Transparent oxygen barrier nanocellulose composite films with a sandwich structure.

Transparent gas barrier materials have extensive applications in packaging, pharmaceutical preservation, and electronics. Herein, we designed transparent films with a symmetric sandwich structure using layer-by-layer assembly of biaxially oriented polypropylene (BOPP) and acrylic resin (AR) followed by a cellulose nanoparticle (CNP) layer. The BOPP as a substrate created a barrier to hinder the transmission of water molecules to the adhesive AR layer and gas barrier functional CNP layer. The aspect ratio of the CNPs was shown to affect the film microstructure, resulting in different values for the oxygen transmission rate (OTR). The well-organized CNP layer exhibited lower OTR when compared with the network layer. The thickness, density, and porosity of the CNP layer exhibited correlations with OTR. The water molecules were able to flow in through an additional pathway, thus increasing the water vapor transmission rate (WVTR). Moreover, these sandwiched cellulose composite films showed excellent light transmittance and tensile strength.

Nanocellulose from recycled indigo-dyed denim fabric and its application in composite films.

In this study, nanocellulose was extracted from indigo-dyed denim fabric and the resultant nanocellulose properties were evaluated in comparison with those derived from bleached cotton fabric and wood pulp in order to investigate the potential of recycling denim waste for nanocellulose production and application. Sulfuric acid hydrolysis and (2,2,6,6-tetramethylpiperidin-1-yl) oxyl (TEMPO)-oxidation were utilized to produce cellulose nanocrystals (CNC) and cellulose nanofibers (TOCN), respectively. A stable CNC suspension with blue color was obtained after acid hydrolysis and the TEMPO process yielded colorless TOCN. The denim-derived nanocellulose possessed similar yield, morphology, size, crystallinity, and thermal stability to those derived from bleached cotton but higher crystallinity and thermal stability compared to the nanocellulose from wood pulp. When used to reinforce polyvinyl alcohol film, the blue indigo-CNC not only enhanced mechanical properties of the film but also provided the film with outstanding UV blocking.

Developing chitin nanocrystals for flexible packaging coatings.

This study assessed the applicability of chitin nanocrystals employed in combination with an existing coating material intended for flexible packaging. The 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO) oxidized chitin nanocrystals (TOCNs) were applied 1) as an additive in a water-based acrylic resin (WBAR) that was then coated onto the surface of a biaxially oriented polypropylene (BOPP) film, and 2) as a neat layer in multilayered BOPP laminates bonded by a WBAR adhesive layer. The results indicated that the flow behavior and shear viscosity of the TOCN/WBAR system were dependent on TOCN contents. The TOCNs as a dispersed phase in the acrylic resin matrix did not improve the oxygen barrier property of the resulting coated BOPP. By contrast, the neat continuous TOCN coating layer improved the oxygen barrier property of the laminates of BOPP and TOCNs bonded by the acrylic resin, a 44% oxygen transmission rate reduction for a laminate with a 8.33-µm TOCN layer compared to the laminate without a TOCN layer. The inclusion of the TOCNs maintained the optical transparency of the resulting films.

Disruption of lignocellulosic biomass along the length of the screws with different screw elements in a twin-screw extruder.

Proper screw design is crucial for effectively pre-treating wood fibers, to assist in the downstream enzymatic conversion of the cellulose into fermentable sugars. Initially, the impact of extruder barrel temperature (50, 100, and 150 °C) and screw speed (25, 50, and 75 rpm) were studied to arrive at the optimum conditions for sugar yield. Lower temperatures and screw speeds resulted in increased sugar yields. To examine the influence of shear imparted by the screws, the residuals samples were recovered from different zones along the screws and evaluated. Sugar yield, crystallinity index, and the particle size distribution of the material collected at different zones were determined. Glucose yield and xylose/mannose yields of the material along the screws, ranged from 23.25 to 42.88% and from 11.95 to 20.54%, respectively. The importance of the screw design was highlighted.

Impacts of prescribed fires and benefits from their reduction for air quality, health and visibility in the Pacific Northwest of the United States.

Using a WRF-SMOKE-CMAQ modeling framework, we investigate the impacts of smoke from prescribed fires on model performance, regional and local air quality, health impacts, and visibility in protected natural environments using three different prescribed fire emission scenarios - 100% fire, no fire, and 30% fire. The 30% fire case reflects a 70% reduction in fire activities due to harvesting of logging residues for use as a feedstock for a potential aviation biofuel supply chain. Overall model performance improves for several performance metrics when fire emissions are included, especially for organic carbon, irrespective of the model goals and criteria used. This effect on model performance is more pronounced for the rural and remote IMPROVE sites for organic carbon and total PM2.5. A reduction in prescribed fire emissions (30% fire case) results in significant improvement in air quality in areas in western Oregon, northern Idaho and western Montana where most prescribed fires occur. Prescribed burning contributes to visibility impairment and a relatively large portion of protected class I areas will benefit from a reduced emission scenario. For the haziest 20% days, prescribed burning is an important source of visibility impairment and approximately 50% of IMPROVE sites in the model domain show a significant improvement in visibility for the reduced fire case. Using BenMAP, a health impact assessment tool, we show that several hundred additional deaths, several thousand upper and lower respiratory symptom cases, several hundred bronchitis cases, and more than 35,000 work day losses can be attributed to prescribed fires and these health impacts decrease by 25-30% when a 30% fire emission scenario is considered. Implications This study assesses the potential regional and local air quality, public health and visibility impacts from prescribed burning activities as well as benefits that can be achieved by a potential reduction in emissions for a scenario where biomass is harvested for conversion to biofuel. As prescribed burning activities become more frequent, they can be more detrimental for air quality and health. Forest residue based biofuel industry can be source of cleaner fuel with co-benefits of improved air quality, reduction in health impacts and improved visibility.

Pretreatment with lower feed moisture and lower extrusion temperatures aids in the increase in the fermentable sugar yields from fine-milled Douglas-fir.

The impact of independent variables of extrusion on dependent variables of pre-milled Douglas-fir forest residuals was studied to enhance the enzymatic hydrolysis for production of fermentable sugar without catalysts. Co-rotating twin screw extruder was operated with three different feedstock moisture contents (30, 40, and 50%) at four different barrel temperatures (25, 50, 100, and 150 °C) as a pretreatment. The specific mechanical energy input ranged from 0.07 and 0.30 kWh/kg and had a very strong positive correlation with torque (r = 0.96, p < 0.01), glucose (r = 0.92, p < 0.01) and xylose/mannose yields with (r = 0.84, p < 0.01). Douglas-fir residuals extruded at lowest moisture content (30%) and temperature (25 °C) had the highest sugar yield, requiring the highest SME. Higher barrel temperature increased the median particle size and had lower glucose and xylose/mannose yields. Recrystallization and agglomeration were observed under higher temperature conditions.

Novel micronized woody biomass process for production of cost-effective clean fermentable sugars.

Thermo-chemical pretreatments of biomass typically result in environmental impacts from water use and emission. The degradation byproducts in the resulting sugars can be inhibitory to the activities of enzymes and yeasts. The results of this study showed that combining existing commercial comminution technology can reduce total energy consumption with improved saccharification yield while eliminating chemical use. Impact mill was found to be the most efficient milling for size reduction of forest residual chips from ca. 2 mm to a specific value below 100 µm. The further micronization effectively disrupted the recalcitrance of the woody biomass and produced the highly saccharifiable substrates for downstream processing. In addition, extrusion can be integrated into a clean cellulosic sugar process for further fibrillation in place of the conventional mixing processing. The highest energy efficiency was observed on the impact-milled samples with 0.515 kg sugars kWh-1.

Facile Fabrication of 100% Bio-based and Degradable Ternary Cellulose/PHBV/PLA Composites.

Modifying bio-based degradable polymers such as polylactide (PLA) and poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) with non-degradable agents will compromise the 100% degradability of their resultant composites. This work developed a facile and solvent-free route in order to fabricate 100% bio-based and degradable ternary cellulose/PHBV/PLA composite materials. The effects of ball milling on the physicochemical properties of pulp cellulose fibers, and the ball-milled cellulose particles on the morphology and mechanical properties of PHBV/PLA blends, were investigated experimentally and statistically. The results showed that more ball-milling time resulted in a smaller particle size and lower crystallinity by way of mechanical disintegration. Filling PHBV/PLA blends with the ball-milled celluloses dramatically increased the stiffness at all of the levels of particle size and filling content, and improved their elongation at the break and fracture work at certain levels of particle size and filling content. It was also found that the high filling content of the ball-milled cellulose particles was detrimental to the mechanical properties for the resultant composite materials. The ternary cellulose/PHBV/PLA composite materials have some potential applications, such as in packaging materials and automobile inner decoration parts. Furthermore, filling content contributes more to the variations of their mechanical properties than particle size does. Statistical analysis combined with experimental tests provide a new pathway to quantitatively evaluate the effects of multiple variables on a specific property, and figure out the dominant one for the resultant composite materials.

Air Quality and Health Impacts of an Aviation Biofuel Supply Chain Using Forest Residue in the Northwestern United States.

Forest residue is a major potential feedstock for second-generation biofuel; however, little knowledge exists about the environmental impacts of the development and production of biofuel from such a feedstock. Using a high-resolution regional air quality model, we estimate the air quality impacts of a forest residue based aviation biofuel supply chain scenario in the Pacific Northwestern United States. Using two potential supply chain regions, we find that biomass and biofuel hauling activities will add <1% of vehicle miles traveled to existing traffic, but the biorefineries will add significant local sources of NO x and CO. In the biofuel production scenario, the regional average increase in the pollutant concentration is small, but 8-hr maximum summer time O3 can increase by 1-2 ppb and 24-hr average maximum PM2.5 by 2 µg/m3. The alternate scenario of slash pile burning increased the multiday average PM2.5 by 2-5 µg/m3 during a winter simulation. Using BenMAP, a health impact assessment tool, we show that avoiding slash pile burning results in a decrease in premature mortality as well as several other nonfatal and minor health effects. In general, we show that most air quality and health benefits result primarily from avoided slash pile burning emissions.

Increased sugar yield from pre-milled Douglas-fir forest residuals with lower energy consumption by using planetary ball milling.

Impact of planetary ball milling on pre-milled wood fiber was studied to improve efficiency of energy consumption for bioconversion using post-harvest forest residuals. Crystalline cellulose decreased from 40.73% to 11.70% by ball milling. Crystallinity index of ball milled wood samples had a negative correlation with glucose yield (r = -0.97, p < .01), xylose/mannose (r = -0.96, p < .01), and a positive correlation with median particle size (r = 0.77, p < .01). Range of glucose yield and xylose/mannose yield for ball milled samples was found to be 24.45-59.67% and from 11.92% to 23.82%, respectively. Morphological changes of the lignocellulosic biomass were observed; the compact fiber bundles of the forest residuals were cleaved to smaller particles with lower aspect ratio with increasing intensity of ball milling. The required energy ranged from 0.50 to 2.15 kWh/kg for 7-30 min of milling respectively.

A co-production of sugars, lignosulfonates, cellulose, and cellulose nanocrystals from ball-milled woods.

This study demonstrated the technical potential for the large-scale co-production of sugars, lignosulfonates, cellulose, and cellulose nanocrystals. Ball-milled woods with two particle sizes were prepared by ball milling for 80min or 120min (BMW80, BMW120) and then enzymatically hydrolyzed. 78.3% cellulose conversion of BMW120 was achieved, which was three times as high as the conversion of BMW80. The hydrolyzed residues (HRs) were neutrally sulfonated cooking. 57.72g/L and 88.16g/L lignosulfonate concentration, respectively, were harvested from HR80 and HR120, and 42.6±0.5% lignin were removed. The subsequent solid residuals were purified to produce cellulose and then this material was acid-hydrolyzed to produce cellulose nanocrystals. The BMW120 maintained smaller particle size and aspect ratio during each step of during the multiple processes, while the average aspect ratio of its cellulose nanocrystals was larger. The crystallinity of both materials increased with each step of wet processing, reaching to 74% for the cellulose.

Preparation and Characterization of Cellulose Nanocrystals from the Bio-ethanol Residuals.

This study was to explore the conversion of low-cost bio-residuals into high value-added cellulose nanocrystals. Two enzymatic hydrolyzed residuals (i.e., HRMMW and HRSPW) were collected from two different bio-ethanol producing processes-hydrolyzing medium-milled wood (MMW) and hydrolyzing acid sulfite pretreated wood (SPW), respectively. The results showed that both residuals contained over 20 wt % glucan with a crystallinity of about 30%, confirming the existence of cellulose in a well-organized structure in two bio-residuals. The cellulose nanocrystals (CNCs) were successfully extracted by first bleaching the hydrolyzed residuals to remove lignin and then hydrolyzing them with sulfuric acid. The resulting CNCs displayed the flow birefringence under two crossed polarizers. Compared with CNCs from microfibrillated cellulose (CNCMCC), HRMMW and its resulted CNC present the smallest particle size and aspect ratio. CNCMCC had the larger particle size, aspect ratio, and higher z-potential value, CNCSPW presented a similar morphology to CNCMCC, and had the largest aspect ratio. The CNCMCC enhanced its high crystallinity to 85.5%. However, CNCMMW and CNCSPW had a better thermal stability and higher activation energy as well as onset temperature and maximum decomposition temperature. As a result, the CNCs from bio-ethanol residuals are valued and promising cellulose nanoparticle resources.

Evaluating the effect of wood ultrastructural changes from mechanical treatment on kinetics of monomeric sugars and chemicals production in acid bisulfite treatment.

Currently, various chemical-mechanical treatments were widely used in biofuel production to achieve high total sugar yields. However, the interaction between two treatments was scarcely investigated. In this study, we employed a ball milling process to create ultrastructural changes for Douglas-fir (Pseudotsuga menziesii) micronized wood powders. The 0, 30, and 60min ball milled wood powders resulted in a crystallinity index of 0.41, 0.21, and 0.10 respectively. It was found that the ultrastructural changes accelerate monomeric sugars production without influencing the yield of sugar degradation products. The optimal acid bisulfite treatment time was substantially decreased from 120min to 40min as the cellulose crystallinity decreased. Meanwhile, total sugar yield increased from 65% to 92% and had a linear relation with a decrease of the cellulose crystallinity.

Peracetic Acid Depolymerization of Biorefinery Lignin for Production of Selective Monomeric Phenolic Compounds.

Lignin is the largest source of renewable material with an aromatic skeleton. However, due to the recalcitrant and heterogeneous nature of the lignin polymer, it has been a challenge to effectively depolymerize lignin and produce high-value chemicals with high selectivity. In this study, a highly efficient lignin-to-monomeric phenolic compounds (MPC) conversion method based on peracetic acid (PAA) treatment was reported. PAA treatment of two biorefinery lignin samples, diluted acid pretreated corn stover lignin (DACSL) and steam exploded spruce lignin (SESPL), led to complete solubilization and production of selective hydroxylated monomeric phenolic compounds (MPC-H) and monomeric phenolic acid compounds (MPC-A) including 4-hydroxy-2-methoxyphenol, p-hydroxybenzoic acid, vanillic acid, syringic acid, and 3,4-dihydroxybenzoic acid. The maximized MPC yields obtained were 18 and 22 % based on the initial weight of the lignin in SESPL and DACSL, respectively. However, we found that the addition of niobium pentoxide catalyst to PAA treatment of lignin can significantly improve the MPC yields up to 47 %. The key reaction steps and main mechanisms involved in this new lignin-to-MPC valorization pathway were investigated and elucidated.

Partial depolymerization of enzymolysis lignin via mild hydrogenolysis over Raney Nickel.

In this work, partial depolymerization of enzymolysis lignin collected from a woody biomass-to-ethanol process was studied via mild hydrogenolysis under the catalysis of Raney Ni. The depolymerized lignin products were low molecular weight oligomers with increased hydroxyl values. The solvent selected, use of base and various reaction parameters were all found to influence yield of depolymerization, the molecular weight and hydroxyl value of the hydrogenated product. The depolymerized lignins displayed greatly enhanced solubility in organic solvents, and therefore would have great potential to be used as feedstock for many valuable thermosetting polymer applications.

Preparation and properties of aligned poly(3-hydroxybutyrate-co-3-hydroxyvalerate)/cellulose nanowhiskers composites.

In this study a unidirectionally aligned cellulose nanowhisker (CNW) composite was developed. CNW in poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) matrix was aligned using an external electric field and the morphology and mechanical properties of the resultant anisotropic composites were studied. PHBV films with 1.5-7 wt% of CNWs were manufactured using solution casting. A DC electric field of 56.25 kV/m was applied during solvent evaporation. Both microstructural and mechanical analyses were performed to study the orientation of CNWs in the films. Mechanical properties of the samples were tested at 0°, 15°, 30°, 45° and 90° with respect to electric field direction by a dynamic mechanical analyzer (DMA). DMA results showed that CNW concentration has a strong influence on the degree of CNW alignment. The electric field was effective in aligning CNWs up to 4 wt% CNW concentration. The samples with higher concentrations showed virtually isotropic behavior, due to significantly enhanced restraints on CNW mobility. The restrains were attributed to CNW/CNW and CNW/polymer interactions. Rheological results confirmed the enhance restraints.

Crystallization kinetics of poly(3-hydroxybutyrate-co-3-hydroxyvalerate)/cellulose nanowhiskers composites.

In this study, biodegradable poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) films with 1.2-4.6 wt% of cellulose nanowhiskers (CNWs) were manufactured by solution casting using N,N-dimethylformide (DMF) as the solvent. Crystallization behaviors of PHBV/CNW composites were studied under isothermal conditions using differential scanning calorimetry (DSC) and polarized optical microscopy (POM). The changes in PHBV crystalline structure were studied using wide angle X-ray diffraction (WAXD). Avrami analysis was performed to study the effects of CNW concentration and temperature on the crystallization rate and crystallinity of PHBV. POM study confirmed the results from the Avrami analysis. In particular, the results revealed the dual effects (i.e., nucleation and confinement) of CNWs on PHBV nucleation. Depending on the concentration of CNWs, the crystallization rate of PHBV could be either increased or decreased due to the combined effects. High crystallization temperatures increased the diffusion rate of PHBV chains and the growth rate of PHBV spherulites. However, the nucleation effect of CNWs decreased at high crystallization temperatures.

Production of natural fiber reinforced thermoplastic composites through the use of polyhydroxybutyrate-rich biomass.

Previous research has demonstrated that production of natural fiber reinforced thermoplastic composites (NFRTCs) utilizing bacterially-derived pure polyhydroxybutyrate (PHB) does not yield a product that is cost competitive with synthetic plastic-based NFRTCs. Moreover, the commercial production of pure PHB is not without environmental impacts. To address these issues, we integrated unpurified PHB in NFRTC construction, thereby eliminating a significant energy and cost sink (ca. 30-40%) while concurrently yielding a fully biologically based commodity. PHB-rich biomass synthesized with the microorganism Azotobacter vinelandii UWD was utilized to manufacture NFRTCs with wood flour. Resulting composites exhibited statistically similar bending strength properties despite relatively different PHB contents. Moreover, the presence of microbial cell debris allowed for NFRTC processing at significantly reduced polymer content, relative to pure PHB-based NFRTCs. Results further indicate that current commercial PHB production yields are sufficiently high to produce composites comparable to those manufactured with purified PHB.

Synthesis of polyhydroxyalkanoates in municipal wastewater treatment.

Biologically derived polyesters known as polyhydroxyalkanoates (PHAs) represent a potentially "sustainable" replacement to fossil-fuel-based thermoplastics. However, current commercial practices that produce PHA with pure microbial cultures grown on renewable, but refined, feedstocks (i.e., glucose) under sterile conditions do not represent a sustainable commodity. Here, we report on PHA production with a mixed microbial consortium indigenous to an activated sludge process on carbon present in municipal wastewaters. Reactors operated under anaerobic/aerobic and aerobic-only mode and fed primary solids fermenter liquor maintained a mixed microbial consortium capable of synthesizing PHA at 10 to 25% (w/w), while reducing soluble COD by approximately 62 to 71%. More critically, an aerobic batch reactor seeded from the anaerobic/aerobic reactor and fed fermenter liquor achieved approximately 53% PHA (w/w). Results presented suggest that environmentally benign production of biodegradable polymers is feasible. We further used PHA-rich biomass to produce a natural fiber-reinforced thermoplastic composite that can be used to offset advanced wastewater treatment costs.

Functional stability of a mixed microbial consortium producing PHA from waste carbon sources.

Polyhydroxyalkanoates (PHAs) represent an environmentally effective alternative to synthetic thermoplastics; however, current production practices are not sustainable. In this study, PHA production was accomplished in sequencing batch bioreactors utilizing real wastewaters and mixed microbial consortia from municipal activated sludge as inoculum. Polymer production reached 85, 53, and 10% of the cell dry weight from methanol-enriched pulp and paper mill foul condensate, fermented municipal primary solids, and biodiesel wastewater, respectively. Using denaturing gradient gel electrophoresis of 16S-rDNA from polymerase chain reaction-amplified DNA extracts, distinctly different communities were observed between and within wastewaters following enrichment. Most importantly, functional stability was maintained despite differing and contrasting microbial populations.