Research Articles

Biochar has the potential for use as a carrier of plant growth promoting rhizobacteria. The biochar in this experiment was produced by the pyrolysis of cotton stalks at high temperatures. Fourier transform infrared spectroscopy (FTIR) and an elemental analyzer characterized the structure and composition of the biochar, while scanning electron microscopy (SEM) observed the relationship between the bacteria and biochar. This study investigated the effects of biochar on the growth of Bacillus subtilis SL-13, a plant growth promoting rhizobacteria, as well as the adsorption of B. subtilis SL-13 to biochar under different conditions. The addition of biochar in a liquid nutrient broth medium was thought to promote the growth of B. subtilis SL-13 bacteria. The SEM images showed that the bacteria entered into the tubular structure of biochar. The adsorption of bacteria onto biochar increased with decreasing biochar particle size. The B. subtilis SL-13 population in biochar was maintained at 106 colony forming units g−1 (CFU) of biochar for up to 120 d. Therefore, the biochar could provide a beneficial microenvironment for the slow release and prolonged survival of bacteria as a carrier in future practical applications.

A tensile test was conducted to investigate the mechanical properties of hybrid bio-composites that have potential for application in helmet shells. Helmets can protect users from serious injuries, reducing traumas and deaths. Military helmets are made with 19 layers of Kevlar, and bicycle helmets are made of glass fibre reinforced plastic materials that are costly. Replacing or reducing these synthetic fibres with plant fibres would reduce costs and may allow for such materials to be recyclable, biodegradable, and more abundant, as the material has been ground or crunched. Flax woven fibre was used to fabricate one panel of composite (Flax only) and three panels of hybrid composite (FLXC, FLXG, and FLXK). In this project, the epoxy resin was modified by weight with 0 wt.%, 0.5 wt.%, 1 wt.%, 1.5%, and 2 wt.% multi-walled carbon nanotubes (MWCNTs). This study examined the effect of multi-walled carbon nanotube (MWCNT) concentration on the tensile properties of hybrid biocomposites. The experimental results suggested that the MWCNTs played an important role in improving the mechanical performance of hybrid biocomposites. It was found that optimum carbon nanotube (CNT) concentration improved the tensile performance of the materials by 2% to 5%. However, an excess CNT concentration led to the deformation of materials and reduced their mechanical performance.

Effects of adding pulping black liquor in the preparation of briquettes were evaluated relative to the properties of the resulting pulp black liquor briquettes. The addition of 2% binder (pregelatinized starch) and a molding pressure of 5 MPa were sufficient to obtain briquettes that complied with DB13/1055 (2009). When 30% of pulping black liquor was added in the preparation of briquettes, the compressive strength, shatter index, moisture content, and the content of volatile matter and ash of the resulting briquettes increased. Moreover, the combustion performance of the briquettes after the addition of black liquor was higher, where the briquettes exhibited an enhanced ignition point, a more stable combustion process, and a 50% higher sulfur-fixation ratio after combustion, compared to the ordinary briquette. However, the thermal stability and calorific value decreased and the ash after combustion of the black liquor briquette contained a higher content of high melting point salts. Therefore, the addition of pulping black liquor in the composition of briquettes should be moderate. The preparation of black liquor briquettes provides an efficient way for utilization of black liquor.

Some mechanical and physical properties and the formaldehyde content of uncoated oriented strand boards (OSBs) that were made from Scots pine (Pinus sylvestris L.), manufactured with different thicknesses, and bonded with polymeric methylene di(phenyl isocyanate) (pMDI) resin were evaluated. All of the mechanical and physical properties were affected significantly by the OSB type (3 and 4) and thickness of the panels, except for the thickness swelling after 24 h and measured formaldehyde content. The measured mechanical and physical properties of the OSB panels satisfied the standard requirements. The densities of the panels ranged from 554.2 kg/m³ to 580.2 kg/m³ and from 573.8 kg/m³ to 610.7 kg/m³ for OSB/3 and OSB/4, respectively, which met the standard requirements. The measured mechanical and physical properties of the OSB/4 panels were higher than those of the OSB/3 panels, but there were no differences in the thickness swelling after 24 h and measured formaldehyde content. Low formaldehyde contents were found for OSB/3 (0.00 mg/100 g and 0.29 mg/100 g) and OSB/4 (0.18 mg/100 g and 0.47 mg/100 g).

Cryogenic treatment via liquid nitrogen (LN) was evaluated as a means to improve the capability of impregnation and penetration in fir and spruce wood. There are a few vital problems that occur during the impregnation process of wood protection. One problem is that refractory woods have different anatomical features that make the impregnation process difficult. For the specimens that were conditioned with the air and oven, the retention changes were determined with an image analysis, scanning electron microscopy (SEM), and energy dispersive X-ray analysis (EDX). In addition, the density and equilibrium moisture content (EMC) values were measured. The LN treatment resulted in degradation in the bordered pits. Then, the margo and torus bonds were torn, the bordered pits were opened, and the liquid transportation of wood was facilitated. It was determined that the LN treatment and impregnation increased the depth and dispersion capability of the penetration. The LN treatment helped facilitate the flows from pores to pores by hindering the aspirations of the bordered pits, and thus the flow of chemicals was facilitated. Obtaining deeper penetration in refractory wood species will result in an improved impregnation process.

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.