[Research Progress of Functional Materials for Conversion of Agricultural Biomass Wastes].

Excess agricultural biomass waste is increasing rapidly, leading to many environmental and governance issues. Therefore, increased attention has been paid to the recycling and value-added application of agricultural biomass waste. In recent years, the research of agricultural biomass waste utilization and derived functional materials has mainly included the following two aspects： ① the extraction of natural polymers and value-added applications and ② the direct preparation of new carbon-based materials, including adsorption, catalysis, energy storage electrode, and composite functional materials. The conversion of agricultural biomass waste into functional materials has been gradually realized and widely used. To enable industrial-scale production and the quality and safety of agricultural biomass waste derivatives and to develop highly feasible and cost-effective biomass waste conversion methods should be the focus of future studies.

Agricultural biomass/waste-based materials could be a potential adsorption-type remediation contributor to environmental pollution induced by pesticides-A critical review.

The widespread use of pesticides that are inevitable to keep the production of food grains brings serious environmental pollution problems. Turning agricultural biomass/wastes into materials addressing the issues of pesticide contaminants is a feasible strategy to realize the reuse of wastes. Several works summarized the current applications of agricultural biomass/waste materials in the remediation of environmental pollutants. However, few studies systematically take the pesticides as an unitary target pollutant. This critical review comprehensively described the remediation effects of crop-derived waste (cereal crops, cash crops) and animal-derived waste materials on pesticide pollution. Adsorption is considered a superior and highlighted effect between pesticides and materials. The review generalized the sources, preparation, characterization, condition optimization, removal efficiency and influencing factors analysis of agricultural biomass/waste materials. Our work mainly emphasized the promising results in lab experiments, which helps to clarify the current application status of these materials in the field of pesticide remediation. In the meantime, rigorous pros and cons of the materials guide to understand the research trends more comprehensively. Overall, we hope to achieve a large-scale use of agricultural biomass/wastes.

Unraveling the relationship between soil carbon-degrading enzyme activity and carbon fraction under biogas slurry topdressing.

Biogas slurry, a by-product of the anaerobic digestion of biomass waste, predominantly consisting of livestock and poultry manure, is widely acclaimed as a sustainable organic fertilizer owing to its abundant reserves of essential nutrients. Its distinctive liquid composition, when tactfully integrated with a drip irrigation system, unveils immense potential, offering unparalleled convenience in application. In this study, we investigated the impact of biogas slurry topdressing as a replacement for chemical fertilizer (BSTR) on soil total organic carbon (TOC) fractions and carbon (C)-degrading enzyme activities across different soil depths (surface, sub-surface, and deep) during the tasseling (VT) and full maturity stage (R6) of maize. BSTR increased the TOC content within each soil layer during both VT and R6 periods, inducing alterations in the content and proportion of individual C component, particularly in the topsoil. Notably, the pure biogas slurry topdressing treatment (100%BS) compared with the pure chemical fertilizer topdressing treatment (CF), exhibited a 38.9% increase in the labile organic carbon of the topsoil during VT, and a 30.3% increase in the recalcitrant organic carbon during R6, facilitating microbial nutrient utilization and post-harvest C storage during the vigorous growth period of maize. Furthermore, BSTR treatment stimulated the activity of oxidative and hydrolytic C-degrading enzymes, with the 100%BS treatment showcasing the most significant enhancements, with its average geometric enzyme activity surpassing that of CF treatment by 27.9% and 27.4%, respectively. This enhancement facilitated ongoing and efficient degradation and transformation of C. Additionally, we screened for C components and C-degrading enzymes that are relatively sensitive to BSTR. The study highlight the advantages of employing pure biogas slurry topdressing, which enhances C component and C-degrading enzyme activity, thereby reducing the risk of soil degradation. This research lays a solid theoretical foundation for the rational recycling of biogas slurry.

Remediation of water tainted with noxious hexavalent chromium using cetylpyridinium-modified bagasse biomass: adsorption and regeneration studies.

Herein, cetylpyridinium-modified bagasse (SB-CPC) biomass was synthesized and applied for removal of noxious Cr(VI) ions from aqueous matrix. Batch mode analyses were conducted, and the results showed that SB-CPC adsorbent has a maximum uptake capacity (qm) of 70.5 ± 3.2 mg g-1 at 303 K. The adsorption isotherms and kinetics for elimination of Cr(VI) by SB-CPC were better fitted by Langmuir model and pseudo-second-order model, respectively. The occurrence of pseudo-second-order kinetic could be mainly influenced by the intra-particle diffusion mass transfer. Electrostatic attraction was the dominant underlying reaction mechanism followed by pore filing effect (minor). Thermodynamic study affirms the endothermic behavior and occurrence of physical adsorption process. SB-CPC adsorbent had exhibited an outstanding desorption-regeneration performance using NaOH solution; accordingly, it can practically be applied for remediation of wastewater tainted with Cr(VI) ions.

Synthesis of magnetic adsorbents from titanium gypsum and biomass wastes for enhanced phosphate removal.

A novel scheme was proposed to prepare magnetic adsorbents by co-pyrolysis of titanium gypsum (TiG) and agricultural biomass wastes for phosphate (P) recovery. Co-presence of biomass wastes could improve TiG decomposition in inert atmosphere to generate magnetic centers and active sites, and P adsorption correlated well with organic volatiles of biomass wastes. The adsorption process evolved from a biomass-controlled process to a TiG-controlled process when increasing the mass ratio of corncob above 10 %. The optimal adsorbent (i.e. GC10) exhibited higher P adsorption capacity (Qm 183 mg/g) than many previous adsorbents; moreover, it can be magnetically separated from water after P adsorption. Active sites including CaO, CaS and Fe3O4 were deemed as the main factors for P chemisorption and surface precipitation. Most of adsorbed P could be released continuously and slowly by dilute NaHCO3. These results highlight potential applications of TiG and biomass waste derived adsorbents in P purification and recovery.

Sustainable Strategy for Algae Biomass Waste Management via Development of Novel Bio-Based Thermoplastic Polyurethane Elastomers Composites.

This work concerns the waste management method of algae biomass wastes (ABW). For this purpose, we prepared bio-based thermoplastic polyurethane elastomer (bio-TPU) composites. Algae biomass wastes are derived from algal oil extraction of Chlorella vulgaris and from biomass of Enteromorpha and Zostera marina. ABWs were used in the bio-TPUs composites as a filler in the quantity of 1, 5, 10, and 15 wt.%. The bio-based composites were prepared via the in situ method. Polymer matrix was synthesized from a bio-based polyester polyol, diisocyanate mixture (composed of partially bio-based and synthetic diisocyanates), and bio-based 1,3 propanediol. In this study, the chemical structure, morphology, thermal and mechanical properties of prepared composites were investigated. Based on the conducted research, it was determined that the type and the content of algae waste influence the properties of the bio-based polyurethane matrix. In general, the addition of algae biomass wastes led to obtain materials characterized by good mechanical properties and noticeable positive ecological impact by increasing the total amount of green components in prepared bio-TPU-based composites from 68.7% to 73.54%.

Adsorption of multicomponent VOCs on various biomass-derived hierarchical porous carbon: A study on adsorption mechanism and competitive effect.

Biomass-derived porous carbon materials are potential adsorbents for VOCs. In this work, biomass-derived nitrogen-doped hierarchical porous carbons (NHPCs) were synthesized by a one-step pyrolysis activation combined with nitrogen doping method from several biomass wastes (corn straw, wheat stalk, bamboo, pine, and corncob). NHPCs have a hierarchical porous structure with micro-meso-macropores distribution, nitrogen doping, large specific surface area, and pore volume. The corncob derived carbon (NHPC-CC) has the best activation result as analyses showed that a lower ash content and higher total cellulose composition content of the biomass result in a better pore activation effect. Single and multi-component dynamic adsorption tests of typical VOCs (benzene, toluene, and chlorobenzene) were conducted on NHPCs in laboratory conditions (∼500 ppm). Promising VOC adsorption capacity and great adsorption kinetics with low mass transfer resistance were found on NHPCs. Correlation analysis showed that the high VOC adsorption capacity and great adsorption kinetics can be attributed to the large surface area of micro-mesopores and the mass transfer channels provided by meso-macropores respectively. The competitive dynamic adsorption tests revealed that the VOC with lower saturated vapor pressure has more adsorption sites on the surface of micro-mesopores and stronger adsorption force, which results in the higher adsorption capacity and desorption caused by substitution reaction in VOCs competitive adsorption process. In detail, the process of toluene and chlorobenzene competitive adsorption was described. Besides, well recyclability of NHPC-CC was revealed as the VOCs adsorption capacity reductions were less than 10% after four adsorption-desorption cycles. All studies showed that the NHPC-CC could be potential adsorbent for VOCs in industrial process.

Biomass-derived carbon nanomaterials for sensor applications.

In recent years, an increasing amount of attention has been paid to utilizing dedicated waste biomass as a sustainable, cheap, and abundant fuel and material source. There is a tremendous opportunity for maximizing energy production by applying different reliable waste biomass as a renewable, affordable, and excellent resource. As a result of renewable hydrocarbons such as biomass, bioenergy is produced, green chemicals are manufactured, and carbon materials are made. Furthermore, biomass can be utilized as a source of advanced carbon materials. Carbon materials derived from biomass can also be used to support catalysts in fuel cells with polymer electrolyte membranes. For the fabrication of electrochemical sensors, porous carbonaceous materials generated from biomass are highly advised owing to their specific qualities, including regenerative nature, affordability, distinctive structure, and sustainability. The surface morphology of the sensor, especially its pore volume, surface area, and pore size affects both its electrochemical and catalytic activity. Metal nanoparticle activation, doping, and dispersion are just a few of the methods that may be used to improve the performance of sensors. To detect a variety of target analytes, such as biomolecules, metal ions, contaminants, food additives, and flavonoids, some of the key or seminal advances in the field of biomass-derived carbonaceous compounds are discussed. The materials and composites made of biomass-derived carbon will be in-depth examined, evaluated, and compared in this review. The associated technological difficulties are also discussed, and future research areas are suggested for use in practical applications. Nano carbon materials have several integrated advantages, including good electrical conductivity, structural and chemical flexibility, reduced chemical functionalization, and bulk production potential, making them viable candidates for various electrochemical processes. In the coming years, bio-carbon production from waste biomass is expected to gain rapid scientific and industrial interest because it will be used in electrochemical devices and rechargeable batteries. We emphasize the variety of waste biomass precursors that are accessible, as well as the recent developments in the manufacture of bio-carbon. Carbonaceous nanoparticles generated from biomass have shown potential for use in fuel cells, bioimaging, medicinal delivery, carbon fixation, catalysis, and gas sensors. Interestingly, this article has covered these nanomaterials' new and innovative energy conversion and storage services. Finally, the remaining difficulties, perspective views, and potential research trajectories in the area are described.

Triple combination of natural microbial action, etching, and gas foaming to synthesize hierarchical porous carbon for efficient adsorption of VOCs.

Fungi residue, vinasse, and biogas residue differ from general biomass waste due to natural microbial action. Microbial fermentation helps create natural channels for the permeation of activators and produces proteins for natural nitrogen doping. Inspired by these advantages on porous carbon synthesis, this study adopted dual activators of KOH and KHCO3 to synthesize porous carbon with different pore ratios for efficient adsorption of volatile organic compounds (VOCs). The fungi residue possessed the least lignin due to the most severe microbial action, contributing to the best pore structures after activation. The etching effect from potassium compounds and gas foaming from the carbonate decomposition contributed to creating hierarchical porous carbon with ultra-high surface area, ca. 1536.8-2326.5 m2/g. However, KHCO3 addition also caused nitrogen erosion, such that lower adsorption capacity was attained even with a higher surface area when the mass ratio of KOH/KHCO3 decreased from 2.5:0.5 to 2:1. The maximum adsorption capacities of chlorobenzene (CB) and benzene (PhH) reached 594.0 and 394.3 mg/g, respectively. Pore structure variations after adsorption were evaluated by freeze treatment to discover the adsorption mechanism. The surface area after CB and PhH adsorption decreased 40.3% and 34.5%, respectively. Most of the mesopores might transform into micropores due to the mono/multilayer stacking of adsorbates. The VOC adsorption kinetics were simulated by the Pseudo-first- and -second-order models and Y-N model. This paper provides a new approach for high-value biomass waste utilization after microbial action to synthesize efficient adsorbents for VOCs.

Constructing N, P-dually doped biochar materials from biomass wastes for high-performance bifunctional oxygen electrocatalysts.

The large scale lignocellulosic biomass wastes could also be regarded as abundantly-available renewable resources, and how to convert them into value-added products via sustainable approaches is still a big challenge. In this work, we demonstrated a facile pyrolysis method to construct N, P-dually doped biochar materials from the lignocellulosic biomass wastes. The as-synthesized N, P-dually doped biochar samples could act as electrocatalysts for oxygen reduction and evolution reactions (ORR/OER), showing excellent catalytic performance and long-term durability, as well as robust tolerance to CO and methanol. The unique hierarchical porous structure, favorable electronic structure modified by the N and P doping, as well as a variety of defect sites induced by the N and P doping into the carbon framework were identified as the main contributions to the prominent catalytic activity of the as-synthesized N, P-dually doped biochar materials. We expect this work would spur more efforts into developing advanced materials from the large scale lignocellulosic biomass wastes.

Review and perspectives of enhanced volatile fatty acids production from acidogenic fermentation of lignocellulosic biomass wastes.

Lignocellulosic biomass wastes are abundant resources that are usually valorized for methane-rich biogas via anaerobic digestion. Conversion of lignocellulose into volatile fatty acids (VFA) rather than biogas is attracting attention due to the higher value-added products that come with VFA utilization. This review consolidated the latest studies associated with characteristics of lignocellulosic biomass, the effects of process parameters during acidogenic fermentation, and the intensification strategies to accumulate more VFA. The differences between anaerobic digestion technology and acidogenic fermentation technology were discussed. Performance-enhancing strategies surveyed included (1) alkaline fermentation; (2) co-digestion and high solid-state fermentation; (3) pretreatments; (4) use of high loading rate and short retention time; (5) integration with electrochemical technology, and (6) adoption of membrane bioreactors. The recommended operations include: mesophilic temperature (thermophilic for high loading rate fermentation), C/N ratio (20-40), OLR (< 12 g volatile solids (VS)/(L·d)), and the maximum HRT (8-12 days), alkaline fermentation, membrane technology or electrodialysis recovery. Lastly, perspectives were put into place based on critical analysis on status of acidogenic fermentation of lignocellulosic biomass wastes for VFA production.

Recent progress in the conversion of biomass wastes into functional materials for value-added applications.

The amount of biomass wastes is rapidly increasing, which leads to numerous disposal problems and governance issues. Thus, the recycling and reuse of biomass wastes into value-added applications have attracted more and more attention. This paper reviews the research on biomass waste utilization and biomass wastes derived functional materials in last five years. The recent research interests mainly focus on the following three aspects: (1) extraction of natural polymers from biomass wastes, (2) reuse of biomass wastes, and (3) preparation of carbon-based materials as novel adsorbents, catalyst carriers, electrode materials, and functional composites. Various biomass wastes have been collected from agricultural and forestry wastes, animal wastes, industrial wastes and municipal solid wastes as raw materials with low cost; however, future studies are required to evaluate the quality and safety of biomass wastes derived products and develop highly feasible and cost-effective methods for the conversion of biomass wastes to enable the industrial scale production.

A Review of Carbon Dots Produced from Biomass Wastes.

The fluorescent carbon dot is a novel type of carbon nanomaterial. In comparison with semiconductor quantum dots and fluorescence organic agents, it possesses significant advantages such as excellent photostability and biocompatibility, low cytotoxicity and easy surface functionalization, which endow it a wide application prospect in fields of bioimaging, chemical sensing, environmental monitoring, disease diagnosis and photocatalysis as well. Biomass waste is a good choice for the production of carbon dots owing to its abundance, wide availability, eco-friendly nature and a source of low cost renewable raw materials such as cellulose, hemicellulose, lignin, carbohydrates and proteins, etc. This paper reviews the main sources of biomass waste, the feasibility and superiority of adopting biomass waste as a carbon source for the synthesis of carbon dots, the synthetic approaches of carbon dots from biomass waste and their applications. The advantages and deficiencies of carbon dots from biomass waste and the major influencing factors on their photoluminescence characteristics are summarized and discussed. The challenges and perspectives in the synthesis of carbon dots from biomass wastes are also briefly outlined.

Valorization of palm biomass wastes for biodiesel feedstock and clean solid biofuel through non-sterile repeated solid-state fermentation.

Palm biomass wastes are currently considered as promising solid biofuels. However, their high potassium content leads to formation of slag in combustion chambers and causes frequent power-plant shutdowns for maintenance. Therefore, this study aimed to develop a low-cost practical biological pretreatment for these wastes. Oleaginous fungi Aspergillus tubingensis TSIP9, which originates from palm wastes, was used to pretreat biomass wastes and simultaneously produce oils through non-sterile solid state fermentation (SoSF). The operating conditions were optimized through response surface methodology. The fungi could grow and produce oils with good biodiesel fuel properties. After SoSF, potassium content in biomass wastes was reduced by 90% and cellulose content increased to >57%, making it suitable as clean solid biofuel. Repeated-SoSF with 90% substrate replacement was highly effective in continuously pretreating biomass wastes and producing fungal oils. This study demonstrates the cost-effective and environmentally friendly process for production of clean renewable energy through zero-waste strategy.

Kinetic analyses and synergistic effects of CO2 co-gasification of low sulphur petroleum coke and biomass wastes.

This study presents thermogravimetric analyses (TGA) of CO2 co-gasification of petroleum coke with low sulphur (PC) and various types of biomass wastes including agricultural (rice husk (RH), rice stalk (RS) and cotton straw (CS)) and by-product wastes (saw dust (SD) and sugar cane bagasse (SCB)). Their reactivities, synergistic effect and kinetics were studied and compared in detail. The homogeneous model (HM) and shrinking core models (SCM) were applied to estimate the kinetic parameters. The results indicated that obvious synergistic effect was observed during the co-gasification of the blends. The PC gasification reactivity was significantly improved by the addition of biomass wastes. The model of R2 was found to be most suitable for the co-gasification. The activation energy of PC was decrease from 293.72 kJ/mol to117.04 kJ/mol by the addition of SD. The co-gasification of PC and biomass waste is a promising way for the efficient utilization of PC and biomass wastes.

Characterization of biomass waste torrefaction under conventional and microwave heating.

To evaluate the potential of microwave heating for biomass torrefaction, the torrefaction performances and energy utilization of coffee grounds and microalga residue, under conventional and microwave heating were investigated and compared with each other. For the two biomass samples, the dehydrogenation of the coffee grounds was more sensitive to torrefaction severity, whereas the microalga residue consumed more energy under the same torrefaction conditions. Microwave heating under lower torrefaction severity had a higher energy efficiency. As regard to the lower solid yields or higher torrefaction severity, the energy efficiency of microwave heating was close to that of conventional heating, irrespective of the feedstocks. This revealed the comparable energy consumption state between the two heating modes. Accordingly, it is concluded that microwave torrefaction is more efficient for biomass upgrading and densification than conventional torrefaction.

Electric field-based technologies for valorization of bioresources.

This review provides an overview of recent research on electrotechnologies applied to the valorization of bioresources. Following a comprehensive summary of the current status of the application of well-known electric-based processing technologies, such as pulsed electric fields (PEF) and high voltage electrical discharges (HVED), the application of moderate electric fields (MEF) as an extraction or valorization technology will be considered in detail. MEF, known by its improved energy efficiency and claimed electroporation effects (allowing enhanced extraction yields), may also originate high heating rates - ohmic heating (OH) effect - allowing thermal stabilization of waste stream for other added-value applications. MEF is a simple technology that mostly makes use of green solvents (mainly water) and that can be used on functionalization of compounds of biological origin broadening their application range. The substantial increase of MEF-based plants installed in industries worldwide suggests its straightforward application for waste recovery.

Symmetric Supercapacitor Electrodes from KOH Activation of Pristine, Carbonized, and Hydrothermally Treated Melia azedarach Stones.

Waste biomass-derived activated carbons (ACs) are promising materials for supercapacitor electrodes due to their abundance and low cost. In this study, we investigated the potential use of Melia azedarach (MA) stones to prepare ACs for supercapacitors. The ash content was considerably lower in MA stones (0.7% ash) than that found in other lignocellulosic wastes. ACs were prepared by KOH activation of pristine, carbonized, and hydrothermally-treated MA stones. The morphology, composition, surface area, porosity, and surface chemistry of the ACs were determined. Electrochemical measurements were carried out in three- and two-electrode cells, 3EC and 2EC, respectively, using 1 M H2SO4 as the electrolyte. The highest capacitance from galvanostatic charge-discharge (GCD) in 2EC ranged between 232 and 240 F·g-1 at 1 A·g-1. The maximum energy density reached was 27.4 Wh·kg-1 at a power density of 110 W·kg-1. Electrochemical impedance spectroscopy (EIS) revealed an increase in equivalent series resistance (ESR) and charge transfer resistance (RCT) with greater ash content. Electrochemical performance of MA stone-derived ACs was compared with that of other ACs described in the recent literature that were prepared from different biomass wastes and results showed that they are among the best ACs for supercapacitor applications.

Improving biogas quality and methane yield via co-digestion of agricultural and urban biomass wastes.

Impact of co-digestion versus mono-digestion on biogas and CH4 yield for a set of five biomass materials (vegetable food waste, cow dung, pig manure, grass clippings, and chicken manure) was investigated considering 95 different biomass mixes of the five materials under thermophilic conditions in bench-scale batch experiments over a period of 65days. Average biogas and CH4 yields were significantly higher during co-digestion than during mono-digestion of the same materials. This improvement was most significant for co-digestion experiments involving three biomass types, although it was independent of the specific biomasses being co-digested. Improvement in CH4 production was further more prominent early in the digestion process during co-digestion compared to mono-digestion. Co-digestion also appeared to increase the ultimate CH4/CO2 ratio of the gas produced compared to mono-digestion although this tendency was relatively weak and not statistically significant.