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Plastic pollution is a global environmental threat with potentially irreversible impacts on aquatic life, ecosystems, and human health. This study is a comprehensive assessment of the global apparel industry's contribution to plastic pollution. It includes plastic leakage of packaging and end-of-life apparel waste in addition to fiber emissions during apparel production and use. We estimate that the apparel industry generated 8.3 [4.8-12.3] million tons (Mt) of plastic pollution in 2019, corresponding to 14% [5.5%-30%] of the estimated 60 Mt from all sectors. In this study, we demonstrate that the main source of plastic pollution from the apparel supply chain is synthetic clothing as mismanaged waste either in the country of its original use or in the countries receiving used apparel exports. A fundamental transformation of the apparel economy towards a circular framework and decreased synthetic apparel consumption is needed to tackle apparel-related plastic pollution., (© 2024. The Author(s).)

Paper sludge biomass represents an underutilized feedstock rich in pulped and processed cellulose which is currently a waste stream with significant disposal cost to industry for landfilling services. Effective fractionation of the cellulose from paper sludge presents an opportunity to yield cellulose as feedstock for value-added processes. A novel approach to cellulose fractionation is the sidehill screening system, herein studied at the pilot-plant scale. Composition analysis determined ash removal and carbohydrate retention of both sidehill and high-performance benchtop screening systems. Sidehill screening resulted in greater carbohydrates retention relative to benchtop screening (90% vs 66%) and similar ash removal (95% vs 98%). Techno-economic analysis for production of sugar syrup yielded a minimum selling price of $331/metric ton of sugar syrup including disposal savings, significantly less than a commercial sugar syrup without fractionation. Sensitivity analysis showed that screening conditions played a significant role in economic feasibility for cellulosic yield and downstream processes., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Optimizing drying energy in the forest products industry is critical for integrating lignocellulosic feedstocks across all manufacturing sectors. Despite substantial efforts to reduce thermal energy consumption during drying, further enhancements are possible. Cellulose, the main component of forest products, is Earth's most abundant biopolymer and a promising renewable feedstock. This study employs all-atom molecular dynamics (MD) simulations to explore the structural dynamics of a small I β -cellulose microcrystallite and surrounding water layers during drying. Molecular and atomistic profiles revealed localized water near the cellulose surface, with water structuring extending beyond 8 Å into the water bulk, influencing solvent-accessible surface area and solvation energy. With increasing temperature, there was a ∼20 % reduction in the cellulose surface available for interaction with water molecules, and a ∼22 % reduction in solvation energy. The number of hydrogen bonds increased with thicker water layers, facilitated by a "bridging" effect. Electrostatic interactions dominated the intermolecular interactions at all temperatures, creating an energetic barrier that hinders water removal, slowing the drying processes. Understanding temperature-dependent cellulose-water interactions at the molecular level will help in designing novel strategies to address drying energy consumption, advancing the adoption of lignocellulosics as viable manufacturing feedstocks., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Efficient utilization of forestry, agriculture, and marine resources in various manufacturing sectors requires optimizing fiber transformation, dewatering, and drying energy consumption. These processes play a crucial role in reducing the carbon footprint and boosting sustainability within the circular bioeconomy framework. Despite efforts made in the paper industry to enhance productivity while conserving resources and energy through lower grammage and higher machine speeds, reducing thermal energy consumption during papermaking remains a significant challenge. A key approach to address this challenge lies in increasing dewatering of the fiber web before entering the dryer section of the paper machine. Similarly, the production of high-value-added products derived from alternative lignocellulosic feedstocks, such as nanocellulose and microalgae, requires advanced dewatering techniques for techno-economic viability. This critical and systematic review aims to comprehensively explore the intricate interactions between water and lignocellulosic surfaces, as well as the leading technologies used to enhance dewatering and drying. Recent developments in technologies to reduce water content during papermaking, and advanced dewatering techniques for nanocellulosic and microalgal feedstocks are addressed. Existing research highlights several fundamental and technical challenges spanning from the nano- to macroscopic scales that must be addressed to make lignocellulosics a suitable feedstock option for industry. By identifying alternative strategies to improve water removal, this review intends to accelerate the widespread adoption of lignocellulosics as feasible manufacturing feedstocks. Moreover, this review aims to provide a fundamental understanding of the interactions, associations, and bonding mechanisms between water and cellulose fibers, nanocellulosic materials, and microalgal feedstocks. The findings of this review shed light on critical research directions necessary for advancing the efficient utilization of lignocellulosic resources and accelerating the transition towards sustainable manufacturing practices., Competing Interests: Declaration of Competing Interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Lokendra Pal reports financial support was provided by Alliance for Pulp and Paper Technology Innovation (APPTI)., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Lignocellulosic materials are widely used for food packaging due to their renewable and biodegradable nature. However, their porous and absorptive properties can lead to the uptake and retention of bacteria during food processing, transportation, and storage, which pose a potential risk for outbreaks of foodborne disease. Thus, it is of great importance to understand how bacteria proliferate and survive on lignocellulosic surfaces. The aim of this research was to compare the growth and survivability of Salmonella Typhimurium and Listeria innocua on bleached and unbleached paper packaging materials. Two different paper materials were fabricated to simulate linerboard from fully bleached and unbleached market pulps and inoculated with each bacterium at high bacterial loads (10 7 CFU). The bacteria propagated during the first 48 h of incubation and persisted at very high levels (>10 7 CFU/cm 2 ) for 40 days for all paper and bacterium types. However, the unbleached paper allowed for a greater degree of bacterial growth to occur compared to bleached paper, suspected to be due to the more hydrophobic nature of the unbleached, lignin-containing fibers. Several other considerations may also alter the behavior of bacteria on lignocellulosic materials, such as storage conditions, nutrient availability, and chemical composition of the fibers., Competing Interests: The authors declare no competing interests., (© 2023 The Authors.)

Nonwoven products are widely used in disposable products, such as wipes, diapers, and masks. Microfibers shed from these products in the aquatic and air environment have not been fully described. In the present study, 15 commercial single-use nonwoven products (wipes) and 16 meltblown nonwoven materials produced in a pilot plant were investigated regarding their microfiber generation in aquatic and air environments and compared to selected textile materials and paper tissue materials. Microfibers shed in water were studied using a Launder Ometer equipment (1-65 mg of microfibers per gram material), and microfibers shed in air were evaluated using a dusting testing machine that shakes a piece of the nonwoven back and forth (~ 4 mg of microfibers per gram material). The raw materials and bonding technologies affected the microfiber generation both in water and air conditions. When the commercial nonwovens contained less natural cellulosic fibers, less microfibers were generated. Bonding with hydroentangling and/or double bonding by two different bonding methods could improve the resistance to microfiber generation. Meltblown nonwoven fabrics generated fewer microfibers compared to the other commercial nonwovens studied here, and the manufacturing factors, such as DCD (die-to-collector distance) and air flow rate, affected the tendency of microfiber generation. The results suggest that it is possible to control the tendency of microfiber shedding through the choice of operating parameters during nonwoven manufacturing processes., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Dissolving pulp (DP) is a specialty pulp product from a variety of lignocellulosic biomass (i.e., hardwoods (HW) and softwoods (SW)) with a broad range of applications. Conducting life cycle assessment (LCA) for DP end applications (e.g., textile products, specialty plastics) is challenging due to the lack of life cycle inventory (LCI) data and environmental information associated with different grades. This research addresses this challenge using process simulations to generate LCI for different DP grades (e.g., acetate and viscose) made from HW and SW, respectively. The LCA results show that biomass feedstock directly affects the environmental impacts of DP. For instance, HW acetate grade has higher global warming potential than SW acetate but lower environmental impacts in other categories related to ecosystems and human health. This HW versus SW comparison has similar results for viscose DP in all impact categories except eutrophication. Additionally, a hotspot analysis identifies that on-site emissions and chemicals are the main contributors to the environmental impacts across all grades in this study. The results and LCI data generated in this work provide critical information to support future LCA and sustainability assessment for end-products derived from DP.

Replacing synthetic polymers with renewable alternatives is a critical challenge for the packaging industry. This research investigated the use of leaf-based proteins as a sustainable co-binder in the coating formulations for paper-based packaging and other applications. Protein isolates from tobacco leaf and alfalfa concentrates were characterized using the Pierce protein assay, Kjeldahl nitrogen, and gel electrophoresis. The proteins were tested as co-binders in a typical latex-based paper coating formulation. The rheology and water retention properties of the wet coating and the surface, optical, structural, and strength properties of coated papers were measured. The coating performance was affected by the purity, solubility, and molecular weight of the tobacco protein and exhibited a shear-thinning behavior with lower water retention than soy protein. Analysis by scanning electron microscopy and time of flight secondary ion mass spectroscopy on the dried coating layer containing tobacco protein showed enhanced porosity (advantageous for package glueability) relative to the control latex coating. The tobacco protein offers adequate coverage and coating pigment distribution, indicating that this protein can be a suitable option in coatings for packaging applications., (© 2021 Wiley Periodicals LLC.)

The presence and biodegradability of textile microfibers shed during laundering or use is an important environmental issue. In this research, the influence of common textile finishes on the persistence of cotton fibers in an aerobic aquatic environment was assessed. The biodegradation of cotton knitted fabrics with different finishes, silicone softener, durable press, water repellent, and a blue reactive dye was evaluated. The rate of biodegradation decreased with durable press and water repellant finishing treatments. In terms of the final extent of biodegradation, there was no significant difference between the samples. All samples reached more than 60% biodegradation in 102 days. The biodegradation rates were in agreement with observed trends of the same samples for cellulase mediated hydrolysis and cellulase adsorption experiments, indicating the finishes impact the initial adsorption of enzymes excreted by the microorganisms and the initial rates of biodegradation, however despite this the cellulosic material maintains its biodegradability., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

The influence of common textile finishes on cotton fabrics on the generation of microfibers during laundering was assessed. Microfiber release was determined to be in the range of 9000-14,000 particles per gram of cotton fabric. Cotton knitted fabrics treated with softener and durable press generate more microfibers (1.30-1.63 mg/g fabric) during laundering by mass and number than untreated fabric (0.73 mg/g fabric). The fabrics treated with softener generated the longest average microfiber length (0.86 mm), whereas durable press and water repellent treatments produced the shortest average microfiber length (0.62 and 0.63 mm, respectively). In general, the changes in the mechanical properties of the fibers and fabrics due to the finishing treatments are the main factor affecting the microfiber release. The abrasion resistance of the fabrics decreases for durable press treatments and water repellent treatments due to the brittleness in the structure originated by the crosslinking treatment. In the case of the softener treatment, the fabric surface is soft and smooth decreasing the friction coefficient between fibers favoring the fibers loosening from the textile and resulting in a high tendency for fuzz formation and microfiber release. These findings are useful for the textile industry in the design and selection of materials and treatments for the reduction of synthetic or natural microfiber shedding from textiles., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

This study aims to understand the effect of micro- and nanofibrillated cellulose (MNFC) on the tensile index, softness, and water absorbency of tissue paper. MNFC was produced from four different fiber sources. The results show that MNFC acts as an effective strength enhancer at the expense of a reduced water absorbency and softness. The impact of the fiber source on MNFC manufacturing cost and the trade-off with performance was also investigated. MNFCs produced from southern bleached hardwood kraft, northern bleached softwood kraft, and deinked pulp exhibited similar performance trends with the MNFC from the deinked pulp having a significantly lower cost. This suggests that MNFCs with similar degrees of fibrillation may be used interchangeably regardless of the fiber source, revealing the possibility to minimize MNFC manufacturing costs based on fiber selection. MNFC produced from bleached Eucalyptus kraft showed the lowest degree of fibrillation and the lowest strength improvements among the MNFCs evaluated., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

The human population is generally subjected to diverse pollutants and contaminants in the environment like those in the air, soil, foodstuffs, and drinking water. Therefore, the development of novel purification techniques and efficient detection devices for pollutants is an important challenge. To date, experts in the field have designed distinctive analytical procedures for the detection of pollutants including gas chromatography/mass spectrometry and atomic absorption spectroscopy. While the mentioned procedures enjoy high sensitivity, they suffer from being laborious, expensive, require advanced skills for operation, and are inconvenient to deploy as a result of their massive size. Therefore, in response to the above-mentioned limitations, electrochemical sensors are being developed that enjoy robustness, selectivity, sensitivity, and real-time measurements. Considerable advancements in nanomaterials-based electrochemical sensor platforms have helped to generate new technologies to ensure environmental and human safety. Recently, investigators have expanded considerable effort to utilize polymer nanocomposites for building the electrochemical sensors in view of their promising features such as very good electrocatalytic activities, higher electrical conductivity, and effective surface area in comparison to the traditional polymers. Herein, the first section of this review briefly discusses the most important methods for polymer nanocomposites synthesis, such as in situ polymerization, direct mixing of polymer and nanofillers (melt-mixing and solution-mixing), sol-gel, and electrochemical methods. It then summarizes the current utilization of polymer nanocomposites for the preparation of electrochemical sensors as a novel approach for monitoring and detecting environmental pollutants which include heavy metal ions, pesticides, phenolic compounds, nitroaromatic compounds, nitrite, and hydrazine in different mediums. Finally, the current challenges and future directions for the polymer nanocomposites-based electrochemical sensing of environmental pollutants are outlined., Competing Interests: The authors declare no competing financial interest.

Hydrogels were synthesized by a copolymerization reaction of nanofibrillated cellulose (CNF) with acrylic acid (AA) and acrylamide (AM) and N , N -methylene-bis-acrylamide (MBA) as a cross-linker and their absorption performance as a function of composition was determined. Hydrogels with 4% by weight CNF had swelling of about 250 g/g and with 7% CNF about 200 g/g for water. Thermodynamic and kinetic studies of the reaction pathways and the electronic properties of the cellulose and monomers were investigated through density functional theory calculations. Thermodynamic investigations revealed that the radical formation of cellulose that initiates the hydrogel process can occur through the breaking of the homolytic covalent bonds C6-OH and C3-OH. The results show that the reaction of CNF with monomers is thermodynamically favorable in the decreasing order of AM, AA, and MBA. The kinetic study also indicates that the reaction kinetics of CNF with AM is faster than with AA which is much faster than with MBA. Overall, this study has elucidated some of the key chemical characteristics that impact the derivatization of nanocellulose structures to produce advanced renewable bioproducts.

Mechanical refining results in fiber deconstruction and modifications that enhance enzyme accessibility to carbohydrates. Further understanding of the morphological changes occurring to biomass during mechanical refining and the impacts of these changes on enzymatic digestibility is necessary to maximize yields and reduce energy consumption. Although the degree of fiber length reduction relative to fibrillation/delamination can be impacted by manipulating refining variables, mechanical refining of any type (PFI, disk, and valley beater) typically results in both phenomena. Separating the two is not straightforward. In this study, fiber fractionation based on particle size performed after mechanical refining of high-lignin pulp was utilized to successfully elucidate the relative impact of fibrillation/delamination and fiber cutting phenomena during mechanical refining. Compositional analysis showed that fines contain significantly more lignin than larger size fractions. Enzymatic hydrolysis results indicated that within fractions of uniform fiber length, fibrillation/delamination due to mechanical refining increased enzymatic conversion by 20-30 percentage points. Changes in fiber length had little effect on digestibility for fibers longer than ~0.5 mm. However, the digestibility of the fines fractions was high for all levels of refining even with the high-lignin content., (© 2019 Wiley Periodicals, Inc.)

The aerobic biodegradation of common textiles that shed microfibers during laundering was evaluated under the action of microbes found in the environment, such as lake and seawater, and activated sludge at a low concentration from a wastewater treatment plant (WWTP). Under these conditions, the biodegradation potential was the same in all the experiments: Microcrystalline Cellulose (MCC) > Cotton > Rayon > Polyester/Cotton ≫ Polyester. Nevertheless, for cotton and rayon yarns, >70% biodegradation was achieved with activated sludge at low concentration and lake water, whereas in seawater, about 50% degradation was reached. Polyester did not appreciably degrade. The biodegradation results herein indicate potential not absolutes in nature. The bacterial diversity analyses in the different biodegradation inoculums show that there are distinct bacterial communities related to the assimilation and mineralization of complex carbohydrates that were promoted with the cellulosic MCC, cotton, and rayon samples different than the polyester sample., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2019. Published by Elsevier Ltd.)

The production of a high-value xylooligosaccharide (XOS) prebiotic product from lignocellulosic autohydrolysate requires processing for the removal of non-carbohydrate components such as lignin and furfural. In this research, the nature of XOS dissolved in autohydrolysate is evaluated including the XOS degree of polymerization (DP) distribution and potential covalent association between XOS and lignin (LCC). The impact of these factors on the yield of XOS during treatment of Miscanthus autohydrolysate with hydrophobic resin is assessed. Over 30% of the XOS in autohydrolysate was found to be likely associated with lignin ("tied" XOS), all of which was removed during hydrophobic resin treatment along with over 90% of the dissolved lignin. However, loss of dissolved XOS during resin treatment was found to not be due solely to XOS association with lignin. Over 50% of the "free," non-lignin-associated XOS was also removed by resin treatment. Interaction between "free" XOS and the hydrophobic resin was found to be highly dependent on DP with higher DP XOS being removed far more readily than low DP XOS. Over 80% of dissolved "free" XOS with a DP of six and above (X6+) was removed from autohydrolysate during treatment while only 17% of xylose (X1) was removed. Efforts to understand the interaction between the hydrophobic resin and XOS and to improve the recovery of XOS during hydrophobic resin treatment are presented., Competing Interests: There are no conflicts of interest to declare., (This journal is © The Royal Society of Chemistry.)

The effect of fiber type (cotton, polyester, and rayon), temperature, and use of detergent on the number of microfibers released during laundering of knitted fabrics were studied during accelerated laboratory washing (Launder-Ometer) and home laundering experiments. Polyester and cellulose-based fabrics all shed significant amounts of microfibers and shedding levels were increased with higher water temperature and detergent use. Cellulose-based fabrics released more microfibers (0.2-4 mg/g fabric) during accelerated laundering than polyester (0.1-1 mg/g fabric). Using well-controlled aquatic biodegradation experiments it was shown that cotton and rayon microfibers are expected to degrade in natural aquatic aerobic environments whereas polyester microfibers are expected to persist in the environment for long periods of time., (Published by Elsevier Ltd.)

Currently, there is very strong interest to replace synthetic polymers with biological macromolecules of natural source for applications that interact with humans or the environment. This research describes the development of drug delivery hydrogels from natural polymers, starch, lignin and hemicelluloses by means of reactive extrusion. The hydrogels show a strong swelling ability dependent on pH which may be used to control diffusion rates of water and small molecules in and out of the gel. Also the hydrogels degradation rates were studied in a physiological solution (pH 7.4) for 15days. The results indicated that for all three macromolecules, lower molecular weight and higher level of plasticizer both increase the rate of weight loss of the hydrogels. The degradation was extremely reduced when the polymers were extruded in the presence of a catalyst. Finally the dynamic mechanical analysis revealed that the degradation of the hydrogels induce a significant reduction in the compressive modulus. This study demonstrates the characteristics and potential of natural polymers as a drug release system., (Published by Elsevier B.V.)

Hemicelluloses, due to their hydrophilic nature, may tend to be overlooked as a component in water-resistant product applications. However, their domains of use can be greatly expanded by chemical derivatization. Research in which hydrophobic derivatives of hemicelluloses or combinations of hemicelluloses with hydrophobic materials are used with to prepare films and composites is considered herein. Isolation methods that have been used to separate hemicellulose from biomass are also reviewed. Finally, the most useful pathways to change the hydrophilic character of hemicelluloses to hydrophobic are reviewed. In this way, the water resistance can be increased and applications of targeted water-resistant hemicellulose developed. Several applications of these materials are discussed., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Lignin-based thermoplastic materials have attracted increasing interest as sustainable, cost-effective, and biodegradable alternatives for petroleum-based thermoplastics. As an amorphous thermoplastic material, lignin has a relatively high glass-transition temperature and also undergoes radical-induced self-condensation at high temperatures, which limits its thermal processability. Additionally, lignin-based materials are usually brittle and exhibit poor mechanical properties. To improve the thermoplasticity and mechanical properties of technical lignin, polymers or plasticizers are usually integrated with lignin by blending or chemical modification. This Review attempts to cover the reported approaches towards the development of lignin-based thermoplastic materials on the basis of published information. Approaches reviewed include plasticization, blending with miscible polymers, and chemical modifications by esterification, etherification, polymer grafting, and copolymerization. Those lignin-based thermoplastic materials are expected to show applications as engineering plastics, polymeric foams, thermoplastic elastomers, and carbon-fiber precursors., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Mechanical refining is widely used in the pulp and paper industry to enhance the end-use properties of products by creating external fibrillation and internal delamination. This technology can be directly applied to biochemical conversion processes. By implementing mechanical refining technology, biomass recalcitrance to enzyme hydrolysis can be overcome and carbohydrate conversion can be enhanced with commercially attractive levels of enzymes. In addition, chemical and thermal pretreatment severity can be reduced to achieve the same level of carbohydrate conversion, which reduces pretreatment cost and results in lower concentrations of inhibitors. Refining is versatile and a commercially proven technology that can be operated at process flows of ∼ 1500 dry tons per day of biomass. This paper reviews the utilization of mechanical refining in the pulp and paper industry and summarizes the recent development in applications for biochemical conversion, which potentially make an overall biorefinery process more economically viable., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

As one of the most abundant natural materials in nature, cellulose has revealed enormous potential for the construction of functional materials thanks to its sustainability, non-toxicity, biocompatibility, and biodegradability. Among many fascinating applications, functional surfaces based on cellulose-derived materials have attracted increasing interest recently, as platforms for diagnostics, sensoring, robust catalysis, water treatment, ultrafiltration, and anti-microbial surfaces. This mini-review attempts to cover the general methodology for the fabrication of functional cellulose surface and a few popular applications including bioactive and non-adhesive (i.e., anti-fouling and anti-microbial) surfaces.

Paper sludge is an attractive biomass source for the conversion to ethanol due to its low cost and the lack of severe pretreatment required. Four sludges from pulp and paper operations including both virgin kraft (VK) and recycled and deinking (RD) paper mills were analyzed. A fractionation process using a laboratory screen was utilized to produce a fiber-rich stream for enzymatic hydrolysis. This process removed 82-98 % of the ash with fiber yields from 39 to 69 %. Even though sludges in both non-fractionated and fractionated scenarios were pH-adjusted, total sugar conversion was still improved by 12-27 % by fractionation with 4.5 times less acid required for pH adjustment. Fermentation of the fractionated sludges showed very high ethanol yields. Acid insoluble clay adsorbs 3-5 mg enzyme per gram of clay depending on enzyme dosage. Acid soluble CaCO3 adsorbs about half of the enzyme compared to clay. Fractionation efficiency was also evaluated by testing different size mesh screen openings (100 to 500 mesh). The 400-mesh screen presented the best fiber yield, ash removal and ash fractionation ratio for both VK and RD sludges. The ash-rich streams have a lower C/N ratio than the original sludge which improves its suitability as soil amendment.

Mechanical refining has been shown to improve biomass enzymatic digestibility. In this study industrial high-yield sodium carbonate hardwood pulp was subjected to lab, pilot and industrial refining to determine if the mechanical refining improves the enzymatic hydrolysis sugar conversion efficiency differently at different refining scales. Lab, pilot and industrial refining increased the biomass digestibility for lignocellulosic biomass relative to the unrefined material. The sugar conversion was increased from 36% to 65% at 5 FPU/g of biomass with industrial refining at 67.0 kWh/t, which was more energy efficient than lab and pilot scale refining. There is a maximum in the sugar conversion with respect to the amount of refining energy. Water retention value is a good predictor of improvements in sugar conversion for a given fiber source and composition. Improvements in biomass digestibility with refining due to lab, pilot plant and industrial refining were similar with respect to water retention value., (Published by Elsevier Ltd.)

This study investigated the effectiveness of mechanical refining to overcome the biomass recalcitrance barrier. Laboratory scale refining was conducted via PFI mill and valley beater refiners using green liquor and Kraft hardwood pulps. A strong positive correlation was determined between sugar recovery and water retention value. Refining produced significant improvements in enzymatic hydrolysis yield relative to unrefined substrates (e.g., sugar recovery increase from 67% to 90%, for 15% lignin Kraft pulp). A maximum absolute enzymatic hydrolysis improvement with refining was observed at enzymatic hydrolysis conditions that produced intermediate conversion levels. For a 91% target sugar conversion, PFI refining at 4000 revolutions allowed for a 32% reduction in enzyme charge for 15% lignin content hardwood Kraft pulp and 96 h hydrolysis time, compared to the unrefined material., (Published by Elsevier Ltd.)

Cellulose nanocrystals (CNCs) from ramie fibers are studied as stabilizers of oil-in-water emulsions. The phase behavior of heptane and water systems is studied, and emulsions stabilized by CNCs are analyzed by using drop sizing (light scattering) and optical, scanning, and freeze-fracture electron microscopies. Water-continuous Pickering emulsions are produced with cellulose nanocrystals (0.05-0.5 wt%) grafted with thermo-responsive poly(NIPAM) brushes (poly(NIPAM)-g-CNCs). They are observed to be stable during the time of observation of 4 months. In contrast, unmodified CNCs are unable to stabilize heptane-in-water emulsions. After emulsification, poly(NIPAM)-g-CNCs are observed to form aligned, layered structures at the oil-water interface. The emulsions stabilized by poly(NIPAM)-g-CNCs break after heating at a temperature above the LCST of poly(NIPAM), which is taken as indication of the temperature responsiveness of the brushes installed on the particles and thus the responsiveness of the Pickering emulsions. This phenomenon is further elucidated via rheological measurements, in which viscosities of the Pickering emulsions increase on approach of the low critical solution temperature of poly(NIPAM). The effect of temperature can be counterbalanced with the addition of salt which is explained by the reduction of electrostatic and steric interactions of poly(NIPAM)-g-CNCs at the oil-water interface., (Copyright © 2011 Elsevier Inc. All rights reserved.)

The colloidal stability and thermoresponsive behavior of poly(N-isopropylacrylamide) brushes grafted from cellulose nanocrystals (CNCs) of varying graft densities and molecular weights was investigated. Indication of the grafted polymer brushes was obtained after AFM imaging of CNCs adsorbed on silica. Also, aggregation of the nanoparticles carrying grafts of high degree of polymerization was observed. The responsiveness of grafted CNCs in aqueous dispersions and as an ultrathin film was evaluated by using light scattering, viscosimetry, and colloidal probe microscopy (CPM). Light transmittance measurements showed temperature-dependent aggregation originating from the different graft densities and molecular weights. The lower critical solution temperature (LCST) of grafted poly(NiPAAm) brushes was found to decrease with the ionic strength, as is the case for free poly(NiPAAm) in aqueous solution. Thermal responsive behavior of grafted CNCs in aqueous dispersions was observed by a sharp increase in dispersion viscosity as the temperature approached the LCST. CPM in liquid media for asymmetric systems consisting of ultrathin films of CNCs and a colloidal silica probe showed the distinctive effects of the grafted polymer brushes on interaction and adhesive forces. The origin of such forces was found to be mainly electrostatic and steric in the case of bare and grafted CNCs, respectively. A decrease in the onset of attractive and adhesion forces of grafted CNCs films were observed with the ionic strength of the aqueous solution. The decreased mobility of polymer brushes upon partial collapse and decreased availability of hydrogen bonding sites with higher electrolyte concentration were hypothesized as the main reasons for the less prominent polymer bridging between interacting surfaces.

Cellulose nanocrystals (CNCs) or nanowhiskers produced from sulfuric acid hydrolysis of ramie fibers were used as substrates for surface chemical functionalization with thermoresponsive macromolecules. The CNCs were grafted with poly(N-isopropylacrylamide) brushes via surface-initiated single-electron transfer living radical polymerization (SI-SET-LRP) under various conditions at room temperature. The grafting process was confirmed via Fourier transform IR spectroscopy and X-ray photoelectron spectroscopy and the different molecular masses of the grafts were quantified and found to depend on the initiator and monomer concentrations used. No observable damage occurred to the CNCs after grafting, as determined by X-ray diffraction. Size exclusion chromatography analyses of polymer chains cleaved from the cellulose nanocrystals indicated that a higher degree of polymerization was achieved by increasing initiator or monomer loading, most likely caused by local heterogeneities yielding higher rates of polymerization. It is expected that suspension stability, interfacial interactions, friction, and other properties of grafted CNCs can be controlled by changes in temperature and provide a unique platform for further development of stimuli-responsive nanomaterials.

Films of microfibrillated celluloses (MFCs) from pulps of different yields, containing varying amounts of extractives, lignin, and hemicelluloses, were produced by combining refining and high-pressure homogenization techniques. MFC films were produced using a casting-evaporation technique and the physical and mechanical properties (including density, roughness, fold endurance and tensile properties) were determined. Homogenization of bleached and unbleached Kraft pulps gave rise to highly individualized MFCs, but not for thermo-mechanical pulp (TMP). The resulting MFC films had a roughness equivalent to the surface upon which the films were cast. Interestingly, after homogenization, the presence of lignin significantly increased film toughness, tensile index, and elastic modulus. The hornification of fibers through a drying and rewetting cycle prior to refining and homogenization did not produce any significant effect compared to films from never-dried fibers, indicating that MFC films can potentially be made from low-cost recycled cellulosic materials., ((c) 2010 Elsevier Ltd. All rights reserved.)

Two distinct pretreatment technologies, autohydrolysis and AFEX, have been applied to coastal Bermuda grass (CBG) followed by enzymatic hydrolysis in order to compare the effects of pretreatment on the subsequent sugar generation. Furthermore, the influence of structural features from each pretreatment on biomass digestibility was characterized with SEM, ATR-FTIR, and XRD. Enzymatic conversion of pretreated solids from the pretreatments increased with elevated temperature and longer residence times. AFEX pretreatment at 100 degrees C for 30 min produced a sugar yield of 94.8% of theoretical possible with 30 FPU/g enzymatic loading, the maximum achieved with AFEX. It was also shown that with autohydrolysis at 170 degrees C for 60 min that 55.4% sugar yield of the theoretical possible was produced with a 30 FPU/g enzymatic loading, the maximum with autohydrolysis. AFEX pretreatment does not change the chemical composition of CBG but autohydrolysis reduces hemicellulose content in the pretreated solids. Both pretreatments cause re-localization of lignin components. There was no observed correlation between crystallinity and enzyme digestibility of the pretreated solids. AFEX pretreatment developed more enzymatic accessibility to pretreated solids of CBG than did autohydrolysis pretreatment, leading to more sugar generation through the whole process. The total amount of sugars accounted for with autohydrolysis decreases with increasing temperature, consistent with increased byproduct generation via thermal degradation reactions., (Published by Elsevier Ltd.)

The objective of this research was to synthesize and characterize high-value foam gel materials with unique absorptive and mechanical properties from starch citrate-chitosan. The effects of starch citrate concentration, pH, solid to liquid ratio, reaction time, and temperature on absorbency, weight loss in water, and strength were determined. The cross-linked starch citrate-chitosan foam is flexible and elastic and has significantly increased absorbance and strength and decreased weight loss in water compared to starch-chitosan foam. A unique characteristic of the starch citrate-chitosan foam is that it absorbs more saline solution than pure water, which is the opposite of current commercial super absorbents. An increased strength, increased degradation temperature, increased storage modulus, and decreased weight loss in water for starch citrate-chitosan relative to starch-chitosan are in agreement with amide bonds formed between the carboxyl group of starch citrate and the amino group of chitosan.

Coastal Bermuda grass (GBG) was pretreated using an autohydrolysis process with different temperatures and times, and the pretreated materials were enzymatically hydrolyzed using a mixture of cellulase, xylanase and beta-glucosidase with different enzyme loadings to evaluate sugar yields. Compared with untreated CBG, autohydrolysis pretreatments at all elevated temperatures and residence times tested enhanced enzymatic digestibility of both cellulose and hemicellulose. Increasing the temperature and residence time also helps to solubilize hemicelluloses, with 83.3% of the hemicelluloses solubilized at 170 degrees C for 60 min treatment. However, higher temperatures and longer times resulted in an overall lower sugar recovery when considering monosaccharides in the prehydrolyzate combined with the enzyme hydrolyzate. Autohydrolysis at 150 degrees C for 60 min provided the highest overall sugar yield for the entire process. A total of 43.3 g of sugars, 70% of the theoretical sugar yield, can be generated from 100g CBG, 15.0 g of monosaccharide in the prehydrolyzate and 28.3 g in the enzyme hydrolyzate. The conversion efficiency could be further improved by optimizing enzyme dosages and xylanases:cellulases ratio and pretreatment conditions to minimize sugar degradation.

We studied the use of cellulose nanocrystals (CNXs) obtained after acid hydrolysis of ramie cellulose fibers to reinforce poly(epsilon-caprolactone) (PCL) nanofibers. Chemical grafting with low-molecular-weight PCL diol onto the CNXs was carried out in an attempt to improve the interfacial adhesion with the fiber matrix. Grafting was confirmed via infrared spectroscopy and thermogravimetric analyses. The polymer matrix consisted of electrospun nanofibers that were collected as nonwoven webs. The morphology as well as thermal and mechanical properties of filled and unfilled nanofibers were elucidated by scanning electron microscopy, differential scanning calorimetry, and dynamic mechanical analysis, respectively. The addition of CNXs into PCL produced minimal changes in the thermal behavior of the electrospun fibers. However, a significant improvement in the mechanical properties of the nanofibers after reinforcement with unmodified CNXs was confirmed. Fiber webs from PCL reinforced with 2.5% unmodified CNXs showed ca. 1.5-fold increase in Young's modulus and the ultimate strength compared to PCL webs. Compared to the case of grafted nanocrystals, the unmodified ones imparted better morphological homogeneity to the nanofibrillar structure. The grafted nanocrystals had a negative effect on the morphology of nonwoven webs in which individual nanofibers became annealed during the electrospinning process and, therefore, could not be compared to neat PCL nonwoven webs. A rationalization for the different effects of grafted and unmodified CNXs in reinforcing PCL nanofibers is provided.