Biomass Lignin Research Articles

Fabrication of PBAT/lignin composite foam materials with excellent foaming performance and mechanical properties via grafting esterification and twin-screw melting free radical polymerization

As one of the mainstream biodegradable materials, poly(butylene adipate-co-terephthalate) (PBAT) foams offer a sustainable alternative to traditional plastic foams, effectively reducing environmental pollution. However, the high cost and poor mechanical performance of PBAT foams impede their practical application. Herein, the glycidyl methacrylate-grafted biomass lignin (GML) was used to produce a PBAT/GML composite foam with good foaming performance and mechanical properties at high lignin-filling amounts by twin-screw melting free radical polymerization and supercritical CO2 foaming process. The compatibility of GML in the PBAT matrix was improved due to the formation of ester bonds in modified lignin, endowing the PBAT/GML (PGML) composite foam with exceptional foaming performance. Additionally, the mechanical properties of PGML composite foam were remarkably enhanced due to the introduction of the abundant aromatic structures of GML and the construction of a stable covalent crosslinking network. The compressive strengths and compression modulus of the PGML foam were improved by 2.53 times and 2.47 times, while its bending strength and bending modulus were improved by 1.27 times and 3.92 times compared to the neat PBAT. This research affords a new strategy for developing low-cost biodegradable biomass PBAT/lignin composite foam materials with good foaming performance and mechanical properties.Graphical abstract

Tracked evolution of single biochar particle’s morphology during pyrolysis in operando x-ray micro-computed tomography

The engineering of biochars with desired morphologies and pore structures is a far-reaching objective towards sustainable pore-dependent environmental technologies, such as water and soil remediation or catalysis. We hereby report a series of experiments that allow the direct following of the shape and porosity of single biochar particles during pyrolysis. Particles ~ 1–2 mm in diameter of unwashed and water-washed raw walnut shells were continuously 3D imaged during pyrolysis to 575 ℃ at a 10 K min−1 in Ar to obtain time- and temperature-resolved x-ray micro computed tomographies to a 0.82 μm resolution. Results showed visual evidence of a 30% and 70% v/v particle shrinkage for unwashed and washed samples, respectively. Particle swelling between 200 and 300 ℃ in the unwashed sample provided evidence of the softening of native biopolymers associated with lignin in untreated biomass. A purpose-defined parameter Λ shows the temperature-dependence of pore re-distribution towards the center of the particle to be linear for both samples. Λ was found to be 3.2×10-4K-1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$3.2\ imes {10}^{-4}{K}^{-1}$$\\end{document} in the washed sample, approximately 3.5 times faster than in the unwashed one. Such linear dependence is significantly slower than an exponential Arrhenius-like trend thereby providing a qualitative measure of the heat and mass transport phenomena limiting the chemical reactions in the porous medium. This evidence is key to resolving the pathways to the thermochemical decomposition of biomass leading to preparation of precision-engineered biochars.Graphical

Facile synthesis, release mechanism, and life cycle assessment of amine-modified lignin for bifunctional slow-release fertilizer

Biomass-based slow-release fertilizers (SRFs) are a sustainable solution for addressing food scarcity, improving fertilizer efficiency, and reducing pollution, whereas they still face complex preparation, high costs, and low release characteristics. This study introduces a simple and innovative approach to producing bifunctional green SRFs with controlled release and conditioning properties for saline soils and harsh environments. The method involves a one-pot preparation of microsphere-structured amine-modified lignin slow-release fertilizer (L-UX) using biomass lignin as the starting material. The L-UX demonstrates an exceptional fertilizer loading rate (66.2 %) and extended slow-release performance (288 h), effectively enhancing the fertilizer's release ability. Compared to traditional fertilizers, the bifunctional L-UX significantly improves soil water retention capacity (824.3 %), plant growth, and germination percentage in challenging soil conditions (133 %). These findings highlight the potential of L-UX as a large-scale controlled-release fertilizer in harsh environments. A life cycle assessment (LCA) was also conducted to evaluate the environmental impact of L-UX from its production to disposal. This revealed that L-UX has a minimal environmental footprint compared to conventional inorganic fertilizers. This study further supports the widespread application of L-UX as an environmentally friendly alternative.

Effect of sintering temperature on ceramic membrane fabricated using coal flyash and natural clay for lignin recovery

This study explores the utilization of coal fly ash combined with natural clay as a precursor for creating ceramic membranes through the uniaxial compaction method, aiming at lignin separation. These membranes were sintered at varying temperatures from 600 to 1000 °C. Thermal Gravimetric Analysis (TGA) revealed the robust thermal stability of the membranes. Fourier Transform Infrared (FTIR) analysis affirmed the presence of silica and alumina within the membranes. X-ray Diffraction (XRD) peaks indicated the crystalline structure and the presence of metal oxides originating from the fly ash and clay components. Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) images illustrated the porous nature and rough surface of the ceramic membranes. The average pore radius of the fabricated membrane expanded from 43.12 to 7.91 nm with increasing temperature. Concurrently, membrane flux decreased from 4.13 to 0.96 ×10−6 m3/m2 s with higher temperatures. Lower contact angles indicated the hydrophilic properties of membranes. All membranes exhibited superior corrosion resistance and negative zeta potential, owing to the significant silica content in the fly ash. Lignin separation efficiency increased from 65 % to 81 % with increasing temperatures. The optimal sintering temperature was determined to be 800 °C, achieving a lignin recovery greater than 76 % and a membrane permeability of about 7×10−9 m3/m2 s kPa. Thus, the fly ash-clay-based ultrafiltration membranes synthesized in this study offer the potential for lignin biomass recovery from biorefinery effluent.

Biomass lignin as dispersion to substantially enhance carbon nanotubes thermoelectric converter for energy harvesting

Carbon nanotubes (CNTs) have attracted much attention as promising thermoelectric materials to harvest waste energy, however the agglomeration between nanotubes greatly limits their application. Despite various dispersants that have been devised to enhance the dispersion of CNTs, biomass lignin has been rarely employed to facilitate the dispersion of CNT for enhancing its TE properties. Herein, green lignin was incorporated with CNTs to synergistically improve the dispersion and TE properties of CNTs, in which π-π interactions between the aromatic ring structure of lignin and CNTs, as well as electrostatic charge brought by ionized groups of lignin promote the exfoliation of nanotubes and reduces CNTs entanglement. The well-dispersed structure of CNTs facilitates efficient charge transfer, and thereby enhances the thermoelectric properties. CNTs/lignin composite could reach a maximum power factor of 198.0 μW m−1K−2 at a lignin content of 11.8 wt%, which was then raised to 223.1 μW m−1K−2 with subsequent partial removal of lignin by alkali immersion treatment, higher than 98.6 μW m−1K−2 of pristine CNTs film. Furthermore, the flexible TE device with five pairs of CNTs/lignin and nickel wires generates a high power of 288 nW at ΔT = 30 K, demonstrating potential applications of lignin for sustainable energy harvesting.

Lignin, extractives and structural carbohydrate characteristics of Thinopyrum intermedium biomass reveal additional valorization opportunities for dual-crop utilization.

Thinopyrum intermedium (Host) Barkworth & D.R. Dewey, or intermediate wheat grass (IWG), is being developed as the first widely-available perennial grain candidate. However, because the crop is still in development, grain yields are lower than those of traditional cereals. Utilization of its non-grain biomass (e.g. for biofuel production and as a source of fine chemicals) would increase the economic value of its cultivation. The present study provides a structural characterization of the lignin and cell wall carbohydrates in IWG biomass and qualitative profiling of biomass extractives and compares them to those of annual wheat (Triticum aestivum) biomass grown in the same location and growing season. The monosaccharide composition and ester-linked phenolic acid contents of vegetative biomass material from annual wheat and IWG were similar. IWG vegetative biomass is rich in feruloylated arabinoxylans (AX) with a very low substitution rate, whereas the AX from IWG bran have a slightly higher substitution rate. The structure of IWG lignin was investigated using both the quantitative derivatization followed by reductive cleavage method and 2D-NMR analysis, revealing an H:G:S lignin that incorporates tricin and is acylated with coumaric acid and smaller amounts of ferulates. IWG and wheat extractives contained fatty acids, various free phenolic compounds (tricin, monolignols and phenolic acids), phenolic conjugates and phytosterols. The present study provides firm support for the further exploration of T. intermedium biomass as a carbohydrate feedstock (e.g, abundant in lightly substituted AX and cellulose polymers) for biofuel production and source of high-value fine chemicals, such as tricin. © 2024 Society of Chemical Industry.

Ionic Lignin Polymers for Controlled CO2 Capture, Release, and Conversion into High-Value Chemicals.

In this study, an innovative and cost-effective ionic polymer for CO2 capture and utilization for the first time, using abundant and nonfood-based biomass lignin is reported. The modified ionic polymer synthesizes through the reaction of glycidyltrimethylammonium chloride with lignin under alkaline conditions to yield quaternary ammonium ionic functionality. Subsequently, the hydroxide-based pure ionic lignin polymer is employed for CO2 capture from both direct air and concentrated CO2 sources at room temperature and atmospheric pressure. Structural characterization of the polymers is accomplished through 1H, 13C, and 2D-heteronuclear single quantum coherence (HSQC)NMR, and FT-IR spectroscopy. The CO2 capture process is established through the formation of bicarbonate ions alongside the presence of CO2. The captured CO2 is precisely quantified by using inverse-gated proton decoupled 13C NMR with an internal standard (trioxane). Remarkably, the captured-CO2 amounts of ionic lignin polymer are 1.06mmol g-1 (47mg g-1) from concentrated-CO2 source and 0.60mmol g-1 (26mg g-1) from direct-air. The captured-CO2 in ionic lignin polymer is released in controlled manner and utilized in the synthesis of cyclic carbonate, showcasing the productive application of the captured carbon. Moreover, the fully controlled recovering of ionic lignin polymer achieves via repeated CO2 release ↔ CO2 capture.

Revisiting biomass compositions determination using thermogravimetric analysis and independent parallel reaction model

The determination of biomass composition via thermogravimetric analysis (TGA) has been a subject of considerable interest for many years. The current work proposes a revised workflow for determining the amounts of cellulose, hemicellulose, and lignin in biomass by combining TGA under an inert atmosphere with analyses of extractives and ash. An independent parallel reaction (IPR) model used for the deconvolution of the derivative thermogravimetry data was improved by constraining model parameters, i.e., thermal decomposition kinetic parameters and char fractions of cellulose, hemicellulose, and lignin, with values compiled from the literature using statistical analysis. The workflow is developed and demonstrated using cellulose and starch mixtures and then applied to biomass with varying levels of ash, including pine, birch, and oak wood, switchgrass, and pine bark. Using extractive-free biomass in the new TGA-IPR workflow improved the composition results compared with untreated biomass. The compositions determined by this method agreed well with values reported in the literature (within approx. 8 wt%) for the tested samples. The results demonstrate improved biomass composition accuracy using an accessible and rapid TGA-based approach.

Organic Synthesis Away from Equilibrium: Contrathermodynamic Transformations Enabled by Excited-State Electron Transfer.

ConspectusChemists have long been inspired by biological photosynthesis, wherein a series of excited-state electron transfer (ET) events facilitate the conversion of low energy starting materials such as H2O and CO2 into higher energy products in the form of carbohydrates and O2. While this model for utilizing light-driven charge transfer to drive catalytic reactions thermodynamically "uphill" has been extensively adapted for small molecule activation, molecular machines, photoswitches, and solar fuel chemistry, its application in organic synthesis has been less systematically developed. However, the potential benefits of these approaches are significant, both in enabling transformations that cannot be readily achieved using conventional thermal chemistry and in accessing distinct selectivity regimes that are uniquely enabled by excited-state mechanisms. In this Account, we present work from our group that highlights the ability of visible light photoredox catalysis to drive useful organic transformations away from their equilibrium positions, addressing a number of long-standing synthetic challenges.We first discuss how excited-state ET enabled the first general methods for the catalytic anti-Markovnikov hydroamination of unactivated alkenes with alkyl amines. In these reactions, an excited-state iridium(III) photocatalyst reversibly oxidizes secondary amine substrates to their corresponding aminium radical cations (ARCs). These electrophilic N-centered radicals can then react with olefins to furnish valuable tertiary amine products with complete anti-Markovnikov regioselectivity. Notably, some of these products are less thermodynamically stable than their corresponding amine and alkene starting materials. We next present a strategy for light-driven C-C bond cleavage within various aliphatic alcohols mediated by homolytic activation of alcohol O-H bonds by excited-state proton-coupled electron transfer (PCET). The resulting alkoxy radical intermediates then undergo C-C β-scission to ultimately provide isomeric linear carbonyl products that are often higher in energy than their cyclic alcohol precursors. Applications of this chemistry for the light-driven depolymerization of lignin biomass, commercial phenoxy resin, hydroxylated polyolefin derivatives, and thermoset polymers are presented as well. We then describe a method for the contrathermodynamic positional isomerization of highly substituted olefins by means of cooperative photoredox and chromium(II) catalysis. In this work, generation of an allylchromium(III) species that can undergo highly regioselective in situ protodemetalation enables access to a less substituted and thermodynamically less stable positional isomer. Product selectivity in this reaction is determined by the large differential in oxidation potentials between differently substituted olefin isomers. Lastly, we discuss a light-driven deracemization reaction developed in collaboration with the Miller group, wherein a racemic urea substrate undergoes spontaneous optical enrichment upon visible light irradiation in the presence of an iridium(III) chromophore, a chiral Brønsted base, and a chiral peptide thiol. Excellent levels of enantioselectivity are achieved via sequential and synergistic proton transfer (PT) and H atom transfer (HAT) steps. Taken together, these examples highlight the ability of excited-state ET events to enable access to nonequilibrium product distributions across a wide range of catalytic, redox-neutral transformations in which photons are the only stoichiometric reagents.

Investigation of the chemical mechanism of pollutant formation in co-firing of ammonia and biomass lignin

Ammonia (NH3) and biomass are recognised as renewable energy carriers with substantial promise for reducing carbon emissions. However, the issue of nitrogen oxides (NOX, including NO and NO2) and nitrous oxide (N2O) emissions from ammonia combustion and soot from biomass combustion, remains a pressing concern due to their detrimental impacts on the environment and human health. This study investigated the mechanism of pollutant formation during ammonia-lignin co-firing through reactive molecular dynamics (RMD) simulations. The results indicate that co-firing a certain amount of ammonia with lignin can reduce the formation of soot. This is mainly due to NH2 radicals converting a portion of polycyclic aromatic hydrocarbon (PAH) precursors into C–N compounds. However, it is necessary to maintain higher ammonia concentrations. Adding a small quantity of ammonia would decrease the extent of oxidative reactions within the system and fail to generate enough NH2 radicals to consume the carbon atoms forming PAH precursors, ultimately resulting in increased soot production. The impact of lignin on the formation of NOX and N2O during ammonia combustion has two main aspects: Firstly, the oxidising radicals formed during the initial decomposition of lignin promote the generation of N–O bonds, leading to an increase in the quantities of NOX and N2O during the initial reaction stage. Secondly, the carbon-containing products produced from lignin decomposition consume nitrogen atoms by forming N–C bonds, thereby diminishing available nitrogen atoms for nitrogen oxides formation. This study provides new insights into the formation of primary pollutants of ammonia and biomass co-firing on an atomic scale, which can help develop pollutant mitigation measures.

Lignocellulosic biomass-derived carbon quantum dots (CQDs): A novel approach utilizing organosolv lignin from Moso bamboo waste

Converting lignocellulosic materials to carbon quantum dots (CQDs) has garnered significant interest to transform biomass wastes into highly valuable products. We chose to use lignin as our feedstock because high-value products more readily utilize cellulose and hemicellulose. Lignin, arguably the most underutilized and complex biopolymer within any biomass, presents an appealing yet overlooked opportunity. While some may argue that lignin-based CQDs are no longer groundbreaking, this is because existing studies typically rely on commercially available lignin, ignoring biomass-derived sources. Therefore, in our pioneering research, we utilized organosolv lignin, prized for its structural purity and extracted from Moso bamboo waste, as the carbon source in a facile two-step technique to synthesize luminous CQDs. The process involved the addition of 2,4-diaminobenzenesulfonic acid, a mild-organic acid that acted as a source for both nitrogen (N) and sulphur (S). A 12-h hydrothermal treatment at 200 °C with 0.1 M of acid addition attained the best result. The resultant CQDs display strong green fluorescence, with the highest quantum yield of 17.7% seen in N and S co-doped CQDs. With their obvious and specific fluorescence quenching impact on Fe3+, CQDs demonstrate great potential as a fluorescent nanoprobe for metal ion detection. This CQD nanoprobe responds very sensitively to Fe3+ between 0 and 500 μM (R2 = 0.9803), with a detection limit of 0.15 μM. This research not only presents a unique alternative nanoprobe for the sensing field using renewable biomass lignin, but it also paves the way for the long-term, cost-effective, and scalable manufacturing of CQDs.

Lattice Strain Engineering on Metal-Organic Frameworks by Ligand Doping to Boost the Electrocatalytic Biomass Valorization.

As an efficient and environmental-friendly strategy, electrocatalytic oxidation can realize biomass lignin valorization by cleaving its aryl ether bonds to produce value-added chemicals. However, the complex and polymerized structure of lignin presents challenges in terms of reactant adsorption on the catalyst surface, which hinders further refinement. Herein, NiCo-based metal-organic frameworks (MOFs) are employed as the electrocatalyst to enhance the adsorption of reactant molecules through π-π interaction. More importantly, lattice strain is introduced into the MOFs via curved ligand doping, which enables tuning of the d-band center of metal active sites to align with the reaction intermediates, leading to stronger adsorption and higher electrocatalytic activity toward bond cleavage within lignin model compounds and native lignin. When 2'-phenoxyacetophenone is utilized as the model compound, high yields of phenol (76.3%) and acetophenone (21.7%) are achieved, and the conversion rate of the reactants reaches 97%. Following pre-oxidation of extracted poplar lignin, >10 kinds of phenolic compounds are received using the as-designed MOFs electrocatalyst, providing ≈12.48% of the monomer, including guaiacol, vanillin, eugenol, etc., and p-hydroxybenzoic acid dominates all the products. This work presents a promising and deliberately designed electrocatalyst for realizing lignin valorization, making significant strides for the sustainability of this biomass resource.

Comprehensive analysis on the combined effects of reaction kinetics and heat transfer on biomass pyrolysis

The current study links the heat transport phenomena and reaction kinetics when the pyrolysis was occurring of sugarcane bagasse (SCB) biomass. A thermogravimetric analyzer was used to conduct a kinetic research on the pyrolysis of biomass in a nitrogen atmosphere, covering a heating rate range of 10–40 °C/min. The thermogravimetric studies (TGA) allowed for the differentiation of three stages associated with the breakdown of hemicellulose, cellulose, and lignin. Using three first-order processes and the Arrhenius theory, the activation energy and pre-exponential factor were determined.Three important components of biomass—lignin, hemicellulose, and cellulose—were assumed to respond independently and in parallel in the kinetics model. Additionally, the transport characteristics of each component were assessed using their respective kinetic values and other thermo-physical characteristics. The regulating mechanism was then anticipated by the heat transfer map for three elements with different particle sizes. The transfer qualities were mainly influenced by particle size, at a crucial dimension dictating the shift in the system for several parts.

Incubation temperature affects growth and efficacy of white-rot fungi to improve the nutritive value of rice straw

Context A great body of evidence is available on the in vitro efficacy of white-rot fungi (WRF) to degrade lignin in fibre-rich biomass (e.g. wheat straw, wood chips and rice straw (RS)) and improve the biomass’ nutritive value for ruminants. Aims Determining the impact of incubation temperature of three WRF to improve the nutritional value of rice straw. Methods Growth of Ceriporiopsis subvermispora, Lentinula edodes and Pleurotus eryngii on RS for 26 days at the following six temperature regimes: continuous at 24°C, 30°C, 35°C and 40°C, and 3 days at 35°C and 40°C, with subsequent days at 24°C. In a follow-up experiment, improvement in fermentability in buffered rumen fluid of RS treated by the three WRF at 24°C and 30°C for up to 8 weeks was investigated. Key results All three fungi grew at temperatures up to 35°C, with no growth observed at 40°C, with C. subvermispora being more temperature sensitive. There were significant differences in cellulose, hemicellulose and lignin degradation of RS at 24°C and 30°C, with C. subvermispora degrading 69% and 90% of the hemicellulose and lignin respectively at 30°C, greater than at 24°C (55% and 80% respectively). For L. edodes, there were significant differences in cellulose degradation between 24°C and 30°C, with 12% more degradation at 30°C, but not for hemicellulose and lignin. In vitro gas production showed no significant differences between the two incubation temperatures for either of the two fungi. Pleurotus eryngii treatment did not show any improvement in terms of in vitro gas production. Conclusions Treatment of RS with L. edodes and C. subvermispora, but not P. eryngii, is robust and temperature changes will not have a major impact on their efficacy as long as the temperature remains below 30°C. Implications Temperature during the incubation of WRF with rice straw needs to be below 30°C for this biotechnology to be applied in practice.

Transfer learning improves predictions in lignin content of Chinese fir based on Raman spectra

Lignin in biomass plays significant role in substitution of synthetic polymer and reduction of energy expenditure, and the lignin content was usually determined by wet chemical methods. However, the methods' heavy workload, low efficiency, huge consumption of chemicals and use of toxic reagents render them unsuitable for sustainable development and environmental protection. Chinese fir, a prevalent angiosperm tree, holds immense importance for various industries. Since our previous work found that Raman spectroscopy could accurately predict the lignin content in poplar, we propose that the lignin content of Chinese fir can be estimated by similar strategy. The results suggested that the peak at 2895 cm−1 is the optimal choice of internal standard peak and algorithm of XGBoost demonstrates the highest accuracy among all algorithms. Furthermore, transfer learning was successfully introduced to enhance the accuracy and robustness of the model. Ultimately, we report that a machine learning algorithm, combining transfer learning with XGBoost or LightGBM, offers an accurate, high-efficiency and environmental friendly method for predicting the lignin content of Chinese fir using Raman spectra.

Sustainable biocomposites from pyrolyzed lignin and recycled nylon 6 with enhanced flame retardant behavior: Studies on manufacturing and quality performance evaluation

AbstractThe recycled nylon (RN)‐based biocomposites were fabricated by adding 25% lignin biocarbon. Lignin was pyrolyzed at 300, 600, and 900°C to produce Lig300, Lig600, and Lig900 biocarbon (BioC) samples, respectively. Higher functionality of Lig600 (unlike Lig900) allowed for improved interfacial interaction with the polar nylon matrix. Mechanical properties were further enhanced for RN_Lig600 composite with enhanced flexural and tensile strength by 18% and 8%, respectively, compared to neat polymer (RN). RN_Lig900 composite showed enhancement in tensile and flexural modulus by 32.6% and 51.1%, respectively, compared to RN. Incorporation of Lig900 in RN matrix resulted in 77.9% reduction in burning rate compared to RN. These results show the potential of lignin BioC as a filler in RN composites for flame retardant applications and mechanical enhancement, such as in the automotive industry.Highlights Effect of pyrolysis temperatures (300, 600, and 900°C) on lignin biomass. Composites prepared from recycled polyamide 6 from carpet waste and biocarbon. Improved interfacial adhesion of 600°C biocarbon with recycled nylon matrix. Enhanced thermal, mechanical properties, reduced flammability of biocomposites. Sustainable biocomposites with 900°C biocarbon reduced burning rate by 78%.

CO2 and Lignin‐Based Sustainable Polymers with Closed‐Loop Chemical Recycling

AbstractThis work highlights the conversion method of chaining up greenhouse gas CO2 with biomass lignin to develop new sustainable, recyclable polymers from abundant and non‐food based renewable resources. A cyclic carbonate monomer has synthesized using a cost‐effective, non‐phosgene‐based, and greener approach under atmospheric pressure and room temperature. The fully programable ring‐opening polymerization is accomplished by varying the catalyst (DBU and TBD), catalyst loading (0.5–5.0%) and reaction time (2–40 min). The best polymer is obtained in 1% TBD with a 30‐min reaction. The precise characterization of the synthesized cyclic carbonate monomer and polymers' structure are established using spectroscopic analyses including 1H, 13C, and 2D HSQC NMR, FT‐IR, and GPC. The new polymers exhibit high molecular weights (Mn: 120.34–154.58 kDa) and adequate thermal stabilities (Td5%: 244–277 °C from TGA and Tg: 33–52 °C from DSC), rendering them advantageous for practical applications. Significantly, the CO2 and lignin‐based polymers have successfully recycled to the monomer for a circular plastic economy by heating at 90 °C for 12 h in the presence of DBU. This process yields original monomers for another polymerization without unwanted changes in chemical structures, presenting an ultimate sustainable solution.

Advancing safe bioenergy production from cadmium-contaminated sweet sorghum through mild synergistic pretreatment

Phytoremediation is an eco-friendly and cost-effective method for treating cadmium (Cd)-contaminated soil. However, safe disposal of harvested hyperaccumulators remains scarce. Herein, a mild synergistic pretreatment combining dilute acid and alkali pretreatment was developed for safe biorefining of the Cd-containing sweet sorghum, and Cd was centrally extracted into the acid pretreatment liquid in the first step. The results showed that the synergistic pretreatment was more effective in removing Cd from the biomass and overcoming biomass recalcitrance. During the synergistic pretreatment, the Cd concentration in biomass dramatically decreased from 4.03 to 0.00626 mg/kg, and a considerable amount of lignin and hemicelluloses in biomass was removed, facilitating enzymatic saccharification and safe bioenergy production. The optimal conditions of the synergistic pretreatment resulted in a total sugar yield of 81.6 wt %, which was 4.7-fold higher than that of the original biomass. This strategy holds promise for reducing the cost of industrial saccharification and is a valuable inspiration for the safe handling and resource utilization of Cd-containing biomass.

Efficient ethanol production from masson pine sawdust by various organosolv pretreatment and modified pre-hydrolysis simultaneous saccharification and fermentation

Pretreatment is a key step in lignocellulosic biorefinery. In this study, the combination of organosolv pretreatment and lignin repolymerization inhibitor was put forward to fractionate the lignocellulosic biomass, providing readily hydrolyzed substrate. Results showed that, acidic 1,4-butanediol pretreatment extensively removed lignin from softwood, reducing the physical blockage effect of lignin. Besides, lignin repolymerization inhibitors were employed to modify lignin, giving rise to lower unproductive binding effect of lignin. As a result, maximum 79.9 ± 0.3 % of original lignin in raw biomass could be removed, and 97.9 ± 0.5 % of glucan in pretreated solid could be converted into fermentable sugars after acidic butanediol pretreatment assisted by sodium 2-naphthol-7-sulphonate and enzymatic hydrolysis at 2 % glucan loading. Furthermore, a modified pre-hysrolysis simultaneous saccharification and fermentation process at 10 % glucan loading produced 45.6 ± 1.7 g/L ethanol, with ethanol yield of 18.7 ± 0.4 g/100 g raw biomass. Finally, the mass balance revealed that the lignocellulosic biorefinery based on acidic butanediol pretreatment assisted by sodium 2-naphthol-7-sulphonate could achieve full utilization of lignocellulosic components to co-produce ethanol, lignin materials and hemicellulose-derived mono-saccharides.

Study on the green extraction of corncob xylan by deep eutectic solvent

Corn as one of the world's major food crops, its by-product corn cob is also rich in resources. However, the unreasonable utilization of corn cob often causes the environmental pollution, waste of resources and other problems. As one of the most abundant polymers in nature, xylan is widely used in food, medicine, materials and other fields. Corn cob is rich in xylan, which is an ideal raw material for extracting xylan. However, the intractable lignin is covalently linked to xylan, which increases the difficulty of xylan extraction. It has been reported that the deep eutectic solvent (DES) could preferentially dissolve lignin in biomass, thereby dissolving the xylan. Then, the xylan in the extract was separated by ethanol precipitation method. The xylan precipitate was obtained after centrifugation, while the supernatant was retained. The components of the supernatant after ethanol precipitation were separated by the rotary evaporator. The ethanol, water and DES were collected for the subsequent extraction of corn cob xylan. In this study, a novel way was provided for the green production of corn cob xylan. The DES was used to extract xylan from corn cob which was used as the raw material. The effects of solid-liquid ratio, reaction time, reaction temperature and water content of DES on the extraction rate of corn cob xylan were investigated by the single factor test. Furthermore, the orthogonal test was designed to optimize the xylan extraction process. The structure of corn cob xylan was analyzed and verified. The results showed that the optimum extraction conditions of corn cob xylan were as follows: the ratio of corn cob to DES was 1 : 15 (g : mL), the extraction time was 3 h, the extraction temperature was 60 °C, and the water content of DES was 70%. Under these conditions, the extraction rate of xylan was 16.46%. The extracted corn cob xylan was distinctive triple helix of polysaccharide, which was similar to the structure of commercially available xylan. Xylan was effectively and workably extracted from corn cob by the DES method. This study provided a new approach for high value conversion of corn cob and the clean production of xylan.