Volume 20 Issue 1

Cellulose is photosynthesized by plants from carbon dioxide and water, and it is the most abundant organic compound available. It is present in the plant cells as structural component in the form of elementary fibrils known as nanofibers. Cellulose nanofibers can be easily extracted from parenchyma tissues of agricultural waste. Although thin sheets made of cellulose nanofibers can be readily obtained by a papermaking method, thicker plates are difficult to make. Here we propose a papermaking-like method to fabricate 1 to 2 mm-thick plates from citrus fruit residue-derived cellulose pulp initially having a solids content of about 1%. The protocol is simple, easy, requires affordable devices and relies on water evaporation to consolidate the fibrils by hydrogen bond interconnections. The pulp morphology seems to consist mostly of cellulose nanofibers and the bending strength and modulus of obtained plates reached 190 ± 30 MPa and 9.6 ± 1.5 GPa, respectively, values that approach those reported in a previous study that molded microfibrillated cellulose but relying on a complex process. This streamlined protocol could be groundwork for further studies aiming the difficult task of molding cellulosic materials.

The large old tree population of Barringtonia racemosa (L.) Spreng plays a crucial ecological and cultural role in rural areas (Danzhou, tropical China). This study investigates the population structure, demographic characteristics, and conservation status of B. racemosa in remnant forest stands. The findings reveal a skewed distribution towards smaller to intermediate-size classes, with a significant decline in larger-size classes. The static life table highlights high mortality rates in the early stages and moderate survivorship in mid-size classes, indicating a bottleneck in the transition from medium to larger-size classes. The study identifies external interference as a potential threat to the B. racemosa population. Based on these findings, a multifaceted conservation approach is proposed to integrate traditional ecological knowledge, implement community-based conservation programs, enhance habitat protection and restoration, and strengthen legal protection and policy support. This research underscores the critical role of large old trees in ecosystem health. It highlights the need for targeted conservation strategies to preserve these vital components of natural landscapes in rural China.

Defect-free, highly-densified panels without springback were prepared from Hyun aspen (Populus alba × glandulosa) wood with different delignification levels by alkaline hydrogen peroxide (AHP) pretreatment. The AHP concentrations were adjusted to 3%, 7%, 10%, while the temperature (100 °C), time (3 h), pH (11), liquor ratio (6.25), and stabilizer (0.5% EDTA) remained constant. The delignification of Hyun aspen wood panels was indirectly quantified by analyzing the UV absorbance of the spent liquor after AHP treatment, wherein delignification ranged from 12% to 58% depending on the AHP concentration. To achieve highly-densified panels, the densification conditions, such as pressure, temperature, and time, were examined. Panels subjected to cold-pressing (25 °C) at 30 MPa for 1 h, followed by hot-pressing (105 °C) at 30 MPa for 6 h, then immediately removed after heating, resulted in durable, highly-densified panels with no springback or cracks.

The water hyacinth Eichhornia crassipes is a rapidly growing weed that grows in shallow fresh water. It can be used for the removal of nutrients and heavy metals from water, as feedstock for biofuels, and as a bulking agent for the vermicompost process. The present study focused on the use of water hyacinth plants for nutrient and heavy metal removal from water. Water hyacinth removed >95% of ammonium nitrogen, nitrite, and nitrate from the water. The bioaccumulation potentials of water hyacinth for Cu, Cd, Cr, As, Li, and Zn after 30 days of treatment were 80 ± 2.3%, 78.6 ± 3.2%, 73.2 ± 1.2%, 69.6 ± 2.1%, 65.5 ± 1.9%, and 44.2 ± 2.2%, respectively. The heavy metal accumulation in water hyacinth was in the following order: Cu>Cd>Cr>As>Li>Zn. Water hyacinth was pretreated with acid and base. It was further digested with cellulolytic enzymes, and Saccharomyces cerevisiae was further inoculated to produce ethanol in a liquid culture. The ethanol yield was 0.09 mL/mL culture. Water hyacinth was cut into small pieces, mixed with goat manure and used for vermicomposting. The microbial C content of the vermicompost ranged between 398 ± 12.8 and 537 ± 11.2 µg/g, and the microbial N content ranged from 104.4 ± 2.2 to 254.9 ± 2.2 µg/g. The vermicompost had an 84.3 ± 2.2% germination index after 48 h in the pots treated with 20% vermicompost.

The behaviour of wood-metal composites was evaluated during cathodic dip coating, which is a standard corrosion protection process for metals in automotive engineering. In this process, the materials are exposed to chemical and thermal stresses, which is a challenge for wood and composites based thereon, especially in terms of the durability of the adhesive and the differences in thermal expansion. In this study, a hydrophobic surface sealant was proposed to mitigate these negative effects by reducing moisture absorption during dipping baths. The mechanical properties, including flexural strength, tensile strength and impact strength of aluminium-plywood composites were evaluated. It was found that impregnation with low-viscosity resins improved the mechanical properties by increasing the bulk density of the wood. Although the dip coating process reduced the strength of the impregnated samples, they maintained higher values compared to the non-impregnated samples. The dip coating process significantly reduced the tensile strength of the non-impregnated samples, while the impregnation protected the samples and maintained the tensile strength. It was concluded that hydrophobic surface sealing by impregnation is crucial for improving the mechanical properties of wood composites in automotive applications, as it reduces moisture absorption and maintains mechanical integrity during the dip coating process.

Numerical modeling was used for mitered joints prepared with wood-based composite members (poly(furfuryl alcohol)) using Linear Elastic Fracture Mechanics (LEFM). The aim was to understand the joint performance under outdoor conditions. Analysis of fracture mechanics properties of wood-based composite is necessary to obtain a good understanding of joint behavior and to predict the reasons for its fracture. The fracture stiffness of furfurylated wood under mixed mode (I/II) was investigated. In both crack systems, the distribution trends of K_IC/K_IIC with furfurylation changed. The results of corner mitered joints showed that the mixed mode I/II was the effective fracture mode under diagonal compression (DC) and tension (DT) load. Based on the results obtained from fracture mechanics, the structural performance of mitered joints increased with increasing furfurylation level. The model results confirmed the experimental results.

Pharmaceutical studies have reported for many years that plants containing antioxidants have many health-promoting properties, mainly due to organic compounds capable of scavenging free radicals. In this work, the activity of two representative plant families was tested: Elettaria cardamomum L. (EC) and Myristica fragrans Houtt. (MF). Results indicate that the antioxidants contained in them decompose into gaseous products at temperatures up to about 640 K. The introduction of EC and MF to the biopolymer matrix resulted in a decrease in the thermal stability of the obtained composites. The resulting char residues acted as a local thermal insulator, which led to reduced flammability of poly(lactic acid) (PLA) composites. As a result, the use of 10 wt% EC and 7.5 wt% MF reduced flammability by 37% and 29%, respectively.

The research aimed to evaluate quality profiles, optimize the antioxidant activity, and total phenolic and flavonoid content in a mixture of three crude drug: turmeric, java tea, and seed-under-leaf, using the Simplex Lattice Mixture Design. Ultimately, a quadratic model was used, as it best adjusted to the experimental behavior. It predicted the optimal composition of herbal mixtures antioxidant activity, determined by 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging and Ferri Reducing Antioxidant Power (FRAP) techniques, also in Total Phenolic Content (TPC) and Total Flavonoid Content (TFC). The crude drugs were of good quality according to selected pharmacognostic quality parameters of the official Malaysian herbal monograph (MHM). The optimum responses with the highest synergistic effect were composed of 5% (w/w) of turmeric, 40% (w/w) of Java tea, and 55% (w/w) of seed-under-leaf. The values were 1796 mM TE/g, 2230 mM TE/g, 355 mg GAE/g, and 177 mg QE/g for DPPH, FRAP, TPC, and TFC, respectively. The greatest contribution of antioxidant activity was shown in that mixture as potential as a functional beverage.

Most bamboo composites are designed referring to the specifications of wood structures. However, this approach is inadequate due to the volume difference between bamboo bundles and other fibers. Previous studies have investigated the effects of strand size of parallel strand bamboo (PSB) in tension and compression. Here, to investigate the impact of varying span-height ratio on the flexural characteristics of PSB, specimens with five different section heights were designed. Numerical simulations were performed to reveal the deformation, the failure process, and the load carrying ability of the PSB beams. The first-order anisotropic beam theory was applied to predict the internal forces. The results show that the bending property of the PSB is closely related to the section height. It is recommended that the dimension of length × width × height (300 mm × 20 mm × 30 mm) should be the most appropriate specimen size for the bending experiment. The error between the theoretical value and the test value was only about 0.4%. These endeavors can facilitate the establishment of bending test standards for bamboo structures.

Lignocellulosic fillers derived from pruned cherry tree branches were studied relative to the mechanical and viscoelastic properties of polypropylene (PP) composites. Tree branches were collected from the orchard after pruning and the wood and bark parts were separated from each other. Both materials were processed into particles of different sizes (below 100 µm and between 100 and 250 µm) and filled into PP at different weight percentages (5%, 10%, 15%, and 20%). The mechanical performances of the biocomposites were evaluated through tensile tests, while their viscoelastic behavior was analyzed using dynamic mechanical analysis (DMA). Results revealed a decline in tensile strength with increasing filler content, which was attributed to poor interfacial adhesion between the PP matrix and fillers. However, tensile modulus increased with increasing filler content, with the highest values were observed at 20% filler loadings. The DMA showed enhanced storage and loss moduli, indicating improved stiffness and energy dissipation. Scanning electron microscopy (SEM) confirmed the presence of voids and filler agglomeration, further explaining the mechanical property reductions. These results demonstrate the potential of cherry tree pruning waste as a bio-filler for sustainable biocomposites with improved stiffness.