Research Articles

Fuel pellets were produced with biomass residue from anaerobic digestion. Single-factor experiment and Box-Behnken design were employed to investigate the effects of pellets-associated variables on the mechanical properties of pellets, and the optimal condition was determined. The results revealed that the pellets-associated variables, including particle size, moisture content, die temperature, and molding pressure had significant influences on the mechanical properties of pellets, such as compressive resistance (CR), durability (DU), and density (DE). The regression models were obtained with the R2 values of 0.9802, 0.9628, and 0.9610 for CR, DU, and DE, respectively, suggesting that the differences between the actual and predicted values could be explained by the regression models. The optimal values of pellets-associated variables were determined (particle size of 0.4 mm, moisture content of 8.4%, die temperature of 115 °C, and molding pressure of 150 MPa); the corresponding responses were 1470 N, 99.6%, and 1180 kg/m3 for CR, DU, and DE, respectively. The results of verification showed a good agreement between the predicted data and experimental outputs. In summary, a novel approach was presented for the preparation of pellet fuels made from biomass residue from anaerobic digestion, and a reliable reference was therefore provided for the comprehensive utilization of biomass materials.

The tracheid and crystalline properties of earlywood and latewood within the stems of Korean-grown Dahurian and Japanese larches were studied to obtain valuable information for identifying these two species and determining their wood quality. The tracheid length and width were examined via optical microscopy, and the relative crystallinity and crystallite widths were examined using the X-ray diffraction method. The tracheid length and width were greater in the Dahurian larch compared to the Japanese larch. In both wood species, the tracheid length and width increased as the growth ring number increased but stabilized at a certain growth ring number. The relative crystallinity was higher in the Japanese larch wood compared to the Dahurian larch wood, while the crystallite width in both species was similar. Neither the relative crystallinity nor the crystallite width displayed a constant trend from pith to bark. The differences in the tracheid properties and the relative crystallinity of both species could be used to identify them and evaluate their wood quality for their effective utilization.

Significant effects of organoclay and poly(melamine-co-formaldehyde)-methylated (PMFM) impregnation on the mechanical, morphological, and thermal characteristics of raw pulai wood were investigated in this work. The material’s modulus of elasticity (MOE) as well as the maximum compression force (MCF) of the impregnated organoclay/PMFM pulai wood samples were optimized using a designed experiment. The MOE and MCF models had R2 values of 0.9228 and 0.8340, respectively. After the impregnation of organoclay/PMFM pulai wood samples, the MOE and MCF increased considerably, indicating that the pulai wood’s mechanical characteristics had improved. The compositional analysis verified the polymerization and dispersion of organoclay and PMFM. Using Fourier transform infrared spectroscopy, reduction in the hydroxyl groups was detected. The impregnated organoclay/PMFM pulai wood samples had successfully filled the pores and cell cavities, as seen by scanning electron microscopy. The thermal stability of the impregnated organoclay/PMFM pulai wood samples was better than that of the raw pulai wood, with a higher glass transition temperature as determined by differential scanning calorimetry. The thermogravimetric study revealed that the impregnated organoclay/PMFM pulai wood samples had higher decomposition temperatures than the raw pulai wood sample.

The optical and mechanical properties of paper sheets were compared following treatment with biopolymers using two different methods, i.e., internal functionalization and surface modification. Industrial chemi-mechanical pulp was provided, and two groups of paper handsheets were made. The first group of paper sheet samples were prepared with incorporated chitosan in a mixed-in-pulp slurry (at three treatment levels, i.e., 0%, 1%, and 2%), and in the second group, untreated handsheets were spray-coated with either 2% chitosan, 2% nanocellulose, 0.5% DTPA, or a mixed solution (0.5% DTPA + 2% chitosan + 2% nanocellulose). Then, the optical and mechanical properties of the prepared paper sheets were analyzed. The brightness, opacity, and greenness/redness of the samples were measured spectrophotometrically using the CIELab system. Additional properties of the paper, i.e., the water absorption, air permeability, and tear, tensile, and burst resistance, of the treated samples were also measured. The results indicated that the treatments had a considerable effect on the relative mechanical and optical parameters, which resulted in an increase in the mechanical properties, especially when the nano-particles were applied to the mixed-in-slurry process. Inversely, results from the spray-coating method indicated better results for the optical specifications.

The aim of this study was to investigate the dimensional stability and mold resistance of slivers from the outer and inner layers of bamboo treated with alkali solutions at various concentrations. The microstructure of the bamboo slivers considerably changed as the parenchyma cells collapsed after alkali treatment followed by a drying process. The water absorption of the treated bamboo slivers increased, while the dimensional stability decreased, especially for the slivers from the inner layer of bamboo. The alkali treatment removed starch from the parenchyma cells in the bamboo slivers treated with a 2% to 15% alkali solution, resulting in a considerable improvement in the mold resistance. The mold resistance performance of inner bamboo slivers was greatly improved when treated at a low concentration (2%). No mold on the bamboo slivers was found even in a high humidity environment for a long period of time, i.e. 87 days. As the concentration increased up to 25%, alkali only removed starch from parenchyma cells that were near the surface of the bamboo slivers and caused partial damage to the parenchyma cells in the outer bamboo slivers. The wettability of the alkali-treated bamboo slivers was higher than that of the untreated samples due to the removal of lignin and a rougher surface. Based on the test results, alkali treatment is a simple yet highly effective method for improving mold resistance but would cause a reduction in the dimensional stability of the bamboo slivers.

Alkali and alkali earth metals (AAEM) can be removed from lignocellulosic biomass via a new demineralization process constituting hydrothermal treatment. The dissolution mechanism of AAEM in different demineralization processes has not been extensively studied. This study employed calcium as a representative of the AAEM group, and changes in the concentration of calcium ions during the hydrothermal demineralization of eucalyptus wood were studied. The dissolution kinetics were modelled using Fick’s second law. The effects of the reaction temperature, hydrolysate pH, and holding time on the dissolution rate of calcium ions were investigated. The kinetic equation for calcium ion dissolution was expressed as ln(1.9532e0.0077T/1.9532e0.0077T-C) = (0.4257P-0.2142e-10622.1/8.314T)t + ln(1.9532e0.0077T/1.056×10-8T3.5263p0.4449). The activation energy of the reaction was 10.62 kJ/mol. The linear regression coefficient (R2) of the predicted and experimental values was 0.9879, which implied high precision of the kinetic model. The results showed that the calcium ions underwent rapid internal diffusion and dissolution during hydrothermal demineralization. The study provides theoretical support for the efficient removal of alkali earth metals via hydrothermal demineralization.

Bamboo is one of the fastest growing plants and has mechanical properties similar to timber. The main reasons for the popularity of bamboo in construction can be attributed to its low cost, local availability, and adequacy of simple, local tools, and skills for fabrication. Application of bamboo in construction is, however, normally limited to low-cost housing and temporary structures due to several factors including irregular shapes, hollow circular cross sections, and durability issues. This report presents the results of an investigation into production of an engineered bamboo lumber product. Bamboo culms were cut into smaller strands and were re-constituted into rectangular sections by gluing and pressing at 140 °C to 145 °C. This approach overcomes the presence of the inherent hollow core and randomizes the inter-nodes and other growth characteristics found in bamboo. The reconstituted bamboo strand lumber (RBSL) was developed using crushed Bambusa bambos species and phenol formaldehyde resin. The physical and mechanical properties of reconstituted bamboo strand lumber were evaluated as per IS 1734 (1983). From the results it was found that the BSL can be used as an alternate to timber to meet Sustainable Development Goals (SDGs) for building applications that will effectively transform the world.

This study aimed to evaluate the sound absorption performance depending on surface finishing of the hardwood cross-section. The sound absorption performance of wood cross-sections was evaluated after band saw cutting, sandpaper polishing, and staining. The sound absorption performance was best following the band saw cutting and no other treatment. On the other hand, stain blocked the pores and decreased the sound absorption performance. This study suggests that finishing methods that preserve the integrity of vessels need to be considered when using wood as a sound-absorbing material.

Pulping using organic solvents is an alternative to kraft pulping and can reduce environmental pollutants. Ethanol is a potential cooking liquor, as it improves the penetration of the cooking chemical due to its low surface tension, and it can be recovered via distillation. The chemical structure and alpha-cellulose content need to be controlled during cooking and bleaching processes to prepare dissolving pulp. Therefore, the effect of ethanol on the cooking efficiency and caustic extraction prior to sequential bleaching on the alpha-cellulose content of the pulp were analyzed. The cooking yield was 50.2% in cooking liquor with 20% NaOH and 50% ethanol at 160 °C for 120 min. The delignification extent was 83.2%, which was better than that of kraft cooking. Caustic extraction was effective in removing the hemicellulose content, and the removal rate of xylan was 61.1% with 10% NaOH added to 1.5% pulp slurry and reacted at 60 °C for 90 min. The alpha-cellulose of bleached pulp could be improved to over 94% by a sequential bleaching process consisting of chlorine dioxide, sodium hydroxide, and hydrogen peroxide.

Leafy mistletoes are semi-parasitic plants that have negative impacts on their hosts, but there is inadequate knowledge about the impacts of Loranthus europaeus Jacq. on Persian oak trees (Quercus brantii Lindl.). This study examined the impacts of L. europaeus Jacq. on morphological and physiological characteristics of Persian oak tree leaves in western Iran. A forested area infested with L. europaeus Jacq. was selected to study. Five infected and five healthy Persian oak trees were selected. Leaf samples were collected from the southern side of infected and healthy tree crowns to quantify and compare the leaf area, leaf weight, and concentrations of leaf minerals. The area and weight of leaves and the amount of leaf K, P, and Ca in healthy trees were statistically more than in infected trees. Leaf N, Mg, Mn, Zn, and Fe contents were not significantly different between healthy and infected trees. The higher amount of leaf area and weight in healthy trees suggested that they had a better growing status, which increased their leaf size and weight. The higher concentrations of K and P in healthy trees indicated their greater growth and resistance to stresses such as mistletoe. Thus, mistletoe causes physiological disorders and decreased growth in oak trees.