Research Articles

Effects were compared for three low-cost pretreatment methods (dilute acid, alkali, and steam explosion) relative to the effectiveness of environmentally friendly enzymatic hydrolysis and ethanol fermentation of aspen, birch, and oak chips. The highest monomeric sugar yield was achieved with the alkali pretreatment of the aspen chips (22 g/L of glucose and 6 g/L of xylose). Additionally, the concentration of lignocellulose degradation products formed during this pretreatment was relatively low, and so the hydrolysis and fermentation efficiencies were 80% and 85%, respectively. The application of dilute acid pretreatment led to lower yield of enzymatic hydrolysis in comparison with alkali pretreatment, resulting in 41% to 62% of theoretical yield for aspen and birch chips, respectively. Increasing the NaOH concentration led to an increase in the monomeric sugar yield, and consequently increased the hydrolysis and fermentation yields. By contrast, increasing the acid concentration resulted in a higher sugar yield, and the fermentation efficiency decreased. The applied steam explosion conditions resulted in the formation of 6.8 to 15.4 g glucose/L, with hydrolysis yield in the range 34 to 42% of theoretical. The most susceptible for pretreatment and enzymatic hydrolysis was found to be aspen biomass.

In the industrial processing of logs, large amounts of bark can be utilized as pellets. This study sought to establish conditions for the efficient use of bark, in the form of pellets, as a solid, renewable fuel. First, the physical properties of the bark (10% moisture content, 618-kg/m³densityfor aspen, and 749-kg/m³ density for birch) and pellets obtained from the shredded bark were determined. Then, the calorific properties (calorific value, calorific density, and ash content) of the shredded native bark and bark treated at 180 °C, 200 °C, and 220 °C for 1h, 2h, and 3 h were determined. The sawdust samples that underwent the torrefaction treatment were analyzed to find the mass loss. The mass losses of the birch bark were 20.0% (native bark) to 39.0% after a heat treatment at 220 °C for 3 h. An increased calorific value, up to 9.6%, showed that both the temperature and duration of the treatment improved the calorific properties of the bark. The findings of this paper highlighted the fact that bark can be used as a fuel source in log processing factories.

Under the premise of an unchanging total thickness in cross-laminated timber (CLT) made from Chinese fir, research into the effect of different CLT laminate thicknesses on the mechanical performance (bending and shear performance) was performed using the existing CLT static analysis theory to calculate and compare the bending performance of CLT specimens. The results showed that at constant total thickness the bending performance increased, the shear performance worsened, and the destruction mode of the CLT structure became simpler with an increase in the CLT laminate thickness. Increasing the odd to even layer thickness ratio effectively improved the bending and shear performance of the CLT specimens for a certain percentage range.

To improve the whiteness of fly ash, fly ash was prepared using calcium hydroxide, water, and carbon dioxide as the reaction system to coat calcium carbonate crystals on the surface of the fly ash. This study investigated the effect of the calcium hydroxide content and stirring rate on the crystallization of the calcium carbonate on the fly ash surface. The results showed that the calcium carbonate nanoparticles prepared with a 7% calcium hydroxide concentration and stirring rate of 500 rpm were coated on the surface of the fly ash, and the whiteness of the modified fly ash reached a maximum of 59.7% ISO. The microscopic process of heterogeneous nucleation of calcium carbonate and the LaMer model were explored to explain the influence of the precursor reactant concentration and stirring rate on the nucleation and growth of the crystal.

In order to determine the possibility of whole-tree wood utilization of a native tree species in Northeast China (P. ussuriensis), this study investigated the air-dried wood density and fiber dimensions for each ring in the branch, stem, and root wood of the tree species. The results showed significant differences in wood densities and fiber dimensions among tree positions (p <0.05). The root had the highest average density (0.596 g/cm3), and branch had the lowest average density (0.506 g/cm3). The root and branch wood exhibited larger fibers than that of the stem wood. The root wood had the highest average fiber wall (6.038 µm). The fiber wall of branch wood appeared thinner than the stem wood, although the difference was not statistically significant. The radial pattern of wood density and fiber dimensions indicated that branches and roots did not have juvenile wood such as was found in the stems. The study concludes that the use of branch or root wood of P. ussuriensis would be favorable for papermaking or wood-based panels.

The promotion of sustainable economic development and issues related to ecological and environmental protection has led to a common interest in the use of raw materials from renewable sources. Recently, there have been many scientific works on the use of different natural wastes as components in the production of new composite materials and polymers. An example of natural waste that is not managed efficiently is grain husk, which is a by-product of the production of flour and other products. This work studied the use of wheat grain husk for plastic processing. A short review is presented of studies concerning the use of natural waste and materials as fillers for natural and synthetic polymers, as well as their potential applications. The authors conducted original research on the influence of the mass fraction and particle size of wheat bran on the selected properties of low-density polyethylene, which can be useful in the evaluation of the suitability of this raw material for particular technical applications.

The efficiency of surface pretreatment with natural essential oils relative to the weathering performance of Norway spruce wood was examined. This study investigated the combination of this pretreatment increasing biological resistance and oil-based coating with protection against ultraviolet light and hydrophobic topcoat with silicon nanoparticles during natural and artificial weathering. The coating systems were exposed to 24 months of natural weathering in climatic conditions of Central Europe and 2,016 hours of artificial weathering. The synergistic effect of a coating system based on safflower with essential oils and commercial oil-based coating was the most efficient. The application of one layer of an oil-based coating in a wet state of surface pretreatment exhibited results comparable to the application of two layers in a dry state. For all coating systems, increasing changes of colour, roughness, and surface wettability were observed, which differed according to the weathering method. Weathering performance of transparent coating systems was evaluated during both weathering tests by exact measurements, laser scanning microscopy and visual evaluation as well. Total colour difference did not prove to be a sufficient evaluation criterion to indicate coating performance during weathering.

Currently, the bending properties of glulam made from fast-growing poplar barely meet the requirements for application. In this study, the bending properties of glulam made from preservative alkaline copper quaternary (ACQ)-treated and phenol-formaldehyde resin reinforced poplar in different laminate configurations were full-scale tested via a four-point bending method. Theoretical models including stiffness model and rigidity model under different loading modes were founded based on the mechanical analysis of composite materials to predict the Young’s modulus of bending and bending strength. The Young’s modulus and bending strength of modified fast-growing poplar glulam was greatly enhanced compared with untreated ones, which can meet the standard requirements for symmetrical mixed-grade composition glulam grade E85-F255. The Young’s modulus was predicted with the rigidity model with high accuracy. The relative error was below 12%. The modified stiffness model with correction factors for normal stress and interlayer tension shearing stress can also accurately predict the failure mode and bending strength.

To elucidate the origin of shrinkage anisotropy of wood during the drying process, wood from three tree species, Quercus sp., Juglans nigra, and Pometia pinnata, was analyzed using thin cryomicrotome sections and sequential drying on a micro-scale. The data on shrinkage, based on the transverse direction, were calculated using Image Pro Plus software to measure the thickness of the cell wall of fibers. The results showed that: (1) In the tangential direction, the shrinkage of wood fibers were all in the “smallest-bigger-smaller (-bigger-smaller)” pattern from A to C (A: The cells closest to the wood rays; C: The cells in the middle between the wood rays) and fibers next to the rays always have the minimum shrinkage at different moisture contents; (2) the width of the rays has no negative correlation with the shrinkage of wood fibers; and (3) the rays have the same effect on the shrinkage of wood fiber cells in both latewood and earlywood. In addition, the shrinkage of latewood is more severe than that of earlywood, which leads to tangential shrinkage.

Wood-based precursors and activated carbon microspheres were prepared through chemical curing and activation. The effects of the hydrochloric acid concentration on the thermal stability of the precursors and pore structures of the wood-based activated carbon microspheres were studied by thermo-gravimetric analysis, Fourier transform infrared spectroscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, and analysis of the specific surface area and pore structure. The results showed that the reaction between the carbocations and benzene rings contributed to an increase in the methylene bonds, which reinforced the cross-linking degree and thermal stability of the wood-based cured microspheres. After activation, a typical microporous structure and part of an irregular mesoporous structure were formed in the wood-based activated carbon microspheres. The specific surface area, micropore volume, and mesopore volume increased, reaching maximum values of 1551 m2/g, 0.506 cm3/g, and 0.246 cm3/g at 4 mol/L hydrochloric acid, respectively, and then decreased as the hydrochloric acid concentration increased. The pore size distributions of the micropore and mesopore areas were in the range of 0.5 nm to 1.4 nm and 2 nm to 10 nm, respectively.