Volume 13 Issue 1

Poplar veneers are typically oven-dried at high temperatures to shorten the dying period, and thus reduce energy consumption, which also leads to poor bonding strength. In this study, an atmospheric cold plasma system was self-designed to quickly modify the surface of oven-dried poplar veneers (dried at 120 °C, 200 °C, and 240 °C) to yield high bonding strength samples. The physical and chemical properties of treated samples were investigated with an optical contact angle measuring apparatus, fluorescence microscope (FM), and X-ray photoelectron spectroscopy (XPS). The results showed that surface wettability and adhesive permeability of poplar wood veneer were improved after the atmospheric cold plasma treatment. Moreover, the plasma treatment resulted in the incorporation of oxygen-containing groups onto the surface of the oven-dried poplar veneer. For example, the O-C=O group saw its relative content dramatically increase from 1.37% to 13.57%. These effects synergistically resulted in a high increase (76.2%) in bonding strength when using urea-formaldehyde (UF) resin as the adhesive. The plasma modification system used in this study can be utilized at atmospheric pressure, which is easier to realize industrially as compared to using a radio frequency plasma treatment, which is the currently preferred technique.

Pinus kesiya var. langbianensis is an important resin resource tree that belongs to the Pinaceae family. It produces a higher yield of resin per year compared to the rest of the pine trees from the same habitat. To identify genes that may be involved in this high resin yield production, the bark transcriptomes of P. kesiya var. langbianensis and a P. kesiya that produce a normal volume of resin were sequenced using RNA-Seq, and their gene expression profiles were compared in regards to specific interest in the resin synthetic metabolism pathways. The results showed that a total of 68,881 transcripts were assembled, 180 of which were involved in terpene metabolism. Surprisingly, in both the transcriptome analysis and the quantitative fluorescent polymerase chain reaction (QF-PCR), nine genes involved in resin biosynthesis were shown to be significantly down-regulated in P. kesiya. In addition, this study provided numerous gene candidates for the further study of resin production in pine trees.

Rice straw burning is the most widely used industrial process for silica production, resulting in the loss of carbohydrate energy and environmental pollution. In this study, dry anaerobic digestion was applied to convert an organic fraction of rice straw into biogas while generating a solid digestate rich in silica. The methane yield obtained from the dry digestion was 119 L per kg of volatile solids of the straw. The silica content in the ash of the digested straw was 20.7% higher than that of the ash from raw rice straw. The X-ray diffraction pattern revealed the existence of amorphous silica in the ash of the digested straw. The Fourier transform infrared analysis dispelled concerns about the addition of silica impurities by the anaerobic digestion process. The transmission electron microscopy results revealed the formation of nanosilica with particle sizes between 15 nm and 30 nm. It was concluded that high-quality nanosilica can be obtained from anaerobically digested rice straw. The application of this process can decrease the annual global greenhouse gas emissions by 10.5 million tons.

Laccase immobilization is a promising method for the purification of pre-hydrolysis liquor (PHL) for large-scale applications based on recyclability and reusability. In this work, magnetic supports made of Fe₃O₄/SiO₂ were synthesized by a sol-gel method and coated with silica. Then, glutaraldehyde was used as a linker between the support and laccase for immobilization. The immobilized laccase was evaluated by purifying the PHL from a kraft-based dissolving pulp production process. The results showed that the optimal immobilization conditions were a molar TEOS/Fe₃O₄ ratio of 0.6, glutaraldehyde concentration of 6%, laccase concentration of 0.4 mL/mg, and time of 3 h, which led to 71% laccase immobilization. The concentration of total sugar in the PHL increased from 71% to 75%, while the lignin content decreased from 15% to 10% after the immobilized laccase treatment. The separation advantage of the magnetic support enhanced the utility of the laccase.

This research investigates the mechanisms behind color changes, hygroscopicity reduction, and mechanical strength loss in pine wood (Pinus kesiya var. langbianensis) and birch wood (Betula alnoides). Elemental composition changes to the surfaces of pine wood and birch wood that had undergone high-temperature heat treatment were investigated with X-ray photoelectron spectroscopy. The O/C (oxygen/carbon) ratios of the wood surfaces were reduced after the thermo-vacuum and superheated steam heat treatments, which indicated a decrease in the amount of oxygen-containing functional groups. The content of C₁ (carbon atoms bonded to carbon or hydrogen atoms) increased, and that of C₂ (carbon atoms bonded to one oxygen atom) decreased after the thermo-vacuum and superheated steam heat treatments. The results also indicated that the relative lignin content increased and the hydroxyl group (-OH) content in the cellulose and hemicellulose decreased. The ratio of O₂ (oxygen atoms bonded to carbon atoms with a double bond) to O₁ (oxygen atoms bonded to carbon atoms with a single bond) increased remarkably. Thus, the content of carbonyl groups in the lignin increased.

A series of metal chlorides with different valences were used during biomass pretreatment and enzymatic saccharification. After pretreatment, the solid substrate (SS), pretreatment liquor (PL), and conversion yield of cellulose (CYC) were characterized. The results showed that the monovalent salts, NaCl and KCl, as well as the divalent salts, MgCl2 and FeCl2, could promote the enzymatic saccharification to a certain extent, while CaCl2 had little influence on the enzymatic saccharification and cellulase activity, and ZnCl2 had an inhibitor effect on them. For a trivalent salt, FeCl3, the removal rate of hemicellulose and the CYC could come up to a high value. The hemicellulose degradation was mainly related to the valences of metal ions. The cellulose models, the enzymatic saccharification, and the enzyme activity assay results showed that most of the metal chlorides had promoter action toward the enzymatic hydrolysis and cellulase activity, with the exception of ZnCl2. Moreover, the metal ions, especially with high valences, had local effects, which could intensify the potentiation or inhibition impacts on the cellulase activities.

One of the most important aspects in the catalytic cracking of bio-oil is understanding the kinetics of the process.The aim of this paper was to study the kinetics of bio-oil cracking with a silica-alumina catalyst using a continuous fixed-bed reactor. The reaction was studied over the temperature range of 450 to 600 °C with a catalyst bed length of 1 to 4 cm. Three models, Models 1, 2, and 3, were proposed to represent the catalytic cracking kinetics of bio-oil. Model 1 was based on the cracking of bio-oil into the products, while Models 2 and 3 were based on the three-and four-lump models, respectively. The results showed that the rate constants of the catalytic cracking of bio-oil increased with an increasing temperature. The reaction rate constants of the catalytic cracking of bio-oil using Model 1 ranged from 0.221 to 0.416 cm³/g cat·min with an activation energy of  22.3 kJ/mol. It was found that the reaction rate constants from Model 2 can be employed to describe the cracking phenomenon of bio-oil, liquid hydrocarbons, and gas and coke, whereas Model 3 can illustrate the kinetics of bio-oil, kerosene, gasoline, and gas and coke cracking.

Differentiating and ecologizing of products have gained an increasing amount of importance, and green logistics has achieved an irreplaceable position as an important tool for competitiveness. Small and medium-sized enterprises (SMEs), in this case wood-processing enterprises, can achieve this position through the innovation of green products. Based on the results of research focused on finding out how customers perceive green wood products, the objective of this work is to propose possible ways to implement green products in wood-processing SMEs in Slovakia, while taking into account the requirements of customers related to green products. The research was evaluated by methods of testing the statistical hypothesis (binomial test, Chi-square test, Friedman test, and Wilcoxon test), descriptive statistics, and data visualization. The survey revealed that primary reasons why customers of wood-processing SMEs do not buy green wood products is their high price and an insufficient amount of available information about them. In addition to the price, respondents mainly take the quality and safety of the products into account when making purchases. Based on the analysis performed, three basic green strategies focused on product innovation are proposed for consideration by wood-processing SMEs in Slovakia and elsewhere.

The effect of weaving pattern and natural filler addition on the dynamic properties of composite structure was investigated. The reinforcement effect of plain, basket, and twill weave were compared with randomly oriented natural fiber in short form. An experimental modal analysis was used to determine the fundamental natural frequency and modal damping factor of composite structure. The results for a woven reinforced composite were compared with those of a randomly oriented short fiber composite. Reinforcement with woven form enhanced the fundamental natural frequency, while randomly oriented short fiber enhanced the damping factor of composite material. In addition, mechanical properties, such as tensile and flexural behavior, were examined to understand the effect of reinforcement on the composite material. The sisal bio fiber with woven form enhanced the properties of the composite material.

Hemp fiber’s origin has a large impact on the physical properties of degummed fibers. In this research, the effect of hemp fiber origin on the treated fibers was studied mainly by evaluation of chemical composition and microstructure, as well as by the evaluation of the degummed fiber’s properties under a biochemical process. The samples were chosen from the stem with two different growth periods (an early and a late harvest time) and three different sections along the hemp stem (top, middle, and bottom). The results showed a vast variety of chemical compositions and microstructures for raw hemp fibers in different growth periods. The results of the chemical composition analysis indicated that the cellulose content in raw fibers ranged from 41.9±2.3% to 44.8±0.8% and that the lignin content ranged between 12.0±1.5% and 16.5±0.9%. Both the Fourier transform infrared (FT-IR) and X-ray diffraction (XRD) results demonstrated the close relation of the raw fiber’s character to the growth period and sampling section. The physical properties of degummed fibers with different origins were also tested, and large variations in length and linear density were found, which ranged from 42 mm to 67 mm for length and from 11.36±0.37 dtex to 21.55±0.54 dtex for linear density.