Research Articles

Two contrasting garage-type solid-state fermentation experiments were designed at pilot scale to reveal the intensification process and effects of adding compound inoculants. Bundled rice straw and fresh pig manure were used as feedstock with a total solids concentration (w/w) of 20% under ambient temperatures of 26 to 35 ºC. The characteristics of biogas production and variations in bacterial community composition were investigated. The results indicated that using microorganisms shortened the start time of anaerobic solid-state fermentation. The target methane content in the biogas production reached 30% 7 days before the control group. A target of 50% was reached 8 days before the control group. Throughout the fermentation cycle, the cumulative gas production of the experimental group was 1340 m3, which was 20.5% higher than the control group. Cumulative methane production increased by 45%. Clustering and principal coordinates analysis suggested that the addition of compound bacteria increased the diversity of the microbial community and stabilized its structure, thus improving gas production efficiency and methane purity. These findings can assist future bioaugmentation research pertaining to the application of composite microbial agents.

Wood-based composite panels continue to be important in the wood building industry. Particleboard is commonly used for non-structural applications, while oriented strand board (OSB) is commonly used for structural applications. For both types of boards, however, manufacturers are interested in minimizing the presence of small particles or “fines” in the panels. The presence of fines can cause an increase in the consumption of resins as well as an increase in the weight of the board. Fines can be produced when a refiner or chipper blade becomes dull or when the wood raw material becomes excessively dry. There is a need for manufacturers to simply and accurately monitor the presence of fines and control their presence. Acoustic emission (AE) is an elastic or plastic wave generated when a surface is deformed or has an external force exerted on it. This research showed the feasibility of using AE to monitor the presence and percentage of fines in particleboard furnish. The research also showed the effect of the experimental setup on the AE signal level.

Oriented strand board (OSB) is commonly used for structural applications. Manufacturers of OSB want to minimize the presence of small particles or “fines” in the panels because fines increase the consumption of resins, leading to an increase in the weight of the board.  Fines are produced when either a refiner or chipper blade becomes dull, or when the wood raw material becomes excessively dry. By accurately monitoring the presence of fines, manufacturers can help control their percentage within a product. Acoustic emission (AE) is an elastic or plastic wave generated when a surface is deformed or has an external force exerted on it. This research shows the feasibility of using AE to monitor the presence and percentage of fines in flakes. The study follows up on previous research conducted years ago by Lemaster (1994). The study also shows the effect of the flake geometry and flake moisture on the AE signal.

Compression of biological materials facilitates their transport and storage. The compressive rheological properties of silage sweet sorghum were studied via stress relaxation test with an electronic creep universal testing machine and a self-made adjustable compression device. The moisture content, compression density, cutting length, and compression speed were analyzed. Relaxation characteristics of sweet sorghum stalk were evaluated in terms of the stress decay time and the equilibrium elastic modulus. The stress relaxation characteristics of sweet sorghum stalks were consistent with the two Maxwell models, and the relevant parameters of the model at different levels were obtained. The rapid stress decay time first increased and then decreased with the increase of compression density, and the length of the smashed sorghum. The moisture content and the compression speed had greater fluctuations. The equilibrium elastic modulus increased with increasing straw compression density and the length of the shredding segment, and the equilibrium elastic modulus gradually decreased with increasing moisture content. The compression speed had little effect on the equilibrium elastic modulus. The research results lay a theoretical foundation and a basis for further study on the stress relaxation characteristics of sweet sorghum.

In the current competitive market, production efficiency and product quality are prioritized by the whole industry. Machinery characterization is an understudied topic, particularly in those sectors focused on basic raw material production, processing, and/or heavy industrialization. For this reason, the wooden housing sector requires evaluation to identify its mechanical potential and support future policies dealing with industrial development. This study aimed to identify the equipment and machinery from Brazilian timber housing producers. Such a sectoral study involved individual personal data collection by way of face-to-face interviews. Sampled producers were asked about equipment/machinery size, drying process availability, and the range of overall obsolescence from these devices. Thus, tools, portable machines, and medium-sized machinery exhibited the highest popularities, revealing a lower industrial level. Most of these producers do not have machined drying processes because of the demand for static infrastructures. The low obsolescence was a result of the greater utilization of compact equipment, which is easier to replace because of its low cost. Lower-cost machinery could also stimulate in the creation of new businesses for this sector.

The biocidal properties of an industrially used copper-based preservative were evaluated at different planing depths on exposure of pine wood to mold fungi in direct and indirect contamination methods, with simultaneous verification of white rot fungi virulence on wood. The preservative was an aqueous solution of copper carbonate, 2-aminoethanol, and quaternary ammonium compounds. Full cell preservative impregnation efficiency against visual mold fungi growth was tested on sapwood surfaces planed to different depths before impregnation. The virulence of two white rot fungal strains of Trametes versicolor (441 and JPEI) against the dried non-impregnated and impregnated wood samples was also tested. The unplaned surface of impregnated timber was occupied by air-borne contaminants, such as Paecilomyces variotti and Aspergillus niger up to 30%, and, even after impregnation it was necessary to process the surface to avoid micro-fungi settlement. The virulence of the tested rot fungi strains was confirmed by the aggressive degradation of non-impregnated wood with a mass loss of over 40%. Both Trametes sp. strains degraded the preservative-impregnated wood with a mass loss of 3.1% to 4.8%, but degradation by the JPEI strain was more intensive and more dependent on planing depth than the other strain (441).

Casuarina equisetifolia (beach sheoak), a fast-growing deciduous tropical hardwood tree, was utilized to assess its suitability for pulp and paper production. Response surface methodology (RSM) based on central composite design (CCD) was used to optimize the kraft pulping process by varying the alkali doses, reaction temperature, and time. Using the best optimum pulping conditions with alkali charge 17.9%, temperature 170.2 °C, and pulping time 82.1 min, a high screened pulp yield of 52.4% with low kappa number of 18.1 and pulp viscosity of 974.5 cm3/g could be achieved. The laboratory handsheets prepared with kraft pulp under optimum conditions showed good mechanical strength properties at an optimum beating level of 45 °SR.

Nanocellulose, derived from bioresources, is a renewable material with broad application prospects. Due to its easily controllable viscosity, it has been studied by many researchers on its potential application on nano-ink for ink-jet printing by mixing dyes and nanocellulose. In this paper, a new method by grafting reactive dyes on nanocellulose is proposed. The well-known fabric dyeing was first applied for dyeing nanocellulose. The dyeing reaction was Reactive Red 120 (RR120) grafting on nanocellulose, which was influenced by the dosage of RR120, reaction time, and reaction temperature. The RR120 was successfully grafted on nanocellulose, and a model for RR120 grafting on nanocellulose was proposed as “y = 0.2 * (0.0039T² – 0.5T + 20) * (e^0.72R) * (3 – 0.99^t)”, to predict the RR120 grafting amount at different reaction conditions.

Lattice truss cores are used to reduce the mass and increase the strength of sandwich boards. These panels are typically manufactured from metal or carbon composites. As a rule, they do not exhibit auxetic properties. Auxetic structures have several extraordinary mechanical properties. The aim of this study was to manufacture lattice auxetic cores from a biodegradable material and determine their elastic properties. The structures were produced from LayWood Olive, a composite containing polylactic acid and 40% wood dust. The cores had comparable relative densities, but their geometry and number of cells differed. As a result of uniaxial compression in individual lattice truss cores, it was shown that the cores whose cells were square in the top view were isotropic. In contrast, cores with rectangular cells were strongly orthotropic. Moreover, the Poisson’s ratio changed depending on the cell size and rib angle. Among the cores that exhibited isotropic properties, the lowest Poisson’s ratio and modulus of elasticity were recorded for the structure composed of 49 cells with ribs that were 2 mm thick. The highest Poisson’s ratio and modulus of linear elasticity were found with the orthotropic structure composed of 15 cells with ribs that were 3 mm thick. This paper was based on numerical calculations that were verified by experimental studies.

The goal to decrease global dependency on petroleum-based materials has created a demand for bio-based composites. Composites that are reinforced with natural fibers often display reduced strength compared with those using synthetic reinforcement, and hybridizing both types of reinforcement within a common matrix system offers a possibly useful compromise. This research investigated the low-velocity impact performance of glass, kenaf, and hybrid glass/kenaf reinforced epoxy composite plates. The aim of the study was to determine the low-velocity impact behavior of biocomposite material in assessing its potential for application in the radome structures of aircraft. Natural fibers possess low dielectric constants, which is a primary requirement for radome. However, the structural integrity of the material to impact damage is also a concern. Composite samples were prepared via a vacuum infusion method. A drop weight impact test was performed at energy levels of 3 J, 6 J, and 9 J. The Impact tests showed that the impact peak force and displacement increased with the energy level. Hybrid glass/kenaf composites displayed damage modes of circular and biaxial cracking. The former is analogous to the damage observed in glass-reinforced composite, while the latter is unique to woven kenaf reinforced composites. The severity of the damage increased with impact energy and was found to be significant at 3 J.