Overcome the recalcitrance of eucalyptus bark to enzymatic hydrolysis by concerted ionic liquid pretreatment

Comparison of Alkaline Sulfite Pretreatment and Acid Sulfite Pretreatment with Low Chemical Loading in Saccharification of Poplar

Sulfite pretreatment is a productive process for lignin dissolution in lignocelluloses and to reduce the hydrophobicity of lignin by sulfonation, thus promoting the hydrolyzability of the substrate. Previously, sulfite pretreatment needs high dosages of chemicals and thus results in the high cost of the pretreatment and the great pressure of environmental pollution. To overcome these problems, it was crucial to research whether alkaline sulfite pretreatment (ALS) and acid sulfite pretreatment (ACS) with low chemical loading could enhance the saccharification of poplar. In this work, the results indicated that with low loading of chemicals in sulfite pretreatment, ALS pretreatment (1.6% Na2SO3 and 0.5% NaOH) at 180 °C removed more lignin, resulted in lower hydrophobicity and higher cellulase adsorption capacity of poplar than ACS pretreatment (1.6% Na2SO3 and 0.5% H2SO4) at 180 °C. A satisfying glucose yield of 84.9% and a xylose yield of 76.0% were obtained from poplar after ALS pretreatment with 1.6% Na2SO3 and 0.5% NaOH at 180 °C for 1 h using 10 FPU cellulase/g dry matter, saving sodium sulfite by 60.0% compared to the loading of sulfite in traditional sulfite pretreatment. The strategy developed in this work reduced chemical loading and cellulase loading in alkali sulfite pretreatment for the saccharification of poplar.

Thermochemical Liquefaction as a Cleaner and Efficient Route for Valuing Pinewood Residues from Forest Fires

Biomass thermochemical liquefaction is a chemical process with multifunctional bio-oil as its main product. Under this process, the complex structure of lignocellulosic components can be hydrolysed into smaller molecules at atmospheric pressure. This work demonstrates that the liquefaction of burned pinewood from forest fires delivers similar conversion rates into bio-oil as non-burned wood does. The bio-oils from four burned biomass fractions (heartwood, sapwood, branches, and bark) showed lower moisture content and higher HHV (ranging between 32.96 and 35.85 MJ/kg) than the initial biomasses. The increased HHV resulted from the loss of oxygen, whereas the carbon and hydrogen mass fractions increased. The highest conversion of bark and heartwood was achieved after 60 min of liquefaction. Sapwood, pinewood, and branches reached a slightly higher conversion, with yields about 8% greater, but with longer liquefaction time resulting in higher energy consumption. Additionally, the van Krevelen diagram indicated that the produced bio-oils were closer and chemically more compatible (in terms of hydrogen and oxygen content) to the hydrocarbon fuels than the initial biomass counterparts. In addition, bio-oil from burned pinewood was shown to be a viable alternative biofuel for heavy industrial applications. Overall, biomass from forest fires can be used for the liquefaction process without compromising its efficiency and performance. By doing so, it recovers part of the lost value caused by wildfires, mitigating their negative effects.

Transforming lignocellulosic biomass into biofuels enabled by ionic liquid pretreatment

Processes that can convert lignocellulosic biomass into biofuels and chemicals are particularly attractive considering renewability and minimal environmental impact. Ionic liquids (ILs) have been used as novel solvents in the process development in that they can effectively deconstruct recalcitrant lignocellulosic biomass for high sugar yield and lignin recovery. From cellulose-dissolving ILs to choline-based and protic acidic ILs, extensive research in this field has been done, driven by the promising future of IL pretreatment. Meanwhile, shortcomings and technological hurdles are ascertained during research and developments. It is necessary to present a general overview of recent developments and challenges in this field. In this review paper, three aspects of advances in IL pretreatment are critically analyzed: biocompatible ILs, protic acidic ILs and combinatory pretreatments.

Evaluating the potential of a novel hardwood biomass using a superbase ionic liquid

Lignocellulosic biomass, being ubiquitous and easily accessible, bears a huge potential for sustainable energy and other products.

Extraction of lignin and quantitative sugar release from biomass using efficient and cost-effective pyridinium protic ionic liquids

Lignocellulosic biomass is enormously abundant around the globe. It bears huge potential for renewable products as its components can be converted to many useful products via cheaper processes. Recently, the component of biomass that has attracted enormous attention is lignin owing to its several aromatic or phenolic constituents. The utilization of lignin, however, is hindered by its troublesome separation mainly due to the difficult nature of the lignocellulosic biomass. Protic ionic liquids have great potential for extraction of lignin from the lignocellulosic biomass to make it viable for various transformations. In this study, protic ionic liquids comprising a pyridinium cation and a dihydrogen phosphate anion (H₂PO₄⁻) were prepared and used for lignin extraction and subsequent saccharification of the cellulose pulp. The ILs exhibited appreciably high lignin yields (optimum 73%) under mild conditions (100 °C) and shorter time (2 h). Fairly good sugar (glucose) yields (77%) verify effective delignification. The analysis of ILs and biomass was accomplished by H-NMR, FT-IR, SEM, HSQC and GPC.

Lignocellulosic biomass is enormously abundant around the globe. It bears huge potential for renewable products as its components can be converted to many useful products via cheaper processes.

Supercritical Fluids: A Promising Technique for Biomass Pretreatment and Fractionation

Lignocellulosic biomasses are primarily composed of cellulose, hemicelluloses and lignin and these biopolymers are bonded together in a heterogeneous matrix that is highly recalcitrant to chemical or biological conversion processes. Thus, an efficient pretreatment technique must be selected and applied to this type of biomass in order to facilitate its utilization in biorefineries. Classical pretreatment methods tend to operate under severe conditions, leading to sugar losses by dehydration and to the release of inhibitory compounds such as furfural (2-furaldehyde), 5-hydroxy-2-methylfurfural (5-HMF), and organic acids. By contrast, supercritical fluids can pretreat lignocellulosic materials under relatively mild pretreatment conditions, resulting in high sugar yields, low production of fermentation inhibitors and high susceptibilities to enzymatic hydrolysis while reducing the consumption of chemicals, including solvents, reagents, and catalysts. This work presents a review of biomass pretreatment technologies, aiming to deliver a state-of-art compilation of methods and results with emphasis on supercritical processes.

Eucalyptus red grandis pretreatment with protic ionic liquids: effect of severity and influence of sub/super-critical CO2 atmosphere on pretreatment performance

Deconstruction of lignocellulosic biomass with low-cost ionic liquids (ILs) has proven to be a promising technology that could be implemented in a biorefinery to obtain renewable materials, fuels and chemicals. This study investigates the pretreatment efficacy of the ionoSolv pretreatment of Eucalyptus red grandis using the low-cost ionic liquid triethylammonium hydrogen sulfate ([N₂₂₂₀][HSO₄]) in the presence of 20 wt% water at 10% solids loading. The temperatures investigated were 120 °C and 150 °C. Also, the influence of performing the pretreatment under sub-critical and supercritical CO₂ was investigated. The IL used is very effective in deconstructing eucalyptus, producing cellulose-rich pulps resulting in enzymatic saccharification yields of 86% for some pretreatment conditions. It has been found that under a CO₂ atmosphere, the ionoSolv process is pressure independent. The good performance of this IL in the pretreatment of eucalyptus is promising for the development of a large-scale ionoSolv pretreatment processes.

Overcoming challenges in lignocellulosic biomass pretreatment for second-generation (2G) sugar production: emerging role of nano, biotechnological and promising approaches

Production of green chemicals and biofuels in biorefineries is the potential alternative for petrochemicals and gasoline in transitioning of petro-economy into bioeconomy. However, an efficient biomass pretreatment process must be considered for the successful deployment of biorefineries, mainly for use of lignocellulosic raw materials. However, biomass recalcitrance plays a key role in its saccharification to obtain considerable sugar which can be converted into ethanol or other biochemicals. In the last few decades, several pretreatment methods have been developed, but their feasibility at large-scale operations remains as a persistent bottleneck in biorefineries. Pretreatment methods such as hydrodynamic cavitation, ionic liquids, and supercritical fluids have shown promising results in terms of either lignin or hemicellulose removal, thus making remaining carbohydrate fraction amenable to the enzymatic hydrolysis for clean and high amount of fermentable sugar production. However, their techno-economic feasibility at industrial scale has not been yet studied in detail. Besides, nanotechnological-based technologies could play an important role in the economically viable 2G sugar production in future. Considering these facts, in the present review, we have discussed the existing promising pretreatment methods for lignocellulosic biomass and their challenges, besides this strategic role of nano and biotechnological approaches towards the viability and sustainability of biorefineries is also discussed.

Deterioration of Wood Plastics Composites by the White-Rot Fungus Pycnoporus sanguineus

Wood plastic composites (WPC) are characterized by the mixing of wood fibers with plastics, allowing the production of new products whose characteristics are in several aspects superior to those of the original products and represent an expanding class of durable and low-cost materials in which their uses can reduce the environmental footprint and the dependence on petroleum products. Nevertheless, WPC has some setbacks, including biodegradation, which shortens its life span. In this study, the wood composite was exposed to the white-rot fungus Pycnoporus sanguineus in order to evaluate its resistance to biodegradation. The WPC was prepared with a 1:1 ratio of Eucalyptus spp. bark as reinforcement agent and polypropylene as matrix. Mechanical and rheological properties and mass loss were evaluated from 15 to 120 days of fungus exposure. After 15 days, a mass loss was detected, which transmitted a negligible effect on the impact resistance of the composite. For the 120-day fungus-exposed composite, the fungus produced a biofilm under the WPC that create a special environment for lignocellulosic consuming led to deterioration of the mechanical properties and minor changes on the thermal–chemical stability of the WPC. Finally, the study gave a great indication of the susceptibility of a Eucalyptus-based composite to biodegradation.

Evaluation of Relationships between Growth Rate, Tree Size, Lignocellulose Composition, and Enzymatic Saccharification in Interspecific Corymbia Hybrids and Parental Taxa

In order for a lignocellulosic bioenergy feedstock to be considered sustainable, it must possess a high rate of growth to supply biomass for conversion. Despite the desirability of a fast growth rate for industrial application, it is unclear what effect growth rate has on biomass composition or saccharification. We characterized Klason lignin, glucan, and xylan content with response to growth in Corymbia interspecific F1 hybrid families (HF) and parental species Corymbia torelliana and C. citriodora subspecies variegata and measured the effects on enzymatic hydrolysis from hydrothermally pretreated biomass. Analysis of biomass composition within Corymbia populations found similar amounts of Klason lignin content (19.7-21.3%) among parental and hybrid populations, whereas glucan content was clearly distinguished within C. citriodora subspecies variegata (52%) and HF148 (60%) as compared to other populations (28-38%). Multiple linear regression indicates that biomass composition is significantly impacted by tree size measured at the same age, with Klason lignin content increasing with diameter breast height (DBH) (+0.12% per cm DBH increase), and glucan and xylan typically decreasing per DBH cm increase (-0.7 and -0.3%, respectively). Polysaccharide content within C. citriodora subspecies variegata and HF-148 were not significantly affected by tree size. High-throughput enzymatic saccharification of hydrothermally pretreated biomass found significant differences among Corymbia populations for total glucose production from biomass, with parental Corymbia torelliana and hybrids HF-148 and HF-51 generating the highest amounts of glucose (~180 mg/g biomass, respectively), with HF-51 undergoing the most efficient glucan-to-glucose conversion (74%). Based on growth rate, biomass composition, and further optimization of enzymatic saccharification yield, high production Corymbia hybrid trees are potentially suitable for fast-rotation bioenergy or biomaterial production.

Efficient Eucalypt Cell Wall Deconstruction and Conversion for Sustainable Lignocellulosic Biofuels

In order to meet the world's growing energy demand and reduce the impact of greenhouse gas emissions resulting from fossil fuel combustion, renewable plant-based feedstocks for biofuel production must be considered. The first-generation biofuels, derived from starches of edible feedstocks, such as corn, create competition between food and fuel resources, both for the crop itself and the land on which it is grown. As such, biofuel synthesized from non-edible plant biomass (lignocellulose) generated on marginal agricultural land will help to alleviate this competition. Eucalypts, the broadly defined taxa encompassing over 900 species of Eucalyptus, Corymbia, and Angophora are the most widely planted hardwood tree in the world, harvested mainly for timber, pulp and paper, and biomaterial products. More recently, due to their exceptional growth rate and amenability to grow under a wide range of environmental conditions, eucalypts are a leading option for the development of a sustainable lignocellulosic biofuels. However, efficient conversion of woody biomass into fermentable monomeric sugars is largely dependent on pretreatment of the cell wall, whose formation and complexity lend itself toward natural recalcitrance against its efficient deconstruction. A greater understanding of this complexity within the context of various pretreatments will allow the design of new and effective deconstruction processes for bioenergy production. In this review, we present the various pretreatment options for eucalypts, including research into understanding structure and formation of the eucalypt cell wall.