NC State
  • Researchpp 3775-3790Gu, R., Khazabi, M., and Sain, M. (2011). "Fiber reinforced soy-based polyurethane spray foam insulation. Part 2: Thermal and mechanical properties," BioRes. 6(4), 3775-3790.AbstractPDF
    Bio-based polyurethane (PU) spray foam insulation was prepared with soy polyol. The effects of adding wood fiber and water on the thermal and mechanical properties of the insulations were studied. The decomposition temperature (Td) of the foams increased with fiber reinforcement due to a higher degree of crosslinking. Alternatively, different fiber length contributed to different crosslinking. In addition, the neat foams, which didn’t contain wood fibers, had exceptional thermal stability with the increase of the amount of H2O by forming more stable polyurea adducts. In addition, PU spray foam blown with a larger content of H2O had higher compressive strength by forming a stiffer phase. Still, PU spray foam reinforced with fiber also had superior compressive strength due to the fiber framing into the foam struts. The effect of the fiber length on the compressive strength was evaluated. The degree of complex networks was influenced by the fiber length. However, the tensile strength was weakened with the addition of wood fiber.
  • Researchpp 3791-3808Kang, L., Wang, W., Pallapolu, V. R., and Lee, Y. Y. (2011). "Enhanced ethanol production from de-ashed paper sludge by simultaneous saccharification and fermentation and simultaneous saccharification and co-fermentation," BioRes. 6(4), 3791-3808.AbstractPDF
    A previous study demonstrated that paper sludges with high ash contents can be converted to ethanol by simultaneous saccharification and fermentation (SSF) or simultaneous saccharification and co-fermentation (SSCF). High ash content in the sludge, however, limited solid loading in the bioreactor, causing low product concentration. To overcome this problem, sludges were de-ashed before SSF and SSCF. Low ash content in sludges also increased the ethanol yield to the extent that the enzyme dosage required to achieve 70% yield in the fermentation process was reduced by 30%. High solid loading in SSF and SSCF decreased the ethanol yield. High agitation and de-ashing of the sludges were able to restore part of the yield loss caused by high solid loading. Substitution of the laboratory fermentation medium (peptone and yeast extract) with corn steep liquor did not bring about any adverse effects in the fermentation. Fed-batch operation of the SSCF and SSF using low-ash content sludges was effective in raising the ethanol concentration, achieving 47.8 g/L and 60.0 g/L, respectively.
  • Researchpp 3809-3823Lee, C. K., Ibrahim, D., Ibrahim, C. O., and Wan Rosli, W. D. (2011). "Pilot scale enzymatic deinking of mixed office wastepaper and old newspaper," BioRes. 6(4), 3809-3823.AbstractPDF
    The performance of a newly developed pilot scale continuous enzymatic deinking system has been evaluated using a mixture of cellulase and xylanase enzymes in the deinking of mixed office wastepaper (MOW) and old newspaper (ONP). Optimizations of the enzymatic deinking processes were carried out, and the optimum conditions obtained for MOW and ONP were different. The highest brightness obtained from enzymatic deinking of MOW and ONP under their respective optimum conditions were about 83.6% and 41.9%, respectively. The deinking efficiency of 6.0% and 6.3% were obtained by enzymatic deinking process using MOW and ONP, respectively. On the other hand, the deinking efficiency of 2.9% and 3.5% were obtained by a chemical deinking process using MOW and ONP, respectively. The findings obtained from present work indicated that enzymes have potential to be used in deinking of MOW, which is difficult to deink by conventional chemical deinking methods.
  • Researchpp 3824-3835, T., Kontturi, E., Leppänen, K., Serimaa, R., and Vuorinen, T. (2011). "Kraft pulping of Juniperus communis results in paper with unusually high elasticity," BioRes. 6(4), 3824-3835.AbstractPDF
    Juniper (Juniperus communis) is a slowly growing softwood species that has unusually high elasticity. To demonstrate the utilization of the material properties of juniper, conventional kraft pulping was used to prepare juniper pulp, whose handsheet and fiber properties were subsequently analyzed. A large number of uncooked fiber bundles remained after pulping, the screened yield was low, and kappa number high. Also the viscosity value of juniper pulp was lower than that of common industrial softwood pulps, due to the harsh pulping conditions required. Juniper fibres had thicker cell walls, smaller diameters, and shorter lengths than those of the more conventional softwood species, while the microfibril angle, which was measured by X-ray diffraction, was significantly higher (22-37°). Moreover, the strength properties of juniper pulp handsheets were lower than those of common softwood pulps. The intriguing elastic properties of juniper wood, however, were apparent in the handsheet properties. Tensile stiffness was determined to be merely half of the value typical for softwood pulps, whereas the breaking stretch was more than twice higher. Although a large-scale industrial use of juniper is not possible, one can speculate that it may be feasible to mimic its properties via transgenic modification to faster growing species.
  • Researchpp 3836-3849Ghali, L., Aloui, M., Zidi, M., Bendaly, H., M'sahli, S., and Sakli, F. (2011). "Effect of chemical modification of Luffa cylindrica fibers on the mechanical and hygrothermal behaviours of polyester/luffa composites," BioRes. 6(4), 3836-3849.AbstractPDF
    Effects of surface chemical modifications of luffa fibers on mechanical and hygrothermal behaviors of polyester/luffa composites were studied. Unsaturated polyester resin was used as matrix. Untreated, alkali-treated, treated with combined process, and acetylated luffa fibers were used. Scanning electron microscopy and infrared spectroscopy were used to characterize the morphology and chemical structure of the luffa fibers. The mechanical properties of the composites were characterized using the three-point flexural bending test. Water absorption tests were conducted on both the fibers and the composite materials by immersion in distilled water at 25°C. The acetylation treatment improved the mechanical properties. As shown by infrared analysis, the process decreased the hydrophilic behaviour of the luffa fibers, improving their adhesion to the polyester matrix. The chemical modifications at the surface of the luffa fibers also decreased the diffusion coefficient and the maximum amount of water absorbed by these fibers. Moreover, it was observed that for the fibers tested in this study, the diffusion process was “Fickian” at earlier times of immersion, but became complicated towards the end of the immersion. Similar results have been obtained for composite materials at earlier stages of water immersion. The diffusion process was found to be affected by external loads applied on the exposed composite materials. As the load increased, the amount of absorbed water increased at a higher rate of diffusion.
  • Researchpp 3850-3858Cui, L., Liu, Z., Hui, L.-F., and Si, C.-L. (2011). "Effect of cellobiase and surfactant supplementation on the enzymatic hydrolysis of pretreated wheat straw," BioRes. 6(4), 3850-3858.AbstractPDF
    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.
  • Researchpp 3859-3875Lee, C. K., Ibrahim, D., Ibrahim, C. O., and Wan Rosli, W. D. (2011). "Enzymatic and chemical deinking of mixed office wastepaper and old newspaper: Paper quality and effluent characteristics," BioRes. 6(4), 3859-3875.AbstractPDF
    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.
  • Researchpp 3876-3882Singh, S., Dutt, D., and Tyagi, C. H. (2011). "Environmentally friendly totally chlorine free bleaching of wheat straw pulp using novel cellulase-poor xylanases of wild strains of Coprinellus disseminatus," BioRes. 6(4), 3876-3882.AbstractPDF
    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.
  • Researchpp 3883-3898Espinoza, O., Bond, B. H., and Buehlmann, U. (2011). "Energy and the US hardwood industry - Part 1: Profile and impact of prices," BioRes. 6(4), 3883-3898.AbstractPDF
    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.
  • Researchpp 3899-3914Espinoza, O., Buehlmann, U., and Bond, B. H. (2011). "Energy and the US hardwood industry - Part II: Responses to increasing prices," BioRes. 6(4), 3899-3914.AbstractPDF
    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.