast and eco-friendly phosphorous-based biorefinery process was developed. • Phosphoric acid was used as pulping and phosphorylating agent. • The phosphorous-based biorefinery process was performed under mild conditions. • The cellulosic pulp, aqueous phase and lignin were phosphorylated. • Phosphorylated functional materials for different applications were produced. [ABSTRACT FROM AUTHOR]

Lignin removal plays a crucial role in the efficient bioconversion of lignocellulose to fermentable sugars. As a delignification process, fungal pretreatment has gained great interest due to its environmental friendliness and low energy consumption. In our previous study, a positive linear correlation between acid-insoluble lignin degradation and the achievable enzymatic saccharification yield has been found, hereby highlighting the importance of the close follow-up of lignin degradation during the solid-state fungal pretreatment process. However, the standard quantification of lignin, which relies on the two-step acid hydrolysis of the biomass, is highly laborious and time-consuming. Vibrational spectroscopy has been proven as a fast and easy alternative; however, it has not been extensively researched on lignocellulose subjected to solid-state fungal pretreatment. Therefore, the present study examined the suitability of near-infrared spectroscopy (NIR) for the rapid and easy assessment of lignin content in poplar wood pretreated with Phanerochaete chrysosporium. Furthermore, the predictive power of the obtained calibration model and the recently published ATR-FTIR spectroscopy-based model were compared for the first time using the same fungus-treated wood data set. PLSR was used to correlate the NIR spectra to the acid-insoluble lignin contents (19.9%–27.1%) of pretreated wood. After normalization and second derivation, a PLSR model with a good coefficient of determination (R CV 2 = 0.89) and a low root mean square error (RMSE CV = 0.55%) were obtained despite the heterogeneous nature of the fungal solid-state fermentation. The performance of this PLSR model was comparably good to the one obtained by ATR-FTIR (R CV 2 = 0.87) while it required more extensive spectral pre-processing. In conclusion, both methods will be highly useful for the high-throughput and user-friendly monitoring of lignin degradation in a solid-state fungal pretreatment-based biorefinery concept. • NIR method development for rapid monitoring of fungal delignification • Lignin calibration data set from >40 solid-state fungal pretreatment set-ups • A PLSR model with good model performance was obtained • Comparison of NIR and ATR-FTIR spectroscopy-based models using the same data set • Reduced analysis time (< 10 min) compared to the traditional method (> 3 h) [ABSTRACT FROM AUTHOR]

Pinewood and various model components were liquefied to bio-oil at 300–310 °C in 1-methylnaphthalene to study the chemistry of the liquefaction process. Cellulose, amylopectin and organosolv lignin were used as model components for the cellulose, hemicellulose and lignin parts of the wood. Furthermore, a few experiments with glucose and wood were performed for a better understanding of the process. The liquefaction products were analysed by 13 C NMR, FTIR, Gel Permeation Chromatography (GPC), GC–MS and C:H:O analysis (elemental analysis). The results indicated that the carbohydrates result in char, gas and light biocrude while the lignin leads mainly to light and heavy biocrude. However, the biocrude shows a very similar phenolic character is all cases, even when coming from carbohydrates. Similarities and differences with liquefaction in near/supercritical water or with pyrolysis are highlighted. [ABSTRACT FROM AUTHOR]

Raman microscope has been applied for the various studies on wood tissues because it can analyze without any pretreatments. In this study, therefore, we have applied Raman microscope to quantify the lignin contents of various wood tissues in various wood species. Lignin contents can be calculated from Raman spectra for each wood tissue by using calibration curve from standard samples. Lignin contents in various wood tissues coincide with the values obtained by conventional lignin quantification methods. Consequently, Raman microscopy, which is very simple without any pretreatments, is applicable and a powerful method to determine the lignin contents of wood tissues. [ABSTRACT FROM AUTHOR]

The development of high-performance composite films using biomass materials have become a sought-after direction. Herein, a green method to fabricate strong, flexible and UV-shielding biological composite film from wood cellulose skeleton (WCS), lignin nanoparticles (LNPs) and polyvinyl alcohol (PVA) was described. In the work, WCS and LNPs were prepared by chemical treatment of wood veneer and Enzymatic lignin, respectively. Then, WCS was infiltrated with the LNPs/PVA mixtures and dried to obtain composite films. WCS enhanced the mechanical properties of the composite films, the tensile stress reached to 85.8 MPa and the tensile strain reached to 6.39 %. The composite films with LNPs blocked over 98 % of UV-light, the water absorption decreased by 30 %, and the thermal stabilities were also improved. These findings would provide some references for exploring high quality biological composite films. [ABSTRACT FROM AUTHOR]

[Display omitted] • Alkaline lignin and DM resins were utilized to modify poplar fast-growing wood. • The materials used were green and environment friendly. • The DM-AL modified wood obviously increased dimensional stability. • The DM-AL modified wood with 12 %AL displayed excellent mechanical properties. • The DM-AL modified wood was found effective against decay fungus. Fast-growing poplar wood was modified by using 1,3-dihydroxymethyl-4,5-dihydroxyethylideneurea (DM) and alkaline lignin (AL) to improve its mechanical properties and decay resistance. AL was first used in combination with DM for wood impregnation modification. The weight percent gain, dimensional stability, mechanical properties, decay resistance and microcosmic changes of all wood samples were evaluated systematically. The results indicated that the maximum weight percent gain and anti-swelling efficiency of poplar wood after modification with DM-AL reached 46.2 % and 52 %, respectively. Compared with the unmodified samples, the bending strength, modulus of elasticity and hardness of the wood samples modified with DM-AL increased by 40 % – 60 %. Notably, the impact strength of samples modified with DM-AL was 18–26 % higher than that of samples modified with DM only, which may be due to the fact that the AL macromolecules slowed down the infiltration of DM-AL into the wood cell walls. The decay resistance of optimal modified samples against the decay fungus was improved by ∼80 % compared with unmodified sample. Furthermore, scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) confirmed that DM-AL modifiers impregnated into wood cell lumens. Fourier transform infrared spectroscopy (FTIR) demonstrated that the DM resin crosslinked with wood cell walls and AL macromolecules. In general, this study provides a facile, low-cost and green method to improve the comprehensive performance of fast-growing poplar, including mechanical properties and decay resistance. [ABSTRACT FROM AUTHOR]

Biomass-based multifunctional electromagnetic shielding materials have attracted extensive interest in academia and industry due to the sustainability of biomass and the environmental adaptability of multifunctional materials. After removing lignin and hemicellulose wood become a porous substrate with aligned cellulose, which is a good platform for building cellulose-based materials. In this work, a cellulose composite with sandwich-like structure was constructed by in-situ polymerization of aniline on delignified wood and coating a PDMS/CNT layer. Benefiting from the natural porous hierarchical structure and the constructed multilayer continuous conductive network, the PDMS/CNT/PANI WA exhibits excellent electrical conductivity (18.6 S/m) and electromagnetic shielding performance (shielding efficiency value of 26 dB at the X band (8.2–12.4 GHz)). The synergistic effect of PANI and CNT endowed the material with excellent flame retardancy (HRR, THR and HRC decreased by 84 %, 53.4 % and 83.3 %) and significant antibacterial activity. Moreover, PDMS imparts a water contact angle of 105° to the material, which acts as a protective layer, further improves the durability of the material. This work provides a new strategy for developing sustainable and multifunctional electromagnetic shielding materials. [ABSTRACT FROM AUTHOR]

Thermal radiation properties of natural wood are mainly affected by its chemical composition and physical structure. In the atmospheric transparency window (8–13 µm), cellulose, hemicellulose and lignin all have high average emissivity of 95.77%, 96.83% and 97.22%, respectively. This allows wood to continuously transfer radiation heat to outer space without hindrance, according to natural radiative cooling principle. It is so attractive to develop its all-day radiative cooling potential for continuous heat dissipation and energy-saving without energy input and pollutant output. Cooling capacity is directly affected by spectral property, for which delignified wood is prepared to explore the relation between lignin content and thermal radiation properties of wood. Results show that, the lower lignin content of wood would cause the higher average solar reflectivity and daytime radiative cooling power density, without affecting infrared emissivity and nighttime radiative cooling performance. With lignin content of 0.94%, delignified wood achieves all-day radiative cooling performance, obtaining average temperature drop of 2.60 K and 3.81 K at daytime and nighttime. Magically, its surface has a redirecting effect on incident heat, to the credit of the removal of amorphous lignin and inherited cellulose arrangement. Such a light-weight, environment-friendly, low-cost and all-day energy-saving material combining natural wood and natural radiative cooling principle provides a novel option for green products. [Display omitted] • Natural wood and natural principle are combined for green products. • Thermal radiation properties of natural poplar are comprehensively explored. • Spectrally modified wood has high infrared emissivity and adjustable reflectivity. • Lignin content is highly related with reflectance and cooling capacity of wood. • Delignified wood can achieve all-day radiative cooling performance. [ABSTRACT FROM AUTHOR]

A large number of bamboo waste is produced from bamboo processing industries. Bamboo waste, with high biomass yield and rich in xylan and glucan, is a promising material for the coproduction of xylo-oligosaccharides and glucose. In this work, a formic acid-facilitated hydrothermal pretreatment of bamboo was investegated to increase the yield of xylo-oligosaccharides by controlling the severity factor (SF) and formic acid concentration. The maximum xylo-oligosaccharides yield was 68.04 % (of initial xylan) and the concentrations of X 2 , X 3 , X 4 , and X 5 were 4.56, 3.08, 2.30 and 2.58 g/L, respectively. The highest enzymatic hydrolysis yield reached 93.05 % at 45 FPU/g cellulase dosage. Additionally, lignin isolated after formic acid pretreatment (FA-lignin), and lignin from alkali extraction (AE-lignin) had better thermal stability than milling wood lignin (MWL), which could be used in fire-retardant material applications. The techno-economic analysis predicts a revenue of 118.86 USD by processing 100 kg of waste bamboo combined with enzyme cost analysis. To conclude, xylo-oligosaccharides (12.56 kg), xylose (4.81 kg), glucose (22.37 kg) and lignin (13.28 kg) were produced from bamboo (100 kg, 18.37 % xylan, 44.29 % glucan, 27.23 % lignin). The results can give insights into establishing an efficient acid pretreatment of bamboo waste to produce xylo-oligosaccharides, glucose and lignin. [Display omitted] • Co-production of XOS, glucose and lignin was achieved by formic acid pretreatment of bamboo. • The total XOS yield could be attained 68.04 % at 160 ℃ for 120 min • XOS (12.56 kg), xylose (4.81 kg), glucose (22.37 kg) and lignin (13.28 kg) were produced from bamboo (100 kg). • The techno-economic analysis predicts a revenue of 118.86 USD by processing 100 kg of waste bamboo using the approach. [ABSTRACT FROM AUTHOR]

Electrochemical oxidation of lignin has been widely regarded as a clean and reliable alternative to obtain value-added products from lignin, such as vanillin or guaiacol. This work aims to go one step beyond the production of low molecular weight molecules and explore the possibility of using lignin residues from electrochemical treatments in the context of biorefinery. To this end, a two-way valorization of lignin by electrochemical oxidation is proposed, in order to obtain a liquid phase enriched in low molecular weight organic oligomers and a solid phase of modified lignin to be used as bioadhesive precursor. Hydroxylation of lignin by electrochemical oxidation using boron-doped diamond (BDD) anodes was observed according to the FTIR and MALDI-TOF results, concluding that an applied current density of 10 mA cm−2 leads to promising modifications for the formulation of bioadhesives. Furthermore, NIPU bioadhesives with electrochemically modified lignin were successfully prepared and tested for use in particleboard panels, showing satisfactory mechanical properties, and thus paving the way for more environmentally friendly lignin modification procedures for the wood industry. • Organosolv lignin oxidation treatment with BDD electrodes. • Double way valorization into low molecular weight oligomers and hydroxylated lignin. • Electrochemically modified lignin to be used as bioadhesive precursor. [ABSTRACT FROM AUTHOR]

[Display omitted] • Mild pretreatments for near-complete saccharification of desirable lignocelluloses. • Integrated green-like biomass pretreatments to achieve maximum cellulosic ethanol. • Green-like pretreatments selectable for generation of nanomaterials and nanocarbon. • Distinct pretreatment mechanisms accounting for biomass recalcitrance reduction. • A novel strategy for cost-effective biofuels and functional materials at high value. Lignocellulose represents the most abundant carbon-capturing substance that is convertible for biofuels and bioproduction. Although biomass pretreatments have been broadly applied to reduce lignocellulose recalcitrance for enhanced enzymatic saccharification, they mostly require strong conditions with potential secondary waste release. By classifying all major types of pretreatments that have been recently conducted with different sources of lignocellulose substrates, this study sorted out their distinct roles for wall polymer extraction and destruction, leading to the optimal pretreatments evaluated for cost-effective biomass enzymatic saccharification to maximize biofuel production. Notably, all undigestible lignocellulose residues are also aimed for effective conversion into value-added bioproduction. Meanwhile, desired pretreatments were proposed for the generation of highly-valuable nanomaterials such as cellulose nanocrystals, lignin nanoparticles, functional wood, carbon dots, porous and graphitic nanocarbons. Therefore, this article has proposed a novel strategy that integrates cost-effective and green-like pretreatments with desirable lignocellulose substrates for a full lignocellulose utilization with zero-biomass-waste liberation. [ABSTRACT FROM AUTHOR]

[Display omitted] • ATR-FTIR method development for easy monitoring of fungal lignin degradation. • Calibration data set from > 40 solid-state fermentation set-ups. • Washing is necessary to prevent interferences of proteins and fungal biomass. • A PLSR model with very good performance indicators was achieved. • Greatly reduced analysis time (<10 min) compared to wet chemistry methods (>3h) Lignin determination in lignocellulose with the conventional two-step acid hydrolysis method is highly laborious and time-consuming. However, its quantification is crucial to monitor fungal pretreatment of wood, as the increase of acid-insoluble lignin (AIL) degradation linearly correlates with the achievable enzymatic saccharification yield. Therefore, in this study, a new attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy method was developed to track fungal delignification in an easy and rapid manner. Partial least square regression (PLSR) with cross-validation (CV) was applied to correlate the ATR-FTIR spectra with the AIL content (19.9 %–27.1 %). After variable selection and normalization, a PLSR model with a high coefficient of determination (R CV 2 = 0.87) and a low root mean square (RMSECV = 0.60 %) were obtained despite the heterogeneous nature of the fungal solid-state fermentation. These results show that ATR-FTIR can reliably predict the AIL content in fungus-treated wood while being a high-throughput method. This novel method can facilitate the transition to the wood-based economy. [ABSTRACT FROM AUTHOR]

Due to the various chemical properties of lignins, one has different effects on the resins prepared with them. The aim of this research was to compare the influence of Soda and Kraft lignins on the physical and mechanical properties of the particleboards bonded with lignin-urea-formaldehyde (LUF) and lignin-phenol-formaldehyde (LPF) resins. According to the FTIR spectra and DSC analysis of lignin, Soda lignin exhibited higher phenolic hydroxyl groups and lower glass transition temperature (T g) value compared to Kraft lignin. Also DSC analysis results indicated that the resins based on Soda lignin need a lower temperature for curing than those based on Kraft lignin. Based on physicochemical test results, the resins containing Soda lignin exhibit a faster gel time and higher viscosity compared to those prepared with Kraft lignin in the both types of resins. Generally physical and mechanical properties results indicated that the panels made from LPF resin have higher mechanical strength and dimensional stability compared to those made from LUF resins at constant level of lignin. The particleboards bonded with Soda-based resin yielded lower water absorption and formaldehyde emission as well as higher flexural strength and internal bonding strength when compared to those bonded with the Kraft-based resin. The mechanical properties of the particleboards bonded with LPG resins could be significantly improved by increasing percentages of lignin while it was decreased for LUF resin. [ABSTRACT FROM AUTHOR]

The Qinling Mountains (Qinling Mts.) are characterized as a distinct transition of bioclimatic zones along the north-south geographic boundary in China. Although ongoing global warming may affect the growth of most tree species across elevation gradients, the effect of modern warming on the stable hydrogen isotopes of tree-ring wood is still unknown. In this study, we developed early- and late-wood δ 2H chronologies from 1900 to 2018 CE of lignin methoxy groups (δ 2H LM) at 700-m intervals from 1700 to 3100 m a.s.l. along the elevation gradient in Mount Taibai (Mt. Taibai), the peak of the Qinling Mts. The δ 2H LM values of the earlywood were relatively enriched in 2H compared to the latewood, and an elevation-dependent depleting trend along the altitudinal gradient was observed. Comparing the δ 2H LM values with modelled δ 2H values of precipitation (δ 2H Pre) of the sample sites, similar isotopic patterns can be obtained. The reconstructions of δ 2H Pre values confirm the strong coherence between the isotopic composition of the source water and the methoxy groups in the growing season. The consistency of δ 2H LM chronologies between the early- and late-wood at the higher sites was stronger than that at the lower sites. The additional lagged effect and climate response revealed significant seasonal and altitudinal differences. At the timberline site, δ 2H LM values of earlywood were mainly related to the January and February temperatures, whereas δ 2H LM values of latewood correlated most strongly with temperature from July to September, and both values were controlled by the amount of total precipitation. In addition, the combined new δ 2H LM chronologies, based on the lag-1 autocorrelation and the weighted average of the current year earlywood and previous latewood, could be used to merge the corresponding temperature signals from the middle- and low-elevation sites. Altitudinal correlations of elevation offset between the annual δ 2H LM chronologies and interpolations of precipitation and temperature suggested that the δ 2H LM values at higher elevations better represent regional climatic changes. Therefore, topographic effects such as elevation differences should be considered in large-scale applications of δ 2H LM values in future studies. • Altitude- and seasonal-differences in δ 2H values of both tree-ring wood and precipitation were revealed in Qinling Mountains, China. • Elevational effects of temperature and precipitation resulted in the variations of δ 2H LM of lignin methoxy. • Timberline δ 2H LM recorded the significantly lagged effects and strong hydroclimatic signals. • Altitude specificity of δ 2H LM should be considered in the large-scale investigations. [ABSTRACT FROM AUTHOR]

This work aims to explore the height-related changes in chemical composition, calorific value, and thermochemical behavior during pyrolysis of four types of hybrid poplars (AF2, Beaupré, I214 and Monviso) and their structural components. The samples were collected from a Short Rotation Woody Coppice (SRWC) located in an abandoned opencast mine in the north of Spain. The effect of lignin and extractives (hydrophilic and hydrophobic ones) on wood pyrolysis, as well as the relationships between thermochemical properties and lignocellulosic composition, extractive content and lignin maturity, are investigated. The higher bark content of the top sections influences chemical and structural compositions. They have higher calorific values and more lignin, extractives, N and S contents, yielding more fixed carbon and ash. Additionally, the lignin of the top sections is less thermally stable. The isolation of structural components from the samples shifts the maximum volatile emission to higher temperatures for lignin and lower temperatures for holocellulose and cellulose, compared with those in the un-extracted samples. Lignin has a notable influence on wood decomposition since: (i) until its β-O-4 linkages and hemicellulose/lignin connections have been broken, cellulose devolatilization does not reach its maximum rate; and (ii) its removal reduces sample thermal stability, its effect being more significant than that of extractive removal. DRIFT spectroscopy is a valuable technique for predicting variations in chemical and thermochemical characteristics with the height of the wood sample. Several indices representing ratios of the maximum absorbance of specific signatures of lignin and cellulose could be appropriate for quick preliminary screening of woody biomass. [Display omitted] • Three sections of four genotypes of hybrid poplars from SRWC were studied. • Tree chemical properties vary with height, which conditioned the optimum process. • Top sections contain more bark and lignin, which is less thermally stable. • Lignin has a relevant impact on holocellulose and cellulose thermal stability. • FTIR indices are adequate for predicting some biomass thermal properties. [ABSTRACT FROM AUTHOR]

Liquid wood (LW) Arboform ® is a novel bio-polymer class of materials consisting in various amounts of lignin, natural fibres, and bio-based additives being a fully biodegradable composite. The full acceptance of LW by industry depends on thermo-mechanical stability as a basic quality condition for engineering applications. The paper aims to investigate the thermal properties and stability of LV3 Nature (LV3) as the uppermost member of Arboform ® class of materials under different conditions (i.e. heating rates) both as primary and processed material. The results are discussed in terms of differential scanning calorimetry (DSC) and infrared (IR) spectrometry analysis. DSC thermograms highlight specific changes in corresponding areas and peak positions revealing the polymer behaviour: higher heating rate results in higher activation energies and delays of both endo and exothermic reactions in the temperature range of applications. The FTIR spectra of primary granules and processed LV3 Arboform ® show maintaining of the initial functional molecular groups supporting a positive response of the material towards reuse. SEM investigations confirm liaising of the processed composite: no changes at the matrix/fibres interface were found. The results create opportunities in process technologies and applications development of this lignin matrix composite material as a candidate for thermo-plastics polymers. [ABSTRACT FROM AUTHOR]

Lignins are by-products from biorefinery and paper industries. Their chemical structures are complex, and they are currently mainly used for energy and heat production generated by their combustion. In a context of higher value applications of lignins, lignin-based composites with lignosulfonate matrix and wood fibers reinforcement were pre-treated with laccase (EC 1.10.3.2) from Pycnoporus cinnabarinus , and laccase/mediator system, to modify, as a proof of concept, their mechanical properties. Composites (120 x 9 x 4 mm) were prepared by compression molding at room temperature. The flexural modulus, the fracture strength, and the fracture energy of obtained agrocomposites were evaluated by three-points bending tests. The best mechanical properties (flexural modulus of 3.51 GPa and a fracture strength of 17.5 MPa) were obtained for a simultaneous enzymatic pre-treatment of both lignosulfonate and wood fibers during 17 h with 13 U of laccase per gram of lignosulfonate. [Display omitted] • Composites made of a lignosulfonate matrix and a wood fibers reinforcement were developed. • Flexural modulus and fracture strength of composites were determined by three-points bending tests. • A laccase pre-treatment of the raw materials allows to significantly modify the mechanical properties of composites. • A simultaneous enzymatic pre-treatment of lignosulfonate and wood fibers improved flexural modulus and fracture strength. [ABSTRACT FROM AUTHOR]

Stable isotopes were used to label lignin and cellulose to accurately explain the chemical association between them in poplar wood. Both the 13C-labeled lignin precursors (coniferin-[Cα-13C] or coniferin-[Cγ-13C]) and the Deuterium-labeled cellulose precursor (UDP-glucose-[6,6-D 2 ]) were added to a growing poplar plant. After 20 d cultivation, hemicellulose and lignin-carbohydrate complexes (LCC) were extracted from the newly-formed xylem by Björkman method, then the abundance of 13C and D were detected. It revealed that both lignin precursors and cellulose precursor could be efficiently deposited in the newly-formed xylem, while cellulose precursor was detected mainly deposited on cellulose. Then the LCC was degraded using cellulase and hemicellulase to obtain enzymatically degraded lignin-carbohydrate complexes (EDLCC). The 13C NMR，1H NMR and 2D NMR analyses of EDLCC clearly showed that lignin subunits in poplar wood were mainly connected through β-O-4, β-5, β-β structures, while cellulose was mainly connected to lignin by ether bonds, acetal bonds and ester bonds. The ether bonds and acetal bonds were between cellulose C6 and lignin Cα, while the ester bonds were between cellulose C6 and lignin Cγ. The study provides new evidence for the structural information between cellulose and lignin in poplar. [Display omitted] • Dual isotopes were used for lignocellulose labeling from both lignin and cellulose sides in a living poplar tree creatively. • Cellulose and lignin in poplar are mainly connected by ether bond, ester bond and acetal bond. • The ether bond is between glucose unit C6 and lignin Cα， while the ester bond is between glucose unit C6 and the lignin Cγ. [ABSTRACT FROM AUTHOR]

Agricultural fiber sources, such as wheat straw, are promising lignocellulosic feedstocks for the generation of renewable substitutes for synthetic materials (e.g., plastics, construction materials, biofuel, and other biorefinery products). The interest in the utilization of lignin has increased rapidly during the last years; the number of publications increased more than five times between 2000 and 2020. The number of publications concerning lignin from wheat straw follows the general trend with an increasing scientific interest in lignin but comprises less than 5% of the total lignin publications. The structure and morphology of lignin in straw and wood differ between the different species. The monolignol composition and spatial location in plant tissue are notably different, as well as the nature and abundance of lignin-carbohydrate linkages involving p-coumaric acid (pCA) and ferulic acid (FA) units in wheat straw lignin. To further enable the utilization of wheat straw as a resource for bio-based materials, a solid understanding of the wheat lignin structure and composition is required. This review aims to consolidate the state-of-the-art in wheat lignin and focuses on lignin and its distribution, fundamental chemical structures, and morphology in wheat straw and compares these features with lignin in wood cell walls. • The state-of-the-art in wheat lignin is consolidated. • Wheat straw lignin has primarily β-O-4 linkages and fewer C-C than wood lignin. • Wheat straw and wood differ clearly in lignin distribution, structure, and morphology. • Main units in wheat straw lignin are (H,G,S), (G) in softwood, and (G,S) in hardwood. • Lignin-carbohydrate linkages are of great significance to biomass refinement. [ABSTRACT FROM AUTHOR]

Adhesives––the resins widely used in particleboards, oriented strength boards, and plywood––are traditionally produced from fossil-based polymers. Owing to the toxicity, environmental pollution, and non-renewable raw materials associated with these polymers, attempts to synthesize environmentally friendly and renewable adhesives from bio-based materials has attracted increasing attention. Lignin is an abundant natural and renewable phenolic polymer with multiple types of functional groups, such as hydroxyl, carboxyl, and aldehyde groups. This has drawn considerable attention to the exploitation of this resource based on these functional groups. Because of the advantages of lignin, continued research efforts have been focused on using lignin to partially or completely replace conventional raw materials for adhesives, such as phenol and melamine. In addition, lignin is also used with other biomass materials to produce formaldehyde-free biomass-based adhesives, such as lignin–furfural, lignin–soy protein, and lignin–tannin adhesives. Despite inspiring progress, the preparation of lignin-based adhesives with performances higher than that of fossil-based adhesives remains a serious challenge. This review summarizes the progress made in recent decades in research and commercial application of lignin-based adhesives for wood products, including lignin-based formaldehyde resins and lignin-based formaldehyde-free adhesives, and proposes perspectives on lignin-based adhesives. • Lignin is an abundant natural and renewable phenolic polymer. • This review summarizes the application of lignin in wood adhesives. • Details of lignin-based adhesives, properties and mechanism are discussed. • More research should be done regarding the chemical structure and curing mechanism. • Challenges and prospects are discussed. [ABSTRACT FROM AUTHOR]

Lignin has been extensively explored as a renewable precursor for materials fabrication. However, its low reactivity is one of the main challenges for material development. Herein, we presented a simple and effective biorefinery strategy to directly prepare reactive lignin with lower molecular weight and enhanced reactivity for the fabrication of high-strength self-healing adhesives. The role of 2-naphthol to suppress lignin condensation during the organosolv pretreatment of two woody biomasses was demonstrated by the less condensed structures and decreased molecular weights of lignin. This promoted the enzymatic hydrolysis of pretreated poplar from 50.2% to 62.9% at the low enzyme loading. Furthermore, the resultant lignins showed 51.7% increase in the modification efficiency during an esterification reaction. Lignin based macro-initiator was used to initiate "grafting from" reversible addition-fragmentation chain transfer polymerization of furan methacrylate and lauryl methacrylate to generate copolymers with tunable properties. Then, the occurrence of reversible Diels-Alder reaction between furan rings and maleimide crosslinker enabled the formation of dynamic network as self-healing adhesive. The adhesiveness analysis revealed that the highest adhesive shear strength reached 6.3 MPa, which was significantly higher than most of previous adhesives used on wood chips. Furthermore, after 10 times self-healing, the shear strength still accomplished 39.6% of original strength. This study has presented an upgraded biorefinery strategy to tune the properties of lignin and its interesting utilization to fabricate functional materials, providing new insights into materials and biorefinery society. • 2-Naphthol promoted enzymatic hydrolysis of organosolv pretreated woody biomass. • 2-Naphthol suppressed condensation of ethanol organosolv lignins (EOLs). • 2-Naphthol modified EOLs showed higher reactivity in an esterification reaction. • A self-healing adhesive with high strength was fabricated with modified EOLs. • Integration of sugar output and reactive lignin utilization from biomass. [ABSTRACT FROM AUTHOR]

In this current scenario, there is a broad range of use of resins in both domestic and industrial applications. Especially the importance of resins for adhesive in the wood industry is inevitable. But most of the commercially available resins for adhesive application are prepared of formaldehyde or fossil fuel-based resources which possess serious health issues. Henceforth, development of environmentally friendly resin from renewable resources through a cost-effective technique is a challenging task. Motivated by these facts and prospects, we present a novel technique for addressing non-renewability difficulties while also improving adhesive strength of the material. In this study, lignin-based composite resin with enhanced sustainability and adhesion strength have been achieved by a simply mixing of high concentration of poly (itaconic acid)-functionalized-lignin (P(IA)-f-Lignin) and aqueous emulsion of polyvinyl acetate. The P(IA)-f-Lignin was synthesized by in-situ free radical polymerization of partly neutralized IA in the presence of aqueous lignin dispersion at 90 °C using ammonium persulfate as initiator. The formation of P(IA)-f-Lignin was confirmed by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), nuclear magnetic resonance (NMR), field emission scanning electron microscope (FESEM) and thermogravimetric analysis (TGA). Here, we have been fabricated 20, 30, 40, 50, and 60 wt% of P(IA)-f-Lignin containing composite resin with desired amount of aqueous emulsion of polyvinyl acetate (PVAc). The changes in physico-chemical interactions were established by FTIR analysis. Various properties like viscosity, thermo-stability, and adhesive properties of all the formulated composite resin were inspected thoroughly. The composite containing 40 wt% of P(IA)-f-Lignin shows excellent improvement of adhesion strength from 3.32 ± 0.12 MPa to 7.83 ± 0.45 MPa. These fabricated composite resin with a high concentration of bio-based P(IA)-f-Lignin content and strong adhesion strength is very promising for fabrication of biobased adhesives with improved sustainability. [Display omitted] • Novel method to functionalize lignin by growing poly(itaconic acid) using free radical polymerization (P(IA)-f-Lignin). • High concentration of P(IA)-f-Lignin into polyvinyl acetate (PVAc) to produce novel P(IA)-f-Lignin/PVAc composite resin. • The PVAc composite resins exhibit outstanding enhancement of adhesion strength with wood failure. • High concentration of biobased P(IA)-f-Lignin in PVAc composite resin would enhance sustainability and scope of bioeconomy. [ABSTRACT FROM AUTHOR]

The aim of this study was to analyze four conceptual beech wood based biorefineries generated during process design in terms of environmental and economic criteria. Biorefinery 1 annually converts 400,000 dry metric tons of beech wood into the primary products 41,600 t/yr polymer-grade ethylene and 58,520 t DM/yr organosolv lignin and the fuels 90,800 t DM/yr hydrolysis lignin and 38,400 t/yr biomethane. Biorefinery 2 is extended by the product of 58,400 t/yr liquid “food-grade” carbon dioxide. Biorefinery 3 produces 69,600 t/yr anhydrous ethanol instead of ethylene. Compared to biorefinery 3, biorefinery 4 additionally provides carbon dioxide as product. Biorefinery 3 and 4 seem most promising, since under basic assumptions both criteria, (i) economic effectiveness and (ii) reduction of potential environmental impacts, can be fulfilled. All four alternatives may reduce potential environmental impacts compared to reference systems using the ReCiPe methodology. Economic feasibilities of the analyzed biorefineries are highly sensitive. [ABSTRACT FROM AUTHOR]

Eucalyptus globulus wood samples were treated with hot, compressed water to separate hemicelluloses (as soluble saccharides) from a solid phase mainly made up of cellulose and lignin. The liquid phase was dehydrated, and the resulting solids (containing pentoses as well as poly- and oligo- saccharides made up of pentoses) were dissolved and reacted in media containing an Acidic Ionic Liquid (1-butyl-3-methylimidazolium hydrogen sulfate) and a co-solvent (dioxane). The effects of the reaction time on the product distribution were studied at temperatures in the range 120–170 °C for reaction times up to 8 h, and operational conditions leading to 59.1% conversion of the potential substrates (including pentoses and pentose structural units in oligo- and poly- saccharides) into furfural were identified. [ABSTRACT FROM AUTHOR]

The photodegradation of white spruce by artificial ageing was studied by several techniques: colourimetry, FTIR-ATR and FT-Raman spectroscopy. Samples were exposed at a xenon lamp for 2000 h. Two distinct colour changes were found by colourimetric analysis, yellowing and silvering. These colour modifications indicate the formation of chromophoric structures which supports previous FTIR-ATR experiments. The degradation of lignin to generate the first chromophoric group for yellowing and then the appearance of surface layer cellulose. New carbonyl compounds conjugated with double bond at 1615 cm − 1 are probably the second chromophoric group. The crystallinity index was also calculated and showed an increase of cellulose crystallinity by prior degradation of amorphous cellulose. The FT-Raman analysis confirms the wood sensitivity to photodegradation but the most remarkable results is the increase of fluorescence as a function of time. In softwood lignin, the compound able to produce fluorescence is a free rotating 5–5′ linkage of one biphenyl structure. At native state these linkages are not free rotating, this phenomenon means the release of 5–5′ linkage of lignin structure by cleavage of both α carbon linkages (Norrish type I reaction). These data confirm also the photosensitivity of α and β carbon in lignin and the resistance of 5–5′ linkages. [ABSTRACT FROM AUTHOR]

The objective of this research was to investigate the effects of the conditions of hot water extraction (HWE) on abundance, properties, and structure of lignin depolymerization products. HWE of extracted softwood (ponderosa pine) was conducted using temperatures from 140 to 320 °C for 90 min. HWE materials were then subjected to a soxhlet extraction process using dichloromethane (DCM). The composition and molecular weight of this DCM-soluble material was conducted using semi-quantitative Py-GC/MS and ESI/MS, which showed that this material is rich in lignin with low molecular weight (<1200 g mol −1 ) and low polydispersity (∼1.4). The highest yield of this material (∼4.2%) was obtained in material processed at 260 °C. Py-GC/MS of the solid fraction after the DCM process showed a progressive reduction of products of the pyrolysis of lignin as the HWE temperature increased. This finding suggests that the lignin content in the solid decreased due in part to migration from the cell walls and middle lamella to the particles surfaces, particularly the inner surface of the cells. SEM and AFM techniques helped to visualize the ability of this DCM-soluble extract to adhere to cellulosic fibers. Therefore, this lignin-rich material presents properties that depend on the conditions of the operation. Results indicate that during HWE it is possible to control the process parameters to limit or increase the amount of DCM-soluble lignin and its properties as required for downstream processes. [ABSTRACT FROM AUTHOR]

Hygrothermal processes are widely used in modification of wood or other lignocellulosic materials to improve their decay resistance and dimensional stability. However, the mechanism behind the improved decay resistance is still unclear. In this study, hygrothermal modification of holocellulose was carried out at different temperature (℃) -duration (min) combinations (180−60, 220−60, 220−180), and the formation of pseudo lignin in modified holocellulose was verified. Its yield, as indicated by the acid insoluble substance, increased with the intensity of the hygrothermal modification from 0.11% for untreated holocellulose to 3.85%, 24.13%, and 65.86% for 180–60, 220–60, 220–180, respectively. According to the results of HPLC, FTIR, solid 13C NMR, 31P NMR, XRD and Py-GC-MS, the formed pseudo lignin contains polyfuran, aromatic, carbonyl and aliphatic structures. The formation pathway of pseudo lignin was proposed. It exhibited a significant inhibition effect against Gloeophyllum trabeum (brown rot fungus) with reduced mass losses from 6.89% for untreated holocellulose to 6.43%, 1.09% and 0.03% for 180–60, 220–60, 220–180, respectively; however, the inhibition effect against Coriolus versicolor (white rot fungus) was much less obvious. This provides an innovative point of view to explain the fungal degradation behavior of thermally modified wood or other carbohydrate materials. [Display omitted] • ·Pseudo lignin formed during the hygrothermal modification of holocellulose. • ·Pseudo lignin was resulted from the thermal degradation products of polysaccharides. • ·Pseudo lignin showed significant inhibition effect on brown rot fungi. [ABSTRACT FROM AUTHOR]

Well-organized and self-assembled structures with hierarchical surface architectures have recently attracted considerable attention due to their potentially wide application range. Herein, remarkable lignin-based petaloid nanoflakes (LPNFs) were formed via the crystallization of polymeric lignin stearoyl esters (LSEs). A solvent exchange self-assembly technique using Tetrahydrofuran (THF) as a solvent in addition to ethanol, acetone, and water as nonsolvents was used to form LPNFs by the crystallization of the stearyl groups in LSEs during evaporation. The grafting level of the stearoyl groups in the LSEs, the difference of the nonsolvent, and the volume ratios of the solvent/nonsolvent during the solvent exchange process predominantly determined the formation of LPNFs via this process. The self-assembled structures could be constructed as spherical particles and as constituted LPNFs structures with well-organized petaloid nanoflakes. By introducing sufficient amounts of LPNFs patterns on the substrates (e.g., glass slide, paper, and wood), the hydrophilic substrates were successfully transformed into superhydrophobic surfaces. Thus, the synthesis of LSEs and the formation of LPNFs with tunable structures offer a new strategy for the derivation and value-added utilization of lignin. [Display omitted] • Lignin stearoyl esters with different stearoyl group contents were synthesized. • Lignin-based petaloid nanoflakes (LPNFs) were prepared. • The solvent-exchange self-assembly technique was applied to prepare LPNFs. • The morphologies could be turned as spheric NPs or well-organized LPNFs. • The LPNFs structures on diverse substrates induced excellent superhydrophobicity. [ABSTRACT FROM AUTHOR]

The isolation of lignin containing micro- and nanofibrillated cellulose (L-MNFC) requires a multistep process. In this study, beech wood was pre-treated by steam explosion (SE), refined or pre-treated by 3 SE and grinded until gel formation. A conventional cooking in an autoclave (SC) was applied in order to get a control sample. The effect of bleaching of a SE pulp was also studied. The chemical composition of the pulps was assessed as well as fiber morphology to compare the effect of the different processes. Quality index and energy consumption during the production process were studied. Results showed that SE can replace SC for the production of pulps with higher lignin content: 8–12% wt. and 3% wt., respectively. Gels contain micro and nanofibrillated cellulose and residual fibers with a dispersion of lignin nanoparticles and some nanocrystals. Optimization of the ultrafine grinding step was required to minimize the energy consumption. [Display omitted] • Use of steam explosion to produce lignin containing micro and nanofibrillated cellulose (L-MNFCs). • Steam explosion can replace conventional alkali cooking to produce pulps containing more lignin with a higher yield. • L-MNFCs gels quality depends on lignin content. • Ultrafine grinding step optimization is mandatory to enhance L-MNFCs quality. • Bleaching is not necessary to enhance the quality. [ABSTRACT FROM AUTHOR]

To expand the application of transparent wood (TW) in the field of photoluminescence, lignin-based carbon quantum dots (CDs) were impregnated into wood cellulose template (CT) as a fluorescent functional material, the photoluminescent transparent wood (PTW) with light conversion was prepared. The results showed that FTW with different wavelength emissions could be obtained by controlling the CDs' conjugated size and surface functional groups. The loading of CDs does not affect the excellent transmittance (86.1%) and optical haze (73%) of TW. Compared to the original wood, the tensile properties of PTW have been enhanced from 368 MPa to 422 MPa. By controlling the content of different CDs, a PTW for white light conversion was prepared with the CIE color coordinates of (0.29, 0.34). This study is a new attempt to apply CDs to TW, providing a broad prospect for uniform light conversion and color display. [Display omitted] [ABSTRACT FROM AUTHOR]

• Superhdryophobic elastomer is directly obtained from nature wood without any post modification. • Cellulose nanoarrays and aromatic moieties in lignin contributes high water contact angle of 152°. • Wood ray is hollowed to shape leaf-spring microstructure which allow elastomer superelasticity. • The elastomer shows excellent self photothermal effect. Herein, we report a superhydrophobic elastomer which was made directly from natural wood with a simple chemicothermal treatment without adding any modification chemicals. One of the most important findings is that the unique micro-nano structure in original wood was well maintained in the final wood elastomer, which result in many unique physical–chemical properties. The chemicothermal process tailors the nano-microstructure of wood by deteriorating polysaccharides into cellulose nanoarrays, and simultaneously, removes the hydrophilic groups in lignin which then re-assembles to cellulose nanoarrays to form a superhydrophobic surface with a contact angle up to 152°. Retained lignin aromatic skeleton also results in significant self-photothermal effect. Meanwhile, ray tissues in natural wood are hollowed to leave leaf-spring-like microstructure, which leads to great elasticity of wood elastomer with 97% stress retention at 60% strain after 103 compression cycles. Thanks to the microstructure and functions arising from wood itself, the elastomer shows many potential applications such as in solar-assisted crude oil recovery as well as water/oily liquids separation. [ABSTRACT FROM AUTHOR]

Studying lignin content is critical for analyzing the inherent constitution, performance, and application of lignocellulosic materials. However, the traditional methods (wet chemical methods) for the determination of lignin content have several limitations such as labor intensive, time-consuming preparations, and the use of toxic reagents. To address these shortcomings, based on 140 groups of poplar samples, a strategy of 1064 nm FT-Raman spectroscopy combined with several algorithms was proposed in our study. Before modeling, smoothing algorithm (Savitzky-Golay), baseline correction algorithm (adaptive iteratively reweighted penalized least squares), and deconvolution algorithm (Gaussian and Lorentzian) were applied to extract the Raman information. Also, several peaks including 1095, 1378, and 2895 cm−1 were selected as the candidates of internal standard peak for normalizing the lignin-related peaks. Subsequently, lignin content predictive models were established based on data extracted from FT-Raman spectra combined with regression algorithms, including principal components regression (PCR), partial least square regression (PLSR), ridge regression (RR), lasso regression (LR), and elastic net regressions (ENR). Consequently, credible models were obtained based on data normalized by peak of 2895 cm−1 combined with RR, LR, and ENR algorithms (Pearson's R > 0.88, RMSE < 0.62, MAE < 0.46, and MAPE < 1.92%). Thus, the lignin quantitative models based on Raman spectroscopy developed here can be used to predict the lignin content in poplar clones accurately and efficiently. [Display omitted] • Predicting models of poplar lignin content were build based on FT-Raman spectroscopy. • Normalized spectra based on peak at 2895 cm−1 and RR, LR, and ENR algorithms are preferred. • Additional groups of sample and 10-fold cross validation ensure models stability and robustness. [ABSTRACT FROM AUTHOR]

The aim of this study was to characterize an aqueous polymer isocyanate (API) type adhesive made from natural rubber latex (NRL) and lignin as base polymers, and to evaluate bond performance of the adhesive as laminated wood adhesive. The base polymers of the adhesive were prepared by blending NRL, polyvinyl alcohol (PVA), and lignin isolated from black liquor of alkaline pretreatment of oil palm empty fruit bunch (OPEFB) and sugarcane bagasse (SB) with compositions of 25/25/0, 25/20/5, 25/15/10, 25/10/15, 25/5/20, and 25/0/25 (w/w/w). The isocyanate crosslinker was added at the level of 15% of the weight of base polymer. The glass transition temperature ( Tg ), heat degradation, and the homogenity of the adhesive blend were analyzed. The adhesive was used for producing laminated wood (20×8 cm 2 ). Results showed that the addition of lignin in the base polymer blends of API adhesive did not significantly affect the Tg of the adhesives. However, it affected the thermal decomposition and bond performance of the adhesives. There were more residues and less homogenous adhesive solution due to the addition of lignin in the base polyemr blends of API adhesives. The addition of lignin in the base polymer blends caused significant decrease in bond performance of the adhesive applied in glue laminated wood. [ABSTRACT FROM AUTHOR]