Research Articles

Xylose residue (XR), the abundant industrial residue from commercial xylose production, was delignified using alkali as a substrate for ethanol production via simultaneous saccharification and fermentation (SSF). It was found that pretreatment with 1.5% (w/v) NaOH at 140 °C for 1.5 h was optimal for delignification efficiency (72.2%) and low cellulose loss (7.1%). The physical changes in samples after alkaline pretreatment were characterized for crystallinity and imaged using scanning electron microscopy (SEM), which demonstrated that the surface of samples became coarser with lignin removal. There were rather significant changes in cellulose crystallinity. The widespread accessibility of cellulose in XR favored enzymatic hydrolysis and achieved considerable bioconversion (98.8% with 15 PFU/g substrate). The maximum for ethanol concentration using SSF bioconversion reached 16.3 g/L, which was about four times more than that of the untreated sample. XR treated using the processes of alkaline pretreatment and SSF was an excellent substrate for bioconversion.

Phenol and p-nitrophenol (PNP) are priority pollutants widely present in wastewater. Developing superior or low-cost sorbents for their removal would be of great benefit. Here, corncob residues (CCR) were converted to hydrochars via hydrothermal carbonization (HTC) and further upgraded to carbon materials by thermal activation in an N2 atmosphere. The influence of HTC conditions including the temperature, residence time, and CCR/water weight ratio on the material properties and their performance for removing phenol and PNP from water were investigated and compared with those that were obtained from pyrochar (directly pyrolyzed CCR). Hydrochars showed lower adsorption capacities for phenols than pyrochar. The initial hydrothermal treatment at 220 °C and 2 h resulted in an improved porosity and 4- to 5-fold higher adsorption capacities for phenol and PNP compared with the pyrochar. However, hydrochars prepared at 250 °C or with a prolonged residence time (4 and 6 h) could not be upgraded to high performance carbon materials by thermal activation. The adsorption isotherms of both phenols on the best performance material were well correlated by the Sips model.

The objective of this study was to evaluate the adhesion strength and glossiness of black alder wood (Alnus glutinosa Gaertn. L.) coated with water-borne and UV varnishes by two application systems. Prior to coating, the samples were prepared by sanding with four combinations of grit size sandpapers, 180 being the final grit. The surface quality of the specimens was measured with a white light profilometer. Any increase in grit size gradually reduced surface roughness, which further influenced the overall coating performance of the samples. UV varnish applied by roller presented higher adhesion strength and gloss as compared to spraying. The specimens varnished with a water-borne finish by spraying exhibited a better adherence to the substrate than those of UV varnished samples by the same method and provided glossiness at 60° geometry in the same range. These results are valuable for the furniture manufacturing industry for generating a better use and efficiency of secondary wood resources in order to achieve value-added products.

The wide use of natural fibers has a long-standing history in Africa. In northern Angola, three native fiber plant species, namely Urena lobata, Triumfetta cordifolia, and Dombeya burgessiae, were investigated with regard to their potential usage in modern applications, such as green composites. Bast fibers of the three species were analyzed morphologically, chemically, and mechanically to determine properties such as fiber density, cellulose content, Young’s modulus, tensile strength, and breaking strain. In comparison to other natural fibers, all three species were characterized by high Young’s moduli up to 60 GPa and tensile strengths up to 950 MPa, yet retting is crucial to unfold the maximum strength of the fibers. Extending the retting time revealed higher values but probably negatively influences economic efficiency. The results demonstrated that the analyzed plants deliver strong and resistant fibers; based on their biomechanical performance, they are alternatives to commercially used natural fibers, such as jute (Corchorus spp.). However, as with other natural fibers, there was high variation in the mechanical properties in the studied species.

Lightweight sandwich engineered wood reinforced with fiber glass using a natural fiber wood foam core was investigated. A prepreg epoxy formulation was used as both wood adhesive and matrix for the prepreg fiber glass. Combining 3 phr of oxybis(benzenesulfonylhydrazide) (OBSH) with 10 phr of ethyl acetate, as foaming agent enhanced the properties of the eucalyptus fiber (EF) wood foam. Incorporation of rice-husk fiber (RF) or bagasse (BG) into the EF reduced the mechanical properties due to the low aspect ratio and high non-compacted bulk density of RF and BG. The high hydrophilicity of BG increased the water uptake and decreased the dimensional stability of the wood core. The mechanical performance of the natural fiber cores was improved by using randomized unidirectional engineered glass (GF), carbon (CF), and Kevlar (KF) fibers. However, the hybridized cores with long fibers and high elastic modulus, with respect to the sample thickness, had a negative impact on the woods due to internal residual stress, leading to a spring-back effect. A fiber glass reinforcement lightweight sandwich structure with engineered wood derived from the EF/BG and its 30% hybrid lightweight cores yielded superior mechanical and durability properties.

Coal and torrefied biomass co-gasification is one of the potential solutions to the reduction of greenhouse gas emissions. For this study, Jatropha seed cake was torrefied at a temperature range of 200 to 300 °C under a nitrogen atmosphere. The torrefied material was then co-pyrolyzed and isothermally co-gasified at 900 °C with two Illinois (IL) #6 coal chars in a fixed-bed reactor connected to an on-line gas chromatography analyzer. Carbon dioxide and carbon monoxide were the primary gas products from the torrefaction process. Kinetic models, such as the shrinking core model, the homogenous model, and the catalysis-controlled model, were used to analyze the gasification mechanism. The results showed that the shrinking core and homogenous models provided the best fits for the gasification reaction data. Jatropha seed cake torrefied at 260 and 280 °C exhibited the best reaction activity with the IL #6 coal chars. The reactivities of coal char with torrefied biomass obtained at 200 and 300 °C were lower in comparison with the others.

This study characterizes and compares coffee chaff (CC) and spent coffee grounds (SCG), the two most useful coffee waste products, and evaluates their performance as fillers and/or reinforcing agents in polymer composites. The morphologies of the CC and the SCG were studied using a scanning electron microscope (SEM). Detailed compositional and elemental analyses of the samples were carried out using several techniques. The thermal stabilities of the two types of biomass were evaluated using thermogravimetric analysis (TGA). Infrared spectroscopy was performed to investigate the functional groups available on the surface of the biomass. It was found that the CC had higher thermal stability, lower fat content, and a denser fibrous structure than the SCG, making it potentially a more suitable material than the SCG for use as a reinforcing filler in polymer composites. To verify this potential, CC and SCG filled polypropylene composites were produced and evaluated.

To reuse waste wood bioresources and determine the factors required for the growth of Lentinus edodes, Quercus baronii wood bioconversion during the artificial cultivation of L. edodes was characterized by X-ray diffraction (XRD), TG, FT-IR, and TD-GC-MS. Mycelia were observed to grow in wood if cellulose was sufficiently degraded and wood extractives were adequately retained. L. edodes grew inwood if the extractives, cellulose, hemicellulose, and lignin maintained a stable quality ratio. Mycelium and L. edodes grew in samples with high cellulose crystallinity. FT-IR spectra showed that L. edodes grew as the intensity of absorbance associated with unconjugated C=O stretching decreased. TG curves suggested that the samples with lower weight loss were suitable for mycelium, but those with higher weight loss were suitable for L. edodes. TD-GC-MS indicated that the samples containing more phenol derivatives and less acetic acid were suitable for mycelium; the opposite trends were observed for L. edodes.

Lignocellulosic biomass as a renewable and valuable resource has been a very active research area during recent years. Ionic liquids (ILs) are an attractive approach for the pretreatment of lignocelluloses. In this work, a series of pyrrolidinium-based ionic liquids were prepared simply and were investigated for the pretreatment of corn stalk at 90 °C for 30 min. The characteristics of regenerated lignin and cellulose-rich materials were determined by Fourier transform infrared spectroscopy (FTIR) analysis. Both ILs and ILs/H2O were studied. Notably, 10.17% lignin based on the original corn stalk was recovered with [Hmp]Cl-pretreatment; 21.34% and 15.83% reducing sugar based on the original corn stalk were observed during pretreatment with [Hmp]HSO4/H2O and [Hmp]Cl/H2O pretreatment, respectively; 80.54% of reducing sugar was obtained based on the cellulose-rich materials with [Hmp]Cl/H2O-pretreatment. Also, the glucose and cellobiose yields were 73.82% and 8.64%, respectively.

Heat-treated wood has an ever-expanding market for exterior and interior applications. The objective of this study was to determine the effect of a heat treatment on the bonding strength of hornbeam (Carpinus betulus L.) wood that was bonded with melamine formaldehyde (MF), polyurethane (PUR), and polyvinyl acetate (PVAc-D4) adhesives. Hornbeam lamellas were heat treated at 150 °C, 175 °C, 200 °C, and 225 °C for 3 h and then bonded. The bonding strength of the specimens was determined. In addition, the density, weight loss, and pH value of the heat-treated wood were investigated. The results showed that the bonding strengths of the heat-treated wood specimens decreased with the temperature of the heat treatment. The bonding strength of the PUR adhesive was higher than the MF and the PVAc-D4.