Research Articles

Wheat straw is a suitable raw material for ethanol production since it has high cellulose content. The objective of this work was to evaluate the effect of cellobiase and surfactant on the enzymatic hydrolysis of lignocellulosic materials. For this purpose, wheat straw was first pretreated by organosolv digestion. The chemical s of raw and pretreated wheat straw were analyzed. Much of the hemicellulose and lignin were removed, and the relative cellulose content of pretreated wheat straw was 26.57% higher when compared to untreated wheat straw. Cellobiase was added into hydrolysate to improve the hydrolysis efficiency. Through experiments and analysis, the optimum cellobiase dosage was found to be 1/10 of the cellulase loading. Surfactant was also added into hydrolysate. Nonionic surfactant (Tween 80) exhibited better effect on improving enzymatic hydrolysis. When 0.06 g/g dry solids (DS) Tween 80 was also added into hydrolysate, the yield of glucose in hydrolyzate could reach 486 g/kg DS.

Enzymatic and chemical deinking not only significantly influence the optical and mechanical properties of deinked paper, but also influence the pulp properties and wastewater effluent generated. Both enzymatic and chemical deinking of mixed office wastepaper (MOW) and old newspaper (ONP) showed improvement in brightness (1.4-4.7 units), tensile index (1-14%), burst index (1.2-3.8%), freeness (1.9-2.9%), and residual ink removal (31.1-51.2%) but caused loss in opacity (0.1-2.6%) and tear index (0.1-9.6%). Chemical Oxygen Demand (COD) analysis indicated that effluent produced from enzymatic deinking were about 33.9% and 33.8% lower compared to chemical deinking of ONP and MOW, respectively. Meanwhile, Biological Oxygen Demand (BOD5) obtained from enzymatic deinking of MOW and ONP were 47.1% and 39.3% lower compared to the chemical deinking process, respectively. The results obtained in this work demonstrated that the quality of the pulp and paper obtained from enzymatic deinking process was better than that from the chemical deinking process. This suggests that enzymatic deinking has high potential as an alternative to the chemical method.

Cellulase-poor crude xylanases of Coprinellus disseminatus, strains SH-1 NTCC 1163 (enzyme-A) and SH-2 NTCC 1164 (enzyme-B) produced under optimum conditions of solid-state fermentation (SSF), were used in bio-bleaching of wheat straw soda-AQ pulp in totally chlorine free (TCF) bleaching sequences. Kappa number reductions of 56% and 58% with respect to oxygen-delignified pulps were obtained after the sequences OXAE and OXBE, respectively. Significant increases in pulp brightness of 6.07% (enzyme-A) and 3.34% (enzyme-B) with slight decreases in some strength properties (due to the removal of hemicelluloses) were observed. Removal of hemicelluloses was further validated by an increase in pulp viscosity (6.07%, and 4.58%), COD (40%, and 38%), and facilitation of lignin removal, as indicated by colour values (48% and 45%) for OXAEQPP and OXBEQPP bleached pulps, respectively, over the control. Crude xylanases from C. disseminatus SH-1 NTCC 1163 and SH-2 NTCC 1164 can successfully be used for TCF bleaching of pulps owing to their high temperature and pH toleranance, and cellulase-poor nature, thus adding to the search for environment-friendly bleaching solutions for the pulp and paper industry.

According to the Energy Information Administration two fifths of the energy used by US wood products manufacturers comes from electricity and natural gas, the costs of which have pointedly increased over the last decade. Empirical indications exist that higher energy prices affect the industry’s profitability. Together with other developments such as, for example, unfavorable trends in hardwood stumpage prices, higher transportation costs, increasing government regulations, a challenging economic situation, or the ongoing globalization of markets, the US hardwood industry has to cope with some serious challenges threatening its profit potential. To understand the impact of energy prices on wood products manufacturers’ profitability and to gain insights regarding actions the industry is taking to respond to energy-related challenges, a survey was conducted among Eastern US primary hardwood products manufacturers in late 2010. Results show that, overall, the share of energy expenses on total production costs of respondents was 7.9%. A majority of respondents (61.8%) agreed that their energy expenses have increased by an average of 18.7% during the last five years. Half of the respondents reported a 5% or higher negative impact of higher energy prices on their profits over the same period. Actions undertaken by the industry to alleviate the negative impact of rising energy prices are presented in a second paper in this two-part series.

This second manuscript in the series about energy and the US hardwood industry reports results from research investigating the impact of energy prices on the US hardwood industry. The manuscript focuses on actions by the industry to improve energy performance. Most companies (63 percent) indicated that they are focusing on improving energy efficiency and/or improving productivity (41.3 and 41.9%, respectively) to cope with rising energy prices; however, only 8.6% of the survey respondents indicated that they have established energy usage baselines and energy performance indicators. Sixty-seven percent of companies indicated that they are training employees on energy saving issues. Other common initiatives for energy costs reductions were installing more efficient lighting, acquiring new high energy-efficient equipment, and measures to reduce the wastage of energy, like switching off high energy consuming equipment or close off or lit off sections with no traffic.

Effects of the impregnation materials borax, boric acid, and Tanalith-E on combustion properties of Oriental beech (Fagus orientalis Lipsky) were investigated. The immersion method was used for long-term impregnation (24 h). After the impregnation process, polyurethane as well as synthetic, acid hardening, and water-based varnishes were applied on the wood sample surfaces according to company’s suggests. The combustion test was performed according to the ASTM-E 69 standard. The mass reduction, release of gasses (CO, NO, O2), and the temperature differences of samples were determined for each 30 seconds during combustion. It was shown that the most mass reduction occurred when both polyurethane varnish and boric acid were applied.

The topochemical distribution of lignin and cellulose in individual cell wall layers of Populus nigra stem was determined by transmission electron microscopy (TEM) and confocal Raman microscopy. TEM images exhibited the fiber wall as being typically differentiated into three layers: middle lamella (ML), primary wall (P), and secondary wall (S1, S2, and S3). Higher magnification views showed the S2 layer to be differentiated into electron lucent and dense areas in the radial direction. In situ Raman images calculated by integrating over the intensity of characteristic spectral bands enabled visualization of the spatial variation in lignin and cellulose. Raman images acquired by integrating over the spectral band at 1605 cm-1 suggested that higher lignin content was visualized in the cell corner (CC), the compound middle lamella (CML), and the secondary wall of ray parenchyma. Cellulose distribution followed by taking the band regions around 2897 cm-1 into account showed the opposite pattern, with the highest content in fiber secondary wall. The SEM-EDXA provided semi-quantitative results, showing that the lignin content ratio in various cell wall layers was 1.4 (CC):1.1(CML):1(S2).

The bark of black spruce was thermo-mechanically refined and used to manufacture binderless bark-based fiberboard with various pressing temperatures, times, and panel structures in order to utilize an abundant bark resource for a better value-added application. The test results indicated that it is technically feasible to manufacture binderless fiberboard with refined black spruce bark through self-bonding under elevated temperatures over a reasonable period of pressing time. Binderless bark-based fiberboards with a homogeneous structure had very poor flexural properties due to the poor strength of bark itself; however, by using a sandwich structure with 30wt% wood fiber in the surface layers and 70wt% bark in the core layer it was possible to sufficiently improve panel flexural properties so that the manufactured binderless bark-based fiberboards was able to meet the mechanical property requirements of 115-grade fiberboard according to ANSI A208.2 (2009). Refining conditions had a great impact on the mechanical properties of binderless bark-based fiberboard.

Effects of drying temperature and artificial UV irradiation on the pH of veneer surfaces, water absorption, thickness swelling, as well as shear strength of plywood manufactured from untreated and treated veneer sheets were evaluated. Rotary cut veneer sheets from beech (Fagus orientalis Lipsky) log were selected. The veneer sheets were dried at either 100°C or 180°C after peeling. Then the surfaces were exposed to artificial UV irradiation in an UV chamber for 1, 2, and 3 days representing a natural sun irradiation of 2, 4, and 6 months, respectively. Tests by UV microspectrophotometry showed that after high temperature drying and UV irradiation treatment, lignin condensation occurs. Also with increasing drying temperature and UV irradiation duration phenolic extractives are mainly concentrated in parenchyma cells and vessel lumens. HPLC analysis of the treated tissue showed distinct signals of catechin and 2,6-dimethoxybenzoquinon, which are two chromophoric compounds in discolored red hearted beech wood. Increasing drying temperature up to 180°C improved water absorption, thickness swelling, and shear strength of plywood samples. Especially, when veneers were exposed to UV irradiation (6 months), increased water absorption and thickness swelling and decreased the shear strength of plywood samples were observed.