Research Articles

1,3-dimethylol-4,5-dihydroxyethyleneurea (DMDHEU) was used to enhance the dimensional stability, fungal resistance, and weathering of wood. The mechanical strength of wood treated with DMDHEU and different catalysts at different treating temperatures was studied. With increasing temperature, the modulus of rupture (MOR) and modulus of elasticity (MOE) of DMDHEU-treated wood first increased and then decreased. Different catalysts exhibited different effects on the MOR and MOE. In the context of SEM, EDAX, and FTIR analyses, the mechanism of strength loss resulting from the treatment with DMDHEU is discussed. In addition, the relationship between strength and pore size distribution determined by DSC was studied. The filling effect of the cured DMDHEU in wood pores reduced the pore size of the samples and may provide mechanical support to the cell wall, which prevents strength loss of the treated wood when the curing temperature is relatively low (90˚C). But at higher curing temperatures (150˚C), the mechanical strength properties of DMDHEU-treated wood decreased greatly.

Three softwood species, spruce (Picea abies Karst.), fir (Abies alba Mill.), and larch (Larix decidua Mill.), and five hardwood species, oak (Quercus petraea Liebl.), ash (Fraxinus excelsior L.), beech (Fagus sylvatica L.), cherry (Prunus avium L.), and black locust (Robinia pseudoacacia L.) were treated at high temperatures under vacuum conditions with Termovuoto® technology. All of the wood species were treated at different temperatures (from 160 to 220°C), different times (from 45 minutes to 5 hours), and under different pressure conditions (160, 210, and 330 mbar). The treated material was characterized in terms of mass loss, color changes, and equilibrium moisture content. Results showed dissimilar behavior of various wood species and their different sensitivities to treatment schedules. Consequently, the series of tests performed allowed a detailed characterization of the Termovuoto® process and its effect on product quality.

The influence of the enzyme addition point on fiber properties was analyzed by treating two industrial recycled pulp samples – with and without industrial refining – with a mixture of cellulases and hemicellulases. The effects of the enzyme treatment variables – enzyme dosage, time, and consistency – on the fiber properties were studied. The aim of this work was to improve the drainability and the recovery of the strength properties of recycled fibers. The properties of the pulps treated enzymatically and refined in a PFI mill were also evaluated. According to the statistical analysis, opposite effects on drainability were obtained by varying pulp consistency, enzyme dosage, and enzyme application point (i.e., before or after the industrial mechanical treatment). Drainability and strength properties increased when the enzymatic treatment was applied to the pulp without industrial refining, whereas no improvement was observed for pulp with industrial refining.

Dewaxed Olea europaea L. was subjected to delignification followed by alkali extraction with 10% KOH containing 1% H3BO3. The released hemicelluloses were fractionated by precipitation through acidification and ethanol solutions with increasing concentrations from 20 to 30, 40, 50, 60, 70, and 90%. The structure of the subfractions obtained was comparatively characterized by sugar analysis, molecular weight, FT-IR, and NMR spectroscopy. Results indicated that 23.5% of hemicelluloses (% of the dewaxed material) were isolated by the alkaline extraction. An increase of ethanol concentration resulted in the precipitation of the more branched hemicelluloses as indicated by the increase of the ratios of arabinose to xylose and uronic acids to xylose. The hemicellulose subfractions Ha (precipitated by acidification to pH 5.5) and H30 (precipitated by 30% ethanol solution) had a similar structure, which was assumed to be glucuroxylan together with a small amount of α-glucan, whereas the hemicellulose subfraction H70 (precipitated by 70% ethanol solution) had a more complicated structure, which was mainly composed of a (1→4)-linked β-D-xylopyranosyl backbone with various side chains. The comprehensive structural characterization of the hemicelluloses of this species provides fundamental information for their potential applications in the fields of materials, chemicals, and energy production.

In this work, kitchen waste was used as substrate for bio-pesticide production by solid-state fermentation. It was assessed to be well suited for the growth of Bacillus thuringiensis in the experiments. The culture medium contents were optimized by an orthogonal test. The optimum mixture was 55.21% kitchen waste, 22.08% wheat bran, 11.04% soybean cake power, 11.04% grain hulls, and 0.63% mixed ions. In the optimized conditions, a spore count of 5.01 × 1010 CFU/g and entomotoxicity of 15200 IU/mg were obtained after 48 h fermentation, while 2.51 × 1010 CFU/g spore count and 12900 IU/mg entomotoxicity were obtained from the conventional medium. Oil and salt had few adverse effects on Bacillus thuringiensis growth, yield of spores, and toxicity when the concentration of oil and salt were controlled below 10% and 0.4% to 1.2%, respectively. Fermentation medium of 35 kg was successfully used to produce bio-pesticides from solid-state fermentation in a scale-up experiment. Therefore, the present study proved the feasibility of using kitchen waste for the production of bio-pesticides. It seemed to be a promising alternative to conventional media to reduce costs.

This work presents dimensional and shape changes of aspen wood due to surface embossing. The influences of wood treatment, degree of pressing, and initial moisture content on the stability of wood were investigated. The stability of the wood was investigated through dimensional changes (volumetric and linear shrinkage) and shape changes (permanent deformations). The aspen wood was treated by steaming and radio frequency (RF) heating. The treatment did not have a significant effect on the moisture and shape stability of wood after pressing. The non-treated wood showed better stability after pressing.

The paper examines copper ion removal and recovery from mining waters using chitosan and cross-linked chitosan beads as insoluble sorbents in acidic and basic solutions. Batch adsorption experiments were carried out as a function of pH, adsorbent dosage, contact time, and initial Cu(II) ion concentration. Equilibrium data were fitted using Langmuir, Freundlich, Elovich, and Temkin models. The experimental data were best represented by using a pseudo-second order kinetic model and a Langmuir isotherm model. Recovery of Cu(II) ions from sorbents was successfully achieved by treating sorbents with an aqueous EDTA solution. A potentiometric method has been employed to detect the Cu(II) ions in synthetic water samples after the adsorption process. The results demonstrated that Cu(II) ions can be efficiently removed from synthetic aqueous solutions, similar to mining waters, using chitosan and cross-linked chitosan beads.

The aim of this paper was to analyze energy-related properties of forestry and agricultural wastes for energy production purposes, and to compare them with fossil fuels. The forestry wastes used were red cedar, Eucalyptus,and Pinus wood shavings. The agricultural wastes analyzed were rice husk, coffee wastes, sugar cane bagasse, maize harvesting wastes, and bamboo cellulose pulp. The forestry wastes presented more suitable properties for bioenergy production than the agricultural wastes. Desirable energetic properties were found for coffee wastes. The opposite was verified for rice husks. Among the biomass studied, coffee wastes presented the highest equivalent in fossil fuel volume and hence may lead to the highest decrease in CO2 emissions by fossil fuels used in Brazil for steam and heat production. The results suggests that CO2 benefits can be obtained if bioenergy is generated in the same locale where biomass is produced, avoiding CO2 cost of logistics and leading to greater end-use efficiency. The present work promotes the widespread use of different lignocellulosic wastes for bioenergy production and gives useful information for the planning and the control of power plants using biomass.

Unbleached and oxygen-prebleached pulps were produced both in industrial and laboratory scale using Eucalyptus urograndis woods from two different sites (A and B) as a raw material. Quantitative chemical analysis of wood and pulp was performed, aiming to find a correlation with bleaching performance. Fiber dimensions measurements in wood were also performed. Carbohydrates and lignin composition in wood from A and B were found to be similar, while extractives in acetone presented variations of about 0.5% between wood from site A and B. Laboratory-made unbleached pulps from A and B had brightness varying 0.3% ISO, whereas pulps from industry presented variations over 4% ISO from each other. By virtue of its high unbleached pulp brightness, the industry-made sample A presented a higher bleachability than its sample B counterpart. The higher bleachability of the industry-made sample A was traced to its much higher content of hexenuronic acids (HexA), which was caused by differences in pulping conditions in mill sites A and B.

Norway spruce (Picea abies [L.] Karst.) is an important forest species, comprising approximately 55.9% of the growing stock of Czech forests. The variations in the wood densities from three different locations were evaluated with respect to their mechanical and physical properties. Also, mechanical properties and formaldehyde emission of particleboard (PB) and medium-density fibreboard (MDF) panels produced from Norway spruce wood were investigated. The overall average density of the spruce wood was 509.22 kg/m3, ranging from 400.95 ± 27.92 to 617.50 ± 29.91 kg/m3 by location. Most of the panels exceeded the requirements of EN standards for the measurements of MOE, MOR, and the internal bond. Furthermore, the results showed highly significant differences (p < 0.001) among the panels for PB and MDF, which could be related to inter-panel variations. The formaldehyde emissions of PB and MDF were below the E1 emission limits. Moreover, positive correlations were found between the formaldehyde emissions (perforator and gas analysis methods) and board density. The results of this study verify our knowledge of wood density variation as affected by location as well as the age of trees and their relationship to mechanical and physical properties. Consequently, the variation in mechanical properties of the produced panels as well as the formaldehyde emission can further contribute to creating models to predict the quality of the product.