Research Articles

The wood properties of 6-year-old Eucalyptus botryoides and Eucalyptus maculata point towards a possible aptitude for solid-wood end uses. Samples from E. botryoides and E. maculata were characterized regarding within-tree variation in wood density, radial and tangential fibre width, fibre wall thickness, fibre coarseness, microfibril angle, and stiffness based on SilviScan measurements taken radially from the pith outwards at varying stem height levels. The mean values of the studied wood properties for E. botryoides and E. maculata were, respectively: density 507 kg m^-3 and 695 kg m^-3, radial fibre width 17.4 µm and 17.2 µm, tangential fibre width 16.7 µm and 16.9 µm, fibre wall thickness 1.8 µm and 2.5 µm, fibre coarseness 161.2 µgm^-1 and 212.9 µgm^-1, microfibril angle 15.5° and 14.7°, and stiffness 9.6 GPa and 12.1 GPa. The variation in wood stiffness was explained to a large extent by microfibril angle and wood density variations. The results of the scans, along with the wood variability, indicated that both species should be considered for solid wood products or pulp production.

Sorghum stem, an agricultural solid waste discarded in large amounts, was effectively fractionated into its chemical components to achieve value-added utilization. The stem was successively extracted using water at 80 °C and alkali aqueous solutions with increased concentrations (1% NaOH; 60% ethanol containing 1% NaOH, 3% NaOH, 5% NaOH, and 8% NaOH) at 50 °C, which yielded hemicellulose and lignin fractions as well as a cellulose-rich residue. The hemicellulose and lignin fractions were characterized in terms of yield, sugar components, alkaline nitrobenzene, and oxidation analysis. In addition, the molecular weights were determined by gel permeation chromatography and the structures were further identified by Fourier transform infrared spectroscopy and nuclear magnetic resonance spectroscopy. The results indicated that the hemicelluloses yielded from the alkali aqueous solution had a linear xylan structure. The alkali lignin had a typical guaiacyl/syringyl/p-hydroxypheny structure and low amounts of contaminating sugars (less than 2%). A high concentration of alkali aqueous solution led to the release of lignin with a large molecular weight, whereas increasing the alkali concentration resulted in lignin degradation. The residual stem after the successive extractions was rich in cellulose and had a low crystallinity. In sum, mild successive extractions are a promising way to fractionate sorghum stem waste for further conversion.

Lignin, which is the most abundant aromatic polymer in nature, was used as a green substitute for the toxic bisphenol A. In particular, the ability of epoxidized lignin to simultaneously serve as a cross-linker and rigid segment was investigated. The epoxidized lignin was preferably reacted with a monofunctional amine, which acted as a chain extender, to evaluate its performance as a cross-linker, and in the presence of poly(ethylene glycol) diglycidyl ether as a soft segment to adjust the resin properties. Different poly(ethylene glycol) diglycidyl ether/lignin stoichiometric ratios were tested, whereas the amine/epoxy equivalent ratio was fixed at 1:2. Some of the remarkable resin samples were subjected to differential scanning calorimetry analysis and compared with blank samples that did not include lignin in the composition. Moreover, the evolution over time of the molecular weight distribution of the selected compositions was analyzed by gel permeation chromatography until the solubility in tetrahydrofuran was appreciable.

This work aimed to investigate the effects of various single factors and their interactions on the preparation of cellulose nanofiber (CNF) using ball milling. These factors included the milling ball size, milling time, mass ratio of milling ball to cellulose pulp, and alkali concentration, as well as their complicated interactions. The Taguchi method was applied to the experimental design to systematically study the influences of these factors on the yield of CNF. A method for evaluating the yield of CNF was developed. Both of the simple analysis (SA) and analysis of variance (ANOVA) of the experimental results indicated that the most significant factor influencing the yield of CNF was the mass ratio of milling ball to cellulose pulp. The interactions between this factor and other single factors, e.g., milling time, also showed significant influence on the yield of CNF. Although the influence of milling ball size was negligible, its interaction with mass ratio of milling ball to cellulose pulp must be considered during production. Based on these findings, a mini scaled-up practice was proposed to demonstrate the possibility of the application of ball milling on the mass production of CNF.

Effects of different boiling treatments were evaluated relative to various physical properties of cork from Quercus variabilis before and after treatment, including volume, density, hardness, compression resilience ratio, and color. The boiling water treatment decreased the density, hardness, and lightness of cork. Water absorption amount of cork boiled at 100 °C for 30 min to180 min increased from 28.85% to 52.50%, and expansion in the radial direction was 15.4% to 19.5%. The total color difference (ΔE*) of cork gradually increased with increased boiling time. The values of the compression resilience ratio of all corks after a pressure release at 24 h were >80%. Cork samples boiled at 100 °C for 60 min, and then dried under different temperatures (140 °C to 240 °C), had volume expansion between 35.6% and 65.3%. With increased drying temperature, the ΔE* of cork increased. Cork boiled at 100 °C for 60 min followed by microwave irradiation of different times (2 min to 8 min) had volume expansion of 39.7% to 54.5%. Microwave treatment had little influence on cork color. The sodium hydroxide solution boiling treatment decreased cork lightness, while the hydrogen peroxide-treated cork lightness increased with the increasing of solution concentration, and ΔE* slightly increased.

When designing wooden structures and furniture, it is very important to consider joints that allow the structure to stay together and upright. There are many different types of wood joints. The selection of a joint type and its properties are some of the most important design choices. This article was dedicated to the Domino joint, which allows for strong joints. The Domino joiner is a loose tenon and mortise manufacturing joining tool. This article discusses the effect of selected parameters, such as the type of stress (tensile and compressive), size of the Domino joiner (one-half and one-third thickness), wood species (beech (Fagus sylvatica L.) and spruce (Picea abies L.)), and adhesive type (polyvinyl acetate and polyurethane), on the joint stiffness. The influence of the annual rings was also monitored.

Five different softwoods were used to investigate fast methods for predicting quantitative chemical information via near-infrared (NIR) spectroscopy. In biomass-related industries, fast collection of chemical information from a feedstock is needed. Prior to predicting quantitative information, a principal component analysis (PCA) using NIR spectra was conducted to evaluate the possibility of discriminating the softwoods. As a result of PCA, the five species were divided into three groups. This result indicated that the extractive compounds were key factors because the powder samples were separated by species having a similar extractive content. The partial least square (PLS) method was applied to develop a calibration model for predicting chemical composition. This model showed good performance in predicting the extractive and lignin content of all species. The calibration results of the extractive and lignin content for all species were indicated as R² = 0.99. The cross-validation of the components for all species also showed an excellent value of R² = 0.98 and 0.97, respectively. Based on our results, it was possible to suggest a useful tool for providing rapid information about wood used in the bioenergy and pulp production fields.

Over the last decade, the consumption of renewable energy within the EU increased by 66%, and corporations have recognized that heating with wood waste is a cost-effective response to fluctuating fuel prices and a means of avoiding waste disposal costs. The main objective of this paper was to determine whether the combustion of biomass compared with the use of fossil fuels as the primary heat source would increase the efficiency in Slovak heating companies. This research was evaluated via methods of synthesis, analyses, and financial analyses. The survey found that heating companies with combined productions had better economic results. Based on the peer group comparison, heating companies using renewable resources achieved remarkably higher performance indicators. Among renewable energy sources, total biomass plays an important role and accounted for just over two thirds (64%) of the gross inland energy consumption of renewables in the EU. Wood pellets and agglomerates are currently the most economical way of converting biomass into fuel and are a fast-growing source of energy in Europe. The economic efficiency and key performance indicators strongly depend on the input prices of the energy carriers. In the last decade, the cost of heat produced from natural gas amounted on average to two to three times the cost of deciduous wood. Biomass production can generate employment, and if intensive agriculture is replaced by less intensively managed energy crops, there are likely to be environmental benefits, such as reduced leaching of fertilizers and reduced use of pesticides.

The effect of high-pressure (HP) densification (30, 90, and 150 MPa for 3, 30, and 300 s) on the moisture sorption properties of Paulownia wood was investigated. After the densification, samples were conditioned at three temperatures (20, 30, and 40 °C) and five equilibrium moisture contents (from 11.20 to 95.62%) during the study, after which the equilibrium moisture contents of the control and treated samples were measured. The HP-treated groups had higher equilibrium moisture contents than the controls at higher relative humidity levels. The hysteresis phenomenon and the scanning electron microscopy observations were explained by the transformation of the structural elements by the HP treatment. Finally, two moisture sorption isotherm (MSI) models (a linear polynomial model for adsorption and a quadratic polynomial model for desorption) were established with good performance to describe the relationship between HP treatment parameters, environmental conditions, and equilibrium moisture contents.

Bamboo is one of the most important raw materials for pulp and paper production in several countries due to its abundance and cost-effectiveness. However, the difficulties in bleaching and low brightness of bamboo chemo-mechanical pulp (CMP) has limited the expansion of its utilization. In this study, the low-cost twin-screw extruder (TSE) was used instead of the high-cost common extruded model screw device (MSD) before chemical impregnation to improve the brightness of the bamboo CMP. There were minor differences in the holocellulose, lignin, and pentose contents in the extruded materials between the two devices. The absorbency of the TSE extruded materials was 4.50 g/g, which was three times that of the material extruded by MSD. Alkali optimization was conducted at levels of 12% H₂O₂. The TSE-CMP achieved the highest brightness, at 57.6% ISO with 6% sodium hydroxide (NaOH), while the MSD-TMP only reached approximately 49.6% ISO with 3% NaOH. At the same time, the physical properties of paper-sheets made from bleached TSE-CMP and MSD-CMP were tested. When bleached at 12% H₂O₂ with 6% NaOH, the tensile index of TSE-CMP was higher compared with that of MSD-CMP, while the other strength properties were nearly unchanged.