Research Articles

The pin-penetration device is a minimally destructive instrument that is widely used to estimate the physical properties of wood, e.g., density, with advantages such as reduced testing times, low costs, and fewer defects induced in the wood being tested. In this study, such a device was used on 25 Indonesian hardwood species with a strength class (SC) distribution from SC II to IV (according to the Indonesian classification of wood SCs). Tests were conducted on three different orthogonal planes, i.e., cross-sectional, radial, and tangential planes. The wood density ranged from 0.28 to 0.88 g/cm3, and the specific gravity was 0.25 to 0.76. The cross-sectional plane penetration depth of the wood was significantly greater than that of either the radial or tangential plane, whereas the pin penetration values of the radial and tangential planes were not significantly different. A prediction model for predicting the density and specific gravity of wood via pin penetration showed a significant regression. Thus, the use of a pin-penetration device was found to be suitable for estimating wood density and specific gravity in a range of SCs of tropical wood species regardless of species.

Tree acoustic tomography is a widely used device supported method for tree stability assessment. In this work, the results of the three most commonly used devices for acoustic tomography of standing trees (ARBOTOM®, ArborSonic®, and PiCUS®) were compared on selected individuals of sessile oak in Brno, Czech Republic. According to the statistical analysis, there was a significant difference between values measured by the PiCUS® acoustic tomograph and those measured by both the ARBOTOM and ArborSonic® acoustic tomographs. Based on the measured data, velocities measured by PiCUS® were considerably lower than those recorded by the other acoustic tomographs (ARBOTOM® and ARBORSONIC®). Measured radial and tangential velocities differed from each other. In data obtained from the defective cross-sections, this difference was attenuated. Image reconstructions (tomograms) from the acoustic tomographs differed from each other. Complex shapes of defects in standing trees can significantly influence acoustic tomography results. According to the statistical analysis, there was no significant relationship between sound velocity and density, while there was a relatively strong positive correlation between sound velocity and moisture content.

Stabilized fertilizers that contain nitrification inhibitors and/or urease inhibitors are widely used in China. A pot experiment was conducted to analyze soil enzymatic characteristics related to carbon and nitrogen turnover and metabolism under the use of rice straw and stabilized fertilizer. Results showed that stabilized fertilizer exhibited the highest yield production, panicle numbers, and above-ground biomass. Compared with urea treatment with straw, adding inhibitors reduced soil organic carbon and the enzyme activity related to acquisition of carbon, but increased soil organic carbon accumulation, rice yield, and above-ground biomass. Stabilized fertilizer increased protease activity; however, it decreased N-acetyl-β-glucosaminide. Addition of straw significantly increased dissolved organic and microbial biomass carbon or nitrogen, as well as the enzyme activities of α-D-glucosidase, β-D-glucosidase, β-N-acetyl-glucosidase, and cellulase at the seedling and tillering stages. The principal components analysis showed that the synthesis of extracellular enzyme related to carbon and nitrogen acquiring act as a proxy for straw decomposing under nitrogen conditions. The combination delayed the release of ammonia, which affected the carbon and nitrogen coupling by microbial organisms. These results demonstrated a relationship between soil carbon and nitrogen dynamics and soil enzymes in different fertilization management.

This paper provides a compendium of the utilisation potential of aquatic invasive plants found in the Owabi Dam in the Ashanti Region of Ghana. In total, seven aquatic invasive plants were identified in the Owabi Dam, which included Ceratophyllum demersum, Nymphaea odorata, Polygonum lanigerum, Arthropteris orientalis, Typha domingensis, Pistia stratiotes, and Cyprus papyrus. Some of the identified invasive plants were found to be highly nutritious and suitable for human consumption or use as feed for livestock, fish, and poultry. Other plants had high medicinal potential and aesthetic value. Several of the invasive plants were suitable for bio-industrial usages as feedstock to produce biofuels, insecticides, and biofertilizer, among other products. Therefore, if an effective utilization method of these currently unutilized aquatic invasive plants is established, it can provide a source of livelihood and income generation for individuals and households and contribute to controlling the impact of invasive plants on the Owabi Dam.

Field investigations conducted in the wild alpine rhododendron forest in the Baili Rhododendron Nature Reserve found that the natural regeneration of the forest was hindered. This paper used GC-MS to identify and analyze the most abundant chemical compounds in the leaves of four of rhododendron species (Rhododendron simsii, Rhododendron decorum, Rhododendron liliiflorum, and Rhododendron pulchrum). The results showed that the chemical substances in the four rhododendron leaf samples were mainly aldehydes, alcohols, and esters. Among them, the ester content in the leaves of R. simsii is the most abundant, the alcohol content in the R. decorum is the most abundant, and the aldehyde content in the R. liliiflorum is the most abundant. These results are conducive to the protection of the rhododendron ecosystem and laid a scientific foundation for studying the difficulties of natural regeneration of rhododendron communities.

To improve the reactive sites of kraft technical lignin, a deep eutectic solvent (DES) composed of ZnCl2 / lactic acid was used to pretreat kraft lignin from coniferous wood. The modified and unmodified lignin were used to replace different proportions of phenol (50%, 60%, and 70%) to prepare the lignin-phenol-formaldehyde (LPF) adhesive. The phenolic hydroxyl content of DES-treated lignin increased from 3.12 wt% to 3.93 wt% and methoxy content decreased from 11.83 wt% to 6.64 wt% under optimized experimental conditions. The bond strength of LPF adhesive prepared by DES reagent activated lignin was higher than that of the control sample. When the substitution degree of modified lignin for phenol reached 70%, the bond strength of the plywood prepared by the DES-pretreated lignin was 0.79 MPa and the free formaldehyde content was 0.28%, which met the requirements of the Chinese national standard GB/T 9846 (2015). However, the viscosity was higher than the control sample, and results indicate that DES reagent modification cannot improve the viscosity of LPF resin.

Sesame cake and meal, byproducts of the sesame oil process industry and mainly used as feed and fertilizer, are often not optimally utilized and are wasted when the material could be used as a high-quality protein source. This research primarily emphasizes the preparation of a sesame protein-based adhesive with urea and glyoxal modification to use as a wood adhesive. The performance and characterization of the urea and glyoxal modified sesame protein adhesive (USP and GUSP, respectively) were measured precisely. After glyoxal was added, the water resistance of the GUSP adhesive was significantly enhanced, reaching the standard for Type II plywood. The formaldehyde emission test showed that the GUSP adhesive could be utilized as a formaldehyde-free wood adhesive, having a significantly lower than the demand of the E0 level (i.e., 0.5 mg/L). Furthermore, increasing the glyoxal content in the adhesives enhanced the thermal stability but not significantly. A substance with a crosslinking structure was formed from the reaction between the sesame protein and glyoxal, which enhanced the water resistance. Meanwhile, the fractured structure of the GUSP adhesive having a compact surface also was propitious to enhance the water resistance. Thus, the GUSP adhesive could be used as a novel adhesive in plywood fabrication.

Mature pods of Leucaena leucocephala (Lam.) de Wit were utilized as raw material for nanocrystalline cellulose (NCC) production. NCC’s isolation begins with L. leucocephala fiber’s alkaline treatment with sodium hydroxide, followed by bleaching treatment at three different percentages (3%, 5%, and 7%) of sodium hypochlorite. Acid hydrolysis was then conducted to obtain NCC, which was comprehensively characterized in terms of morphology, chemical functional groups, whiteness index, and crystallinity. Fourier-transform infrared spectroscopy (FTIR) and chemical composition results showed that alkali treatment (NaOH) and bleaching (3%, 5%, and 7% of sodium hypochlorite, NaClO) were effective in the removal of lignin and hemicellulose. The variation of sodium hypochlorite concentration affected physical and structural characteristics of the NCC produced, which exhibited a rod-shaped structure with diameters ranging from 17 to 49 nm. These observations provide insight into the potential utilization of L. leucocephala as raw material for preparing nanocellulose, which may address problems of the underutilized mature pods.

The potential utilization of melamine impregnated paper (MIP) waste in thermoplastic composites was investigated. Composites were also manufactured utilizing wood flour (WF) at the same filler rates for comparison. The composites were manufactured using a compression molding method. The effects of filler type and filler rate on the mechanical properties of low-density polyethylene (LDPE)-based composites were evaluated. Mechanical properties, such as tensile and flexural strengths, were determined in accordance with ASTM D638 (2001) and ASTM D790 (2003), respectively. Results showed that filler type and filler content had significant effects on all mechanical properties investigated. Both fillers improved all mechanical properties except for tensile strength and elongation at break of LDPE. In conclusion, MIP waste has a potential to be utilized in thermoplastic-based composite manufacturing and might generate some economic and environmental benefits.

The morphological and thermal properties of composites containing a bioplastic blend and micro/nano-sized biochar from pyrolyzed jatropha seeds from microwave pyrolyzed jatropha seeds were investigated using scanning electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, and differential scanning calorimetry. The biocomposite samples exhibited a brittle structure with a slightly ductile chip-like appearance. The Fourier transform infrared spectroscopy results for the PLA/PEMA/BC bio-composites were comparable to the PLA/BC biocomposites. A lower bio-filler content had more pronounced peak intensities than the higher bio-filler content biocomposites. The added PEMA compatibilizer in the PLA/PEMA/BC biocomposite showed more pronounced peaks, which indicated slightly improved bonding/interaction between the bio-filler and the matrix. Overall, increasing bio-filler content did not drastically affect the functional groups of the biocomposites. Thermogravimetric and differential scanning calorimetry analysis showed the developed biocomposites had a slight improvement in thermal stability, in comparison to the PLA sample. Improvements in the thermal stability of the PLA/PEMA/BC biocomposite could be attributed to the additional hydroxyl group, which was due to the added PEMA in the PLA and PLA/BC. According to the results of the analysis of the developed biocomposites, the biocomposites were more brittle and had reasonable thermal stability.