Integrated pretreatment of poplar biomass employing p-toluenesulfonic acid catalyzed liquid hot water and short-time ball milling for complete conversion to xylooligosaccharides, glucose, and native-like lignin

Efficient conversion of lignin fractions in lignocellulose using multifunctional polyoxometalate catalysts

The efficient catalytic conversion of lignin represents a critical challenge in biomass valorization, primarily due to the inherent difficulty in selectively depolymerizing lignin while maintaining the structural integrity of cellulose and hemicellulose. Herein, we present an innovative approach involving the synthesis of ionic liquid polyoxometalate (IL-POM) catalysts, which integrate both redox-active and Lewis acid sites, and are further modified with a choline chloride monomer. Among the synthesized catalysts, ChH4PMo11Al0.5V0.5O40 demonstrated exceptional catalytic performance, achieving an aromatic compound yield of 16.35 % under optimized conditions. Comprehensive characterization of the catalyst revealed that its catalytic efficacy is intrinsically linked to its acidity profile, with the synergistic interplay between Brønsted and Lewis acids facilitating the cleavage of CC and CO bonds. Notably, the incorporation of choline chloride was found to be pivotal in ensuring the catalyst's recyclability. This study underscores the potential of multifunctional IL-POM catalysts in advancing biomass valorization, providing a promising pathway to bridge the gap between homogeneous and heterogeneous catalysis for sustainable biomass conversion.

Enhanced Enzymatic Hydrolysis of Tobacco Stalk via Simultaneous Deconstruction and Modification through Triton X-100-Mediated Organosolv Pretreatment

Tobacco stalks (TS) present substantial potential for biofuel and biochemical production; however, their complex lignin structures and tightly bound carbohydrates pose significant challenges for enzymatic hydrolysis due to high recalcitrance. This study explores Triton-X 100-mediated 1,4-butanediol combined with AlCl3 pretreatment for TS fractionation towards improving enzymatic hydrolysis. Optimized pretreatment conditions achieved a significant removal of 87.8 % of hemicellulose and 81.0 % of lignin while maintaining a high cellulose retention of 90.1 %. Subsequently, the pretreated biomass recorded 91.2 % glucose yield after enzymatic hydrolysis at 10 % w/w solid with 12 FPU/g enzyme loadings, substantially outperforming controls. The presence of Triton-X 100 in pretreatment reduced enzyme requirements by up to 33.3 %. Structural characterization of the pretreated TS indicated effective disruption of lignin-carbohydrate complexes and an increase in biomass porosity by 1.2-2.3 folds, contributing to improved cellulose accessibility and enzymatic hydrolysis efficiency. Moreover, structural characterization of lignin revealed that Triton-X 100 grafted onto lignin by etherification, yielding a 21 % reduction in phenolic hydroxyl content and enhancing surface negative charge. These modifications effectively weaken both hydrogen bonding and electrostatic interactions between lignin and cellulase, thereby improving enzymatic hydrolysis efficiency. Overall, the proposed pretreatment presents a promising strategy for efficient fractionation and hydrolysis of TS biomass.

Transformation of Lignin Under Protection Strategies: Catalytic Oxidation and Depolymerization by Polyoxometalates Catalysts

The efficient utilization of lignin, a pivotal component of lignocellulosic biomass, is crucial for advancing sustainable biorefinery processes. However, optimizing lignin valorization remains challenging due to its intricate structure and susceptibility to undesirable reactions during processing. In this study, we delve into the impact of various pretreatment agents on birch lignin, aiming to enhance its catalytic oxidation and depolymerization under polyoxometalates (POMs) catalysis. Our results reveal that pretreatment with formaldehyde effectively safeguards aryl ether linkages in lignin, leading to a notable increase in aromatic compound yields under POMs catalysis. Furthermore, gel permeation chromatography (GPC) analysis underscores the inhibition of aryl ether linkage hydrolysis upon formaldehyde addition. Gas chromatography-mass spectrometry (GC-MS) analysis demonstrates that formaldehyde pretreatment boosts lignin monomer yield by 2 to 3 times compared to untreated lignin, underscoring the effectiveness of tailored pretreatment strategies. This research underscores the significance of adopting rational pretreatment methods to advance lignin valorization pathways catalyzed by POMs, thereby contributing to the evolution of sustainable biomass conversion technologies.

Advances in sustainable nano-biochar: precursors, synthesis methods and applications

Nano-biochar, characterized by its environmentally friendly nature and unique nanostructure, offers a promising avenue for sustainable carbon materials. With its small particle size, large specific surface area, abundant functional groups and tunable pore structure, nano-biochar stands out due to its distinct physical and chemical properties compared to conventional biochar. This paper aims to provide an in-depth exploration of nano-biochar, covering its sources, transformation mechanisms, properties, applications, and areas requiring further research. The discussion begins with an overview of biomass sources for nano-biochar production and the conversion processes involved. Subsequently, primary synthesis methods and strategies for functionalization enhancement are examined. Furthermore, the applications of nano-biochar in catalysis, energy storage, and pollutant adsorption and degradation are explored and enhanced in various fields.

Harnessing recalcitrant lignocellulosic biomass for enhanced biohydrogen production: Recent advances, challenges, and future perspective

Biohydrogen (Bio-H2) is widely recognized as a sustainable and environmentally friendly energy source, devoid of any detrimental impact on the environment. Lignocellulosic biomass (LB) is a readily accessible and plentiful source material that can be effectively employed as a cost-effective and sustainable substrate for Bio-H2 production. Despite the numerous challenges, the ongoing progress in LB pretreatment technology, microbial fermentation, and the integration of molecular biology techniques have the potential to enhance Bio-H2 productivity and yield. Consequently, this technology exhibits efficiency and the capacity to meet the future energy demands associated with the valorization of recalcitrant biomass. To date, several pretreatment approaches have been investigated in order to improve the digestibility of feedstock. Nevertheless, there has been a lack of comprehensive systematic studies examining the effectiveness of pretreatment methods in enhancing Bio-H2 production through dark fermentation. Additionally, there is a dearth of economic feasibility evaluations pertaining to this area of research. Thus, this review has conducted comparative studies on the technological and economic viability of current pretreatment methods. It has also examined the potential of these pretreatments in terms of carbon neutrality and circular economy principles. This review paves the way for a new opportunity to enhance Bio-H2 production with technological approaches.

Biphasic pretreatment excels over conventional sulfuric acid in pinewood biorefinery: An environmental analysis

This study assesses the environmental impact of pine chip-based biorefinery processes, focusing on bioethanol, xylonic acid, and lignin production. A cradle-to-gate Life Cycle Assessment (LCA) is employed, comparing a novel biphasic pretreatment method (p-toluenesulfonic acid (TsOH)/pentanol, Sc-1) with conventional sulfuric acid pretreatment (H2SO4, Sc-2). The analysis spans biomass handling, pretreatment, enzymatic hydrolysis, yeast fermentation, and distillation. Sc-1 yielded an environmental impact of 1.45E+01 kPt, predominantly affecting human health (96.55%), followed by ecosystems (3.07%) and resources (0.38%). Bioethanol, xylonic acid, and lignin contributed 32.61%, 29.28%, and 38.11% to the total environmental burdens, respectively. Sc-2 resulted in an environmental burden of 1.64E+01 kPt, with a primary impact on human health (96.56%) and smaller roles for ecosystems (3.07%) and resources (0.38%). Bioethanol, xylonic acid, and lignin contributed differently at 22.59%, 12.5%, and 64.91%, respectively. Electricity generation was predominant in both scenarios, accounting for 99.05% of the environmental impact, primarily driven by its extensive usage in biomass handling and pretreatment processes. Sc-1 demonstrated a 13.05% lower environmental impact than Sc-2 due to decreased electricity consumption and increased bioethanol and xylonic acid outputs. This study highlights the pivotal role of pretreatment methods in wood-based biorefineries and underscores the urgency of sustainable alternatives like TsOH/pentanol. Additionally, adopting greener electricity generation, advanced technologies, and process optimization are crucial for reducing the environmental footprint of waste-based biorefineries while preserving valuable bioproduct production.