Research Articles

Rice straw as a source of energy could substitute for fossil fuels and reduce greenhouse gas (GHG) emissions. Thus, the aim of this paper was to analyze the energy and GHG emissions of rice straw to the energy chain in Egypt. The analysis was performed starting from paddy production, straw collection and transportation, and energy generation for two scenarios: power plant and anaerobic digestion plant. The results showed that the paddy production and transportation stage represented the highest contribution of the total energy consumption and GHG emissions for the two scenarios, respectively. The energy potential was estimated with 4193 GWh electricity and 25,647 × 106 MJ of biogas energy. It was also found that use of rice straw as an energy source could reduce the use of fossil fuel and mitigate air pollution from direct burning of rice straw by 3 Mt CO2-eq of GHG emissions.

Use of electrostatic powder coating technology for wood-based panels has considerably increased in the last decade. In this study, oriented strand boards (OSB; OSB/2 and OSB/3 grades) were coated with powder coatings using an electrostatic corona spray gun. Epoxy/polyester (hybrid:1/1) coating that is suitable for indoor applications was applied to the surface of OSB specimens (150 g/m2) at three different curing temperatures, 120 °C for 15 min, 140 °C for 10 min, and 160 °C for 10 min using the electrostatic corona gun. The surface properties of the OSB specimens, roughness, wettability, scratch resistance, abrasion resistance, and film thickness were determined. The abrasion resistance and scratch resistance of the coated OSB specimens improved with increasing curing temperature from 120 to 160 °C. The highest mechanical surface strength was obtained from the OSB/3 specimens cured in the infrared oven at 160 °C for 10 min, while the lowest strength was found in the OSB/2 specimens cured in the infrared oven at 120 °C for 15 min. The contact angle values of the coated OSB specimens increased with increasing curing time, while the surface roughness decreased. The curing temperature of the electrostatic powder coating may be a useful indicator to users to obtain better surface quality on the substrate.

An albumin adhesive derived from animal blood was used for the first time for the production of two kinds of fiberboard in a dry process: medium-density fiberboard (MDF) and wood fiber insulation board (WFI). Additionally, the curing for WFI was completed using an innovative hot-air/hot-steam (HA/HS) process. There is a general importance to develop alternatives to substitute common binding agents, such as urea-formaldehyde (UF) or polymeric methylene diphenylene diisocyanate (pMDI) resins, and to develop value-added opportunities for such waste material from slaughterhouses. An adhesive analysis was performed to understand the curing reaction of these protein adhesives, which showed good properties in regards to viscosity or gel time. The physical-mechanical results showed on the one hand that the albumin adhesive could compete with UF-bonded MDF regarding tensile strength and modulus of rupture in conformity to the European Standard, but it failed to meet requirements for thickness swelling. The albumin adhesive also can compete with pMDI bonded WFI regarding tensile and compression strength, but it showed non-viable results for short-term water absorption.

Propolis is an important antifungal agent found naturally in beehives and used as a food supplement for many purposes. This study aimed to use methanolic propolis extract (MPE) as a treatment material as an antifungal agent for wood preservation. Scots pine and paulownia woods were exposed to Trametes versicolor and Neolentinus lepideus fungi for 12 weeks, and untreated woods were used as the controls. Compared with the control, paulownia wood exposed to N. lepideus had a 47.2% mean mass loss, while the treated wood with 7% MPE had an 11.6% mean mass loss. In addition, a 27.2% mass loss occurred with the control for Scots pine when exposed to N. lepideus, and a 2.5% mass loss occurred with the 7% propolis-treated specimens. Total phenolic content and the phenolic profile of the raw propolis samples were also analyzed. Scanning electron microscopy images showed that the propolis extracts still remained in the wood cells without being degraded after the fungal destruction and the propolis-treated specimens were more durable against fungal decay compared to the untreated control specimens. The results from this study indicated that propolis could be used as an environmentally compatible and natural wood preservative to protect wood against fungal attack.

The dynamic-mechanical behavior of phenol-formaldehyde-impregnated beech wood (Fagus sylvatica L.) veneers was evaluated at various relative humidities. The aim was to identify the plasticizing effects of moisture on phenol-formaldehyde-impregnated veneers. Thin beech veneer samples were impregnated with a low and a medium molecular weight phenol-formaldehyde resin. The measurements were performed with a dynamic-mechanical thermal analysis equipped with a humidity generator. The storage modulus and the loss factor of the uncured phenol-formaldehyde-impregnated and the untreated control veneers were determined at a relative humidity of 15%, 60%, and 85% and a constant temperature of 25 °C. The untreated control veneers exhibited the smallest reduction of the normalized storage modulus. In contrast, the phenol-formaldehyde-impregnated samples exhibited a more intense relative reduction of the storage modulus with increasing relative humidity. This effect was more distinct for samples impregnated with low molecular weight phenol-formaldehyde than for those impregnated with medium molecular weight phenol-formaldehyde. In addition, higher solids contents in the resins led to even smaller normalized storage modulus. Consistently, the loss factor indicated a greater softening of the samples with an increasing humidity and higher solids content of the phenol-formaldehyde.

The pretreatment of lignocellulosic bioresources is a key step in obtaining fermentable sugars. The present study explored the recycling of an HNO3 cooking solution during one-step chemical pretreatment of oat hulls and examined the enzymatic hydrolysis performance of the resultant substrates. Two series of experiments on solution recycling were performed: stabilization and experimental elevation of HNO3 concentration by adding 70 wt% HNO3. When the HNO3 concentration was stabilized at 4.4 wt%, the solution could be used five times. Meanwhile, when the HNO3 concentration was experimentally elevated from 4.4 wt% to 5.6 wt% (at the tenth pretreatment) by adding 70 wt% HNO3, the cooking solution could be used ten times. The yield of reducing sugars on a hydrolyzables content basis was 95% to 99% for ten substrates. In this case, the lignin contents of the substrates did not increase and had no adverse effect on the enzymatic hydrolysis performance.

Birch wood meal was added to the ionic liquid 1-ethyl-3-methylimidazolium acetate ([Emim][OAc])/dimethyl sulfoxide (DMSO) to investigate the conditions required for the complete dissolution of the lignocellulose. Cellulose was treated with [Emim][OAc], and its molecular weight distribution was analyzed by size exclusion chromatography as a model compound. The solubilities of lignocellulose were compared under different treatment conditions, such as the ball-milling time of the raw material and the temperature of the [Emim][OAc]/DMSO treatment. The insoluble fraction was analyzed by pyrolysis-gas chromatography-mass spectrometry (Py-GC/MS) to investigate the lignin structure. Cellulose treated with [Emim][OAc] under a nitrogen atmosphere for 1 to 12 h was remarkably depolymerized. It was demonstrated that lignocellulose is easily dissolved when the temperature of [Emim][OAc]/DMSO and the ball-milling times of lignocellulose are increased; a ball-milled sample was completely dissolved in the ionic liquid. The well-dissolved sample had a low cellulose molecular weight. Ball-milling reduced the primary particle size of the sample and facilitated the dissolution and extraction of guaiacyl lignin units.

A set of reformulated theoretical formulas was developed to measure the relationships between moisture content (MC) and stress wave propagation velocity, dynamic modulus of elasticity ( “E” _”d” ), and modulus of stress-resistograph of the wood. The theory of wood science, elastic mechanics, wave science, and stress wave propagation were used as the theoretical basis. Using larch as the material, both stress wave and micro-drilling resistance technologies were used to study the timber property changes under different moisture contents. The results showed that when the MC of wood did not reach the fiber saturation point (FSP), the wood property decreased sharply with increased MC. However, the study also found that when the MC of wood was higher than the FSP, the wood property decreased with increased MC. In addition, the experimental results showed that the variation trend calculated by the new set of theoretical formulas was consistent with the numerical variation trend measured by the experiment, and the coupling effect of stress wave and micro-drilling resistance was high. This set of theoretical formulas can provide a reference for the research on nondestructive testing and performance evaluation of ancient building timber.

The use of wollastonite as a natural additive for the welding of Scots pine improved the water resistance and shear strength of the welded joint. The X-ray computed tomography images revealed that the welding of Scots pine with wollastonite could postpone crack formation in the welded joints. The specimens welded for a longer time (5 s) had a more uniform distribution of wollastonite particles in welded joints. The microstructure of the wood and the thickness of the wood cell walls also had a great influence on the thickness and strength of the welded joints. Water immersion tests showed that the use of wollastonite in wood joints was able to meet the requirement of resistance to frequent short-term and long-term exposure to water.

The hydrochloric acid-catalyzed hydrothermal pretreatment of brown seaweed residues (Laminaria japonica) was optimized with respect to three operating factors: temperature, time, and the concentration of HCl, using response surface methodology (RSM). In order to confirm the significance of the quadratic model, an analysis of variance was performed, which resulted in an F-value of 11.09. Therefore, the regression model was highly significant. Additionally, the pareto chart was used to contrast the absolute values of the standardized effects. Response surface and contour plots were used to illustrate a surface with a maximum. The perturbation plot showed the sensitivity of the reducing sugars yield to the independent factors. Under the reaction conditions of 142 °C, 9 °C, 18.6 min, and 0.1 N HCl concentration, the experimental yield of 113.0 mg/g and the predicted yield of 107.5 mg/g were obtained.