Research Articles

Understanding employment trends is important for discerning the economic vitality of U.S. hardwood lumber users. After a period of growth in the 1990s, employment in industries consuming hardwood lumber has declined in the 21st century. The wood household furniture industry has experienced the greatest decline, with North Carolina, Virginia, and California being the states most affected. Nearly all of the decline in employment in the furniture industry can be attributed to increased importation of this product. Millwork and kitchen cabinets are industries associated with home construction. Both of these industries experienced declines in employment in the 21st century. Employment in millwork started to decline after 2000, while employment in the kitchen cabinet industry started to decline after 2006. While there was little change in the relative regional employment rankings in the millwork industry, Indiana displaced California and Texas to become the largest employer in the kitchen cabinet industry. Employment in the pallet industry has declined in the 21st century, but mostly during the two recessionary periods. The pallet industry was the only industry that had an employment increase after 2009. Ohio was once the major pallet producing state, but it was displaced by California and Texas after 2002.

Sulphate removal from mine water is a problem because traditional chemical precipitation does not remove all sulphates. In addition, it creates lime sediment as a secondary waste. Therefore, an inexpensive and environmental-friendly sulphate removal method is needed in addition to precipitation. In this study, carbon residues from a wood gasification process were repurposed as precursors to a suitable sorbent for SO42- ion removal. The raw material was modified using ZnCl2, BaCl2, CaCl2, FeCl3, or FeCl2. Carbon residues modified with FeCl3 were selected for further consideration because the removal efficiency toward sulphate was the highest. Batch sorption experiments were performed to evaluate the effects of the initial pH, initial SO42- ion concentration, and contact time on sulphate removal. The removal of SO42- ions using Fe-modified carbon residue was notably higher compared with unmodified carbon residue and commercially available activated carbon. The sorption data exhibited pseudo-second-order kinetics. The isotherm analysis indicated that the sorption data of Fe-modified carbon residues can be represented by the bi-Langmuir isotherm model.

This study investigated the effect of heat-treated wood content on the water absorption, mechanical, and thermal properties of wood plastic composites (WPCs). The WPCs were produced from various loadings (30, 40, and 50 wt%) of heat-treated and untreated alder wood flours (Alnus glutinosa L.) using high-density polyethylene (HDPE) with 3 wt% maleated polyethylene (MAPE) coupling agent. All WPC formulations were compression molded into a hot press for 3 min at 170 ºC. The WPCs were evaluated using mechanical testing, Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). The mechanical property values of the WPC specimens decreased with increasing amounts of the heat-treated wood flour, except for the tensile modulus values. The heat treatment of alder wood slightly increased the thermal stability of the WPCs compared with the reference WPCs. The crystallization degree (Xc) and the enthalpy of crystallization of the WPCs slightly decreased with increasing content of the heat-treated wood flour. However, all WPCs containing the heat-treated alder wood flour showed a higher crystallinity degree than that of the virgin HDPE.

A 56-kDa β-glucosidase (TthBgl) derived from Thermotoga thermarum DSM 5069 was expressed and purified from Escherichia coli BL21 (DE3). The purified enzyme showed hydrolytic activity towards only p-nitrophenyl-β-D-glucopyranoside among the synthetic glycosides tested. The pH maximum was 5.0, and under the conditions tested, maximal activity was at 85 ºC, and pH stability occurred from 5.0 to 6.0. After being incubated at 80 ºC for 120 min, TthBgl retained 80% of its original activity. The β-glucosidase had no apparent requirement for metal ions or other co-factors, but its activity was significantly inhibited by 0.1% SDS and 1mM Cu2+, in which only 3% and 10% residual activity was maintained, respectively. The Vmax of TthBgl was 8.79 U mg-1 for p-nitrophenyl-β-D-glucopyranoside, while the Km was 2.41 mM. The Enzyme activity was gradually inhibited by the addition of glucose, but remained approximately 50% of its original value in 500 mM glucose. 789.25 mg/L glucose was released from cellobiose by the incubation of 0.2 U/mL TthBgl for 9 h at 75 ºC. According to a phylogenetic analysis, TthBgl belongs to the glycosyl hydrolase family 3 (GH3).

In this study, activated carbon fibers (ACFs) were prepared from liquefied wood by chemical activation with ZnCl2, with a particular focus on the effects of temperature and ZnCl2: liquefied wood-based fiber (LWF) ratio on yield, porous texture, and surface chemistry. The characterization and properties of these ACFs were investigated by nitrogen adsorption/desorption, Fourier transform infrared (FTIR) spectroscopy, and X-ray photoelectron spectroscopy (XPS). When using a 6:1 impregnation ratio, the specific surface area (SBET) of the resultant ACFs was as high as 1423 m2/g. The effect of an increase in impregnation ratio on the porosity of ACFs was stronger than that of an increase in the activation temperature. However, the former had a weaker impact on the surface chemistry and structure. It was also found that the yields of ACFs obtained by ZnCl2 activation were higher than those obtained by physical activation. Besides, the prepared ACFs presented higher adsorption than other raw materials in the adsorption test, indicating that ACFs prepared from LWF by ZnCl2 activation could be used as an adsorbent for the adsorption of medium size organic compounds.

Sugarcane bagasse was pretreated by green liquor combined with ethanol (GL-Ethanol) and green liquor combined with H2O2 (GL-H2O2). After 72 h of enzymatic hydrolysis, the glucose yields of sugarcane bagasse pretreated with GL-Ethanol and GL-H2O2 were 97.7% and 41.7%, respectively. The reason that GL-Ethanol was more effective than GL-H2O2 has not been elucidated clearly. In this study, the chemical composition of the sugarcane bagasse and chemical structure of the isolated lignins after these two pretreatment methods were characterized to investigate their correlation with the enzymatic hydrolysis of sugarcane bagasse. The removal of lignins with GL-Ethanol pretreatment was much higher than that of GL-H2O2. In addition, the decomposition of cellulose was lower in the case of GL-Ethanol than in that of GL-H2O2. According to Fourier transform infrared spectroscopy (FT-IR) and 1H-nuclear magnetic resonance (NMR) studies, the ester bonds (belonging to lignin-carbohydrate complex) could be broken during GL-Ethanol treatment. It was also found that the molecular weight of lignins obtained from GL-Ethanol was lower than that of lignins from GL-H2O2.

Xylanase pretreatment was used to improve the chlorine dioxide bleaching of bagasse pulp. The pulp was pretreated with xylanase, which was followed by a chlorine dioxide bleaching stage. The HexA content of the pulp and the AOX content of the bleaching effluent were measured using UV-Vis and GC-MS methods, respectively. The results showed that a good correlation occurred between HexA and kappa number. HexA content of the pulp decreased significantly after the xylanase pretreatment. The AOX content of the bleaching effluent decreased as HexA was removed from the pulp. It was found that AOX could be reduced by up to 29.8%, comparing XD0 with a D0 stage. Fourier transform infrared spectroscopy (FTIR) was employed to determine the breakage of chemical bonds in the pulp. It revealed that some lignin and hemicellulose were removed after xylanase treatment. The GC-MS results showed that some toxic chloride such as 2,4,6-trichlorophenol could be completely removed after xylanase pretreatment.

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.

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.