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BioResources, Volume 4, Issue 1
NOTE: Each current issue of BioResources continues to build as new articles are approved.
It is proposed that the prefix “retro” can serve as an irreverent, but timely buzzword for the development of new technology to meet human needs. Society has carried out experiments at a very large scale for the last century or so to meet our collective needs though the use of fossil-based fuels and synthetic materials. Those experiments have seemed successful in the short term, feeding more of us and supplying a lot of us with rising standards of living. But the experiments often have failed us in terms of sustainability. A health crisis, global warming, and resource depletion are urgent problems caused by careless use of fossil fuels and related synthetic organic chemicals. The prefix “retro,” as in “retrotechology,” signals a disciplined return to a reliance on nature-based products, as well as a respect for the beauty, but also the fragile character of our natural environment. PDF
The plant cell wall exhibits a hierarchical structure, in which the organization of the constituents on different levels strongly affects the mechanical properties and the performance of the material. In this work, the interactions between cellulose and xylan in a model system consisting of a bacterial cellulose/glucuronoxylan (extracted from aspen, Populus tremula) have been studied and compared to that of a delignified aspen fiber material. The properties of the materials were analyzed using Dynamical Mechanical Analysis (DMA) with moisture scans together with dynamic Infra Red -spectroscopy at dry and humid conditions. The results showed that strong interactions existed between the cellulose and the xylan in the aspen holocellulose. The same kinds of interactions were seen in a water-extracted bacterial cellulose/xylan composite, while unextracted material showed the presence of xylan not interacting with the cellulose. Based on these findings for the model system, it was suggested that there is in hardwood one fraction of xylan that is strongly associated with the cellulose, taking a similar role as glucomannan in softwood. PDF
Fuel ethanol can be produced from pretreated spruce wood through enzymatic hydrolysis and fermentation. Processed spruce wood samples (acid-catalyzed steam hydrolysis followed by enzymatic hydrolysis and fermentation) were fractionated into water-soluble products and residual solids. The dioxane/water soluble portions of the solids were fractionated by liquid-liquid extraction. A substantial portion of the processed wood (20-70 %) was insoluble in both water and dioxane/water. An almost pure lignin fraction, corresponding to about 20 % of the total lignin of the wood, was isolated. Examinations by 1H NMR spectroscopy showed that the processes led to extensive cleavage of arylglycerol b-aryl ethers in the lignin. The lignin content of other fractions could be estimated very roughly by IR spectroscopy. Purified lignin from SO2-catalyzed steam hydrolysis contained approx. 0.2 % sulphur. PDF
This article describes the pyrolysis behavior of precipitated washed lignin in a Laminar Entrained Flow Reactor between 700 and 1000°C and at different residence times. Lignin was precipitated by acidification of softwood black liquor using CO2. After acid washing, the solid material was dried and sieved (80-100 μm). This material was then fed into the reactor at a rate of about 0.1 g/min. The formed gases were analyzed with respect to CO, CO2, and CH4, and char was collected and weighed. A traditional first order Arrhenius kinetic expression, based on the temperature of the particles with respect to residence time, was adapted to the experimental results. The activation energy was found to be 32.1 kJ/mol. The low ash content in the washed lignin gave a very low solid material residue after the reactor. PDF
In this work a green route is reported to prepare a TiO2 macroporous network using corn starch microspheres flake as a bio-template. The starch microspheres prepared by emulsion technology were used as a template into which precursor tetrabutyl titanate (TBOT) was permeated using supercritical carbon dioxide (scCO2) as a forceful carrier or infiltration media, resulting in the formation of an organic/inorganic hybrid material; then the coated template was gelled and dried during the scCO2-coating and the depressurization processes, followed by removal of the template by calcination at 700°C; finally, TiO2 inverse-opals-like material reversely replicating the starch microspheres template was obtained. Scanning electron microscopy (SEM), nitrogen sorption measurements, and X-ray diffraction (XRD) indicated that the products were the inverse replicas from their templates. The obtained TiO2 inverse opals-like material showed a wide dispersion of pore sizes from mesopores to macropores – a few nanometers to several micrometers –with the BET surface area up to 103 m2/g, and a predominantly anatase crystalline phase. In addition, the wall thickness of the macropores varied with tunable pressure for closed cells or open-cell foams. So this facile and environmentally friendly process for the preparation of high-surface area, thermally-stable, metal-oxide catalysts and supports by a starch microsphere templating approach may have widespread potential applications in catalysis, absorbents, photoelectric materials, and so on. PDF
Müller, G., Schöpper, C., Vos, H., Kharazipou, A., and Polle, A. (2009). "FTIR-ATR spectroscopic analysis of chages in wood properties during particle- and fibreboard production of hard- and softwood trees," BioRes. 4(1), 49-71.
Fourier transform infrared attenuated total reflectance (FTIR-ATR) spectroscopy was combined with multivariate data analysis to investigate the chemical changes in wood during particle- and medium density fibreboard (MDF) production of grand fir (Abies grandis [Douglas ex D. Don] Lindl.) and European beech (Fagus sylvatica L.). The mechanical and technological properties of the novel particle- and fibreboards from beech or grand fir wood were similar to those of conventional panels from pine and spruce. This indicates that these timbers can be used as resources for wood-based panel production. Principal component analysis of FTIR spectra differentiated wood, fibres, particles, MDF, and particleboards of both species in the whole production process. Modifications in the spectra of fibres and particles suggested that cellulose properties of wood were changed during mechanical pulping. Different binders and hydrophobic additives were clearly traceable and discernable in wood composites. Samples from the same production step were clustered together, indicating high homogeneity of the raw materials, and intermediate and final products, respectively. This suggests that FTIR spectroscopy in combination with cluster analysis is a useful tool to assess product quality and can be further developed to control and optimize production processes for innovative wood-based panels. PDF
The carcinogenicity and mutagenicity of chemicals may be modulated by other chemicals, including those prepared by organic synthesis. Considering the several drawbacks of synthetic compounds vis-a-vis the human organism, the lignin biomass component was examined for this purpose. The binding affinity of lignin samples prepared by chemical and biological modification of lignin products derived from chemical wood treatment towards for N-nitrosodiethylamine (NDA) was examined. The protective role of the lignin samples against carcinogenesis was tested on a well-known model carcinogen, N-methyl-N´-nitro-N-nitrosoguanidine (MNNG). The observed ability of a series of lignin preparations to reduce alkylation damage of deoxyribonucleic acid (DNA) on hamster cells in vitro could be explained by their affinity to bind N-nitrosoamines. The results indicate that lignin has potential to protect living organisms against damaging effects of different genotoxicants. PDF
Carboxylation of cotton linters was investigated relative to its use in ion exchange. The effects of different treatments of cotton linters, such as alkali, acid, and activating agents, e.g. LiCl, on the molecular structure and carboxylation of cotton linters were taken in our consideration. The absence or presence of a crosslinking was considered, and the efficiency of these prepared carboxylated cotton linters toward metal ions uptake, as well as thermal analysis of treated and carboxylated cotton linters, was investigated. It was found that treatment of cotton linters with alkali and activating agent decreased the crystallinity index (band intensity at 1425/band intensity at 890 cm-1). On the other hand, the prepared carboxylated cotton linters had lower crystallinity index than uncarboxylated linters. Thermal analysis of the treated and carboxylated cotton linters allowed calculation of the activation energy of thermally treated materials. It was found that the crosslinked and acid treated cotton linters had a higher activation. PDF
The adsorption of Trametes hirsuta and Melanocarpus albomyces laccases on cellulose and lignin model substrates was studied by quartz crystal microbalance with dissipation, QCM-D. The laccase-treated surfaces were also analyzed by atomic force microscopy (AFM) and x-ray photoelectron spectroscopy (XPS). The laccases were found to adsorb at acidic and neutral pHs on both surfaces. The adsorbed amounts increased rather linearly with the change in dissipation when the lignin or cellulose was treated with T. hirsuta laccase. Higher adsorbed amounts were obtained using M. albomyces laccase. The adsorption of M. albomyces laccase on lignin was strongly dependent on pH. At low pH thin and rigid laccase layers were formed and the amount adsorbed was high, while at high pH the laccase layers formed were dissipative and loose and the amount adsorbed was low. A good correlation between the adsorbed amount of laccase and the surface nitrogen content was found. The adsorption of laccases made the surface structure of the cellulose and lignin substrates more granular. PDF
Flax fibre reinforced polypropylene composites were fabricated using a high speed mixer followed by injection moulding. Prior to composite production, the fibre was modified by acetylation in the presence of perchloric acid. The effect of acetylation of the fibre was assessed on the basis of moisture resistance and dielectric properties of the resulting composites. It was found that the moisture absorption and swelling properties of the composites were reduced respectively to 60% and 30% due to acetylation. Two different types of biocide were mixed with untreated flax fibre, and the samples were exposed to decay fungi for up to 3 months along with control polypropylene. The composites with acetylated fibres showed good protection against fungi, and biocide had less effect on biological resistance. The dielectric properties of the flax-polypropylene composites were also estimated as a function of aging period. The composites with modified fibre showed more improvement in dielectric properties compared to the composites with untreated fibres. The mechanical properties were investigated for those composites. Tensile and flexural strengths of composites were found to be increased following acetylation due to modification, and strength properties of both untreated and acetylated flax fibre reinforced polypropylene composites decreased with respect to aging period. The Charpy impact strengths of composites were found to increase with increasing aging periods. PDF
The purpose of this investigation was to study the effect of fiber characteristics, especially fiber wall thickness, on the hygroexpansion behavior of paper due to humidity changes. Five different eucalyptus Kraft pulp samples were studied with an OPTIDIM hygroexpansivity tester. As a reference, birch and acacia were included. In all, seven pulp samples were refined at low consistency (LC), using a Voith Sulzer refiner. Both anisotropic and isotropic sheets were investigated. The sheets were dried under restraint. The results showed that fiber wall thickness is an important factor in controlling the hygroexpansivity of paper through fiber network activation. PDF
Chalamcherla, V., Maringanti A., S., Muvva, V. L., Mangamoori, L. N., and Ramireddy, M. R. (2009). "Use of lignocellulolytic mutants of Pleurotus ostreatus in ruminant feed formulations," BioRes. 4(1), 142-154.
Two lignolytic mutants (POM1 - U.V. irradiated and POM2 – X ray irradiated) of P. ostreatus wild type (POW) were developed and used in new feed formulations for ruminants. Paddy straw (10 kg) amended with coconut cake, glyricidia leaves, urea (2%), and rice bran (5%) along with mutant forms of P. ostreatus substantially increased the reducing sugars, crude protein, and In Vitro Dry Matter Digestibility (IVDMD), while reducing the lignin contents. Maximum amounts of reducing sugars (555 mg/100 ml) were reported in ration 1 with strain POW in 10 days of incubation period, while a minimum was recorded in POM1 (380 mg / 100 ml) in ration 1 in 30 days of incubation. U.V. irradiated mutant was responsible for accumulation of high crude protein (CP : 42.1 mg / 100 g) in ration 1 after 30 days of incubation. The percent lignin loss was more by mutant forms, and this loss was increased with increased incubation. As a consequence, IVDMD% has been gradually improved and maximized with feed formulations 3 (49.71%) and 1 (47.07%). PDF
Nazir, A., Soni, R., Saini, H. S., Manhas, R. K., and Chadha, B. S. (2009). "Regulation of expression of multiple beta-glucosidases of Aspergillus terreus and their purificaiton and characterization," BioRes. 4(1), 155-171.
This study reports the regulation and purification of b-glucosidases from a thermotolerant Aspergillus terreus AN1 strain, previously reported for efficient deinking of composite paper waste. The differential expression of four beta-glucosidase isoforms, in response to carbon sources in production medium, was studied by electrophoretically resolving proteins by polyacrylamide gel electro-phoresis analysis (PAGE) and developing zymograms using methylum-belliferyl b-D glucoside as substrate. Three b-glucosidases (bGI, bGII & bGIII) were purified using chromatographic techniques. SDS-PAGE revealed the respective molecular masses of bGI, bGII, and bGIII, as 29, 43, and 98 KDa, and isoelectric point (pI) to be 2.8, 3.7, and 3.0. The b-glucosidases exhibited diverse pH and temperature optima as well as stability. b-Glucosidase I (bGI) specifically recognized pNP-b-glucopyranoside (pNPG) as a substrate, whereas, b-glucosidase II (bGII) and III (bGIII) also showed activities against cellobiose and salicin. In contrast to bGII and bGIII, the activity of bGI was positively influenced in the presence of hexoses/pentoses and alcohols. Km and Vmax for hydrolysis of pNPG by bGI, bGII, andbGIII were found to be 14.2 mM and 166.9 µmol -1mg protein -1, 4.37 mM, and 34.7 µmol -1mg proteins -1, and 11.1 mM and 378.7µ mol -1 mg protein -1, respectively. PDF
Rutkowska, E. W., Wollboldt, P., Zuckerstätter, G., Weber, H. K.., and Sixta, H. (2009). "Characterization of structural changes in lignin during continuous batch kraft cooking of Eucalyptus globulus," BioRes. 4(1), 172-193.
Eucalyptus globulus wood originating from plantations in Uruguay was subjected to continuous batch kraft cooking (CBC), applying mill-like conditions. Pulp samples were taken at different stages of CBC cooking being representative for all three cooking phases. The residual lignin was successfully isolated in a reasonable yield by a new method, the dissolved wood lignin (DWL) protocol, which is based on the total dissolution of ball milled wood and pulp samples in dimethylsulfoxide and N-methylimidazole (DMSO/NMI) followed by precipitation in dioxane/ water to separate lignin and carbohydrate fractions. For comparative reasons, the lignin was also isolated by a conventional mild acidolysis (AL) method. Extensive structural lignin characterization using 1D and 2D NMR revealed that the DWL protocol allows the isolation of less altered lignin than the AL method. During bulk and residual delignification, the S/G ratio of lignin remaining in the fibers continuously decreased, while the content of b-O-4 units and phenolic OH groups remained almost unaffected, suggesting that the CBC process permits enhanced delignification efficiency and good bleachability. PDF
A number of important anatomical features and chemical composition in opposite, normal, and compression wood of Norway spruce (Picea abies) were evaluated to optimally utilize spruce logs containing compression wood. A comparison of axial tracheid and ray cell features in the opposite, normal, and compression wood was provided. Lignin, cellulose, acetone-soluble, and water-soluble extractive contents of the woods were also determined. Results revealed a major variation in the anatomical and chemical characteristics of the woods. Compression wood showed extremely different microscopic features, and chemical composition compared to normal and opposite wood. In most of features investigated in the present study, normal wood occupied a transitional position between opposite and compression wood. PDF
Peat with an approximate 60% carbon content collected in the suburbs of Palangka Raya, Indonesia, was carbonized, followed by activation with steam in an electric furnace. The resultant activated carbon (AC) had ca. 900 m2/g of BET surface area and 1000 mg/g of iodine adsorption. This performance implies that this AC can be used as an adsorbent for environmental purification. We had a carbonizing furnace manufactured in Palangka Raya, which did not require electric power. Some AC having 350 mg/g of iodine adsorption was obtained by using this furnace. Although the adsorption ability was much lower than that of commercially available AC, the AC achieved significant decoloration and decrease in chemical oxygen demand of polluted river water. Thus, this article demonstrated the potential of tropical peat soil as a source of AC. PDF
Ekhtera, M. H., Azadfallah, M., Bahrami, M., and Mohammadi-Rovshandeh, J. (2009). "Comparative study of pulp and paper properties of canola stalks prepared by using dimethyl formamide or diethylene glycol," BioRes. 4(1), 214-233.
Comparision between pulping of canola stalks with dimethyl formamide and diethylene glycol was studied in order to investigate the effects of cooking temperature (190˚C, 210˚C, and 230˚C), cooking time (120 min, 150 min, and 180 min) and dimethyl formamide or diethylene glycol (50%, 60%, and 70%) on the properties of pulp and paper. SCAN viscosity was applied to estimate the extent of cellulose degradation. Responses of pulp and handsheet properties to the process were analyzed using statistical software (MINITAB 15). The results showed that DMF pulp of canola was better than DEG pulp of Canola under the same conditions of cooking and organosolv ratio. In DMF pulping and DEG pulping, cooking temperature is a significant factor affecting paper properties. Analysis of results revealed that DMF pulp canola obtained at 230 °C, 180 min, and 70% DMF had a low kappa number (25) , indicating that the desired properties of the final product dictated the optimized pulping conditions. PDF
Yokota, S., Matsuo, K., Kitaoka, T., and Wariishi, H. (2009). "Retention and paper-strength characteristics of anionic polyacarylamides conjugated with carbohydrate-binding modules," BioRes. 4(1), 234-244.
The retention behavior of polymers having the specific affinities of glyco-hydrolases for pulp fibers was investigated with regard to paper-strength enhancement in contaminated papermaking systems. Carbohydrate-binding modules (CBMs) of cellulases derived from Trichoderma viride and T. reesei, and of xylanase from Thermomyces lanuginosus, were obtained by site-directed digestion with papain, then introduced into anionic polyacrylamide (A-PAM) via a peptide condensation reaction. Three types of CBM-conjugated A-PAMs (CBM-A-PAMs) displayed different retention behavior, depending on the kind of pulp substrates, i.e. hardwood and softwood fibers. The CBM-A-PAM from T. viride demonstrated good additive retention for hardwood pulp fibers, resulting in high tensile strength of paper sheets, even under contaminated conditions in the presence of Ca2+ ions and ligninsulfonate. The CBM-A-PAM from T. reesei showed better performance for softwood than for hardwood sheets. The xylanase CBM-A-PAM was preferentially retained on hardwood fibers in which hemicelluloses might be present. Such an additive retention system, with inherent affinities of enzymes for pulp fibers, is expected to expand the application range of CBM-polymers in practical wet-end processes. PDF
A fundamental study was carried out to explore the properties of canola stalks with regards to pulp and paper production. In this study the morphological properties, chemical composition, and soda pulping properties of canola stalks were investigated. The mean values of length, diameter, and cell wall thickness of canola stalks fibers were measured as 1.17 mm, 23.02 mm, and 5.26 mm, respectively. The morphological properties analysis indicated that despite the thicker cell wall, the morphological properties of canola stalks fibers were comparable to those of non-woods and hardwoods fibers. The holocelluloses, alpha-cellulose, lignin, and ash contents of canola stalks were determined to be 73.6, 42.0, 17.3, and 8.2 wt%, respectively. The hot water and dilute alkali extractives of canola stalks were determined as 18 and 46.1 wt%. In comparison to most other non-wood papermaking raw materials, soda pulping of canola stalks required higher chemical charge and cooking time. Soda pulping of canola stalks gave a low yield bleachable grade pulp. The strength properties of bleached canola stalks soda pulp appeared to be similar to those of common non-wood papermaking resources. The overall results showed that canola has a promising potential to be used in pulp and paper production. PDF
Rubber wood (Hevea brasiliensis) was esterfied with phenylisothiocya-nate, and dimensional stability, decay resistance, and photo stability of the modified wood was assessed. The chemically modified wood was characterized by FTIR and CP/MAS 13C NMR spectroscopy. Unmodified and modified samples were exposed to a brown rot (Polyporus meliae) and a white rot (Coriolus versicolor) fungus for 12 weeks. Modified wood samples exhibited good dimensional stability and were very resistant to decay. However, phenylisothiocyanate modification of wood was not effective in decreasing photo-yellowing. PDF
Patel, H., Gupte, A., and Gupte, S. (2009). "Effect of different culture conditions and inducers on production of laccase by a basidiomycete fungal isolate Pleurotus ostreatus HP-1 under solid state fermentation," BioRes. 4(1), 268-284.
The production of laccase by an indigenous strain of Pleurotus ostreatus HP-1 was studied on solid state fermentation. Culture parameters such as type and concentration of substrate, inoculum size, moisture content, pH, surfactant presence, temperature, and nitrogen source were optimized by conventional “one factor at a time” methodology. A maximum laccase yield of 3952 U g-1 of dry substrate optimized was obtained with wheat straw as substrate with five agar plugs as the inoculum, 60% moisture content, pH 5.0, surfactant concentration 0.015 gl-1, and nitrogen source (combination of L-asparagine and NH4NO3 at 10 mM concentration each) at incubation temperature 28oC. Enhancement in laccase activity was achieved with the use of various aromatic inducers and copper sulphate. Highest laccase activity of 14189 U g-1 of dry substrate was achieved using 0.28 mM copper sulphate under optimized conditions. Thus, the indigenous isolate seems to be a potential producer of laccase using SSF and can be exploited for further biotechnological applications. The process also promises economic utilization and value addition of agro-residues. PDF
Lignocellulosic biomass is the most abundant organic raw material in the world. Cellulose and hemicellulose from plants and other biomass can be hydrolyzed to produce sugars. Native lignocellulosic biomass provides limited accessibility to cellulase enzymes due to structural features. The investigations were carried out with waste lignocellulosic raw material, consisting of maize stalks and cobs. Enzyme hydrolysis was performed after acid hydrolysis with a cellulasic product. It was established that the enzyme stage, as a first treatment phase, was inefficient. It was found that cellulase activity was considerably improved after acid hydrolysis of a crushed mass. A two-stage process with acidic and then enzyme hydrolysis method was most efficient and promising for obtaining sugars for ethanol production. PDF
Lignocellulosic fibers have received much more attention than ever before from the research community all over the world during the past few years because of their enormous advantages. A study on the preparation of new series of polymer composites using Pine Needles as a reinforcing material in Urea - Formaldehyde resin has been made. Mechanical properties of intimately mixed particle reinforced (Pine Needles) composites have been studied. Effects of different loading of reinforcement in terms of weight % on static mechanical properties such as tensile, compressive, flexural and wear properties have also been evaluated. The Urea-Formaldehyde resin prepared was subjected to evaluation of its optimum mechanical properties. The reinforcing of the resin with Pine Needles was accomplished in particle size of 200 micron by employing optimized resin. The present work reveals that mechanical properties of the Urea- Formaldehyde resin increases to a considerable extent when reinforced with Pine Needle Particles. Thermal (TGA/ DTA/DTG) and morphological studies (SEM) of the resin and polymer composites thus synthesized have also been studied. The results obtained suggest that Pine Needles can be a premium candidate for the reinforcement of high-performance polymer composites. PDF
Dehkhoda, A., Brandberg, T., and Taherzadeh, M. J. (2009). "Comparison of vacuum and high pressure evaporated wood hydrolyzate for enthanol production by repeated fed-batch using flocculating Saccharomyces cerevisiae," BioRes. 4(1), 309-320.
With the aim of increasing the sugars concentration in dilute-acid lignocellulosic hydrolyzate to more than 100 g/l for industrial applications, the hydrolyzate from spruce was concentrated about threefold by high-pressure or vacuum evaporations. It was then fermented by repeated fed-batch cultivation using flocculating Saccharomyces cerevisiae with no prior detoxification. The sugars and inhibitors concentrations in the hydrolyzates were compared after the evaporations and also fermenta-tion. The evaporations were carried out either under vacuum (VEH) at 0.5 bar and 80°C or with 1.3 bar pressure (HPEH) at 10 7.5 °C, which resulted in 153.3 and 164.6 g/l total sugars, respectively. No sugar decomposition occurred during either of the evaporations, while more than 96% of furfural and to a lesser extent formic and acetic acids disappeared from the hydrolyzates. However, HMF and levulinic acid remained in the hydrolyzates and were concentrated proportionally. The concentrated hydrolyzates were then fermented in a 4 l bioreactor with 12-22 g/l yeast and 0.14-0.22 h-1 initial dilute rates (ID). More than 84% of the fermentable sugars present in the VEH were fermented by fed-batch cultivation using 12 g/l yeast and initial dilution rate (ID) of 0.22 h-1, and resulted in 0.40±0.01 g/g ethanol from the fermentable sugars in one cycle of fermentation. Fermentation of HPEH was as successful as VEH and resulted in more than 86% of the sugar consumption under the corresponding conditions. By lowering the initial dilution rate to 0.14 h-1, more than 97% of the total fermentable sugars were consumed, and ethanol yield was 0.44±0.01 g/g in one cycle of fermentation. The yeast was able to convert or assimilate HMF, levulinic, acetic, and formic acids by 96, 30, 43, and 74%, respectively. PDF
Liimatainen, H., Haavisto, S., Haapala, A., and Niinimäki, J. (2009). "Influence of adsorbed and dissolved carboxymethyl cellulose on fibre suspension dispersing, dewaterability, and fines retention," BioRes. 4(1), 321-340.
The effect of adsorbed and soluble carboxymethyl cellulose (CMC) on dispersing, dewaterability, and fines retention of pulp fibre suspensions was investigated. CMC was added to a suspension in the presence of electrolytes, causing its adsorption to the fibre surfaces, or to a suspension without electrolytes, so that it stayed in the liquid phase. Both the CMC adsorbed on fibre surfaces and that in the liquid phase were able to disperse the fibre suspension due to the ability of CMC to reduce fibre-to-fibre friction in both phases. Adsorbed CMC promoted the formation of a water-rich microfibrillar gel on the fibre surfaces through the spreading out of microfibrils, leading to a decrease in friction at the fibre-fibre contact points and to the increased dispersion of fibres. CMC in the liquid phase of the suspension was in turn thought to prevent fibre-to-fibre contacts due to the large physical size of the CMC molecules. CMC in both phases had detrimental effects on dewatering of the pulp suspension, but adsorbed CMC caused more plugging of the filter cake, and this was attributed to its ability to disperse fibre fines, in particular. Thus, adsorbed CMC also reduced fines retention considerably more than did CMC in the liquid phase of a suspension. PDF
An improved understanding of lignocellulosic biomass availability is needed to support proposed expansion in biofuel production. Fifteen studies that estimate availability of lignocellulosic biomass quantities in in the U.S. and/or Canada are reviewed. Sources of differences in study methods and assumptions and resulting biomass quantities are elucidated. We differentiate between inventory studies, in which quantities of biomass potentially available are estimated without rigorous consideration of the costs of supply, versus economic studies, which take into consideration various opportunity costs and competition. The U.S. economic studies, which included reasonably comprehensive sets of biomass categories, estimate annual biomass availability to range from 6 million to 577 million dry metric tonnes (dry t), depending on offered price, while estimates from inventory studies range from 190 million to 3849 million dry t. The Canadian inventory studies, which included reasonably comprehensive sets of biomass categories, estimate availability to range from 64 million green t to 561 million dry t. The largest biomass categories for the U.S. are energy crops and agricultural residues, while for Canada they are expected to be energy crops and logging residues. The significant differences in study estimates are due in large part to the number of biomass categories included, whether economic considerations are incorporated, assumptions about energy crop yields and land areas, and level of optimism of assumptions of the study. PDF
Wood heat treatment has increased significantly in the last few years and is still growing as an industrial process to improve some wood properties. The first studies on heat treatment investigated mainly equilibrium moisture, dimensional stability, durability and mechanical properties. Mass loss, wettability, wood color, and chemical transformations have been subsequently extensively studied, while recent works focus on quality control, modeling, and study the reasons for the improvements. This review explains the recent interest on the heat treatment of wood and synthesizes the major publications on this subject on wood properties, chemical changes, wood uses, and quality control. PDF
Hubbe, M. A., Chen, H., and Heitmann, J. A. (2009). "Permeability reduction phenomena in packed beds, fiber mats, and wet webs of paper exposed to flow of liquids and suspensions: A review," BioRes. 4(1), 405-451.
Filter media, including those prepared from cellulosic materials, often suffer from permeability loss during continued use. To help understand such issues, one can take advantage of an extensive body of related research in such fields as industrial filtration, water purification, enhanced oil recovery, chromatography, paper manufacture, and the leaching of pollutants from impoundments. Though the mechanisms that appear to govern permeability-loss phenomena depend a lot on the details of various applications, the published research has revealed a number of common features. In particular, flow through a porous bed or fiber mat can be markedly reduced by deposition of particles or colloidal matter in positions that either block or partially restrict fluid flow. Progress has been achieved in the development of mechanistic models, as well as the use of such models in numerical simulations to explain various experimental findings. Further research of this type needs to be applied to cellulosic materials, which tend to be much more elongated in comparison to the bed materials and suspended matter considered most often by most researchers active in research related to permeability loss. PDF