Research Articles

Freshly harvested alfalfa was fractionated using centrifugation and filtration, whereby alfalfa was separated into a fiber-rich cake and a nutrient-rich juice. The solid cakes from the above separation processes were used as the feedstock for ethanol production using separate hydrolysis and fermentation. The filtration process proved to be more efficient at reducing the solids mass transfer to the juice than the centrifuge process. Glucose from filtered alfalfa solid cake can be efficiently fermented to ethanol with 75% of the theoretical yield. In conclusion, centrifugation was not as effective as filtration in removing particulates and colloidal matter from alfalfa. The filtration process resulted in a solid cake with a higher cellulose digestibility, which leads to a higher ethanol production.

The Hildebrand solubility parameter (d-value) was applied to explain the effect of organic solvent concentration on lignin removal during organosolv extraction of lignin from enzymatically hydrolyzed cornstalks under atmospheric pressure and low temperature (≤ 75 °C) without additional catalyst. The d-value of lignin, calculated using the group-contribution method, was 13.70 (cal/cm3)1/2. The proximity of the d-value between organic solvent-water and lignin explained the delignification capacity of the organic solvent-water. The concentration of organic solvent in the aqueous mixture that led to the highest delignification (i.e., 34.5%, 41.8%, and 53.7% delignification for ethanol-water, 1,4-dioxane-water, and tetrahydrofuran-water, respectively) was around 65 to 75% vol., which was in keeping with the prediction by the solubility parameter theory.

In the present paper changes of validity in Euler-Bernoulli’s elementary theory of flexural vibration for homogeneous materials were tested with respect to changing severity and position of a single defect in wood. As an orthotropic material, wood has different material properties or strengths in different orthogonal directions. A set of absolutely clear specimens of oriental beech was chosen and hand drilled in different diameters (severities) at different relative distances from an end oriented in the R direction. A clear specimen showed a steady decrease in evaluated moduli of elasticity related to increasing mode numbers. After creating the defects, this steady decrease line showed some breakages. The slope breakages of modally evaluated elastic moduli in LT and LR vibrations are suggested as potential finger-prints of single hole defects in the specimen by considering the shape and rate of breakages in the decreasing lines. The recognition scenarios of slope breakages for defect severity and position are summarized.

Boric acid was employed to improve the homogeneity and mechanical properties of a composite based on cellulose fibres and polyvinyl alcohol (PVOH). The influence of boric acid, under different pH values, on the mechanical properties cellulose fibres (handsheets) was investigated. The presence of the boric acid, under alkaline conditions, further improved the mechanical properties of the handsheets. A composite based on PVOH and cellulose fibres was prepared in the presence of boric acid and glycerol, a plasticizer. The employment of the boric acid, under alkaline conditions, was necessary to obtain a homogenous composite. The morphology of the final product was analysed by SEM, and their tensile properties were measured.

Chemical and enzymatic modifications intended to improve the reactivity of dissolving pulp rapidly decrease its yield. In this study, a beating post-treatment intended to increase the reactivity of bamboo dissolving pulp was investigated. Beating post-treatment can create microfibrils on the surface of fibers. The reactivity of unrefined bamboo dissolving pulp prepared via pre-hydrolysis and a subsequent kraft cooking and Op-H-P (oxygen delignification enhanced with H2O2 and sodium hypochlorite) bleaching process was very low. The reactivity increased drastically as the Canadian standard freeness (CSF) of the bamboo dissolving pulp was decreased (i.e., the degree of beating increased). The CSF decreased to 236 mL from its original, higher freeness. The average fiber width was larger and the curling and kink indexes were lower in the pulp of CSF 236 m L compared to those of pulps with greater freeness. However, there was little impact of beating on the crystallinity index of bamboo dissolving pulp.

This research involved the most widely used wood-species of veneers in Hungary (oak, ash, beech, cherry, and maple). The resulting changes in color produced at treatment temperatures between 80 and 200 °C in different treatment times were evaluated using the CIELab color stimulus evaluation system. For higher temperature treatments, a tight functional relationship was observed between the treatment time and the difference in color stimulus. Heat treatments within a temperature range above 160 °C produced visually perceptible results, while color change resulting from heat treatments at lower temperatures was almost imperceptible. For higher temperature treatment a tight functional relationship was observed between the difference in color stimulus and treatment time (r2>min. 0.84). Different tree species produced different extents of change in hue depending on the treatment parameters. Among the color components, the perceptible discoloration was mostly produced by the change in the lightness factor (L*). As the treatment temperature rose, the change in the red (a*) and yellow (b*) components was less significant regardless of the species.

A fed-batch process and high-temperature simultaneous saccharification and fermentation (SSF) process were investigated to obtain high sugar yield and ethanol concentration. Different amounts of alkali-pretreated sugarcane bagasse were added during the first 24 h. For the highest final dry matter (DM) content of 25% (w/v), a maximal glucose and total sugar concentration of 79.53 g/L and 135.39 g/L, respectively, were achieved with 8.3 FPU/g substrate after 120 h of hydrolysis. Based on the hydrolysis experiment, two processes for ethanol production from sugarcane bagasse, simultaneous saccharification and fermentation (SSF) and separate hydrolysis and fermentation (SHF), were also compared using S. cerevisiae. The results indicated that ethanol concentration and yield in the SHF were higher, while ethanol productivity (gram per unit volume and over time) was lower. For 25% substrate loading, the ethanol productivity and ethanol concentration could reach 0.38 g.L-1.h-1 and 36.25 g/L SSF in 96 h, respectively, while that of SHF could reach 0.32 g.L-1.h-1, with an ethanol concentration of 47.95 g/L in 152 h for SHF. When high-temperature simultaneous saccharification and fermentation (SSF) process was performed by using Kluyveromyces marxianus NCYC 587 at 42 °C, 42.21 g/L ethanol (with an ethanol productivity of 0.44 g.L-1.h-1) was produced with 25% dry matter content and 8.3 FPU cellulase/g substrate, which meant 16.4% more ethanol when compared with SSF of S. cerevisiae.

Fique is a biodegradable natural fiber derived from the Colombian Agavaceae family, originating in tropical America and traditionally used for the manufacture of packaging and cordages. Today, however, new uses are being developed. To meet the need for new good-quality, sustainable, low-cost construction materials for social housing, construction materials have been produced that combine different kinds of natural fibers, including fique, to improve their strength and physical properties. To assess these potential new construction materials made with fique fiber, we have characterized samples of different grammages and thicknesses manufactured using short fique fibers extracted from long fibers. We have measured the sound absorption coefficient at normal incidence in an impedance tube, air flow resistivity, and thermal conductivity as a function of grammage.

Based on traditional kinetic models of the gasification process of char, a new modified random pore model (MRP) was proposed. This model can be reduced to a traditional volume model (VM), an unreacted shrinking core model (URCM), a hybrid model (HM), and a random pore model (RPM) by varying the model parameters. Furthermore, not only is the relationship between the reaction rate and conversion rate well described by MRP, as it is in other models, but the position of the maximum reaction rate is also described, which is out of the application range of other traditional models. MRP was validated by gasification of different kinds of chars under different experimental conditions, such as in a carbon dioxide atmosphere, in the presence of water vapor, or with the addition of catalyst. The char gasification process under various conditions could be simulated by MRP with better fitting results than the traditional RPM.

Novel biosurfactant-producing strains were isolated from hydrocarbon-contaminated environments that exclusively utilize agro-waste as their primary carbon source for the expression of biosurfactants. These were quantified using various standardized methods. Among the agro-waste screened, Beta vulgaris (Beetroot) proved to be the most suitable substrate, for which the biosurfactants produced by three bacterial isolates–B. licheniformis STK01, B. subtilis STK02, and P. aeruginosa STK03–lowered the surface tension of the culture media to 30.0, 32.98, and 30.37 mN/m, respectively. The biosurfactants achieved considerable emulsification activity, particularly for heavy hydrocarbons, with the highest emulsification indices being 65.5% and 95% for anthracene and lubricant oil, respectively. The emulsion formed with lubricant oil was thermally stable even up to 50 °C for 21 days. The results showed the proficiency of the novel bacterial isolates used, as well as the suitability of solid agro-waste for biosurfactant production, thus suggesting that exclusive utilization of solid agro-waste is a promising option for use in biosurfactant production for environmental remediation. The outstanding emulsification activity and thermal stability demonstrated by the biosurfactants produced showed their potential applications in enhancing bioavailability and bioremediation of recalcitrant and hydrophobic environmental contaminants.