Research Articles

The selective biodegradation of grape pomace tannins was studied using Aspergillus niger strains. The conditions were optimized in terms of monomeric catechin production. The optimal degradation conditions were: 10.0 g·L-1 of tannins in the induced medium, pH 6.5, and cultured on a shaking table at a rate of 120 r·min-1 at 28 °C for 36 h. The biodegraded tannins were used to partially substitute for phenol-formaldehyde in adhesive formulations. The biodegradation enabled the production of adhesives and wood panels with better properties (lower resin viscosity, higher internal bond strength, and lower thickness swelling). A particleboard in which the resin contained 60% biodegraded grape tannins displayed good performances (IBdry = 0.46 MPa, IBwet = 0.15 MPa) and passed the standard specifications for dry and wet conditions.

This study investigated two classifications of wood cellulose of particle sizes 300 µm to 424 µm and 600 µm to 849 µm. The cellulose samples were characterized using X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), and scanning electron microscopy (SEM). The cellulose crystal revealed a preferred orientation along the (200) plane for the most prominent peak. The XRD diffractogram revealed an orthorhombic structure obtained from the powder diffractogram file (PDF). Furthermore, the crystallinity index and crystalline size were calculated and the increase in crystalline size of the isolated cellulose indicated higher thermal stability. The EDX analysis showed chemical components of carbon (C), sodium (Na), chlorine (Cl), and oxygen (O) in the isolated cellulose. The morphology of the cellulose appeared as strings of fibres. The isolated cellulose has applications in the production of biomaterial, thermal insulating devices, and domestic applications.

To perform a non-destructive evaluation of wood, the Christoffel equation is frequently used to describe the relationship between the ultrasonic wave velocity and the mechanical parameters. In the context of acoustical tomography imaging of standing trees, the key contribution of this numerical study is to determine the influence of mechanical parameters of the wood radial-tangential plane on the wave velocity computation using the Christoffel equation. Mechanical parameters from six species were selected. A sensitivity analysis was carried out by increasing and decreasing every parameter by a given percentage, and then by computing the variation of velocity for a set of wave direction of propagations. The evolution of the wave velocity, according to the direction of propagation, depended on the considered species; there was a difference between the softwoods and the hardwoods. The sensitivity analysis showed a bigger influence of the Young’s moduli, followed by the Poisson’s ratio, and finally by the shear modulus. However, these last two parameters cannot be neglected when using the Christoffel equation to solve the inverse problem of standing tree tomography. A proposed solution involves determining the propagation paths using the Young’s moduli as variables and then inversing the set of equations in accordance with the overall parameters.

This research aimed to develop economical, high-performance acoustic oil palm boards (OPB) using the convection (CV) and microwave (MW) wood drying technologies under variable thermal conditions. The results revealed that the CV and MW oven temperatures were positively correlated with moisture desorption but inversely correlated with drying time. The CV heating temperatures were inversely and positively correlated with the density and volumetric shrinkage, respectively, and the MW power output was positively correlated with density and shrinkage. Thus, the MW-treated OPB specimens exhibited stronger mechanical characteristics than the CV-treated OPB specimens. Importantly, the CV-treated OPB specimens acoustically outperformed the MW-treated counterparts, as evidenced by the former’s higher noise reduction coefficients (NRC). This phenomenon was attributed to the abundance of fissures between the vascular bundles and the parenchyma. Thus, the CV technology was more operationally and economically suited to the high-performance acoustic OPB.

The present work studied the numerical modelling of heat transfer in a pile of Pinus radiata samples of a square cross-section by using radio frequency heating.  More precisely, the study focused on the effects of the energy transferred to a dielectric material (wood) from an electromagnetic field, which required the calculation of the dielectric loss factor and its correlation with conservative equations. In this way, the temperature distribution across Pinus radiata samples was obtained through the integration of the energy equation using the finite volume method. The numerical results were compared to experimental data obtained from three experiments of radio-frequency heating of wood samples of a cross-sectional area of 4 in × 4 in, 3.1-m-long, and 20 cm of separation between plates. According to the observed linear behavior of the heat transfer process, the numerical results of the transient variation of temperature were in agreement with the experimental data.

This paper presents a kinetic study of ethanol production by simultaneous saccharification and fermentation (SSF) from Mn(II)-catalyzed cornstalks. The optimal conditions of ethanol production were as follows: 1:2 inoculation proportion (ratio of Pachysolen tannophilus to Saccharomyces cerevisiae), 30 °C fermentation temperature, 15% inoculation quantity, 4 mg/g addition amount of Mn2+, and 10 U/g cellulase dosage. An optimal ethanol yield of 0.359 g/g was obtained from cornstalks under optimum conditions. A 38.5% increase in the yield was observed compared with the control group without the addition of Mn2+. The relationship between ethanol yield and fermentation time followed a Langmuir isotherm model. The relationship between the rate constant and fermentation time in the conversion of cornstalks to ethanol was fractal like. The findings elucidate the complex characteristics of ethanol production from cornstalks with Mn2+ catalysis and will be useful in improving production yield.

The yield of macadamia shells (MSs) is huge. The preparation of hydrochar of MSs for the purpose of energy has broad prospects. This study investigated the possible optimum conditions for the most appropriate yield and higher heating value (HHV) of hydrochar through hydrothermal carbonisation (HTC) of MSs. The yield and HHV via HTC were systematically analysed by response surface methodology (RSM) using a synthetic weighted scoring method. The operating parameters included reaction temperature, reaction time, and water-to-biomass ratio. According to the mathematical model of RSM, the maximum response value was obtained under the following optimum conditions: reaction temperature, 220 °C; reaction time, 60 min; and water-to-biomass ratio, 11. The results showed that the reaction temperature exerted more remarkable influence than time and water-to-biomass ratio. Under the optimal conditions, the hydrochar yield and HHV were 57.58% and 22.69 MJ/kg, respectively. The results of elemental, proximate, Brunauer–Emmett–Teller, scanning electron microscopy, and Fourier transform infrared spectroscopy analyses showed that the hydrochar fuel properties improved compared with those of raw MSs. Furthermore, the surface structure and functional groups changed.

Lipase and cutinase belong to the esterase family and have biological applications in many fields. To develop more efficient biocatalysts that can be used for waste paper deinking, a chimeric lipase-cutinase (Lip-Cut) was constructed and successfully overexpressed in Pichia pastoris. The chimeric Lip-Cut exhibited lipase and cutinase activities that were 127% and 210% higher than their parent enzymes, respectively. Cut was superior to Lip in ink removal and improvement of paper brightness than Lip. The Lip-Cut displayed a better ink removal efficiency and paper brightness than that of the Lip, Cut, and Lip/Cut mixture. When the chimeric Lip-Cut was used, the ink removal efficiencies were 25.8% and 16.2% higher than that of the control-treated laser-printed paper and newspaper, which had sheet brightness values of 88% ISO and 59% ISO, respectively. The results demonstrated that the proper construction of bi-functional Lip-Cut could enhance the catalytic properties through the synergistic action of the two moieties because of the complementary advantages in the substrate specificities and catalysis patterns of both enzymes. This may provide an effective way to engineer more efficient bi-functional lipases and cutinases for deinking waste paper.

The effects of temperature, reaction time, biomass/water feedstock ratio, NaOH concentration, and ZSM-5 catalyst amount were investigated relative to the hydrothermal liquefaction (HTL) of sugarcane bagasse. The experimental results showed that the maximum yield of bio-oil (46.9%) was achieved with the following conditions: 10 g of sugarcane bagasse, 200 mL of distilled water, 30 min, and 285 °C. It was seen that the products of oxygenation (phenols, acids, ketones, alkenes, and esters) were abundant in the bio-oil. With the addition of NaOH, the residue yield decreased remarkably, and the yield of organics dissolved increased. The yields of acids and furfurals in the bio-oil decreased with the presence of NaOH during HTL. Additionally, ZSM-5 effectively decreased the acidic compounds and improved the liquid properties during HTL. Sugarcane bagasse in HTL with catalysts significantly improved the quality of bio-oil with lower oxygen content and higher HHV. Moreover, the gaseous products H2 and CH4 were noticeably affected by the temperature, NaOH concentration, and ZSM-5 amount.

Hydrothermal carbonization (HTC) is an efficient conversion process that treats solid digestates from anaerobic digestion plants and converts it into valuable solid products. In this study, digestates of swine manure (DS_M) and rice straw (DS_S) were HTC-treated at 190 °C with biomass-to-water ratios of 1:4 and 1:9. The hydrochars were characterized physically and chemically to elucidate their potential as a valuable resource. The hydrochars from the solid digestates were acidic, and the dissolved organic carbon (DOC), dissolved organic nitrogen (DON), and Brunauer-Emmett-Teller surface area (SBET) were significantly (P < 0.05) higher compared with that of the feedstocks and pyrochars. Mesopores were dominant in the hydrochars, where the pores had slit-type holes and a stratified structure. The hydrochars possessed more O functional groups and aromatic C=C and C-H band than the feedstocks and pyrochars. The hydrochars derived from solid digestates were better as a solid fuel because of their combustion property. The increase in the crystallinity of the hydrochars enhanced their stability. The hydrochars produced from the DS_M were more acidic than those from the DS_S. The HTCDS_S had a better adsorptive effect on pollutants than the HTCDS_M because of the higher SBET and optimal functional groups.