Research Articles

Fungi and microbes can remarkably degrade the appearance and durability of organic materials, such as wood. The inhibitory effects of natural phenolics may offer more sustainable alternatives to preserve wood than the toxic biocides that are currently used. Although pure caffeine has been proven to have antibacterial properties, the applicability of spent coffee in wood preservation has not been determined. This work conducted in vitro tests with three brown rot and one white rot fungi and demonstrated the potential of spent coffee-derived cinnamates, analyzed with high-performance liquid chromatography, as antimicrobial agents. Spent coffee at concentrations of 1% and above in the growing media caused significant growth suppression of all of the fungi. This was not only because of the caffeine, but also the other chemicals present in the residue extracts, which demonstrated that spent coffee could be used as a source of green chemicals in wood preservative formulations.

Biomass from agricultural waste can be an excellent source of sustainable energy, the most notable of which is bioethanol. This study aimed to adapt and improve bioethanol production using a yeast strain that ferments the sugar content in undiluted and non-added nutrient vineplant bunch hydrolysates. Yeasts that were previously isolated and molecularly characterized were screened for their pentose fermenting capabilities, first in solid and then liquid mediums. Then, 10 native xylose fermenting yeast strains were tested for their ability to produce ethanol from acid hydrolysates from vineplant lignocellulosic waste. The five strains that exhibited the highest ethanol production underwent fermentation in the pure (non-detoxified) hydrolysate. The strain Pichia kudriavzevii D12 in the undiluted hydrolysate medium gave the highest ethanol concentrations and yields. Hence, P. kudriavzevii was selected for adaptation with sequential fermentations. As a result, a 59% increase in the ethanol production (g/L) was recorded for the D12 strain in the undiluted hydrolysate medium during the adaptation studies. A 2.9-fold increase in the yield (g/g) was obtained for this sample when compared with the reference medium. This study determined that a nondetoxified, organic waste medium prepared from vineplant bunches without added nutrients is a suitable substrate alternative for bioethanol production.

To obtain a lightweight and high-strength wood sandwich structure, a wooden lattice sandwich cell element was designed in combination with a pyramid-type structure. After inserting glue to prepare the cell unit, the influence of panel thickness and core diameter on the unit cell force was analyzed and compared under the condition of flat pressure. Under the condition of flat pressure, the specific strength of the unit cell was higher than that of the specific strength of the composition material, and the unit cell may be regarded as a structure with high specific strength. Theoretical predictions, simulation analysis, and experimental tests demonstrated that the structure compressive capacity depended on the diameter of the core when the core length was set. The larger the diameter of the core is, the stronger the bearing capacity of the unit cell will be. When the diameter of the core is constant, the longer the core length is, the weaker the bearing capacity of the unit cell will be. The simulation analysis was in agreement with the experimental test results, indicating that the destruction of the structure was mainly caused by the failure of the core.

Long fibers from fast growing hemp (Cannabis sativa L.) were used as a raw material for the production of insulation boards in this preliminary work. Hemp fiber boards with densities that ranged from 300 kg/m³ to 1100 kg/m³ were studied. The boards were pressed as one- or three-layered structures. In the three-layered structure, the core was formed of hemp fibers and the outer layers were manufactured from 1.5-mm thick birch veneers. The basic insulation properties of the boards were tested. The heat transfer coefficient value for the boards without veneers allowed this material to be classified as an insulating material. Although the additional veneer layers significantly impaired the heat transfer coefficient, its value was still lower than that of standard wood-based board materials with a similar density. The produced boards were characterized as having good noise reduction properties. The acoustic insulation factor was higher compared with boards intended to be used as thermal insulation, such as mineral wool or light fiberboards with four times greater thicknesses.

An ecofriendly approach for the synthesis of plastic biomaterials based on renewable materials suitable for 3D printing application or other applications has been developed. The material was prepared from native (microcrystalline) or amorphous cellulose, citric acid, and glycerol or ethylene glycol, by a pretreatment at 40 °C and a curing at 175 °C for 1 h. The results showed that tensile properties and the water absorption level of the material were acceptable. The highest strain at break (14%) was obtained from materials made of 10% amorphous cellulose with 90% glycerol/citric acid. It had a maximum stress at 37 MPa. Moreover, materials were without ash content. Possible applications of the material in 3D-printers were discussed. In addition, application of mechanical pulp and wood powder into novel plastic material production was discussed. Foaming during curing might be a problem for this type of material, but this can be avoided by using amorphous cellulose in the recipe.

Wheat straw samples at the plant scale (> 1 mm), tissue scale (100 to 500 μm), and cellular scale (30 to 50 μm) were produced to characterize their microstructure and adsorption properties. The effects of changes in the microstructure and adsorption properties on the adsorption capacity of Pb2+ were investigated. The results implied that specific surface areas and pore volumes in the cellular-scale sample were four to five times larger than at other scales, as superfine grinding destroyed the structure of tissues and cell walls. The crystallinity declined significantly from 53% to 34% with decreasing fragmentation scale. Changes in adsorption properties (point of zero charge, acidic functional groups, and cation exchange capacity) were not apparent. The pseudo-second-order model and Langmuir isotherm model fit the experimental data better than alternate models. The adsorption capacity of Pb2+ increased significantly with decreasing fragmentation scale. The main mechanism improving the adsorption capacity of Pb2+ was intensive complexation owing to an increase in cellulose accessibility to water and enhanced chemical reaction activity of the hydroxyl groups, rather than physical and electrostatic adsorption.

The use of mineral fillers in the paper industry has attracted much attention due to its low cost and ability to improve optical properties and printability. Besides the filler characteristics, paper properties, such as bulk, tensile, and opacity, are greatly affected by filler distribution in the z-direction. Therefore, optimization of filler distribution is an effective way to maximize the value of fillers. In this work, a filler distribution factor (Fc) was proposed to quantitatively describe the concentrated degree of filler distribution in the z-direction. The reduction in Fc resulted in an increase in paper bulk, porosity, and opacity, due to the generation of more interfaces between fibers and fillers. When filler particles were concentrated in one layer (Fc = 1), the tensile strength of the filled paper increased between 26 to 40% in comparison to the paper with various Fc values. For a given Fc, better tensile and opacity properties were achieved by increasing filler concentration on the surface layer of paper.

A totally chlorine free (TCF) bleaching sequence was studied for an acid sulfite pulp mill that produces dissolving pulps. Laboratory analyses of the last two bleaching stages, an oxidant-reinforced alkaline extraction stage (EOP), and a subsequent pressurized peroxide with oxygen stage (PO), were performed on a eucalypt pulp that had been delignified by an ozone (Z) stage in the pulp mill. The goal was to predict the optimal costs and operational conditions for the (EOP)(PO) partial bleach sequence for three different specialty pulp products. Four independent variables affecting the pulp quality properties were examined for each stage (i.e., reaction temperature, reaction time, NaOH dosage and H2O2 dosage). The dependent variables were various pulp properties, such as intrinsic pulp viscosity, alpha-cellulose content, kappa number, and GE brightness. Three scenarios were considered to optimize the bleaching process, which related to a regenerated cellulose product (viscose) that is widely commercialized, and to two novel products (nanocrystalline cellulose (NCC) and nanofibrillated cellulose (NFC). Statistical response surface models indicated that the bleaching behavior of the ozone-treated pulp could be represented by second-order polynomial equations. These non-linear optimization models predict cost savings of 62.2%, 73.4%, and 63.3% for producing viscose, NCC, and NFC pulp grades, respectively.

High biomass loading is a key technique to reduce the pretreatment cost of lignocellulosic biomass. In this work, various biomass species such as bagasse, erianthus, cedar, and eucalyptus were pretreated using an ionic liquid, 1-ethyl-3-methylimidazolium acetate, at different biomass loadings, particularly focusing on a high loading region. Cellulose structural changes in pretreated biomass were investigated via X-ray scattering and 13C solid-state nuclear magnetic resonance (SSNMR) spectroscopy. The structural behaviors roughly fell into two categories, corresponding to either grassy (bagasse and erianthus) or woody (cedar and hardwood) biomass. The grassy biomass gradually transformed from cellulose-I to cellulose-II in a monotonic manner against the biomass loading. In contrast, the transformation in the woody biomass occurred abruptly as solids was decreased within the high loadings range (50 wt% to 33 wt%). Below 33 wt%, a reformation of cellulose-I from cellulose-II proceeded readily. In terms of cellulose crystallinity, erianthus as well as bagasse showed a minimum value at 25 wt% loading, whereas the crystallinity for the woody biomass did not possess such a clear minimum. Acid hydrolysis of these pretreated biomass was also conducted and the relationship between the reactivity and the cellulose structural changes was discussed.

Furfural residue (FR), a solid waste from the furfural production industry, is rich in cellulose and lignin. It has great potential for producing bio-fuels and bio-chemicals through pyrolysis. To examine the effects of heating programs on the product distribution of FR pyrolysis, stepwise and one-step pyrolysis processes were compared using a commercial Py-GC/MS system. During the stepwise pyrolysis, the acids had a maximum yield at 300 °C, while the outputs of the ketones/aldehydes, furans, esters, alcohols, and sugars were the most abundant at 350 °C. The production of aromatics increased, whereas the nitrogen-containing compounds decreased as the temperature increased from 300 °C to 500 °C. The relative percentages of the aromatics and furans from the one-step pyrolysis were much higher than those from the stepwise pyrolysis. In contrast, the acids, sugars, alcohols, nitrogen-containing compounds, and alkanes/olefins from the stepwise pyrolysis were higher than those from the one-step pyrolysis at 500 °C. The kinetic analysis showed that the activation energy of the FR was reduced from between 212 and 214 kJ/mol to between 189 and 191 kJ/mol as the degree of conversion (α) increased from 20% to 60%, before increasing from 191 kJ/mol to 478 kJ/mol as α further increased from 70% to 90%.