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Algae are being explored as a sustainable energy feedstock, having potential to reduce dependence on petrofuels and offset greenhouse gas emissions. Economic considerations and principles of green design suggest that if algae-to-fuel technology is to be successful, biofuels must be produced simultaneously with value-added co-products. At present, the algae industry is centered around a limited number of products, such as low-volume/high-value speciality nutrients. New products for medium- and high-volume markets will be needed as biomass production increases in scale. This Perspective highlights non-fuel applications of algal biomass that have received relatively little attention to date but are promising for future development. It is our goal to draw attention to some of the unique opportunities that algae present with respect to biochemical composition as compared to lignocellulosic energy crops. [ABSTRACT FROM AUTHOR]

This study shows a functional deep eutectic solvent (DES) employing choline chloride (ChCl) and glyoxylic acid (GA) for lignocellulose fractionation. This DES exhibited a higher pretreatment efficiency (92.15%) than that composed of ChCl and lactic acid (10.36%). Molecular dynamic (MD) simulations indicated that the ChCl : GA DES showed a higher total binding energy (ΔE) with lignin than the ChCl : LA DES, resulting in a higher dissolution of lignin. GA prevented lignin condensation during pretreatment. The stabilized lignin containing 69.39% β-O-4 linkages can be used for phenolic monomer production with a bio-oil yield of 59.60% and lignin-based sunscreen preparation with a SPF of 58.46. The cellulose residues with a mild pretreatment severity exhibited a high enzymatic saccharification yield of 91.99%. Meanwhile, an esterification reaction occurred between cellulose and GA during pretreatment. The inhibition of enzymatic hydrolysis and microbial growth enables the use of functional cellulose to produce antibacterial paper. Furthermore, 96.80% of the DES could be easily recycled and reused for biorefinery purposes. [ABSTRACT FROM AUTHOR]

Pure subcritical water autohydrolysis is an economical and green biorefinery method and potentially applicable technology. Elucidating and regulating the energy input effects on the structural dissociation and chemical depolymerization of lignocellulosic biomass will progress the industrialization of pure subcritical water autohydrolysis biorefineries. In this work, a method for determining the degree of tissue dissociation was invented. Combined with the analysis of the microstructure, ultrastructure, chemical composition, and aggregation state, this paper reveals the process and mechanism of the P-factor effect as an energy input measurement on the bio-structural dissociation and chemical depolymerization during naked oat stem autohydrolysis. A method of using the P-factor to regulate the biostructural dissociation and chemical depolymerization was developed. For the first time, a critical point for the autohydrolysis of naked oat stem in pure subcritical water between 170–210 °C was found to be at a P-factor = 233, around which an essential change in biostructural dissociation and chemical depolymerization occurred. The findings indicate that the control of naked oat-stem tissue and cell dissociation, ultrastructure, and chemical depolymerization can be accomplished using the P-factor as an energy input measurement for autohydrolysis. The revealed mechanism and method created in this study enable the stepwise separation of gramineae tissues, cells, and major chemical components, enabling a full-composition multi-purpose biorefinery of lignocellulose. [ABSTRACT FROM AUTHOR]

The use of chemical and energy intensive delignification processes in industrial pulping generates cellulosic fibres that are hydrophilic, hygroscopic and functionally restricted to paper and cardboard applications. Here, we propose a bio-based alternative to chemical pulping utilising herbivores to harvest and grind lignocellulosic materials followed by natural fungal growth to delignify and hybridise them to generate hierarchical composite papers with altered, water-repelling surface properties. These papers comprise cellulose and fungal biopolymers produced by cultivation of T. versicolor and P. ostreatus on elephant manure. Papers with considerably more hydrophobic surfaces were obtained at glucosamine contents as low as 0.1 wt%. Paper tensile strengths and elastic moduli were improved with longer fungal growth periods, spanning several weeks, resulting in comprehensive interfacing of cellulose microfibrils through tough nanoscale fungal chitin-β-glucan networks within the papers. Papers produced from lignocellulosic material colonised with P. ostreatus for 16 weeks exhibited the highest tensile strengths and more hydrophobic surfaces than T. versicolor. Hybridisation of lignocellulose with fungal biopolymers resulting in improved surface and mechanical properties highlights the extended opportunities of fungal delignification bioprocessing and demonstrates the considerable potential of the fungal biorefinery as an economical, and as of yet underexploited technology. [ABSTRACT FROM AUTHOR]

Cellulose in particular and phytomass in general are at the heart of our food system. They are also a central energy vector and a vital source of materials. In this article, a multiscale approach to the complex issue of lignocellulose sustainability is developed. Global thermodynamic concepts help to place current biomass exploitation in a global energetic context. In particular, the notion of entropy appears pivotal to understand energy and material fluxes at the scale of the planet and the limits of biomass production. Entropy is, however, best described at the microscopic scale, despite its large-scale consequences. Recent advances in entropy-driven colloid assembly parallel nature's choices and lignocellulose assembly at the nanometric scale. The functional concept of exergy is then developed and a few examples of its concrete use in photosynthesis and biorefinery research are given. In a subsequent part, an evaluation of the relative importance of biomass is performed with respect to non-renewable materials. This discussion helps to explain the interdependence of resources, including ores and fossil fuels. This interdependence has important consequences for current and future biomass uses. Some of these dependences are then quantitatively discussed using life cycle analysis (LCA) results from the literature. These results are of importance to different technological fields such as paper, biobased insulation, construction wood, information and communication technologies, and biobased textiles. A conclusion is then drawn that exposes the research tracks that are the most likely to be sustainable, including self-assembly, exergetically favourable options and low tech solutions. [ABSTRACT FROM AUTHOR]

The chemical industry is increasingly looking to develop bio-based alternatives to petroleum-based platform chemicals, in order to reduce dependence on diminishing fossil resources and to decrease GHG emissions. 5-Hydroxymethylfurfural (HMF) and 2,5-furandicarboxylic acid (FDCA) are two examples of bio-based chemicals which could allow for the synthesis of a wide range of chemicals and materials, particularly polymers, from renewable feedstocks. This review paper summarises and critically evaluates results from existing life cycle assessment (LCA) and technoeconomic analysis (TEA) studies of HMF and FDCA synthesis and, by doing this, provides several points of advice for future investigations and assessments of synthetic routes towards these bio-based products. Chemical considerations such as choice of solvent system, catalyst and energy production are reviewed; and methodological issues in LCA, such as treatment of biogenic carbon and allocation methods, are discussed. Overall, results suggest that the production of HMF and FDCA-based products may offer lower impacts from CO2 emissions than their fossil-based counterparts, but this often comes with an increase in environmental impacts in other impact categories. Higher operating costs from expensive fructose feedstocks and high energy demands also make HMF and FDCA less economically viable than current chemicals. Moving forwards, further investigation into different lignocellulosic feedstocks, energy production units and the development of new catalytic systems may help in making HMF and FDCA production more favourable than the production of fossil-based counterparts. [ABSTRACT FROM AUTHOR]

Supercritical methanol depolymerization and hydrodeoxygenation (SCM-DHDO) is a process to produce fuel from biomass with supercritical methanol and CuMgAlOx catalyst. Previous research has shown that SCM-DHDO can convert cellulose, lignin and whole biomass feedstock in a single reaction step. In this paper, we show that SCM-DHDO can convert pyrolytic lignin derived from pyrolysis oil at approximately 50% carbon yield to an upgraded oil product. The upgraded oil mainly contains lignin monomers and dimers while an additional 50% of the carbon was converted into undesired products including methanol, insoluble pyrolytic lignin and coke. We demonstrated that after a 4 h SCM-DHDO reaction the pyrolytic lignin molecular weight did not significantly change, but the ketones, acids and aldehydes in the pyrolytic lignin were completely converted. Increasing the reaction time of SCM-DHDO reaction from 2 to 10 h increased the lignin monomer and dimer yield. The reduced CuAlMgOx catalyst hydrogenated 57.4% of the aromatic carbons to aliphatic carbons and removed 64% of the oxygen. However, the product oil could still not be distilled because of the thermal instability of the upgraded pyrolytic lignin. [ABSTRACT FROM AUTHOR]

Ionic liquids have found their way into many applications where they show a high potential to replace traditional chemicals. But concerns over their ecological impacts (toxicity and biodegradability) and high cost have limited their use so far. The outcome of existing techno-economic and life-cycle assessments comparing ionic liquids with existing solvents has proven hard to interpret due to the many metrics used and trade-offs between them. For the first time, this paper couples the concept of monetization with detailed process simulation and life-cycle assessment to estimate the true cost of ionic liquids. A comparative case study on four solvents used in lignocellulosic biomass pretreatment is conducted: triethylammonium hydrogen sulfate [TEA][HSO4], 1-methylimidazolium hydrogen sulfate [HMIM][HSO4], acetone from fossil sources, and glycerol from renewable sources. The results show that the total monetized cost of production accounting for externalities can be more than double the direct costs estimated using conventional economic assessment methods. [TEA][HSO4] is found to have the lowest total cost, while glycerol presents the highest total cost. We expect this methodology to provide a starting point for future research and development in sustainable ionic liquids. [ABSTRACT FROM AUTHOR]

This paper reports a new concept for the biorefinery of lignocellulosic biomass where the derivatisation and fractionation of lignocellulose are accomplished at the same time. Methylation of sawdust of Larix kaempferi (Lamb.) Carriεave;re in dimethyl sulfoxide/tetrabutylammonium fluoride followed by fractionation provided three different polymeric derivative fractions: methylated cellulose, lignin, and hemicellulose. An aqueous solution of the methylated hemicellulose fraction was amphiphilic and possessed surface activity similar to that of industrially-produced methylcellulose. The azido-functionalised methylated cellulose and lignin fractions reacted with peracetyl propargyl β-cellobioside via Huisgen 1,3-dipolar cycloaddition followed by the removal of acetyl groups to yield a methylcellulose-block-cellobiose and methylated lignin-graft-cellobiose, respectively. An aqueous solution of diblock methylcellulose analogue, methylcellulose-block-cellobiose, formed thermoreversible supramolecular hydrogels near human body temperature. Methylated hemicellulose exhibited amphiphilic properties and acted as a surfactant. Methylated lignin-graft-cellobiose formed nanoparticles. Three major components in lignocellulosic biomass, cellulose, hemicellulose, and lignin, were successfully converted into three different functional materials. [ABSTRACT FROM AUTHOR]

Four principal intra-particle phenomena occur in a highly concerted manner during the pyrolysis of lignocellulosic materials: heat transfer, mass transfer, chemical reactions, and phase changes. Achieving a holistic understanding of these processes has been challenged by their intricate coupling, high temperatures, and rapid rates at which they occur. Heat and mass transfer have been well studied at the single-particle level but their coupling with chemical reactions and phase change within single particle models remains problematic. Equally challenging is the multiscale coupling of reactor- and single particle-scale models. Too little attention has been given to phase change. Similarly, the presence of oligomeric compounds (constituting up to 20% of the oil) has not been fully accounted for in chemical reaction schemes and physical models developed for pyrolysis. Recent studies have shown that a multiscale approach is key to predictive modelling across a variety of reactor systems. Historical and recent developments are outlined in this pyrolysis review paper regarding these four intra-particle phenomena, as well as modelling efforts to capture their effect on product yields and composition. It is critical for the design of future biomass pyrolysis systems to appropriately account for all four intra-particle phenomena and their inter-connectivities in order to predict, achieve, and maintain optimal operation. [ABSTRACT FROM AUTHOR]

This paper reports a new method of applying Deep Eutectic Solvents (DES) for extracting lignin from woody biomass with high yield and high purity. DES mixtures prepared from choline chloride (ChCl) and four hydrogen-bond donors – acetic acid, lactic acid, levulinic acid and glycerol – were evaluated for treatment of hardwood (poplar) and softwood (D. fir). It was found that these DES treatments can selectively extract a significant amount of lignin from wood with high yields: 78% from poplar and 58% from D. fir. The extracted lignin has high purity (95%) with unique structural properties. We discover that DES can selectively cleave ether linkages in wood lignin and facilitate lignin removal from wood. The mechanism of DES cleavage of ether bonds between phenylpropane units was investigated. The results from this study demonstrate that DES is a promising solvent for wood delignification and the production of a new source of lignin with promising potential applications. [ABSTRACT FROM AUTHOR]

Lignin quantitation of lignocellulosic biomass is an essential and routine assay in the areas of plant chemistry, forage, biomass conversion, and pulp & paper. The two-step sulfuric acid method (or the Klason method) is the most widely used protocol for lignin quantitation, but the method is a time-consuming and labor-intensive procedure. In this study, a facile and quick method was developed to quantitate lignin in lignocellulosic biomass. The new method used acidic lithium bromide trihydrate (ALBTH, LiBr·3H2O) as a reaction medium, which was able to quickly and completely dissolve and hydrolyze cellulose and hemicelluloses in the biomass under mild conditions and leave lignin as an insoluble residue for gravimetric quantitation. The soluble lignin generated in the ALBTH assay was determined by UV spectrophotometry. The recommended conditions for the ALBTH method were 60 wt% LiBr solution containing 40 mM HCl, 110 °C, and 30 min. The ALBTH method was applied to different species of biomass including softwood (Douglas fir), hardwood (aspen, poplar, and eucalyptus), and herbage (corn stover and switchgrass). The results indicated that the ALBTH method gave a comparable lignin (both insoluble and soluble lignin) quantity with the Klason method for the biomass investigated. The ALBTH method is a one-step procedure and much faster for lignin quantitation (∼30 min) than the Klason method (＞3 h). In addition, the ALBTH assay was conducted in glass vials under atmospheric pressure, and no autoclave was required. The ALBTH method also avoided the potential hazard of concentrated sulfuric acid. [ABSTRACT FROM AUTHOR]

Lignin, a renewable polymer derived from the lignocellulosic biomass represents more than 20% of the total mass of the Earth's biosphere. However, 98% of lignin is burned as a source of energy in the pulp and paper industry, essentially due to its complex structure. Today, the valorization of lignin into the production of value-added chemicals represents a real challenge in terms of both sustainability and environmental protection. The present contribution aims to provide a critical discussion on the crucial choice of the starting material to study lignin valorization. Next, a comparison between the different oxidation routes investigated by chemists over the past several years is presented, with emphasis on the major difficulties encountered. The main current challenges regarding the heterogeneous catalytic oxidation of lignin and its derivatives are also highlighted. Particular focus is given to innovative strategies favoring mild reaction conditions. Finally, we provide some recommendations and routes worthy of interest in this studied area of research in order to generate value-added chemicals from lignin oxidation through the use of heterogeneous catalysts. [ABSTRACT FROM AUTHOR]

The fractionation of lignocellulose in its three main components, hemicellulose, lignin and cellulose pulp can be achieved in a biphasic system comprising water and bio-based 2-methyltetrahydrofuran (2-MeTHF) as solvents and oxalic acid as catalyst at mild temperatures (up to 140 °C). This so-called OrganoCat concept relies on selective hemicellulose depolymerization to form an aqueous stream of the corresponding carbohydrates, whereas solid cellulose pulp remains suspended and the disentangled lignin is to a large extent extracted in situ with the organic phase. In the present paper, it is demonstrated that biomass loadings of 100 g L−1 can be efficiently fractionated within 3 h whereby the mild conditions assure that no significant amounts of by-products (e.g. furans) are formed. Removing the solid pulp by filtration allows to re-use the water and organic phase without product separation in repetitive batch mode. In this way, (at least) 400 g L−1 biomass can be processed in 4 cycles, leading to greatly improved biomass-to-catalyst and biomass-to-solvent ratios. Economic analysis of the process reveals that the improved biomass loading significantly reduces capital and energy costs in the solvent recycle, indicating the importance of process integration for potential implementation. The procedure was successfully scaled-up from the screening on bench scale to 3 L reactor. The feedstock flexibility was assessed for biomasses containing moderate-to-high hemicellulose content. [ABSTRACT FROM AUTHOR]

Metal halides are selective catalysts suitable for production of the fuel precursors furfural and 5-HMF from sugars derived from lignocellulosic biomass. However, they do not perform nearly as well when applied to biomass even in combination with immiscible extracting solvents or expensive ionic co-solvents. Here, we couple metal halides with a highly tunable co-solvent system employing renewable tetrahydrofuran (THF) to significantly enhance co-production of furfural and 5-HMF from biomass in a single phase reaction strategy capable of integrating biomass deconstruction with catalytic dehydration of sugars. Screening of several promising metal halide species at 170 °C in pH-controlled reactions with sugar solutions and larger 1 L reactions with maple wood and corn stover revealed how the interplay between relative Brønsted and Lewis acidities was responsible for enhancing catalytic performance in THF co-solvent. Combining FeCl3 with THF co-solvent was particularly effective, achieving one of the highest reported simultaneous yields of furfural (95%) and 5-HMF (51%) directly from biomass with minimal levulinic acid formation (6%). Furthermore, over 90% of the lignin from biomass was extracted by THF and recovered as a fine lignin powder. Tuning the volume ratio of THF to water from 4 : 1 to 1 : 1 preserved 10% to 31% of the reacted biomass as a glucan-rich solid suitable for further catalytic reaction, enzymatic digestion, or possible pulp and paper production. [ABSTRACT FROM AUTHOR]

This paper reviews the application of ionic liquids to the deconstruction and fractionation of lignocellulosic biomass, in a process step that is commonly called pretreatment. It is divided into four parts: the first gives background information on lignocellulosic biomass and ionic liquids; the second focuses on the solubility of lignocellulosic biomass (and the individual biopolymers within it) in ionic liquids; the third emphasises the deconstruction effects brought about by the use of ionic liquids as a solvent; the fourth part deals with practical considerations regarding the design of ionic liquid based deconstruction processes. [ABSTRACT FROM AUTHOR]

Ionic liquids are of great interest as potential solvents/catalysts for the production of fuels and chemicals from lignocellulosic biomass. Attention has focused particularly on the pretreatment of lignocellulose to make the cellulose more accessible to enzymatic hydrolysis. Any biomass processing requires a reduction in the size of the harvested biomass by chipping and/or grinding to make it more amenable to chemical and biological treatments. This paper demonstrates that significant energy savings can be achieved in the grinding of pine wood chips when the ionic liquid is added before the grinding operation. We show that this is due to the lubricating properties of the ionic liquids and not to physico-chemical modifications of the biomass. A brief impregnation of the chipped biomass results in higher savings than a longer treatment. [ABSTRACT FROM AUTHOR]

Pyrolysis oils are the cheapest liquid fuel derived from lignocellulosic biomass. However, pyrolysis oils are a very poor quality liquid fuel that cannot be used in conventional diesel and internal combustion engines. In this paper we show that hydrogen, alkanes (ranging from C1to C6) and polyols (ethylene glycol, 1,2-propanediol, 1,4-butanediol) can be produced from the aqueous fraction of wood-derived pyrolysis oils (bio-oils). The pyrolysis oil was first phase separated into aqueous and non-aqueous fraction by addition of water. The aqueous phase of bio-oil contained sugars; anhydrosugars; acetic acid; hydroxyacetone; furfural and small amounts of guaiacols. The aqueous fraction was subjected to a low temperature hydrogenation with Ru/C catalyst at 125–175 °C and 68.9 bar. The hydrogenation step converts the various functionalities in the bio-oil (including aldehydes; acids; sugars) to corresponding alcohols. Undesired methane and light gases are also produced in this low-temperature hydrogenation step. Diols (ranging from C2 to C4) and sorbitol are obtained as major products in this step. After the low temperature hydrogenation step either hydrogen or alkanes can be produced by aqueous-phase reforming (APR) or aqueous-phase dehydration/hydrogenation (APD/H) respectively. APR was done with a 1 wt% Pt/Al2O3catalyst at 265 °C and 55.1 bar. Hydrogen selectivities of up to 60% were observed. The hydrogen selectivity was a function of space velocity. A 4 wt% Pt/SiO2-Al2O3catalyst at 260 °C and 51.7 bar was used for alkane production by APD/H. The carbon conversion to gas phase products of 35% with alkane selectivity of 45% was obtained for a WHSV of 0.96 h−1when hydrogen is produced in situfrom bio-oil. Alkane selectivity can be improved by supplying hydrogen externally. Alkane selectivities as high as 97% can be obtained when HCl is added to the aqueous-phase of the bio-oil and hydrogen is supplied externally. Model compounds for further bio-oil conversion studies are suggested. [ABSTRACT FROM AUTHOR]

A review on the use of polyoxometalates (POMs) and oxygen, for the delignification of lignocellulosic pulps is presented. Two main processes using POMs for the delignification of pulp have been investigated: an anaerobic process in which the POMs have been used, in aqueous solutions, as stoichiometric reagents for the oxidative degradation of residual lignin, with their re-oxidation by oxygen occurring in a subsequently separate stage; and an aerobic process in which the POMs were designed to perform as catalysts in the oxygen delignification. In the aerobic approach, the lignin oxidation and the reactivation of the POM take place in the same stage of the process. The feasibility of the catalytic system was shown by pilot plant experiments. Following the green chemistry goals, these processes are environmentally friendly approaches and may allow a significant decrease of chlorine-based chemical consumption by the pulp-and-paper industry. The use of the POMs together with laccase for the oxygen delignification of lignocellulosic pulps will also be considered. Final comments regarding the practical application of the POMs are pointed out. [ABSTRACT FROM AUTHOR]

A reductive lignocellulose fractionation in a flow-through system in which pulping and transfer hydrogenolysis steps were separated in time and space has been developed. Without the hydrogenolysis step or addition of trapping agents to the pulping, it is possible to obtain partially depolymerized lignin (21 wt% monophenolic compounds) that is prone to further processing. By applying a transfer hydrogenolysis step 37 wt% yield of lignin derived monophenolic compounds was obtained. Pulp generated in the process was enzymatically hydrolyzed to glucose in 87 wt% yield without prior purification. [ABSTRACT FROM AUTHOR]

This tutorial review aims to describe the status of the scaling up of organosolv treatment. It is a process where various lignocellulosic materials are fractionated, selective depolymerization mechanisms are catalyzed, and their main components (polysaccharides, lignin and extractives) can be extracted, separated and isolated using liquid organic solvents such as alcohols, ketones and proton-donating acid molecules. Organosolv fractionation can be applied to several renewable biomasses, allows the production of pure species systems to prepare valuable chemicals, polymers and biomaterial compositions with a related environmental impact, lower than that of classical industrial plants, and optimizes the resource carbon efficiency. However, the high energy consumption for the recovery after dissolution, input costs and feedstock flexibility robustness are slowing down the piloting of commercial operations. As a critical indicator evaluation, a summary of reasons why engineering organosolv is still extremely interesting, together with an overview of the most important organosolv technologies, describing current equipment scale range economics, limitations and market research opportunities, is presented in detail. A variety of sources (wood, straw, bagasse, wastes...), media (water, methanol, ethanol, formates, acetates...) and products (biogas, bioethanol, (nano)cellulose, glucose, furans...) are comparatively benchmarked. Existing (model) validated, demonstrational or patented configurations are collected, listing strengths as well as challenges. [ABSTRACT FROM AUTHOR]

Engineered lignocellulose valorization enables the formation of superior energy and environmental materials which are developed to achieve the aim of sustainable carbon-neutral technologies. In this work, sequential manufacture under the trigger of hydrothermal fractionation is proposed for the "two-in-one" valorization of wheat straw into highly dispersed Fe, N-codoped carbon spheres (Fe–N–C) and Co nanoclusters anchored on biochar (Co–N–C) via using synchronous pyrolysis/activation. Taking advantage of the ordered ion-diffusion shortcut, suitable geometric/nanosized porous structure, ultrahigh surface area, well-developed packing architecture, and multiple redox possibilities (i.e., Fe species and N functional groups), the durable, conductive Fe–N–C microspheres can function as supercapacitor electrodes, exhibiting superior specific capacitance, rate-performance, and long-cycling lifespan. Benefitting from well-exposed Co nanoclusters and N coordination, the recyclable Co–N–C catalysts enabling efficient persulfate activation are conducive to expediting tetracycline removal with a working pH from 3 to 9, and a concomitant mechanism involving reactive oxygen species and interface electron shuttling is revealed via radical trapping, direct charge-transfer, and theoretical simulation. Hence this work provides multifaceted insights into a coupling strategy for lignocellulose conversion that involves matching the brand-new "biomass–energy–water" interplay with improved biorefining value. [ABSTRACT FROM AUTHOR]

Upgrading renewable lignocellulose into bulk chemicals and drop-in-fuels has been identified as a state-of-the-art paradigm to fulfill alternative energy demands. Lignin, as the largest precursor of alkyl aromatics, can be depolymerized effectively to maneuver task-specific phenols. Toward an ecofriendly lignin-first depolymerization, photocatalytic lignocellulose conversion, also termed photobiorefining, is of utmost importance to boost economic and technical feasibility of holistic biomass valorization. It is still an urgent but challenging task to rationally design light-driven lignin deconstruction with decent photocatalytic selectivity and durability for developing scalable photobiorefining. A bottom-up approach, beginning with representative model compounds as lignin intermediates, enables a chance to encompass well-defined photocatalytic mechanism/system for providing insights, feasibility, and guidelines before the technical or proto-lignin conversion. The emphasis of this review is mainly placed on photocatalytic lignin-first strategy that includes versatile photocatalyst types, transformation pathways, photoreactors, and reaction medium. The cleavage mechanisms of C–O (e.g., β-O-4′ and α-O-4′) and C–C (e.g., β-1′ and β-5′) linkages in native lignin and its models to form light aromatic hydrocarbons through homogeneous or heterogeneous photocatalysis are proposed. At the end, the remaining challenges for the selective control and practical spread of photocatalytic lignocellulose fractionation are elaborated, and burgeoning prospects to inspire opportunities on photocatalyst manipulation for efficient and sustainable light-mediated lignin conversion are also discussed. The present work sheds light on the structure–property–performance relationship in photocatalytic lignin valorization and forthcoming knacks to spark the bright pearl of high-performance photobiorefining. [ABSTRACT FROM AUTHOR]

The quantitation of lignin is essential for the evaluation, conversion, and utilization of lignocellulosic biomass. However, the existing lignin quantitation methods like the widely used Klason method still have some disadvantages, such as requiring hazardous reagents, complicated steps, heating, introducing interfering substances, and low sensitivity. In this study, a novel green method for lignin quantitation based on the completely dissolved solution of lignocellulosic biomass in LiCl/DMSO and UV spectrophotometry (LiCl/DMSO CDS-UV method) was developed. The process does not require complex chemical pretreatment and separation of lignin from lignocellulosic biomass. The biomass samples extracted with benzene/ethanol (v/v 2 : 1) can be completely dissolved in an 8% LiCl/DMSO solvent system at room temperature (25 °C) and atmospheric pressure after short-time ball milling (3 h). For the chemical delignified samples with a low lignin content, the completely dissolved solution can be obtained only by heating the solution to 60 °C and stirring at atmospheric pressure for 2 h. Then the lignin content of the solution was determined by UV spectrophotometry. Different species of biomass including herbage (wheat straw), hardwood (black poplar), softwood (redwood), bark (eucalyptus bark and redwood bark), and above biomass treated by different delignification methods and degrees were applied to establish the LiCl/DMSO CDS-UV method and extend the applicability of this method. The results quantified by the LiCl/DMSO CDS-UV method were compared with the total lignin content measured by the Klason method and a good correlation was observed. The LiCl/DMSO CDS-UV method only requires trace samples (0.1 g) to achieve a precise determination of the lignin content, the conditions are mild, no hazardous reagents are used and no interfering substances are produced in the process. [ABSTRACT FROM AUTHOR]

In the past few years, cellulose nanomaterials obtained from lignocellulose have attracted extensive attention as functional nanomaterials with excellent properties and great application potential in a variety of high-tech fields. However, the preparation of cellulose nanomaterials is facing several challenges such as the large amount of energy consumption, chemical recovery issues, and complicated purification and pretreatment processes, which have limited their large-scale application. Fortunately, lignin-containing cellulose nanomaterials have emerged as a new type of cellulose nanomaterial because of the low energy and chemical consumption, easy preparation process, and special properties. This review showcases a comprehensive overview of research status on the preparation and application of lignin-containing cellulose nanomaterials, focusing on recently developed green and low-cost preparation processes. The potential applications of lignin-containing cellulose nanomaterials as building blocks and reinforcing agents for the design of various advanced materials are summarized as well. Finally, the current challenges and future directions for the preparation and application of lignin-containing cellulose nanomaterials are provided. [ABSTRACT FROM AUTHOR]

The conversion of lignocellulose into a value-added chemical with high selectivity is of great significance but is a big challenge due to the structural diversities of biomass components. Here, we have reported an efficient approach for the one-step conversion of raw lignocellulose into diethyl maleate by the polyoxometalate ionic liquid [BSmim]CuPW12O40 in ethanol under mild conditions. The results reveal that all of the fractions in biomass, i.e., cellulose, lignin and hemicellulose, were simultaneously converted into diethyl maleate (DEM), achieving a 329.6 mg g−1 yield and 70.3% selectivity from corn stalk. Importantly, the performance of the ionic liquid catalyst [BSmim]CuPW12O40 was nearly twice that of CuHPW12O40, which can be attributed to the lower incorporation of the Cu2+ site in [BSmim]CuPW12O40. Hence, this process opens a promising route for producing bio-based bulk chemicals from raw lignocellulose without any pretreatment. [ABSTRACT FROM AUTHOR]

Integrating multifarious capabilities within a waste-free biorefinery has been the cornerstone to ignite scalable design of holistic biomass valorization. Fostering the versatile utilization of industrial effluents and residual lignin from traditional biorefineries has become an imminent issue to be tackled. A green and tandem approach was proposed to simultaneously produce carbon dots (CDs), fermentable sugar, and lignin-installed lithium–sulfur (Li–S) cells from eucalyptus with the aid of L -cysteine-catalyzed hydrothermal pretreatment. The total yield of xylooligosaccharides (XOS) reached up to 50.16% (w/w) of xylan that was directly extracted from the wood skeleton by a moderate acidic hydrothermal environment, including 22.03% of XOS with a low degree of polymerization (DP 2–6). The graphite N, S-doped CDs with a bright blue fluorescence, which mainly originated from the irregular conjugation of xylan, lignin and L -cysteine, had an average diameter at 4.7 nm confined to a quasi-spherical shape. The proper alleviation of amorphous ingredients and recalcitrant intercellular structure can be attributed to autohydrolysis with the assistance of an amino acid, thereby fostering the enzymatic digestibility of well-preserved cellulose from 15.1% to 82.4%. From cellulose enzymatic lignin (CEL) capable of high abundance of β-aryl ether and hydroxyl groups, a hierarchically structured heteroatom-doped biochar with exposed active sites (N, S, O-induced intrinsic defects and surface states) was synthesized via using a dual-template. It can serve as an available candidate for the molten sulfur host to install a Li–S cathode that retained 582 mA h g−1 at 1C after 300 cycles with the average coulombic efficiency and capacity decay per cycle being 93.79% and 0.098% respectively. With the advent of bioethanol techniques, the all-round pathway brings a graceful prelude for boosting the revenue of waste-free biorefineries that has inspired application-worthy products from biomass waste streams, including photoluminescent CDs and rechargeable Li–S cells. [ABSTRACT FROM AUTHOR]

The conversion of lignocelluloses into fermentable sugars by enzymatic hydrolysis is a key step in biorefining. However, there are still some bottleneck problems such as low hydrolysis efficiency, high cost of cellulase and low utilization of lignin. In this work, the nonionic surfactant monomethoxy polyethylene glycol (MPEG) was grafted on enzymatic hydrolysis lignin (EHL) to obtain a pH-responsive polymer (EHL-MPEG). EHL-MPEG could achieve rapid dissolution–precipitation conversion by the ionization and protonation of carboxyl groups. By adjusting the grafting amount of MPEG, EHL-MPEG could not only enhance the enzymatic hydrolysis of lignocelluloses, but also efficiently recover cellulase after hydrolysis. Adding 3 g L−1 EHL-MPEG40 (the mass ratio of MPEG to EHL was 40%) could increase the glucose yield of corncob residue (CCR) and pretreated eucalyptus from 79.4% and 48.3% to 92.5% and 89.5%, respectively, which was comparable to the effect of the nonionic surfactant PEG4600. By simply adjusting the pH of solutions, more than 85% of cellulase proteins could be recovered by EHL-MPEG40 with almost complete recovery of β-glycosidase, exoglucanase V and xylanase. Compared with a pH-responsive lignin amphoteric surfactant (pH-LAS) obtained by grafting ionic groups on lignin, EHL-MPEG40 had a more sensitive pH response and a stronger cellulase recovery ability. In the enzymatic hydrolysis of CCR, a pH-LAS could save about 50% of cellulase, while EHL-MPEG40 could save more than 60% of cellulase. Furthermore, approximately 96% of EHL-MPEG40 could be reused. This new method can not only evade the process of immobilization, but also avoid the activity loss and component change of cellulase through immobilization. Using recyclable EHL-MPEG to improve glucose yield and recover cellulase during lignocellulosic hydrolysis is of great significance for improving the enzymatic saccharification process, reducing the cost of cellulase and realizing comprehensive utilization of lignocelluloses. [ABSTRACT FROM AUTHOR]

Lignocellulosic materials were conventionally treated as wastes for disposal, but have now become very important in modern life due to their great roles in the supply of renewable resources. Recently, significant attention has been paid to the dissolution of cellulose, hemicellulose, and lignin, and the production of chemicals and fuels from these feedstocks. It has been demonstrated that lignocellulose has great potential from a sustainable economy perspective and this field has been developing rapidly. Thus, it is critical to review the recent progress in studies on the utilization of lignocellulosic materials. In particular, this work was designed to highlight recent computation-based studies on the chemistry of lignocellulosic materials, from the structural and energetic properties of individual lignocellulose components to their reaction mechanisms in various systems. Importantly, this review summarizes some major simulation studies on the utilization of cellulose, hemicellulose, and lignin via dissolution, catalytic conversion, and pyrolysis by using density functional theory, first-principles calculation, molecular dynamics simulation, and conductor-like screening models. It has been shown that the theoretical and computational investigations play a key role in the understanding of the efficient utilization of lignocellulose. [ABSTRACT FROM AUTHOR]

In order to enhance the enzymatic hydrolysis of lignocelluloses and recycle surfactants after enzymatic hydrolysis, a pH-responsive lignin amphoteric surfactant (SLQA) was prepared by the quaternization of sulfonated lignin (SL). Compared with SL, SLQA could much more effectively enhance the enzymatic hydrolysis of lignocelluloses. With an increase in the quaternization degree, enhancement of the enzymatic hydrolysis of lignocelluloses by the SLQA gradually increased. Adding 2 g L−1 SLQA-80 (mass radio of quaternizing agent to SL was 80%) could increase the enzymatic digestibility of pretreated eucalyptus and corncob residues (CCR) from 36.7% and 37.8% to 84.3% and 90.5%, respectively. The adsorption of SLQA on lignin film was larger than that of SL, and the lignin film became more hydrophilic after adsorbing SLQA. Thus, SLQA could cause more effective steric hindrance and form a hydration layer to reduce the non-productive adsorption of cellulase on lignin. The purified SLQA-80 exhibited sensitive pH-responsive property, and 90.8% of SLQA-80 could be recycled by adjusting the pH of hydrolysate after enzymatic hydrolysis. Adding recyclable SLQA could not only obviously enhance the enzymatic hydrolysis of lignocelluloses, but could also enable the comprehensive utilization of lignocelluloses. This method is of great significance to reducing the cost of cellulosic ethanol. [ABSTRACT FROM AUTHOR]

Alkali lignin, recovered from the pulping black liquor, was chemically modified by acetylating, and then used as a biomass resource to prepare uniform colloidal spheres via self-assembly. The self-assembled structure and colloid formation mechanism of the acetylated lignin (ACL) were investigated by DLS, SLS, TEM, AFM, XPS, FTIR, elemental analysis and contact angle measurements. Results show that ACL colloidal spheres are obtained from gradual hydrophobic aggregation of ACL molecules, induced by continuously adding water into the ACL-THF solution. ACL molecules start to form colloidal spheres at a critical water content of 44 vol% when the initial concentration of ACL in THF is 1.0 mg mL-1, and the colloidization process is completed at a water content of 67 vol%. An excessive amount of water is added into the dispersions to ''quench'' the structures formed and then the ACL dispersion is treated by rotary evaporation for recycling THF and acquiring colloidal spheres. The ACL colloidal spheres have an of 110 nm with a polydispersity (μ2/Γ2) of 0.022. The average aggregated number () in each colloidal sphere and the average density () are estimated to be 1.0 × 105 and 0.187 g cm-3. Preparation of water-dispersive lignin nanoparticles opens up a green and valuable pathway for value-added utilization of lignin biomass recovered from pulping spent liquor, which is of great significance for both the utilization of renewable resources and environmental protection. [ABSTRACT FROM AUTHOR]

Lignocellulosic biomass, a potentially important renewable organic source of energy and chemical feedstock, resists degradation to glucose in industrial hydrolysis processes and thus requires expensive thermochemical pretreatments. Understanding the mechanism of biomass breakdown during these pretreatments will lead to more efficient use of biomass. By combining multiple probes of structure, sensitive to different length scales, with molecular dynamics simulations, we reveal two fundamental processes responsible for the morphological changes in biomass during steam explosion pretreatment: cellulose dehydration and ligninhemicellulose phase separation. We further show that the basic driving forces are the same in other leading thermochemical pretreatments, such as dilute acid pretreatment and ammonia fiber expansion. [ABSTRACT FROM AUTHOR]

Catalytic transformation of readily available widely distributed and renewable non-food lignocelluloses to value-added chemicals has been recognized as an efficient approach for the alleviation of the increasing energy crisis and climate change. An efficient catalytic transformation process for agricultural residual lignocelluloses in cooperative ionic liquid pairs was achieved. The promotion of the dissolution equilibrium, combined with rapid, in situ acid-catalyzed degradation of cellulose and hemicellulose, resulted in significantly greater conversion of the biomass to biochemicals and selective delignification through further comparative analyses of the raw materials, products and residues by GC-MS, GPC, FT-IR, SEM and elemental characterization. [ABSTRACT FROM AUTHOR]

Rapid dissolution of bagasse and southern yellow pine has been achieved in the ionic liquid (IL) 1-ethyl-3-methylimidazolium acetate ([C2mim]OAc) by using a dissolution temperature above the glass transition of lignin (ca. 150 °C). When 0.5 g of bagasse or pine is added to 10 g of [C2mim]OAc, complete dissolution can be obtained in 5–15 min for bagasse at a temperature of 175–195 °C, compared to 15–16 h at 110 °C, and over 90% of added pine can be dissolved with heating at 175 °C for 30 min. Upon regeneration in acetone/water, lignin and carbohydrate can be partially separated as lignin and a cellulose-rich material (CRM, pulp). Compared to published methods with lower temperatures and longer times (e.g., 110 °C, 16 h), processing bagasse in [C2mim]OAc at 185 °C for 10 min results in higher yields of both recovered lignin (31% vs. 26% of the available lignin) and carbohydrate (carbohydrate yield = 66% vs. 63% of the available carbohydrate). In addition, the CRM pulp recovered using the higher temperature method has much lower residual lignin content (6% vs. 20%). Similar results were obtained for pine (lignin content in CRM with higher vs. lower temperature method = 16.1% vs. 23.5%). The IL was recycled and reused although the efficiency decreased and ca. 15% of the IL had degraded after the higher temperature process. These latter results suggest further optimization of the choice of IL and heating conditions might be needed to develop an energy and chemical efficient process. [ABSTRACT FROM AUTHOR]

Lignocellulosic biomass composite fibers (southern yellow pine and bagasse) were successfully prepared directly from the ionic liquid, 1-ethyl-3-methylimidazolium acetate ([C2mim]OAc) with a dry-jet wet spinning process using short dissolution times (10–30 min) and temperatures above the glass transition temperature of lignin. Fibers could not be spun at all from solutions of pine dissolved using previously reported dissolution methods (110 °C, 16 h), while bagasse fibers spun using the higher temperature/shorter time method were stronger than those obtained using the lower temperature/longer time method. [ABSTRACT FROM AUTHOR]