Biomass and waste materials as potential sources of nanocrystalline cellulose: Comparative review of preparation methods (2016 - Till date)

Nanocellulose synthesis via synergistic application of solid acid and cellulase

Nanocellulose stands out in numerous applications due to its excellent properties. Yet, achieving its preparation in a cost-effective, efficient, and environmentally benign manner remains challenging. This study introduces a green synthesis approach by employing a non-polluting solid acid, combined with a cellulase enzyme, for nanocellulose production. We explored the impact of varying the addition sequence of solid acid and cellulase on nanocellulose yield. Experimental results showed that under optimal cellulase hydrolysis conditions, solid acid hydrolysis yielded 41.3 % nanocellulose, whereas cellulase hydrolysis resulted in a 27.1 % yield. In co-treatment experiments, with the following process steps: 1) sequential hydrolysis with solid acid, followed by cellulose (SA-E); 2) simultaneous hydrolysis with solid acid and cellulase (SA + E); 3) cellulase followed by solid acid hydrolysis (E-SA). the nanocellulose yields were: 73.37 %, 70.43 %, and 57.21 %, respectively. These results proved a synergistic effect between solid acid and cellulase in both SA-E and SA + E scenarios. In addition, the synergistic mechanism between solid acid and cellulase was proposed. This approach presents a highly promising strategy for achieving high yields of nanocellulose.

Surface modification of cellulose nanocrystals for biomedical and personal hygiene applications

The increasing demand for sustainable and effective materials in biomedical and personal hygiene applications has driven the exploration of cellulose nanocrystals (CNCs) derived from biomass. These nanomaterials are highly valued for their exceptional mechanical properties, biocompatibility, and renewable nature. Researchers are exploring CNCs for advancing medical and hygiene products, but surface modification is often needed to maximize their benefits. Techniques such as chemical functionalization, physical coating, and hybridization can significantly enhance CNCs dispersibility, stability, and interaction with biological systems. This versatility makes CNCs suitable for a variety of applications, including drug delivery systems, wound dressings, and personal hygiene products. Despite their advantages, maintaining the inherent properties of CNCs while integrating new functionalities through modification poses a challenge. Understanding the impact of various modification techniques on CNC performance is crucial for optimizing their effectiveness. This review aimed to consolidate current knowledge on the surface modification of biomass-derived CNCs, offering insights into different methods and their implications for biomedical and personal hygiene applications. By highlighting advancements, challenges, and prospects, it served as a crucial resource for advancing the development and application of CNCs in these critical fields.

Facile synthesis of a 3D magnetic graphene oxide/Fe3O4/banana peel-derived cellulose composite aerogel for the efficient removal of tetracycline

Many initiatives have incorporated graphene oxide (GO) and biomass into aerogels for wastewater treatment. We report on the facile fabrication of a magnetic GO/Fe3O4/banana peel-derived cellulose (bio-cellulose) aerogel using an ultrasound-assisted mechanical mixing method and freeze-drying technique for the removal of tetracycline (TC). The component materials and composite aerogel were characterized using Fourier-transform infrared spectroscopy (FTIR), X-ray powder diffraction (XRD), Raman spectroscopy, field-emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDX), nitrogen adsorption-desorption analysis, and vibrating sample magnetometry (VSM). The effects of solution pH and adsorbent dose on the adsorption performance of the synthesized adsorbents were investigated. The adsorption behavior at the equilibrium of the GO/Fe3O4/bio-cellulose aerogel was studied and analyzed using four well-known non-linear models: Langmuir, Freundlich, Sips, and Temkin. The results showed that the experimental data fitted well with the Freundlich and Sips isotherm models. The maximum adsorption capacity achieved from the Sips model was 238.7 mg g-1. The adsorption kinetics were studied and proved to follow the Elovich kinetic model with an initial rate of 0.89 g g-1 min-1. These results confirm the favorable adsorption of TC on the heterogeneous surface that exhibits a wide range distribution of adsorption energies of the desired GO/Fe3O4/bio-cellulose aerogel. The experimental findings demonstrate that the aerogel possesses the notable features of environmental friendliness, cost-effectiveness, and comparatively high TC adsorption capacity. Therefore, utilizing biomass to develop the structure of the magnetic GO-based composite aerogel is significantly promising for antibiotic-containing wastewater treatments.

New Excipient For Oral Drug Delivery: CNC Derived From Sugarcane Bagasse-Derived Microcrystalline Cellulose

Nanocrystalline cellulose (CNC) has emerged as a subject of researcher's interest because of its diverse attributes encompassing biocompatibility, sustainability, a high aspect ratio, and an abundance of -OH groups suitable for modifications. Sugarcane bagasse microcrystalline cellulose (SCBMCC) was used as the raw material for the preparation of CNC due to its pure cellulose content, which is mildly compromised by the pectin, hemicellulose, lignin, and other lignocellulosic components. In the present work, CNC was extracted from SCBMCC and used as a disintegrant. The classic hydrolysis technique was used for the preparation of CNC. Hydrolytic conditions were optimized using the response surface methodology (RSM). The optimized batch of CNC was characterized using techniques such as field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy. Notably, CNC prepared under a hydrolysis time of 90 min exhibited the highest crystallinity of 69.9%. The average particle size and zeta potential were found to be 145 nm and -34.4 mV, respectively. Thermal analysis suggested that an intermediate hydrolysis time resulted in CNC with enhanced thermal stability, showcasing its potential for pharmaceutical applications. Diclofenac potassium was used as the model drug to evaluate the disintegrant properties of CNC as an excipient. Tablets were prepared using the direct compression method. SCBMCC and CNC were used as disintegrants and were compared with the commercial product. The disintegration times (DTs) attained for the tablets prepared using CNC and SCBMCC are 219 and 339.83 s, respectively. The dissolution study of CNC showed a dissolution efficacy (DE%) of 66 and a mean dissolution time (MDT) of 12. The research findings showed that tablets prepared using CNC as disintegrants exhibited the fastest disintegration compared to other formulations.

Biocomposites of Cellulose Isolated from Coffee Processing By-Products and Incorporation in Poly(Butylene Adipate-Co-Terephthalate) (PBAT) Matrix: An Overview

With its extensive production and consumption, the coffee industry generates significant amounts of lignocellulosic waste. This waste, primarily comprising coffee biomasses, is a potential source of cellulose. This cellulose can be extracted and utilized as a reinforcing agent in various biocomposites with polymer matrices, thereby creating high-value products. One such biodegradable polymer, Poly(butylene adipate-co-terephthalate) (PBAT), is notable for its properties that are comparable with low-density polyethylene, making it an excellent candidate for packaging applications. However, the wider adoption of PBAT is hindered by its relatively high cost and lower thermomechanical properties compared with conventional, non-biodegradable polymers. By reinforcing PBAT-based biocomposites with cellulose, it is possible to enhance their thermomechanical strength, as well as improve their water vapor and oxygen barrier capabilities, surpassing those of pure PBAT. Consequently, this study aims to provide a comprehensive review of the latest processing techniques for deriving cellulose from the coffee industry's lignocellulosic by-products and other coffee-related agro-industrial wastes. It also focuses on the preparation and characterization of cellulose-reinforced PBAT biocomposites.

Synthesis of cellulose nanofibers from jute fiber by using chemomechanical method

Background

Jute fiber is one of the most versatile natural fibers that is widely used as a raw material for packaging, textiles, and construction; and as a reinforcement in composite materials for heavy-duty applications. In the past, acid hydrolysis and mechanical treatment via the ball milling method were common in the extraction of cellulose nanofiber (CNFs) from natural plant fibers. However, there are some drawbacks of using those methods where there will be a huge quantity of acidic wastewater generated when the acid hydrolysis method is performed.

Method

This study investigated the potential use of a combination of chemical and mechanical methods in the extraction of jute CNFs. Through this method, the jute fibers were first chemically treated using sodium hydroxide (NaOH), sodium chlorite (NaClO 2) and sulphuric acid (H 2SO 4) to remove the non-cellulosic elements followed by mechanical milling by using a planetary ball mill.

Results

The shape and size of the obtained CNFs were observed under a field emission scanning electron microscope (FESEM). This study revealed that jute CNFs were successfully extracted through the combination of chemical and mechanical treatment methods where the obtained CNFs reveal themselves in smooth fibrous morphology with a diameter of 23 nm and 150-200nm in length.

Conclusions

Jute cellulose nanofibers were successfully drawn out from raw jute fibers by means of a combination of chemical and mechanical treatment. The results obtained confirmed that the chemomechanical method is an effective technique for isolating the CNFs and its potential use as reinforcement material was explained.

Biochar production and its environmental applications: Recent developments and machine learning insights

Biochar production through thermochemical processing is a sustainable biomass conversion and waste management approach. However, commercializing biochar faces challenges requiring further research and development to maximize its potential for addressing environmental concerns and promoting sustainable resource management. This comprehensive review presents the state-of-the-art in biochar production, emphasizing quantitative yield and qualitative properties with varying feedstocks. It discusses the technology readiness level and commercialization status of different production strategies, highlighting their environmental and economic impacts. The review focuses on integrating machine learning algorithms for process control and optimization in biochar production, improving efficiency. Additionally, it explores biochar's environmental applications, including soil amendment, carbon sequestration, and wastewater treatment, showcasing recent advancements and case studies. Advances in biochar technologies and their environmental benefits in various sectors are discussed herein.

Design of Bifunctional Nanocatalysts Based on Zeolites for Biomass Processing

Bifunctional catalysts consisting of metal-containing nanoparticles (NPs) and zeolite supports have received considerable attention due to their excellent catalytic properties in numerous reactions, including direct (biomass is a substrate) and indirect (platform chemical is a substrate) biomass processing. In this short review, we discuss major approaches to the preparation of NPs in zeolites, concentrating on methods that allow for the best interplay (synergy) between metal and acid sites, which is normally achieved for small NPs well-distributed through zeolite. We focus on the modification of zeolites to provide structural integrity and controlled acidity, which can be accomplished by the incorporation of certain metal ions or elements. The other modification avenue is the adjustment of zeolite morphology, including the creation of numerous defects for the NP entrapment and designed hierarchical porosity for improved mass transfer. In this review, we also provide examples of synergy between metal and acid sites and emphasize that without density functional theory calculations, many assumptions about the interactions between active sites remain unvalidated. Finally, we describe the most interesting examples of direct and indirect biomass (waste) processing for the last five years.

Cellulose nanocrystalline from biomass wastes: An overview of extraction, functionalization and applications in drug delivery

Cellulose nanocrystals (CNC) have been extensively used in various fields due to their renewability, excellent biocompatibility, large specific surface area, and high tensile strength. Most biomass wastes contain significant amounts of cellulose, which forms the basis of CNC. Biomass wastes are generally made up of agricultural waste, and forest residues, etc. CNC can be produced from biomass wastes by removing the non-cellulosic components through acid hydrolysis, enzymatic hydrolysis, oxidation hydrolysis, and other mechanical methods. However, biomass wastes are generally disposed of or burned in a random manner, resulting in adverse environmental consequences. Hence, using biomass wastes to develop CNC-based carrier materials is an effective strategy to promote the high value-added application of biomass wastes. This review summarizes the advantages of CNC applications, the extraction process, and recent advances in CNC-based composites, such as aerogels, hydrogels, films, and metal complexes. Furthermore, the drug release characteristics of CNC-based material are discussed in detail. Additionally, we discuss some gaps in our understanding of the current state of knowledge and potential future directions of CNC-based materials.

Biomass carbon mining to develop nature-inspired materials for a circular economy

A transition from a linear to a circular economy is the only alternative to reduce current pressures in natural resources. Our society must redefine our material sources, rethink our supply chains, improve our waste management, and redesign materials and products. Valorizing extensively available biomass wastes, as new carbon mines, and developing biobased materials that mimic nature's efficiency and wasteless procedures are the most promising avenues to achieve technical solutions for the global challenges ahead. Advances in materials processing, and characterization, as well as the rise of artificial intelligence, and machine learning, are supporting this transition to a new materials' mining. Location, cultural, and social aspects are also factors to consider. This perspective discusses new alternatives for carbon mining in biomass wastes, the valorization of biomass using available processing techniques, and the implementation of computational modeling, artificial intelligence, and machine learning to accelerate material's development and process engineering.

Preparation and research of PCL/cellulose composites: Cellulose derived from agricultural wastes

For the rational use of agricultural wastes, bagasse, orange peel and wheat bran were used to fabricate bio-based polymer materials. Cellulose was extracted from the three different agricultural wastes, and poly(ε-caprolactone) (PCL) was used as the matrix material. PCL was mixed with nanocrystalline cellulose (CNC), extracted bagasse cellulose (GC), orange peel cellulose (JC) and wheat bran cellulose (MC) by solution casting. Morphology and structure of the extracted cellulose were studied by Scanning Electron Microscope, Fourier Infrared spectrometer, thermogravimetry and X-ray diffractometer. The influence of GC, JC, MC on the crystallization process and mechanical properties of PCL was investigated by DSC and tensile test. Experimental results show that the addition of CNC, GC, JC, MC increases the crystallization temperature of PCL, accelerates the crystallization process of PCL, and improves the tensile property of PCL.

Banana Peel Waste: An Emerging Cellulosic Material to Extract Nanocrystalline Cellulose

Nanocrystalline cellulose (NCC) has gained attention due to its versatile properties such as biocompatibility, sustainability, high aspect ratio, and abundance of -OH groups that favor modifications of NCC. The objective of this paper is to develop NCC by extracting and characterizing NCC prepared from banana peel powder (BPP). BPP was subjected to alkali and bleaching treatment to remove lignin and hemicellulose and then subjected to acid hydrolysis to prepare NCC. Under optimal conditions (200 mL of sulfuric acid 55% v/v at 50 °C for 60 min), the NCC yield was found to be 29.9%. The particle size and zeta potential of the NCC were found to be 209 nm and -43 mV, respectively. Attenuated total reflectance Fourier transform infrared spectroscopy showed successful removal of lignin and hemicellulose from BPP after the alkali treatment, bleaching, and acid hydrolysis. Field emission scanning electron microscopy showed needle-shaped crystals and transmission electron microscopy showed particles in the nano range. X-ray diffraction analysis showed that the crystallinity index of NCC was 64.12% while keeping the cellulose I crystal structure intact. Thermogravimetric analysis showed good stability which paves way for NCC to be explored for various applications. All the parameters evaluated indicated that NCC was successfully prepared from BPP using alkali treatment, bleaching, and acid hydrolysis.

Recent Progress on Tailoring the Biomass-Derived Cellulose Hybrid Composite Photocatalysts

Biomass-derived cellulose hybrid composite materials are promising for application in the field of photocatalysis due to their excellent properties. The excellent properties between biomass-derived cellulose and photocatalyst materials was induced by biocompatibility and high hydrophilicity of the cellulose components. Biomass-derived cellulose exhibited huge amount of electron-rich hydroxyl group which could promote superior interaction with the photocatalyst. Hence, the original sources and types of cellulose, synthesizing methods, and fabrication cellulose composites together with applications are reviewed in this paper. Different types of biomasses such as biochar, activated carbon (AC), cellulose, chitosan, and chitin were discussed. Cellulose is categorized as plant cellulose, bacterial cellulose, algae cellulose, and tunicate cellulose. The extraction and purification steps of cellulose were explained in detail. Next, the common photocatalyst nanomaterials including titanium dioxide (TiO2), zinc oxide (ZnO), graphitic carbon nitride (g-C3N4), and graphene, were introduced based on their distinct structures, advantages, and limitations in water treatment applications. The synthesizing method of TiO2-based photocatalyst includes hydrothermal synthesis, sol-gel synthesis, and chemical vapor deposition synthesis. Different synthesizing methods contribute toward different TiO2 forms in terms of structural phases and surface morphology. The fabrication and performance of cellulose composite catalysts give readers a better understanding of the incorporation of cellulose in the development of sustainable and robust photocatalysts. The modifications including metal doping, non-metal doping, and metal-organic frameworks (MOFs) showed improvements on the degradation performance of cellulose composite catalysts. The information and evidence on the fabrication techniques of biomass-derived cellulose hybrid photocatalyst and its recent application in the field of water treatment were reviewed thoroughly in this review paper.

Deep Eutectic Solvents: Alternative Solvents for Biomass-Based Waste Valorization

Innovative technologies can transform what are now considered "waste streams" into feedstocks for a range of products. Indeed, the use of biomass as a source of biopolymers and chemicals currently has a consolidated economic dimension, with well-developed and regulated markets, in which the evaluation of the manufacturing processes relies on specific criteria such as purity and yield, and respects defined regulatory parameters for the process safety. In this context, ionic liquids and deep eutectic solvents have been proposed as environmentally friendly solvents for applications related to biomass waste valorization. This mini-review draws attention to some recent advancements in the use of a series of new-solvent technologies, with an emphasis on deep eutectic solvents (DESs) as key players in the development of new processes for biomass waste valorization. This work aims to highlight the role and importance of DESs in the following three strategic areas: chitin recovery from biomass and isolation of valuable chemicals and biofuels from biomass waste streams.

Investigation of the Structural, Thermal, and Physicochemical Properties of Nanocelluloses Extracted From Bamboo Shoot Processing Byproducts

Nanocellulose has gained increasing interest due to its excellent properties and great potential as a functional component or carrier in food and pharmaceutical industries. This study investigated the structural, thermal, and physicochemical properties of nanofibrillated cellulose (NFC) and nanocrystalline cellulose (CNC) extracted from bamboo shoot (Leleba oldhami Nakal) processing byproducts. NFCs were prepared through low concentration acid hydrolysis combined with ultrasonic treatment. CNCs were further isolated from NFCs using sulfuric acid hydrolysis treatment. TEM images showed that NFC and CNC exhibited typical long-chain and needle-like structures, respectively. CNC suspension was stable due to its zeta potential of -34.3 ± 1.23 mV. As expected, both NFC and CNC displayed high crystallinity indexes of 68.51 and 78.87%, and FTIR analysis confirmed the successful removal of lignin and hemicellulose during the treatments. However, the thermogravimetric analysis indicated that sulfuric acid hydrolysis decreased the thermal stability of CNCs. The improved physicochemical properties of NFC and CNC suggested their potential in various applications.

Lignocellulosic Biomass Waste-Derived Cellulose Nanocrystals and Carbon Nanomaterials: A Review

Rapid population and economic growth, excessive use of fossil fuels, and climate change have contributed to a serious turn towards environmental management and sustainability. The agricultural sector is a big contributor to (lignocellulosic) waste, which accumulates in landfills and ultimately gets burned, polluting the environment. In response to the current climate-change crisis, policymakers and researchers are, respectively, encouraging and seeking ways of creating value-added products from generated waste. Recently, agricultural waste has been regularly appearing in articles communicating the production of a range of carbon and polymeric materials worldwide. The extraction of cellulose nanocrystals (CNCs) and carbon quantum dots (CQDs) from biomass waste partially occupies some of the waste-recycling and management space. Further, the new materials generated from this waste promise to be effective and competitive in emerging markets. This short review summarizes recent work in the area of CNCs and CQDs synthesised from biomass waste. Synthesis methods, properties, and prospective application of these materials are summarized. Current challenges and the benefits of using biomass waste are also discussed.

Bio-nano-composites containing at least two components, chitosan and zein, for food packaging applications: A review of the nano-composites in comparison with the conventional counterparts

Both chitosan and zein are safe industrial biopolymers for the 21St century, respecting environmentally concerns. This review mainly is focused on preparations, properties and applications of a promising food packaging material, chitosan-zein nano-composite (NC). The properties and applications of the NCs were compared with their conventional counterparts. The structure of chitosan- zein composites was proposed. A procedure for preparations of conventional and nano zein-chitosan composites was proposed. The sizes of composites depend on molecular weight of chitosan and zein, the ratio of chitosan/zein, and pH of chitosan-zein solutions. The NCs had superior mechanical, antimicrobial, antioxidant, and barrier properties compared with the conventional ones. The properties of the composites were further improved by introduction of bioactive compounds, fillers or plasticizers. The composites have potential to employ as coatings/packaging materials to protect mushroom, meats, and fresh fruits and vegetables.

A critical review on the techniques used for the synthesis and applications of crystalline cellulose derived from agricultural wastes and forest residues

In order to meet the growing energy crisis of the 21st century, the utilization of bio-based materials has become a field of high research endeavour. In view of that, the present review paper is focused on different techniques that are frequently explored for the synthesis of value-added crystalline derivatives of cellulose like MCC and NCC from agricultural wastes and forest residues. Moreover, a comparative analysis between thermochemical and biochemical methods is carried out for such valorization of biomass considering the mechanism involved with various reactions. Further, a critical analysis is performed on various individual techniques specifically used for the applications of MCC and NCC in different fields including environmental, polymer industry, pharmaceutical and other emerging sectors. This article will assist the readers not only to explore new biomass sources but also provides an in-depth insight on various green and cost-effective methods for sustainable production of crystalline cellulose.

High yielding, one-step mechano-enzymatic hydrolysis of cellulose to cellulose nanocrystals without bulk solvent

Traditional methods of enzymatic hydrolysis of cellulose to cellulose nanocrystals (CNCs) are limited due to the low enzymatic efficiency and large amount of waste liquid. The purpose of this study is to improve the yield and production efficiency of CNCs by enzymatic hydrolysis. A one-step mechano-enzymatic hydrolysis method was developed by utilizing the synergy of wet grinding and enzymatic hydrolysis reaction to efficiently prepare CNCs. Under the optimal reaction conditions, the maximum CNCs yield of 49.3% was achieved with higher thermal stability and crystallinity index of 76.7%. Mechano-enzymatic hydrolysis followed the first order pseudo-kinetics, and fractal kinetics demonstrated that mechanical force of rotation speed affected the fractal dimensions and binding ability between substrate and enzyme. This study provides an alternative method to prepare CNCs, which can significantly avoid the use of bulk water, improve the production efficiency of CNCs and thus lower the production cost.

A review of nanocellulose as a new material towards environmental sustainability

Synthetic polymers, commonly referred to as plastics, are anthropogenic contaminants that adversely affect the natural ecosystems. The continuous disposal of long lifespan plastics has resulted in the accumulation of plastic waste, leading to significant pollution of both marine and terrestrial habitats. Scientific pursuit to seek environment-friendly materials from renewable resources has focused on cellulose, the primary reinforcement component of the cell wall of plants, as it is the most abundantly available biopolymer on earth. This paper provides an overview on the current state of science on nanocellulose research; highlighting its extraction procedures from lignocellulosic biomass. Literature shows that the process used to obtain nanocellulose from lignocellulosic biomass greatly influences its morphology, properties and surface chemistry. The efficacy of chemical methods that use alkali, acid, bleaching agents, ionic liquids, deep eutectic solvent for pre-treatment of biomass is discussed. There has been a continuous endeavour to optimize the pre-treatment protocol as it is specific to lignocellulosic biomass and also depends on factors such as nature of the biomass, process and environmental parameters and economic viability. Nanofibers are primarily isolated through mechanical fibrillation while nanocrystals are predominantly extracted using acid hydrolysis. A concise overview on the ways to improve the yield of nanocellulose from cellulosic biomass is also presented in this review. This work also reviews the techniques used to modify the surface properties of nanocellulose by functionalizing surface hydroxyl groups to impart desirable hydrophilic-hydrophobic balance. An assessment on the emerging application of nanocellulose with an emphasis on development of nanocomposite materials for designing environmentally sustainable products is incorporated. Finally, the status of the industrial production of nanocellulose presented, which indicates that there is a continuously increased demand for cellulose nanomaterials. The demand for cellulose is expected to increase further due to its increasing and broadening applications.

Approaches in Animal Proteins and Natural Polysaccharides Application for Food Packaging: Edible Film Production and Quality Estimation

Natural biopolymers are an interesting resource for edible films production, as they are environmentally friendly packaging materials. The possibilities of the application of main animal proteins and natural polysaccharides are considered in the review, including the sources, structure, and limitations of usage. The main ways for overcoming the limitations caused by the physico-chemical properties of biopolymers are also discussed, including composites approaches, plasticizers, and the addition of crosslinking agents. Approaches for the production of biopolymer-based films and coatings are classified according to wet and dried processes and considered depending on biopolymer types. The methods for mechanical, physico-chemical, hydration, and uniformity estimation of edible films are reviewed.

Sustainable isolation of nanocellulose from cellulose and lignocellulosic feedstocks: Recent progress and perspectives

As a type of sustainable nanomaterials, nanocellulose has drawn increasing attention over the last two decades due to its great potential in diverse value-added applications such as electronics, sensors, energy storage, packaging, pharmaceuticals, biomedicine, and functional food. Sourcing nanocellulose from lignocellulose is commonly accomplished via the use of mineral acids, oxidizers, enzymes, and/or intensive mechanical energy. Yet, the economic and environmental concerns associated with these conventional isolation techniques pose major obstacles for commercialization. Considerable progress has been achieved in the last few years in developing sustainable nanocellulose isolation technologies involving organic acid/anhydride, Lewis acid, solid acid, ionic liquid, and deep eutectic solvent. This paper provides a comprehensive review of these alternatives with regard to general procedures and key advantages. Important knowledge gaps, including total biomass utilization, complete life cycle analysis, and health/safety, require urgently bridging in order to develop economically competitive and operationally feasible nanocellulose isolation technology for commercialization.

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.

Comparative Study on Pretreatment Processes for Different Utilization Purposes of Switchgrass

Switchgrass (Panicum virgatum, L., Poaceae) with the advantages of high cellulose yield, and high growth even under low input and poor soil quality, has been identified as a promising candidate for production of low-cost biofuels, papermaking, and nanocellulose. In this study, 12 chemical pretreatments on a laboratory scale were compared for different utilization purposes of switchgrass. It was found that the pretreated switchgrass with sodium hydroxide showed considerable potential for providing mixed sugars for fermentation with 11.10% of residual lignin, 53.85% of residual cellulose, and 22.06% of residual hemicellulose. The pretreatment with 2.00% (v/v) nitric acid was the best method to remove 78.37% of hemicellulose and 39.82% of lignin under a low temperature (125 °C, 30 min), which can be used in the production of nanocellulose. Besides, a completely randomized design analysis of switchgrass pretreatments provided the alternative ethanol organosolv delignification of switchgrass for the papermaking industry with a high residual cellulose of 58.56%. Finally, scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier-transform infrared spectroscopy (FT-IR) were carried out to confirm the changes in functional groups, crystallinity, and thermal behavior of the three materials, respectively, from the optimal pretreatments.

Extending Cellulose-Based Polymers Application in Additive Manufacturing Technology: A Review of Recent Approaches

The materials for additive manufacturing (AM) technology have grown substantially over the last few years to fulfill industrial needs. Despite that, the use of bio-based composites for improved mechanical properties and biodegradation is still not fully explored. This limits the universal expansion of AM-fabricated products due to the incompatibility of the products made from petroleum-derived resources. The development of naturally-derived polymers for AM materials is promising with the increasing number of studies in recent years owing to their biodegradation and biocompatibility. Cellulose is the most abundant biopolymer that possesses many favorable properties to be incorporated into AM materials, which have been continuously focused on in recent years. This critical review discusses the development of AM technologies and materials, cellulose-based polymers, cellulose-based three-dimensional (3D) printing filaments, liquid deposition modeling of cellulose, and four-dimensional (4D) printing of cellulose-based materials. Cellulose-based AM material applications and the limitations with future developments are also reviewed.

Cellulose Nanocrystals/Graphene Hybrids-A Promising New Class of Materials for Advanced Applications

With the growth of global fossil-based resource consumption and the environmental concern, there is an urgent need to develop sustainable and environmentally friendly materials, which exhibit promising properties and could maintain an acceptable level of performance to substitute the petroleum-based ones. As elite nanomaterials, cellulose nanocrystals (CNC) derived from natural renewable resources, exhibit excellent physicochemical properties, biodegradability and biocompatibility and have attracted tremendous interest nowadays. Their combination with other nanomaterials such as graphene-based materials (GNM) has been revealed to be useful and generated new hybrid materials with fascinating physicochemical characteristics and performances. In this context, the review presented herein describes the quickly growing field of a new emerging generation of CNC/GNM hybrids, with a focus on strategies for their preparation and most relevant achievements. These hybrids showed great promise in a wide range of applications such as separation, energy storage, electronic, optic, biomedical, catalysis and food packaging. Some basic concepts and general background on the preparation of CNC and GNM as well as their key features are provided ahead.

Nanocellulose: From Fundamentals to Advanced Applications

Over the past few years, nanocellulose (NC), cellulose in the form of nanostructures, has been proved to be one of the most prominent green materials of modern times. NC materials have gained growing interests owing to their attractive and excellent characteristics such as abundance, high aspect ratio, better mechanical properties, renewability, and biocompatibility. The abundant hydroxyl functional groups allow a wide range of functionalizations via chemical reactions, leading to developing various materials with tunable features. In this review, recent advances in the preparation, modification, and emerging application of nanocellulose, especially cellulose nanocrystals (CNCs), are described and discussed based on the analysis of the latest investigations (particularly for the reports of the past 3 years). We start with a concise background of cellulose, its structural organization as well as the nomenclature of cellulose nanomaterials for beginners in this field. Then, different experimental procedures for the production of nanocelluloses, their properties, and functionalization approaches were elaborated. Furthermore, a number of recent and emerging uses of nanocellulose in nanocomposites, Pickering emulsifiers, wood adhesives, wastewater treatment, as well as in new evolving biomedical applications are presented. Finally, the challenges and opportunities of NC-based emerging materials are discussed.

Preparation of Nanocellulose Using Ionic Liquids: 1-Propyl-3-Methylimidazolium Chloride and 1-Ethyl-3-Methylimidazolium Chloride

Cellulose nanocrystals were prepared using ionic liquids (ILs), 1-ethyl-3-methylimidazolium chloride [EMIM][Cl] and 1-propyl-3-methylimidazolium chloride [PMIM][Cl], from microcrystalline cellulose. The resultant samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), dynamic light scattering (DLS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The XRD results showed that nanocellulose obtained by treatment with both ILs preserved basic cellulose I structure, but crystallinity index of samples (except for Sigmacell treated with [EMIM][Cl]) was lower in comparison to the starting microcrystalline cellulose. The DLS results indicated noticeably smaller particle sizes of prepared cellulose for material treated with [PMIM][Cl] compared to cellulose samples hydrolyzed with [EMIM][Cl], which were prone to agglomeration. The obtained nanocellulose had a rod-like structure that was confirmed by electron microscopy analyses. Moreover, the results described in this paper indicate that cation type of ILs influences particle size and morphology of cellulose after treatment with ionic liquids.

Waste biomass valorization through production of xylose-based porous carbon microspheres for supercapacitor applications

Sequential potassium hydroxide (KOH)-phosphoric acid (H3PO4) activation was applied to biomass waste to fabricate activated carbon microspheres (mCMs) with a controllable porous structure. Carbon microspheres (CMs) were first synthesized from xylose using a bottom-up approach of hydrothermal carbonization. Sequential KOH and H₃PO₄ activation was applied to the CMs in a KOH-carbon solid reaction. This created pores, which were further enlarged by adsorption of H₃PO₄. The KOH:carbon (C) and H₃PO₄:C molar ratios, and the H₃PO₄ heating rate and activation time, were varied to investigate the effect on average pore size and pore distribution. A uniform porous structure was formed without destruction of the spherical shape, and an almost 700-fold increase in surface area was obtained over the non-activated CMs. Following activation with H₃PO₄, phosphorous groups were found to be present at the surface of the carbon microspheres. The mCM was tested as a supercapacitor electrode and was shown to have a maximum specific capacitance of up to 277F g^-1. A Ragone plot showed the maximum power density to be 173.88 W Kg^-1. This increased specific capacitance was attributed to the increase in surface area and the presence of phosphorous-containing acid sites on the material surface.

Microbial dynamics for lignocellulosic waste bioconversion and its importance with modern circular economy, challenges and future perspectives

An extensive use of microbial dynamics for utilizing the lignocellulosic wastes has been attributed to their efficiency in bioenergy and bioproducts development as a cost effective high nutritional value. The integration of lignocellulosic waste into the circular economy can scaleup the sustainable bioproducts and bioenergy development. In this review paper, the aim is to describe the existing research efforts on organic lignocellulosic waste, cellulase producing microbes, their potential enzyme, modern circular economy with associated challenges and future perspectives. Presently, it has been reviewed that microbial cellulases have provided treasure bioproducts visions into industrial bioproducts marvels unveiled through lignocellulosic waste cutting-edge microbial explorations. Furthermore, the review focused on new insights of the growing circular economy of lignocellulosic waste used for many bioproducts and bioenergy dealings and explored the emergent lignocellulosic biorefinery approaches which could then be applied to review industrial-scale sustainable economic models for upgraded bioproducts and other production associated problems.

The Effect of Nanofillers on the Functional Properties of Biopolymer-based Films: A Review

Waste from non-degradable plastics is becoming an increasingly serious problem. Therefore, more and more research focuses on the development of materials with biodegradable properties. Bio-polymers are excellent raw materials for the production of such materials. Bio-based biopolymer films reinforced with nanostructures have become an interesting area of research. Nanocomposite films are a group of materials that mainly consist of bio-based natural (e.g., chitosan, starch) and synthetic (e.g., poly(lactic acid)) polymers and nanofillers (clay, organic, inorganic, or carbon nanostructures), with different properties. The interaction between environmentally friendly biopolymers and nanofillers leads to the improved functionality of nanocomposite materials. Depending on the properties of nanofillers, new or improved properties of nanocomposites can be obtained such as: barrier properties, improved mechanical strength, antimicrobial, and antioxidant properties or thermal stability. This review compiles information about biopolymers used as the matrix for the films with nanofillers as the active agents. Particular emphasis has been placed on the influence of nanofillers on functional properties of biopolymer films and their possible use within the food industry and food packaging systems. The possible applications of those nanocomposite films within other industries (medicine, drug and chemical industry, tissue engineering) is also briefly summarized.