Volume 11 Issue 2

One of the most persistent problems with mechanically densified wood is its inherent dimensional instability. The effects of heat post-treatment on the changes in spring-back (SB), compression ratio recovery (CRR), thickness swelling (TS), and water absorption (WA) of newly-tested Uludağ fir (Abies bornmuelleriana Mattf.) and black poplar (Populus nigra L.) wood samples that had been thermo-mechanically densified were investigated. Samples were densified with compression ratios of 25% and 50% with temperatures of 100 and 140 °C, respectively. Then, the heat post-treatment was applied to the samples at 185 and 212 °C for 2 h. For the two newly-tested wood types, results of the preliminary study show that SB and TS were higher at a 50% compression ratio compared with 25%. Regarding densification temperature, TS was lower in samples densified at 140 °C, while SB was higher. WA values were lower in compressed samples (50%) at high rates. The effect of the densification temperature on WA was insignificant. Heat post-treatment had a considerable effect on the dimensional stability and hygroscopicity of the densified Uludağ fir and black poplar samples. With an increase in heat treatment temperature, the dimensional stability increased, while the hygroscopicity of densified samples decreased. As a result of heat post-treatment applied at 212 °C, SB, CRR, TS, and WA decreased by 88%, 85%, 79%, and 53%, respectively.

Cellulose solvent- and organic solvent-based lignocellulose fractionation (COSLIF) has been repeatedly shown to be a cost-effective and promising process to modify the structure of different lignocelluloses. It has been repeatedly reported to improve enzymatic hydrolysis and ethanol production from different lignocelluloses. In this study, COSLIF was used to improve biomethane production from pine (softwood), poplar (soft hardwood), and berry (hard hardwood) via solid state anaerobic digestion (SSAD). Feed to inoculum (F/I) ratio, which plays a major role in SSAD, was set to 3, 4, and 5. After the pretreatment, 39, 33, and 24% higher methane yield from pine was achieved for F/I ratios of 3, 4, and 5, respectively. However, the methane yield from the hardwoods was not improved by the pretreatment, which was related to overloading of the digester. Compositional analysis showed considerable reduction in hemicellulose and lignin content by the pretreatment. Structural changes in the woods, before and after the pretreatment, were examined by X-ray diffractometer and scanning electron microscopy. The results showed that the crystallinity of cellulose was decreased and accessible surface area was drastically increased by the pretreatment.

A slow pyrolysis of pinewood was investigated in this paper. Through the briquette process, the pinewood sawdust becomes molded biomass. The molded bio-char was produced from molded biomass with different pyrolysis factors, and the bio-char’s heating value, char yield rates, and physicochemical and morphological properties were investigated. Molded bio-char’s characteristics depended principally on pyrolysis factors. At low temperature (400 °C), the char yield rate was positively correlated to the heating rate. But at higher temperatures (500 to 700 °C), the char yield rates decreased as heating rates increased. As pyrolysis temperature increased from 400 to 700 °C, the following increased in molded bio-char: fixed-carbon content, percentage carbon, heating value, ash content, as well as surface areas. And its pore structure, graphite degree, and polymerization degree achieved a higher level. Compared with pulverized bio-char, the molded bio-char had a higher char yield rate, ash content, graphite degree, and structure ordering. The molded bio-char obtained from a low temperature (400 °C) and high heating rate (15 °C/min) can be used as a reducing agent, the molded bio-char from 600 °C is recommend as an activated carbon precursor, and the molded bio-chars from low temperature (400 °C) have a higher efficiency as fuel.

The possibility of preparing molding-bioengineered materials, such as woodchip boards (WCB), from sawdust using technical lignosulfonate (LGS), a wood waste product, and a culture liquid (CL) of levan microbial polysaccharide producer by Azotobacter vinelandii D-08 is explored in this article. The parameters of the derived materials are comparable to those of traditional materials made from toxic phenol-formaldehyde resins. The various physical and mechanical characteristics of the materials depend on the quantity of the bonding agent used for the preparation. Adding a culture liquid increases the humidity resistance of the molding materials. Using electron microscopy and X-ray micro-tomography, it is clear that the structure of woodchip boards become more homogeneous without microcracks with the addition of CL. The strength of the best samples prepared was approximately 24 to 29 MPa with a density of 1170 to 1255 kg/m3 and a swell on wetting of 6.7%. During hot pressing, noticeable changes were observed by Fourier transform infrared spectroscopy (FTIR) at frequencies typical of LGS sulfonic-acid groups, levan fructose fragments, and skeletal vibrations of a syringal/guaiacyl core in lignin and of C-H groups of hemicelluloses. This indicates the involvement of these functional groups in the process of binding wood particles with hot pressing.

The fuel properties of wood obtained from sugar maple (SM) and yellow birch (YB) of temperate hardwood stands located in the Province of Québec, Canada were studied to see how tree vigor affects the chemical composition and calorific value of the wood. This study focused on the physical and chemical properties of wood with the aim of using the material for the production of solid biofuels. Specific items measured included the wood’s calorific values, and the levels of extractives, ash, and lignin. Changes in chemical composition were found among tree vigor classes. The low vigor trees had higher extractives, ash, and lignin contents than the vigorous trees. Total extractives ranged between 4.88 and 7.32% in SM, and between 3.35 and 5.12% in YB. Klason lignin ranged between 21.46 and 23.53% in SM, and between 18.60 and 21.51% in YB. Ash content ranged between 0.38 and 0.97% in SM, and between 0.26 and 0.47% in YB. The combined effects of higher lignin content that could contribute to a better self-bonding of particles and of higher extractives content that could facilitate the pelletization process makes the low vigor trees more suitable for conversion into solid biofuels. The higher amounts of extractives and lignin present in the low vigor sugar maple and yellow birch trees could also have a positive role in maintaining the high calorific values of this wood despite higher ash content.

Fiber membranes prepared from jute fragments can be valuable, low cost, and renewable. They have broad application prospects in packing bags, geotextiles, filters, and composite reinforcements. Traditionally, chemical adhesives have been used to improve the properties of jute fiber membranes. A series of new laccase, laccase/mediator systems, and multi-enzyme synergisms were attempted. After the laccase treatment of jute fragments, the mechanical properties and surface hydrophobicity of the produced fiber membranes increased because of the cross-coupling of lignins with ether bonds mediated by laccase. The optimum conditions were a buffer pH of 4.5 and an incubation temperature of 60 °C with 0.92 U/mL laccase for 3 h. Laccase/guaiacol and laccase/alkali lignin treatments resulted in remarkable increases in the mechanical properties; in contrast, the laccase/2,2’-azino-bis-(3-ethylthiazoline-6-sulfonate) (ABTS) and laccase/2,6-dimethoxyphenol treatments led to a decrease. The laccase/ guaiacol system was favorable to the surface hydrophobicity of jute fiber membranes. However, the laccase/alkali lignin system had the opposite effect. Xylanase/laccase and cellulase/laccase combined treatments were able to enhance both the mechanical properties and the surface hydrophobicity of jute fiber membranes. Among these, cellulase/laccase treatment performed better; compared to mechanical properties, the surface hydrophobicity of the jute fiber membranes showed only a slight increase after the enzymatic multi-step processes.

The effect of timber length on time-of-flight acoustic longitudinal measurements was investigated on the structural timber of four Spanish species: radiata pine (Pinus radiata D. Don), Scots pine (Pinus sylvestris L.), laricio pine (Pinus nigra Arn.), and maritime pine (Pinus pinaster Ait.). Time-of-flight longitudinal measurements were conducted on 120 specimens of dimensions 90 × 140 mm using three commercially available acoustic instruments (Sylvatest Duo, USLab, and Microsecond Timer). Time-of-flight data were initially obtained from the full-length (4 m) specimens, and then from the specimens cut to 3, 2, and 1 meter in length by successively cutting off 0.5 m from each end. The acoustic longitudinal velocity of the timber specimens of different lengths was also measured using a resonance-based acoustic method. The apparent acoustic longitudinal velocity for all species increased linearly as the timber length decreased from 4 to 1 meter. Acoustic velocity determined from time-of-flight data was significantly higher than the acoustic velocity determined using the resonance method, indicating systematic measurement errors associated with the time-of-flight instruments. Empirical models were developed for the relationships between time-of-flight measurements on timber specimens and timber lengths in the range of 1 to 4 m. Finally, a procedure was proposed to correct the time-of-flight data.

To achieve value-added utilizations of plantation timbers, eucalyptus veneer/high-density polyethylene film composites were prepared, with process-factors (PF) (hot-pressing temperature, HT; hot-pressing duration, HD; hot-pressing pressure, HP; HDPE-film content, HC) and composite-properties (CP) (water-resistant bonding-strength, BS; modulus of rupture, MOR; modulus of elasticity, MOE) investigated. According to thermal analyses, 140 to 180 °C was appropriate for HT. Based on statistical analyses, HD was easier to affect CP, while MOE was easier to be affected by PF. Quantitative relationships between PF and CP were determined by the neural-network (ANN) modeling. In ANN simulation surveys, CP displayed Gaussian distributions (R2 > 0.9) when PF changed in current ranges, with positive correlations between BS and MOR (R2 ≈ 0.5). Combining ANN and the genetic-algorithm, optimal processes (HT, 160 °C; HD, 50 s/mm; HP, 1.3 MPa; HC, 6 layers) were found, and optimal results (BS, 1.30 MPa; MOR, 86.94 MPa; MOE, 8.33 GPa) were comparable to various reported poplar-plywoods. Microscopic images demonstrated that composite interfaces were formed by the mechanical interlocking. The optimal BS attained Chinese standards for water-resistant plywoods, so proposed composites can serve as water-resistant and formaldehyde-free building materials for furniture and interior design.

This study demonstrated the reinforcing potential of kenaf core fiber (KCF) to complement and sustain oil palm fiber supply chain in the production of natural fiber-thermoplastic biocomposites. The lignin-rich KCF was incorporated into cellulose-rich oil palm empty fruit bunch fiber (EFBF)- and oil palm mesocarp fiber (OPMF)-poly(lactic acid) (PLA) composites, aimed at achieving synergism. The hybrid biocomposites developed by melt blending and subsequent compression molding were characterized for possible application as an alternative to medium-density fiberboards. The mechanical properties and dimensional stability of both single fiber- and hybrid fiber-PLA biocomposites were evaluated and compared. The test results showed a synergistic improvement as a consequence of fiber hybridization. Also, the findings suggested the best material performance with the incorporation of 5% KCF into 55% EFBF or OPMF and 40% PLA matrix. The OPMF-KCF-PLA hybrid biocomposites gave better results than the EFBF-KCF-PLA hybrid biocomposites.

The objective of this study was to explore the influence of pyrolysis temperature on the physicochemical properties of biochar synthesized from durian wood (Durio zibethinus) sawdust. Surface morphological features, including the porosity and BET surface area of biochars, provide appropriate dimensions for growing clusters of microorganisms with excellent water retention capacity in soil. Oxygen-containing surface functional groups play a vital role in improving soil fertility by increasing its cation and anion exchange capacities with reduced leaching of nutrients from the soil surface. Biochar was produced via slow pyrolysis of woody biomass (WS) using a fixed bed reactor under an oxygen-free atmosphere at different pyrolysis temperatures (350, 450, and 550 °C). The biochars obtained were characterized using ultimate and proximate analyses, Brunauer-Emmett-Teller (BET) surface area, field-emission scanning electron microscopy (FE-SEM), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD). The yield of biochar decreased from 66.46 to 24.56%, whereas the BET surface area increased sharply from 2.567 to 220.989 m2/g, when the pyrolysis temperature was increased from 350 to 550 °C. The results highlighted the effect of pyrolysis temperature on the structure of the biochar, which could be advantageous for agricultural industries.