Research Articles

Densifying alfalfa into briquettes is one of the effective ways to increase its density and reduce the cost of storage and transportation. To explore the influence of vibration frequency on alfalfa briquetting, vibration-assisted compression tests with six vibration frequencies of 0, 9.52, 15.56, 21.24, 27.50, and 33.44 Hz were carried out. The results showed that the compression with vibration could reduce the maximum forming pressure and the energy consumption. The quality of alfalfa briquettes was improved compared with the compression without vibration. Within the range of test, when the vibration frequency was 21.24 Hz, the maximum pressure was the minimum, which was 5.83 MPa. In addition, the specific energy consumption was the lowest, which was 1374 J/g/cm3. The experimental results provided a basis for determining the optimum vibration parameters of alfalfa compression.

The physical and mechanical properties of particleboard panels were evaluated relative to various loading levels of nanocellulose (NC) and boric acid (BA) in the urea-formaldehyde (UF) resin used for panel production. The results showed that NC and BA reinforcement substantially affected the performance properties of the particleboard panels. It was determined that using 3% NC and 3% BA in the panels afforded the best results relative to thickness swelling (TS), water absorption (WA), moisture content (MC), modulus of rupture (MOR), modulus of elasticity (MOE), and internal bonding strength (IB). It was concluded that the performance properties of the particleboard panels could be enhanced by adjusting the loading levels of NC and BA. The study also showed that it is possible to apply NC and BA as modifiers for the formaldehyde resin in the process of manufacturing particleboard panels. The NC and BA reinforcement techniques could be used to develop novel furniture components and interior design materials.

Over half of the large African mahogany plantation estate in northern Australia has reached the mid-point of the target rotation length of 20 to 25 years. As such, there is increasing interest in understanding the potential volume and grade qualities recovered from these young trees using different processing methods. The objective of this study was to compare the recovery rates and product grade quality for rotary veneer using spindleless lathe technology and sawn boards using traditional sawing techniques. Net veneer recovery ranged between 42% and 55% of log volume, with most veneers being limited to D-grade. Compression, surface roughness, and grain breakout were the most prominent defects limiting veneer grade. The sawn-dried-dressed recovery was low, with less than 20% of the log volume representing a potential saleable product. The small log diameter combined with defects including wane, heart shake, pith, and knots reduced the potential recovery. A high presence of sawn board distortion was observed that negatively impacted the efficiency of sawn timber processing along with product recovery. While low, the recovery of veneers and sawn timber from young African mahogany was like other young plantation grown hardwoods.

Reinforcement with natural fibres is a common method to improve impact properties of poly(lactic acid) (PLA). In this study, composites made from PLA and bamboo particles were melt-compounded in a twin-screw extruder and formed by compression moulding. Tensile, flexural, and impact tests were conducted. Particle size (A), particle loading (B), screw speed (C), and die temperature (D) were varied at three levels. Tensile strength and modulus, flexural strength and modulus, and impact strength were the response variables. The experiment design was based on Taguchi’s (L9) orthogonal array. Through variance analysis, the particle loading was found to be the dominant factor influencing the mechanical properties, followed by die temperature. The optimum parameters were validated with a confirmation test. The results showed a noticeable improvement of impact properties compared to neat PLA by 55%, without compromising tensile and flexural properties. Flexural strength, flexural modulus, and tensile modulus of the composites were greater than that of pure PLA. However, only tensile strength was reduced by about 28% compared to pure PLA. Importantly, the DOE method with maximizing the desirability properties was found to be an effective systematic approach to identify an optimal parameter setting of the extrusion moulding process.

This study characterized the lignin peroxidase (LiP) activity of soil via an enzyme assay to determine the reaction rates and activation energies for 5 wt%, 10 wt%, 15 wt%, and 20 wt% lignin loads in urea crosslinked starch biocomposites. The results revealed that a mixed mode of LiP inhibition occurred after the soil was mixed with these biocomposites with different loads of lignin. Loading of lignin at 5 wt% and 10 wt% lignin resulted in higher values of catalytic activity of LiP: -39.58 and 49.14 µM h-1 g-1 soil, respectively. In comparison, with higher loading of lignin at 15 wt% and 20 wt%, decreases in the catalytic activity of LiP were found and were 28.72 to 37.25 µM h-1 g-1 soil, respectively. The activation energy of LiP increased approximately 1.11- to 1.22-fold when 15 and 20 wt% of lignin was loaded in biocomposites. Research findings established the possibility of unfavorable binding of the LiP to lignin with an increase in the load of lignin, possibly due to the complex structure of intact lignin and presence of inhibitory biodegradation products of lignin accumulates during lignin biodegradation in biocomposites. It was concluded that higher lignin contents (15 wt% and 20 wt%) were effective in reducing the activity of the soil LiP. Hence, higher lignin content possibly protects against losses of lignin, while acting as a filler in the formulation of biocomposites.

Nitrogen removal under low C/N ratio in cold season is an arduous task. In this study, riboflavin was used as an eco-friendly electron mediator to improve the denitrification process in an SBR reactor under conditions of low temperature (10 °C to 15 °C) and limited carbon source (C/N ratio = 4.0). The results indicated that riboflavin created a suitable pH in the system for denitrification. Under water temperature of 10 °C to 15 °C, riboflavin (10 mg/L) stimulated the NO3–N and TN removal rate by 16.5%, and 51%, respectively. Riboflavin promoted the utilization efficiency of limited carbon source, driving the denitrification process with low residual acetate as electron donor. The rising cost of riboflavin supplement (10 mg/L) was 0.025 USD per m3 of wastewater. To satisfy the efficient nitrogen removal from municipal wastewater, the optimum C/N ratio and the selection of solid/immobilized redox mediators should be developed in future work.

Wheat straw produced annually in the Shaanxi Guanzhong region is a potential biomass feedstock for the production of transportation fuels and specialized chemicals through combustion, pyrolysis, or gasification. In this work, the pyrolytic characteristics, evolved gas products, and kinetics of Guanzhong wheat straw and its components were first investigated with a thermogravimetry-Fourier infrared spectroscopy (TG-FTIR) system. A comparative kinetic study was conducted using different model-free methods of Flynn-Wall-Ozawa (FWO), Kissinger-Akahira-Sunose (KAS), Kissinger, and the Coats-Redfern methods. The main pyrolysis products identified by FTIR include H2O, CH4, CO2, and CO as well as aromatics, acids, ketones, and aldehydes. Kinetic results showed that the pyrolytic apparent activation energy of the straw is approximately 200 kJ/mol obtained via FWO and KAS methods at the conversion range of 0.4 to 0.75, which was 30 kJ/mol higher than the value 171.1 kJ/mol obtained by the Kissinger method. The apparent activation energy of cellulose in its main pyrolysis region is 135.5 kJ/mol and is about three times larger than that of hemicellulose (49.5 kJ/mol). The apparent activation energy of lignin at the temperature range of 45 to 116 °C was 34.5 kJ/mol, while that value at the temperature range of 120 to 252 °C was 6.64 kJ/mol.

The Fenton reaction has been widely used in the pretreatment of lignocellulose. It offers the advantages of simple operation, fast reaction speed, and low pollution. In this study, the effects of different proportions of Fenton reagents on the enzymatic hydrolysis of poplar were compared and analyzed, and the optimal ratio of Fenton reagents was obtained. The maximum yield of enzymatic hydrolysis of glucose in Fenton pretreatment samples was 406 mg/g at H2O2 and Fe2+ concentrations of 1.0 mol/L and 0.01 mol/L, respectively, which was 2.5 times that of untreated samples. Meanwhile, the composition analysis and FT-IR analysis showed that Fenton pretreatment could degrade lignin and hemicellulose effectively. X-ray diffraction (XRD) analysis showed that Fenton pretreatment can partially destroy the amorphous region of poplar. These findings will contribute to efforts to improve the viability of the Fenton pretreatment process for converting biomass into energy.

Pinus elliottii wood from different radial locations within trees was used to prepare two-layer preservative-treated wood joints with alkaline copper quaternary preservative and emulsion polymer isocyanates (EPI) or resorcinol-phenol-formaldehyde (RPF) adhesives. The radial variations in shear strength and wood failure percentage were analyzed. Radial variations in wood density and average penetration depth (AP) of adhesives were investigated to establish relationships between shear strengths and characteristics of bonded joints. The shear strengths of EPI- and RPF-bonded joints showed similar increasing trends from pith to bark, and they varied in ranges of 2.92 to 8.13 MPa and 2.03 to 7.12 MPa, respectively. The wood failure percentage of EPI joints (93% to 100%) had no significant differences in all the radial locations, but that of RPF joints (60% to 100%) showed a clear decreasing trend from pith to bark. High positive linear correlations were found between the shear strengths and wood density, and Pearson’s correlation coefficients for EPI and RPF were 0.934 (p < 0.01) and 0.931 (p < 0.01), respectively. Wood density is a very important factor influencing radial variations of bonding strengths. The correlation between the AP and shear strength was not significant at the 0.05 level.

Microcrystalline cellulose-based hydrogels were made using never-dried MCC (AaltoCellTM) as a raw material for a high-pressure mechanical treatment consisting of one to five passes at 700 bars. The effects of the mechanical treatment on the crystalline structure, morphology, geometrical dimensions, and specific surface area as well as rheological properties of the manufactured cellulose gel product were investigated. The results indicated that the process detached part of the crystalline area of the cellulose, resulting in loose particle architecture, increased surface area and porosity, and thus more accessible and reactive material. Due to the creation of the new internal surface area and porosity, more hydrogen bonds were formed between the cellulose particles, consequently creating more stable cellulose hydrogel-like slurries. The properties of the produced hydrogels were greatly influenced by the number of the treatment passes through the process equipment. Several passes through the process produced stronger cellulose hydrogels capable of retaining more water.