NC State
  • Editorialpp 4490-4494Okpala, C. O. R. (2017). "Reflecting in the woods: Can it help to enhance the formulation of (our) research questions?" BioRes. 12(3), 4490-4494.AbstractArticlePDF
    Nowadays, reflecting and reflective practice are being incorporated into undergraduate and postgraduate learning across disciplines, and thus, both can be seen as prerequisite(s) to achieving effective research activity. On the other hand, trees represent organisms characterized by a perennial lifestyle to produce a majority of terrestrial biomass. Trees, when put together as a group, take on the identity as “the woods”, which can be seen in many parts of the globe. In science, the choice and use of research questions has been considered as very useful in the definition, collection and reporting of (relevant) information. But, can reflecting in the woods enhance the formulation of (our) research questions? In this editorial, an attempt is made to respond to this question, to show that the woods has promising potential to provide a positive atmosphere for effective reflective activity for any (scientific) researcher.
  • Editorialpp 4495-4496Lenahan, O. M. (2017). "Book review: Fabriano: City of Medieval and Renaissance Papermaking – The first 500 years," BioRes. 12(3), 4495-4496.AbstractArticlePDF

    The Italian town of Fabriano is known for producing high-quality handmade paper – an industry that began in the 13th century and that has endured for eight centuries. How did the industry take hold in this Italian town and how did it endure for so long? Author Sylvia Rodgers Albro tells this story in her new book, Fabriano: City of Medieval and Renaissance Papermaking. Readers who appreciate history and engineering will enjoy Albro’s narrative, wonderful photography, and diagrams as they bring to life the art, science, and social history of papermaking in Fabriano.

  • Editorialpp 4497-4499Hubbe, M. A. (2017). "Book review of an open textbook: Sustainability: A Comprehensive Foundation," BioRes. 12(3), 4497-4499.AbstractArticlePDF

    Paper was once the lightest, lowest-cost way to make information widely available in a form suitable for study and self-improvement. But paper-based textbooks, in the modern era, tend to be heavy and they can also strain the budgets of typical students. Given the fact that you are now reading an open-access journal, you may understand why many faculty members would possibly want to use an open-access textbook for some of their courses. This editorial considers one such course, and the assessment is generally favorable. But in addition to the classroom, a good open textbook may be regarded as a suitable foundation for one’s research. By citing an open textbook in the introduction to your research article, you can provide your readers with the option of gaining enough background to better appreciate your latest research findings.

  • Researchpp 4500-4514Li, T., Li, G., Lu, Q., Zhou, J., Li, M., Zhang, S., and Li, J. (2017). "Characterization of Tectona grandis extractives by GC-MS and IR and their infusion into rubberwood to modify dimensional stability," BioRes. 12(3), 4500-4514.AbstractPDF
    Teak (Tectona grandis) has been popularly known in the wood industry as a precious material due to its natural dimensional stability. To explore the main components affecting the dimensional stability of teak wood, the teak wood samples were extracted with different polar solvents, and the extractives were impregnated into rubberwood specimens to determine their effect on the dimensional stability of the modified rubberwood. The results showed that the methanol extractives of the teak wood exhibited the most significant effect on the dimensional stability of the rubberwood. The extractives were characterized by infrared (IR) and gas chromatograph/ mass spectrum (GC/MS). The GC/MS results showed that the methanol extractives primarily contained 9,10-anthracenedione, 1,1-dimethyl-3,4-bis(1-methylethenyl), and alcohol compounds. It was speculated that the alcohol compounds in the methanol extractives reacted with polar hydroxyl groups in the cell wall, which resulted in a decrease in the size of the site combined with bound water. Moreover, the hydrophobic hydrocarbon compound was impregnated into rubberwood to form a thin layer of protective film in the cells into which the water could not enter under 20 °C and 80% RH.
  • Researchpp 4515-4526Yamada, H., Miyafuji, H., Ohno, H., and Yamada, T. (2017). "Rapid and complete dissolution of softwood biomass in tetra-n-butylphosphonium hydroxide with hydrogen peroxide," BioRes. 12(3), 4515-4526.AbstractArticlePDF

    The wood dissolution properties of tetra-n-butylphosphonium hydroxide ([P4,4,4,4]OH) were investigated. Cedar wood meal was treated with several concentrations of aqueous (aq.) [P4,4,4,4]OH with hydrogen peroxide (H2O2) in a glass tube at 121 °C. The solution of 60% aq. [P4,4,4,4]OH with H2O2 at 121 °C showed the best dissolution capability for woody biomass with a high dissolution rate of 0.152 g min-1. Under this condition, 98.5% of the woody biomass, including both lignin and holocellulose, was dissolved after 3 h of treatment. The molecular weight distribution of lignin in the soluble fraction of the [P4,4,4,4]OH mixtures was determined via size exclusion chromatography, and its weight-average molecular weight decreased from approximately 7500 g/mole after 0.5 h to 2 h of treatment to 5700 g/mole after 3 h and 2500 g/mole after 5 h of treatment. Lower molecular weight components were determined by high-performance liquid chromatography, and vanillin and vanillic acid were identified. The dissolved cellulose was precipitated, and its polymerization degree decreased significantly after 0.5 h of treatment compared to that of the original cellulose.

  • Researchpp 4527-4546Hassan, N., Hamid, N. H., Jawaid, M., Tahir, P. M., and Ujang, S. (2017). "Decay resistance of acetic, propionic, and butyric anhydrides modified rubberwood against brown rot (Coniophora puteana)," BioRes. 12(3), 4527-4546.AbstractArticlePDF
    Rubber trees were cut to the dimensions 25 mm x 140 mm x 1000 mm (R x T x L) and kiln-dried (10% to 12% moisture content, MC). The specimens (20 mm x 20 mm x 5 mm) (R x T x L) were prepared, and a Soxhlet extraction with toluene/methanol/acetone (4:1:1 by volume) was performed for 8 h. The specimens were oven-dried (103 °C for 24 h) and cooled (gel silica). Then, vacuum impregnation was conducted, and reactions with acetic, propionic, and butyric anhydrides took place for 0.25 h, 1 h, 4 h, 8 h, 10 h, 15 h, 24 h, 30 h, 36 h, and 48 h at 120 °C. The chemical bonding was confirmed by Fourier transform infrared (FTIR) analysis. The specimens were leached in deionized water and exposed to brown rot (Coniophora puteana) in an incubation room at 22 °C for 16 weeks. The fastest reaction was with butyric anhydride, then propionic and acetic anhydrides. The lowest weight loss occurred with acetic anhydride after being decayed by C. puteana at 14.0% weight percent gain (WPG). All of the modified rubberwoods (acetic, propionic, and butyric anhydrides) at the maximum WPG were classified as durability class 1. The scanning electron microscopy (SEM) observation confirmed that the hyphae penetrated the cells in both the untreated and anhydride modified rubberwood.
  • Researchpp 4547-4566Steffen, F., Janzon, R., Wenig, F., and Saake, B. (2017). "Valorization of waste streams from deinked pulp mills through anaerobic digestion of deinking sludge," BioRes. 12(3), 4547-4566.AbstractArticlePDF

    Based on the results of this study, a total energy amount of 3,111 TJ/year can be produced from the anaerobic digestion of deinking sludge (DS) arising from German deinked pulp mills, which can then be used to replace up to 5% of the total energy demand for those mills. The DS examined was generated by flotation deinking at the laboratory scale from selected mixes of paper for recycling (PfR). The results from the batch fermentation tests indicated a strong dependence of the methane potential of the DS on the carbohydrates and lignin contents, which in turn are linked to the original PfR quality. The highest methane yield was observed for DS100 (25.8% carbohydrates; 5.1% lignin) with 280.4 mL/g of volatile solids (VS) added, while DS70 (14.2% carbohydrates; 24.9% lignin) showed the lowest methane yield, with 122.1 mL/gVS. All of the DS samples showed high methane production rates, in the range between 59.4 (DS70) and 118.6 mL/gVS d-1 (DS100), and kinetic constants of 0.66 to 0.79 d-1. Additionally, no distinguishable lag phases were observed, which strongly indicates the rapid biodegradation of the DS.

  • Researchpp 4567-4593Jones, B. W., Venditti, R., Park, S., and Jameel, H. (2017). "Optimization of pilot scale mechanical disk refining for improvements in enzymatic digestibility of pretreated hardwood lignocellulosics," BioRes. 12(3), 4567-4593.AbstractPDF
    Mechanical refining has potential application for overcoming lignocellulosic biomass recalcitrance to enzyme hydrolysis and improving biomass digestibility. This study highlighted the ability for a pilot scale disc refiner to improve the total carbohydrate conversion to sugars from 39% (unrefined hardwood sodium carbonate biomass) to 90% (0.13 mm gap, 20% consistency, ambient temperature) by optimizing the refining variables. The different biomass properties that changed with refining indicated the expected increase in sugar conversion. Controlling the refining parameters to narrower gaps and higher consistencies increased the resulting refined biomass hydrolysis. Positive correlations that increases in net specific energy (NSE) input and refining intensity (SEL) improved the enzymatic hydrolysis. In some severe cases, over-refining occurred when smaller gaps, higher consistencies, and more energy input reached a point of diminished return. The energy input in these scenarios, however, was much greater than realistically feasible for industrial application. Although well-established in the pulp and paper industry, gaps in understanding the fundamentals of refining remain. The observations and results herein provide the justification and opportunity for further mechanical refining optimization to maximize and adapt the mechanical refining technology for maximum efficiency within the process of biochemical conversion to sugar.
  • Researchpp 4594-4605Ahmad Yahaya, A. N., Hossain, M. S., and Edyvean, R. (2017). "Analysis of phenolic compounds in empty fruit bunches in oyster mushroom cultivation and in vermicompositing," BioRes. 12(3), 4594-4605.AbstractArticlePDF

    Analyses of total phenolic compounds were carried out for oil palm empty fruit bunches (EFBs) vermicomposting in oyster mushrooms cultivation. The oyster mushrooms (Pleurotus sajor-caju) were cultivated according to the large-scale vermicomposting trial (LSVT) methods. Both oyster mushrooms cultivation and vermicomposting of EFB with earthworms enhanced the lignin degradation of EFB. Analysis of total phenolic compounds EFB vermicomposting treated with earthworms showed a decrease in total phenolics concentration from 31.1 GAE/100g extract (raw EFB) to 5.66 g GAE/100g extract (after oyster mushroom cultivation) and to less than 1.5 g GAE/100g extract at the end of vermicomposting. Gas chromatography–mass spectrometry (GC-MS) analysis of the mushroom fruiting body, spent mushrooms, and vermicompost showed no trace of phenolphenol, pyrocatechol, 4-hydrobenzoic acid, or antioxidant and flavonoid phenolics, e.g., phenol, 3,4-dimethoxy-, vanillic acid, and cinnamic acid. This indicates that the mushroom fruiting body is fit for human consumption and the final vermicompost is a useful agricultural product without the detrimental effects of spreading phenolics-loaded EFBs on the land.

  • Researchpp 4606-4626Myronycheva, O., Bandura, I., Bisko, N., Gryganskyi, A. P., and Karlsson, O. (2017). "Assessment of the growth and fruiting of 19 oyster mushroom strains for indoor cultivation on lignocellulosic wastes," BioRes. 12(3), 4606-4626.AbstractPDF
    Twelve Pleurotus ostreatus (Jacq. ex Fr.) P. Kumm and six Pleurotus pulmonarius (Fr.) Quél. strains were characterized from the National Culture Collection of Mushrooms, Institute of Botany Kholodny, National Academy of Science, Kyiv, Ukraine (IBK). The strains were grown under commercial conditions on a mixture of wheat straw and sunflower shells under both winter and summer temperatures typical for those climatic conditions. The strains were divided into three groups according to their growing patterns. Important characteristics were compared with a commercial analogue, HK-35, such as vegetative growth, generative growth, and biological efficiency (1.9- to 3.1-fold), and were recorded for strains 2251, 2292, 2316, 2319, and 2320 of P. ostreatus and 2314 of P. pulmonarius. Strains 2251, 2292, 2301, 2321 and 2323 were the most suitable for commercial production, while strains 2319 and 2320 could satisfy processing industry requirements with their high biological efficiency. Strains 2287 and 2317 produced high-quality fruit bodies but probably required a higher temperature for cultivation. Strain 2318 might be attractive for some consumers due to its unique and unusual fruit body shape. Strain 2314 was the most promising for summer cultivation, while strain 537 produced the highest quality fruit bodies.
  • Researchpp 4627-4638Wang, M., Zhang, Y., Yan, S., Yi, B., Niu, W., and Yuan, Q. (2017). "Enhanced biogas yield of Chinese herbal medicine extraction residue by hydrothermal pretreatment," BioRes. 12(3), 4627-4638.AbstractArticlePDF

    Chinese herbal medicine extraction residue (CHER) is a special organic waste produced in China. Because of the high content of lignocelluloses, CHER have a weak bioconversion efficiency for bio-products production. This study investigates the effect of a hydrothermal pretreatment (HTP, 140 to 220 °C, 15 min) on the organic matter solubilisation, biochemical methane potential, and methanation kinetics of CHER during anaerobic digestion (AD). The AD test was conducted with 5 g/L total solid at 35 °C for 30 d. The results showed that the HTP clearly improved the solubilisation of CHER, and the obtained soluble COD (%) reached over 30% (only 4.5% in untreated). Acetic acid, xylose, and glucose were found to be the main products in the hydrolysate. The methane yield and methanation speed of the treated CHER were also enhanced. The highest methane yield of 306 mL/g volatile solid was achieved at a HTP temperature of 180 °C, while the untreated control was only 175 mL/g VS. Moreover, a carbonisation phenomenon was observed at HTP temperatures over 200 °C, which resulted in a loss of organic matter and methane yield.

  • Researchpp 4639-4651Shao, L., You, T., Wang, C., Yang, G., Xu, F., and Lucia, L. A. (2017). "Catalytic stepwise pyrolysis of technical lignin," BioRes. 12(3), 4639-4651.AbstractArticlePDF

    The stepwise pyrolysis of technical lignin with and without a catalyst was investigated by pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS). Lignin was first pyrolyzed at 260 or 360 °C, and then the residue was subsequently pyrolyzed at 650 °C. It was found that stepwise pyrolysis of lignin concentrated the phenolic compounds in lignin-derived bio-oil. In a stepwise 260 to 650 °C process, the maximum total phenolic compounds were 86.2%. Among the phenolic compounds, guaiacol-type and phenol-type phenolic compounds were predominant. Further addition of a catalyst (HZSM-5) in the stepwise pyrolysis process enhanced control over the product distribution through conversion of phenolic compounds into aromatic hydrocarbon products. The aromatic hydrocarbons achieved the highest yield of 30.4% in the catalytic stepwise 260 to 650 °C process.

  • Researchpp 4652-4669Zhang, Y., Ma, Z., Zhang, Q., Wang, J., Ma, Q., Yang, Y., Luo, X., and Zhang, W. (2017). "Comparison of the physicochemical characteristics of bio-char pyrolyzed from moso bamboo and rice husk with different pyrolysis temperatures," BioRes. 12(3), 4652-4669.AbstractPDF
    Bio-char pyrolyzed from biomass waste has been notably applied in various industries due to its versatile physicochemical characteristics. This paper investigated the difference of the properties of the bio-char derived from moso bamboo and rice husk under different pyrolysis temperatures (200 °C to 800 °C). As the temperature increased, the bio-char yield for both bamboo bio-char (BC) and rice husk bio-char (RHC) decreased, while the carbon element content and fixed carbon, the value of higher heating value (HHV) and pH increased for both BC and RHC. At 800 °C, BC had a higher HHV of 32.78 MJ/kg than RHC of 19.22 MJ/kg, while RHC had a higher yield of char (42.99 wt.%) than BC (26.3 wt.%) because of the higher ash content (47.51 wt.%) in RHC. SiO2 was the dominant component in the ash of RHC, accounting for 86.26 wt.%. The surface area (SBET) of RHC (331.23 m2/g) was higher than BC (259.89 m2/g). However, the graphitization degree of BC was higher than RHC at the same temperature. The systematic study on the evolution of the basic properties of BC and RHC will provide a good reference for their high value-added application.
  • Researchpp 4670-4689Meekum, U., and Kingchang, P. (2017). "Compounding oil palm empty fruit bunch/cotton fiber hybrid reinforced poly(lactic acid) biocomposites aiming for high-temperature packaging applications," BioRes. 12(3), 4670-4689.AbstractPDF

    The manufacture of poly(lactic acid) (PLA) composites reinforced with both oil palm empty fruit bunch (EFB) and cotton fiber was investigated. The positive and significant effect of EFB on the heat distortion temperature (HDT) and flexural properties was determined by a 2k design of experiment study. Adding solid epoxy into the PLA matrix manifested inferior mechanical properties with no improvement to the HDT. The HDT and mechanical properties of the biocomposites were further improved by using an EFB/cotton hybridized system. The PLA/hybridized EFB/cotton biocomposites showed biodegradability and an HDT higher than 100 °C. However, the flowability of the material was retarded at high cotton fractions. Finally, adding talc filler into the biocomposites improved the flowability of the hybridized biocomposite systems, especially at low fiber and high talc contents. Nevertheless, inferior mechanical properties of the biocomposites were found for high talc and low fibers’ contents.

  • Researchpp 4690-4706Xie, L., He, G., Wang, X., Gustafsson, P. J., Crocetti, R., Chen, L., Li, L., and Xie, W. (2017). "Shear capacity of stud-groove connector in glulam-concrete composite structure," BioRes. 12(3), 4690-4706.AbstractArticlePDF

    A timber-concrete composite structure (TCC) is economically and environmentally friendly. One of the key design points of this kind of structure is to ensure the reliability of the shear connectors. The objective of this paper is to study the mechanical property of stud-groove-type connectors and to provide shear capacity equations for stud-groove connectors in timber-concrete composite structures. Based on the Johansen Yield Theory (European Yield Model), some mechanical models and capacity equations for stud-groove-type connectors in timber-concrete structures were studied. Push-out specimens with different parameters (stud diameter, stud length, groove width, and groove depth) were tested to obtain the shear capacity and slip modulus. The experimental strengths were used to validate equations given in the paper. The shear capacity and slip modulus of stud-groove-type connectors was in direct proportion to the diameter of studs and the dimension of the groove. Comparison between the theoretical and the experimental shear strength results showed reasonable agreement. The highlight of this study on shear capacity equations could significantly reduce the push-out tests before investigating the other properties of TCC.

  • Researchpp 4707-4721Shi, S., Zhou, X., Chen, W., Wang, X., Nguyen, T., and Chen, M. (2017). "Thermal and kinetic behaviors of fallen leaves and waste tires using thermogravimetric analysis," BioRes. 12(3), 4707-4721.AbstractArticlePDF
    Thermal decomposition characteristics and kinetic parameters of fallen leaves (FLs), waste tires (WTs), and their blends (1:1 weight ratio) were investigated. Pyrolysis experiments were conducted with four different heating rates of 5 °C/min, 10 °C/min, 20 °C/min, and 40 °C/min from 35 °C to 800 °C in a nitrogen atmosphere using a thermogravimetric analysis (TGA). The thermogravimetry/derivative thermogravimetry (TG/DTG) curves indicated that the three samples were mainly degraded in a wide temperature range of 350 °C to 450 °C, and that a greater weight loss rate corresponded to a higher heating rate. An elemental analysis demonstrated that FLs/WTs blends embraced a maximum calorific value that reached 25.24 MJ/kg. Two model-free methods, iso-conversional Kissinger-Akahira-Sunose (KAS) and Flynn-Wall-Ozawa (FWO) were applied on the TGA data of samples to calculate the activation energies. The results showed that the average activation energies of the same feedstock based on KAS and FWO methods were approximately the same, with the highest error within 1.6%. Then, the activation energies obtained were introduced in the Coats/Redfern (CR) model-fitting method to derive the pre-exponential factors, based on first order rate of reaction.
  • Researchpp 4722-4736Ma, Y., Wang, C., and Chu, F. (2017). "Effects of fiber surface treatments on the properties of wood fiber-phenolic foam composites," BioRes. 12(3), 4722-4736.AbstractArticlePDF

    Wood fibers were modified with alkaline solution and silane coupling agent to study changes on the fiber surface and the influence of these treatments on the mechanical properties, flame resistance, thermal conductivity, and microstructure of wood fiber-phenolic foam composites. Test results indicated that the lignin, waxes, hemicelluloses, and other impurities from the fiber surface were partially dissolved and removed. The mechanical properties of treated wood fiber-phenolic foam composites increased dramatically, the cellular pore distribution was more regular, the size of bubble cells was smaller and more uniform, and the thermal conductivity was reduced, and, in particular, the fragility of treated wood fiber-phenolic foam composites decreased. However, with increasing wood fiber content, the mechanical properties and limited oxygen index (LOI) of composite foam decreased. By comprehensive analysis, it was shown that the interfacial compatibility between the fibers and phenolic resin was improved. Nevertheless, the amount of wood used could not be too high, and the optimum amount was approximately 5%.

  • Researchpp 4737-4753Liu, H., Zhu, J. Q., Li, X., Li, H. Z., Qin, L., Li, H., Wang, X., Bai, X., Li, W. C., Li, B. Z., and Yuan, Y. J. (2017). "Hybridization improves inhibitor tolerance of xylose-fermenting Saccharomyces cerevisiae," BioRes. 12(3), 4737-4753.AbstractPDF

    Although some engineered S. cerevisiae strains exhibit good xylose utilization ability, the lack of tolerance to inhibitors generated in biomass pretreatment limits the application of such strains in the production of bioethanol from lignocellulosic biomass. By applying a sexual mating method, inhibitor tolerance was developed in xylose-utilizing strains. The final ethanol concentrations in simultaneous scarification and co-fermentation (SScF) process at 38 °C with hybrid strains were 50% higher than the SScF process with the xylose-fermenting parent strain. The strain viability of the hybrid strain E7-12 at 24 h was 282 times higher than the parent strain in the SScF process at 25% solid loading. Due to the improved sugar utilization, the final ethanol concentration reached 69.7 g/L (E7-11) and 70.0 g/L (E7-12), which were 25.3 g/L and 25.6 g/L higher than that of SScF with the xylose-fermenting strain, respectively.

  • Researchpp 4754-4775Young, T. M., Han, L. D., Perdue, J. H., Hargrove, S. R., Guess, F. M., Huang, X., Chen, C. H. (2017). "Impact of trucking network flow on preferred biorefinery locations in the southern United States," BioRes. 12(3), 4754-4775.AbstractPDF

    The impact of the trucking transportation network flow was modeled for the southern United States. The study addresses a gap in existing research by applying a Bayesian logistic regression and Geographic Information System (GIS) geospatial analysis to predict biorefinery site locations. A one-way trucking cost assuming a 128.8 km (80-mile) haul distance was estimated by the Biomass Site Assessment model. The “median family income,” “timberland annual growth-to-removal ratio,” and “transportation delays” were significant in determining mill location. Transportation delays that directly impacted the costs of trucking are presented. A logistic model with Bayesian inference was used to identify preferred site locations, and locations not preferential for a mill location. The model predicted that higher probability locations for smaller biomass mills (feedstock capacity, the size of sawmills) were in southern Alabama, southern Georgia, southeast Mississippi, southern Virginia, western Louisiana, western Arkansas, and eastern Texas. The higher probability locations for large capacity mills (feedstock capacity, the size for pulp and paper mills) were in southeastern Alabama, southern Georgia, central North Carolina, and the Mississippi Delta regions.

  • Researchpp 4776-4794Guo, H., Lin, C., Wang, S., Jiang, D., Zheng, B., Liu, Y., and Qin, W. (2017). "Characterization of a novel laccase-producing Bacillus sp. A4 and its application in Miscanthus degradation," BioRes. 12(3), 4776-4794.AbstractPDF
    Bacillus sp. A4 exhibiting laccase production was isolated from forest soil. Its laccase secreted into a LB medium exhibited a maximum activity of 3.9 U mg-1 protein at the optimal temperature (37 °C) and pH (6.0). The purified laccase of Bacillus sp. A4 demonstrated a low molecular mass of 33 kDa, and its optimal temperature and pH were 40 °C and 4.6, respectively, when using ABTS as a substrate. The activity of the purified laccase was significantly increased in the presence of Cu2+, methanol, and ethanol, but it was totally inhibited by L-cysteine. The laccase production of this strain was markedly stimulated when the strain was incubated with 0.5% different lignocellulosic biomasses. The highest activity of laccase (22.6 U mg-1 protein) was obtained in using algal biomass. This new strain efficiently decreased the lignin content of lignocellulose biomasses after 9 d of incubation at 37 °C, especially lignin from grasses. Further analysis showed that, compared to that of all tested biomasses, the new strain was a more efficient decomposer of the lignin of Miscanthus, which exhibited much more lignin loss and cell wall structure destruction in a short span of time. Therefore, the potential use of this strain could be advantageous for using lignin in Miscanthus for industrial processes.
  • Researchpp 4795-4809Pan, X., Zhuang, X. W., and Chen, S. W. (2017). "Rice husk char/poly-(acrylic acid-co-acrylamide) superabsorbent hydrogels: Preparation, characterization, and swelling behaviors," BioRes. 12(3), 4795-4809.AbstractArticlePDF

    A series of novel rice husk char/poly-(acrylic acid(AA)-co-acrylamide(AM)) superabsorbent hydrogels were synthesized by graft copolymerization. The effects of the rice husk char (RHC) loading on their miscibility, shapes, and chemical structures were studied, and their swelling behaviors, kinetics, and pH response were evaluated. During the preparation, RHC reacted with acrylic acid. The RHC at lower loads (< mass ratios of RHC and AA of 1%) was scattered well within the polymer matrix, but an excessive load might result in the formation of large agglomerates. The swelling capacity and swelling rate of the hydrogels first were both increased with the rising RHC loading to 1% and then declined with further RHC loading. The superabsorbent hydrogel containing 1% RHC had the highest water absorbency (869 g/g in deionized water and 97 g/g in 0.9% NaCl solution).

  • Researchpp 4810-4829Ye, H., Zhang, Y., and Yu, Z. (2017). "Effect of desulfonation of lignosulfonate on the properties of poly(lactic acid)/lignin composites," BioRes. 12(3), 4810-4829.AbstractArticlePDF

    To utilize the lignin generated by the paper industry and reduce the cost of poly(lactic acid) (PLA), PLA/lignin composites were prepared from PLA and different ratios of lignosulfonate (LS) or desulfonated lignosulfonate (DLS) particles using a casting method. The physicochemical properties of the lignins were characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), gel permeation-high performance liquid chromatography (GPC), and elementary analysis. The results indicate that the sulfur content of the original LS was successfully reduced to half by desulfonation to produce DLS, which was found to have a higher thermal stability and a lower average molecular weight than LS. Additionally, the thermal stability, crystallization, compatibility, mechanical, hydrophobicity, and optical properties of the PLA/lignin composites were also meticulously evaluated. Comparison of the PLA/DLS and PLA/LS composites revealed that the incorporation of DLS into PLA improved compatibility, thermal stability (T5% and Tmax), and hydrophobicity, while the mechanical properties remained almost unchanged. In addition, both PLA/DLS and PLA/LS exhibited UV light absorption capacity. Finally, the low-rate addition of both LS (10%) and DLS (5%) accelerated the crystallization of PLA, but crystallization was delayed with higher lignin content.

  • Researchpp 4830-4853Wang, Y., Chen, M., Yang, J., Liu, S., Yang, Z., Wang, J., and Liang, T. (2017). "Hydrogen production from steam reforming of acetic acid over Ni-Fe/Palygorskite modified with cerium," BioRes. 12(3), 4830-4853.AbstractArticlePDF

    The steam reforming of acetic acid (SRA) was carried out in a fixed-bed tubular reactor with Ni-Fe/ceria-palygorskite (CPG) catalysts. The as-prepared catalysts were analyzed by N2 adsorption-desorption, scanning electron microscopy coupled with energy dispersive spectroscopy (SEM-EDS), H2 temperature programmed reduction (H2-TPR), and X-ray diffraction (XRD). The results of H2-TPR and XRD showed that the addition of CeO2 increased the hydrogen consumption of catalysts and the interaction force between active component (Ni-Fe alloy) and carrier. Moreover, the Ni-Fe alloys were successfully synthesized in the Ni-Fe/CPG catalysts and their crystallite sizes were decreased by adding CeO2. In addition, these catalysts were employed to SRA at 600 °C, GHSV = 14427 h-1 and different molar ratio of S/C. The experimental results revealed that the Ni-Fe/C0.4PG0.6 catalyst can achieve the highest yield of H2 (87%) and HOAc conversion (95%), as well as the highest stability during the process of steam SRA. Additionally, the spent catalysts were characterized by XRD, SEM, and thermogravimetric analysis (TGA). The results showed that the addition of CeO2 enhanced the stability and activity of Ni-Fe/palygorskite catalyst and reduced the coke deposition rate on the catalyst surface.

  • Researchpp 4854-4866Hu, G., Fu, S., Chu, F., and Lin, M. (2017). "Relationship between paper whiteness and color reproduction in inkjet printing," BioRes. 12(3), 4854-4866.AbstractArticlePDF

    Paper is widely used as a substrate for inkjet printing, where the paper feature heavily impacts the print quality, especially the color reproduction. The unprinted area on paper is visible and applied as a background reflectance for the toner layer. Hence, it is worthwhile to understand the effects of paper whiteness on print color reproduction. In this study, the tested papers were treated with different dyes, which resulted in the change of the paper’s optical properties, but not surface roughness. The print density was impacted by the paper whiteness and ISO brightness. The effect of the paper whiteness on the print density is a stronger linear correlation compared to the ISO brightness. Paper whiteness has a positive correlation with the ISO brightness. The print colorimetric values (lightness and chroma values) increased with increasing paper whiteness up to a certain level, after which the paper whiteness did not have a noticeable impact on its print lightness and chroma values. The print color (a* and b* values) was affected by its corresponding paper color.

  • Researchpp 4867-4880Shao, S., Wu, C., and Chen, K. (2017). "Refining, dewatering,  and paper properties of soda-anthraquinone (Soda/AQ) pulp from rice straw," BioRes. 12(3), 4867-4880.AbstractArticlePDF

    The dynamic drainage, zeta potential, cationic demand, fiber morphology, ash content, and silica content of rice straw soda-anthraquinone (soda/AQ) pulps were measured to study the effects of a mechanical treatment on the drainage performance. The physical properties of handsheets prepared from each beaten sample were also analyzed. It was indicated that pulp fibers played an important role in increasing the beating degree in comparison with non-fibrous cells during refining. The dynamic drainage curve could be divided into three different stages in terms of the drainage rate, and the difference between the pulps screened-out non-fibrous cells (Pnof), and unremoved non-fibrous cells (Pf) decreased with refining. Due to the absence of a large quantity of non-fibrous cells, as the beating proceeded, the straw pulp presented an ever-increasing tendency in terms of kink index and curl index. Also, cationic demands of pulps increased linearly and the zeta potential of the fibers decreased gradually with beating. Rice straw was found to be favorable for papermaking, helping to compensate for an acute shortage of wood in China.

  • Researchpp 4881-4896Vančo, M., Jamberová, Z., Barcík, S., Gaff, M., Čekovská, H., and Kaplan, L. (2017). "The effect of selected technical, technological, and material factors on the size of juvenile poplar wood chips generated during face milling," BioRes. 12(3), 4881-4896.AbstractArticlePDF


    The effects of technical, technological, and material factors affecting the size of juvenile poplar wood chips were evaluated. Each analysis was performed on two species of poplar, namely natural poplar Populus tremula L. and plantation poplar clones Populus euramericana Serotina, and on juvenile and mature wood within each poplar species. A cutter with angular geometry was selected for the face milling: b = 55° (angle of cutting wedge), g = 15° (rake angle). The cutting conditions were a feed rate of vf = 2.5 and 15 m·min-1, cutting speed of vc = 30 m·s-1, 45 m·s-1, and 60 m·s-1, and the depth of cut ap = 1 mm. An image analysis of the size of the largest and smallest fraction was performed. Most of the chips generated during the face milling of poplar wood were classified as flat grain wood. A small percentage of the generated chips could be included in the group of rod-shaped fibrous bulk particles with a considerable extension in one direction (smaller fractions generated at a feed rate of 2.5 m·min-1, and at the finest fractions- dust generated in all of the combinations of technical and technological parameters).

  • Researchpp 4897-4911Li, J., Ma, Q., Shao, H., Zhou, X., Xia, H., and Xie, J. (2017). "Biosynthesis, characterization, and antibacterial activity of silver nanoparticles produced from rice straw biomass," BioRes. 12(3), 4897-4911.AbstractArticlePDF

    Silver nanoparticles (AgNPs) were synthesized from AgNO3 using rice straw biomass as the reducing agent at room temperature via light irradiation. Full wavelength scanning with UV/Vis spectrophotometer was used to study the effect of light intensity, reaction time, and concentrations of rice straw biomass and AgNO3 during AgNPs synthesis. Surface plasmon resonance (SPR) showed that the peak wavelength of synthesized silver nanoparticles arose at 425 nm, the optimal light intensity observed was 60,000 lx, and the optimal reaction time was 140 min. The optimum concentrations of the rice straw biomass and AgNO3 used were 4 mg/mL and 2 mM, respectively. The AgNPs were characterized by X-ray diffraction (XRD) analysis. The zeta potential of AgNPs reached -21.2 mV. In addition, the AgNPs synthesized by rice straw biomass revealed antimicrobial activity against Escherichia coli, Pseudomonas aeruginosa, Bacillus subtilis, and Staphyloccus aureus. The inhibition rate reached about 97.17 ± 2.01% when the concentration of AgNPs solution used was 8 μg/mL. In the detection of antimicrobial effect of AgNPs and antibiotics, the antibacterial activity was found to be superior to that of antibiotics alone.

  • Researchpp 4912-4925Cui, L., Chen, T., Quan, G., Xiao, B., Ma, Y., Pan, M., Liu, Y., Liu, B., Yin, C., Yan, J., Han, X., Ding, C., Cui, J., Bian, M., and Hussain, Q. (2017). "Renewable material-derived biochars for the efficient removal of 2,4-dichlorophen from aqueous solution: Adsorption/desorption mechanism," BioRes. 12(3), 4912-4925.AbstractArticlePDF

    This study investigated the efficiency of peanut hull (PBC), bush branch (BBC), Spartina alterniflora (SBC), and rape straw (RBC) in removing 2,4-dichlorophen (2,4-DCP) from an aqueous solution. The 2,4-DCP removal efficiency of the four kinds of biochars (BCs) increased in the order BBC > PBC > SBC > RBC. The adsorption process was affected by the pH, contact time, temperature, BC’s particle size, and dosage. Based on the results of Fourier transform infrared spectrometry (FTIR) and scanning electron microscope (SEM), the adsorption mechanism of 2,4-DCP was associated with the functional groups and the microtissue and structure of BCs. Furthermore, the organic components of the BCs played an essential role during the adsorption process of the 2,4-DCP. The remediation of organic pollutants by BCs is a complicated process that is characterized by the physical-chemical reaction between the two components (organic pollutants and BCs).

  • Researchpp 4926-4942Yuan, J., He, Y. Z., Guo, Z. W., Gao, H. F., Chen, F. B., Li, L. Z., Li, Y. Y., and Zhang, L. Y. (2017). "Utilization of sweet sorghum juice for efficient 2,3-butanediol production by Serratia marcescens H30," BioRes. 12(3), 4926-4942.AbstractArticlePDF

    Sweet sorghum juice (SSJ) is considered a good carbon source for biorefinery due to its low price and high fermentable-sugar content. In this study, 2,3-butanediol (2,3-BD) production from SSJ by Serratia marcescens H30 was investigated. First, the medium compositions including the contents of SSJ, nitrogen source, and mineral salts were optimized in conical flasks using a single factor and orthogonal design method. Under the optimal conditions, the 2,3-BD concentration reached up to 33.40 g/L. Then the optimized medium was used to perform fermentative experiments in a 5-L bioreactor. In batch experiments, the effects of various agitation speeds on 2,3-BD production were compared. Based on batch process results, an efficient two-stage fermentative control strategy was developed, where the agitation speed was maintained at 300 rpm in the first 12 h and subsequently switched to 200 rpm. About 43.32 g/L 2,3-BD was obtained by using this strategy. Finally, fed-batch fermentation was conducted through feeding the concentrated SSJ and a maximum 2,3-BD concentration of 109.44 g/L with the productivity of 1.40 g/L·h; a yield of 83.02% was achieved. The results showed that SSJ could be used as an economical substrate for efficient 2,3-BD production by S. marcescens H30.

  • Researchpp 4943-4957Palanti, S., Vignali, F., Elviri, L., Lucchetti, C., Mucchino, C., and Predieri, G. (2017). "Effect of amine functionalization and ageing on copper and boron leaching from wood preservatives grafted to siloxane networks," BioRes. 12(3), 4943-4957.AbstractArticlePDF
    The study evaluated copper, boron, and silicon release from wood samples treated with sol-gel formulations based on tetraethoxysilane (TEOS) and 3-aminopropyltriethoxysilane (APTES) functionalized with copper (II) chloride and boric acid, respectively. The adopted leaching procedure was Japanese protocol JIS K 1571 (2004). Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES) and Electron Spray Ionization Mass Spectrometry (ESI-MS) were employed for analyzing the leached solutions. The obtained results highlighted the important role of the amine function that was derived from the APTES precursor, in anchoring both copper and boron through coordinative and ionic interactions, respectively. In fact, copper formulations with TEOS alone (without APTES) showed higher copper leaching. In contrast, the silicon leaching was decreased due to better siloxane reticulation performed by TEOS alone. In addition, ageing (two months) of the samples treated with APTES containing formulation TEOS/APTES/Cu 10:1:0.2 resulted in a reduction of copper leaching (from 27% in the fresh samples to 7% in the aged ones), which was attributable to increased efficiency of inorganic sol-gel polymerization. The TEOS/APTES/B 1:1:0.2 formulation gave a leaching value of 20%, which was lower in comparison with the values reported in previous literature.
  • Researchpp 4958-4971Liu, Z., Wang L., Zhang, Y., Li, Y., Li, Z., and Cai, H. (2017). "Cellulose-lignin and xylan-lignin interactions on the formation of lignin-derived phenols in pyrolysis oil," BioRes. 12(3), 4958-4971.AbstractArticlePDF

    To gain a better understanding of the effect of the interactions between two biomass components (cellulose-lignin and xylan-lignin) on lignin-derived phenolic products, two analysis methods are introduced. With 3:1, 2:1, and 1:1 ratios of cellulose and lignin, and xylan and lignin, the mixtures were subjected to fast pyrolysis, which was carried out in a fixed-bed tubular furnace at 450 to 600 °C. The phenolic content in the bio-oils was analyzed by gas chromatography-mass spectrometry. The product distributions showed that cellulose, xylan, and lignin were the main contributors to the mass of biomass bio-oil, gas, and char, respectively. The char yields decreased and the bio-oil and gas yields increased in the presences of cellulose and xylan. Comparative analyses of both the phenol content and peak area of the two methods suggest that in the case of cellulose and lignin co-pyrolysis, the formation of three kinds of phenolic products is promoted. The strength of this positive effect increased with increasing lignin content. However, the production of hydroxyphenols is promoted, while the productions of guaiacols and syringols are inhibited by the effect of xylan, which creates a different interaction between xylan and lignin.

  • Researchpp 4972-4985Ziaei-tabari, H., Khademieslam, H., Bazyar, B., Nourbakhsh, A., and Hemmasi, A. H. (2017). "Preparation of cellulose nanofibers reinforced polyether-b-amide nanocomposite," BioRes. 12(3), 4972-4985.AbstractArticlePDF

    A new kind of thermoplastic elastomer nanocomposite reinforced with cellulose nanofibers has been reported. The aim of this investigation was to study the interaction and dispersion of cellulose nanofibers into the Pebax matrix. These copolymers are considered as polyether-b-amide thermoplastic elastomers. They are from renewable resources, and their hydrophilic character allows them to interact with nanocellulose. The interaction and reinforcement effect of nanocellulose at 3 levels of nanocellulose, (1%, 3%, and 5%), were examined by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), and other mechanical tests. The results achieved from these tests indicated appropriate effects of cellulose nanofibers for the strong interaction and close contact with the polyamide phase of the Pebax polymer via strong hydrogen bonding.

  • Researchpp 4986-5000Leng, W., Hunt, J. F., and Tajvidi, M. (2017). "Effects of density, cellulose nanofibrils addition ratio, pressing method, and particle size on the bending properties of wet-formed particleboard," BioRes. 12(3), 4986-5000.AbstractArticlePDF
    Wet-formed particleboard bonded with cellulose nanofibrils (CNF) was prepared in this work. The effects of density, CNF addition ratio, pressing method, and particle size on the bending strength were evaluated. The results showed that density had the most important effect on the modulus of elasticity (MOE), while the CNF addition ratio had the most important effect on the modulus of rupture (MOR). For panels with low density (< 640 kg/m3), the MOE and MOR did not change much with the configuration changes between particle size and pressing method. This was due to the synergistic effect of incomplete compression and poor bonding in the core area using a constant thickness (CT) pressing method, and lower face density and higher core density using a constant pressure (CP) pressing method. For panels with medium density (640 kg/m3 to 800 kg/m3), the combination of larger particles, higher CNF addition ratio, and CT pressing method contributed to the highest bending strength. Further increase to high density (> 800 kg/m3), the pressing method’s effect was more important, compared to panels with low and medium densities. With increased density and CNF addition ratio, panels were able to meet low-density and some medium-density standard MOE and MOR requirements.
  • Researchpp 5001-5016Guo, D., Liu, B., Tang, Y., Zhang, J., Xia, X., and Tong, S. (2017). "Catalytic depolymerization of alkali lignin in sub- and super-critical ethanol," BioRes. 12(3), 5001-5016.AbstractArticlePDF
    The effects of reaction parameters on catalytic depolymerization of alkali lignin in sub- and super-critical ethanol were investigated using a high pressure autoclave, and the liquid oil and solid char products were characterized. The experimental data indicated that Rh catalysis, controlling reaction conditions at ethanol critical temperature (240 ºC) and pressure (7.0 MPa), high ethanol/water ratios (100/0), and the medium reaction time (4 h) enhanced the depolymerization of alkali lignin to liquid oil and decreased the char formation. A gas chromatography/mass spectroscopy (GC/MS) analysis showed that the main compositions of liquid oils were phenols, esters, ketones, and acid compounds, and the supercritical state favored the formation of bio-phenols, but the subcritical state improved the generation of bio-esters. Scanning electron microscopy (SEM) and Fourier transform infrared spectrometer (FTIR) spectra analysis showed that the addition of the Raney/Ni and Rh/C catalysis could inhibit the re-fusion of alkali lignin micron-sized spheres in the supercritical ethanol, which led to an increase in the occurrence of the depolymerization reactions.
  • Researchpp 5017-5030Geffert, A., Vacek, O., Jankech, A., Geffertová, J., and Milichovský, M. (2017). "Swelling of cellulosic porous materials - mathematical description and verification," BioRes. 12(3), 5017-5030.AbstractArticlePDF

    The swelling of natural porous materials, including bleached pulp, as represented by mathematical descriptions, is influenced by a variety of different operating factors. The formerly used Generalised Hygroscopicity Model leads to either a disproportion between a model and a limit value of the sorption capacity or to noticeable deviation in the early swelling phase. Alternatively, the so-called Simple Bounded Growth model solely depends on the maximum sorption capacity, ignoring the physical properties that affect the fibre swelling rate. This research shows that the combination of the two models best describes the swelling process of bleached pulp – a rapid swelling phase and a slower swelling phase. The combined model was found to be useful in characterizing the well-known hornification process.

  • Researchpp 5031-5044Park, C. W., Han, S. Y., Namgung, H. W., Seo, P. N., Lee. S. Y., and Lee, S. H. (2017). "Preparation and characterization of cellulose nanofibrils with varying chemical compositions," BioRes. 12(3), 5031-5044.AbstractArticlePDF
    Cellulose nanofibrils (CNF) can be divided into lignocellulose nanofibrils (LCNF), holocellulose nanofibrils (HCNF), and pure cellulose nanofibrils (PCNF), dependent upon their chemical composition. The effect of the chemical composition on the defibrillation efficiency and the properties of the CNFs prepared by wet disk-milling was investigated using six different wood species. The defibrillation efficiency was improved when the lignin and hemicellulose was removed, and smaller fibers with diameters in the order of PCNF > HCNF > LCNF were produced. The average diameter of the hardwood LCNF was finer than that of the softwood LCNFs, but there was no noticeable difference in the diameters of the HCNF and the PCNF from the different wood species. The filtration time of CNF suspensions and the tensile properties of nanopaper sheets were longer and higher, respectively, in the order of HCNF > PCNF > LCNF from different wood species.
  • Researchpp 5045-5056Liu, X., Jiang, Y., Xie, Q., Nie, S., and Song, X. (2017). "Effect of alkali pectinase pretreatment on bagasse soda-anthraquinone pulp," BioRes. 12(3), 5045-5056.AbstractArticlePDF
    Pectinase pretreatment prior to bagasse soda-anthraquinone (AQ) pulping was conducted, and the effects of pectinase pretreatment on the pulp strength properties, energy consumption, and pulpability were evaluated in this study. Considering the pulp properties, the optimal conditions for the pectinase pretreatment were a pectinase dosage of 60 U/g (with respect to oven-dry bagasse) and 60-min treatment time. Compared with the control pulps obtained under the same treatment conditions with enzyme pretreatment (just without enzyme addition), the pretreated pulps attained a reduction in kappa number of 17.8% and an increase in total pulp yield of 15.8%. Moreover, higher breaking length, burst factor, and tear factor after soda-AQ pulping were found in the pectinase-pretreated samples, which suggests some improvements in pulp strength properties. With pectinase treatment, a 1% reduction in alkali charge and 20% decrease in pulping time were observed in subsequent pulping stages without affecting the pulp properties. Pectinase treatment prior to pulping seems to be a promising, economically feasible, and eco-friendly concept.
  • Researchpp 5057-5070Weng, J., Qiu, R., and Chen, L. (2017). "Composite paper sheet containing TiO2-diatomite for removing phenol in aqueous solution," BioRes. 12(3), 5057-5070.AbstractArticlePDF
    Composite paper sheet containing titanium dioxide and diatomite (TiDI) was prepared via a papermaking technique. The composite sheet was applied to remove phenol from aqueous solution. The composite sheet with a 2:1 mass ratio of cellulosic-fiber to TiDI removed phenol more effectively under UV irradiation than the composite paper sheet that utilized titanium dioxide (TiO2) alone. Composite paper sheets that contained TiDI with a TiO2/diatomite mass ratio of 1:2 removed phenol most effectively. The results showed that the TiDI composite paper could serve as a functional material to photodegrade phenol from aqueous solution under UV irradiation effectively.
  • Researchpp 5071-5085Jin, X. B., Jiang, Z. H., Wen, X. W., Zhang, R., and Qin, D. C. (2017). "Flame retardant properties of laminated bamboo lumber treated with monoammonium phosphate (MAP) and boric acid/borax (SBX) compounds," BioRes. 12(3), 5071-5085.AbstractPDF

    This study aimed to improve the flame-retardant properties of laminated bamboo lumber (LBL) using phosphorus-nitrogen-boron flame retardants (FRs). The combination of a 7:3 ratio of monoammonium phosphate (MAP) and boric acid/borax compounds (SBX), and 74.32 kg/m3 of FRs (10.3% weight gain), exhibited enhanced fireproofing performance for LBL materials. A commercial flame retardant (guanylurea phosphate) (GUP) was systematically studied as a comparison. A cone calorimeter and a thermal analyzer were used to characterize the combustion behavior and thermal stability, respectively. The flame retardants morphology in bamboo cell cavities was investigated using scanning electron microscopy (SEM) and an energy dispersive X-ray analysis (EDXA). The results showed that at a heat flux of 50 kW/m2, the heat release rate and the total heat release of LBL samples treated with MAP-SBX flame retardants decreased more considerably than that of the untreated samples. The use of MAP-SBX not only promoted carbonization of LBL greatly but also indicated a good performance of smoke and combustion suppression as well as for the GUP. Flame retardants were confirmed to penetrate into the cell cavities of the bamboo using SEM and EDXA.

  • Researchpp 5086-5101Meekum, U., and Kingchang, P. (2017). "Peroxide/silane crosslinked poly(lactic acid) hybrid biocomposite reinforced with empty fruit bunch and cotton fibers for hot-fill food packaging," BioRes. 12(3), 5086-5101.AbstractArticlePDF

    A biocomposite manufactured from peroxide/silane crosslinked poly(lactic acid) reinforced with hybridized empty fruit bunch (EFB) oil palm and cotton fibers was investigated. Optimization of dicumyl peroxide (DCP) and the vinyltrimethoxysilane (VTMS) crosslink system by using the 2k factorial design of experiment (DOE), with k = 2 was preliminary employed. There was no significant effect of the designed parameters, DCP(A) and VTMS(B), on the properties of the biocomposite. Concerning the environmental and economical aspects, the DPC and VTMS ratio was important. A crosslink agent content from 0.5 phr of DCP with 1 phr to 2 phr VTMS was recommended to manufacture a biocomposite with high heat distortion temperature (HDT) at above 100 °C and reasonable flow and mechanical properties. Also, the direct addition of the DCP/VTMS crosslink agent onto the PLA/rubber compound mixture and fed into a twin screw extruder for producing crosslinked PLA/EFB/cotton hybrid biocomposites were the optimized mixing methods. Shorter process line/time, ease of process steps, and reasonable engineering properties were justified. A HDT above 100 °C with a better toughness property of the biocomposite material was obtained. The PLA/PLA and PLA/ENR crosslinks via silane/moisture condensation during the sauna incubation was the prime explanation.

  • Researchpp 5102-5117Zhou, C., Dong, A., Wang, Q., Yu, Y., Fan, X., Cao, Y., and Li, T. (2017). "Effect of common metal ions and anions on laccase catalysis of guaiacol and lignocellulosic fiber," BioRes. 12(3), 5102-5117.AbstractArticlePDF

    The effects of 12 common metal ionic compounds on the laccase catalytic activity in reactions using guaiacol as the substrate was determined using spectrophotometry. Furthermore, the influence of several metal ionic compounds on the generation of reactive oxygen species (ROS) by oxidation of lignin in jute fiber under laccase catalysis was studied by electron paramagnetic resonance (EPR) spectroscopy using N-tert-butyl-alpha-phenylnitrone (PBN) as the spin-trapping agent. Common metal cations, such as K+, Na+, Mg2+, Ca2+, and Cu2+ and the anion SO42- had almost no effect on laccase activity during the initial stage of the catalytic reactions. High concentrations of the Mn2+ ion exhibited weak inhibition of laccase; Ag+ and NO3- showed a moderate inhibitory effect on laccase activity during the initial stage of the catalytic reactions. Fe2+ had no direct effect on the binding of laccase to its substrate, but strongly retarded the progress of the catalytic reaction by reducing the intermediate free radicals. The ions Cl-, Fe3+, and Ag+ exhibited either strong inhibitory effects on the catalysis of the substrate or a destructive effect on the structure of laccase itself. Furthermore, the results showed that an appropriate concentration of Cu2+ helped to promote the thermal stability of laccase during the enzymatic reaction. This study could help researchers to avoid the use of inhibitory exogenous metal ions and anions in the application of laccase and to maximize the value of laccase.

  • Researchpp 5118-5127Matthews, S., Toghyani, A. E., Eskelinen, H., Luostarinen, L., Kärki, T., and Varis, J. (2017). "Method for limiting waste in wood plastic composite post-production by means of press unit control parameters utilizing temperature-related dimensional changes," BioRes. 12(3), 5118-5127.AbstractArticlePDF

    Wood plastic composites are an interesting development in composite materials. They have gained wide market interest recently because of their sustainable material sources and beneficial material properties. Because thermosets or thermoplastics are involved in the composites, the material is temperature-dependent and susceptible to considerable dimensional changes with the variation of temperature. To minimize waste generation and enable reheated material post-processing, the distortion and displacement of the composite material has to be controlled precisely in different temperature ranges. This article studies ways to control this displacement and proposes a solution with an odometer and polynomial curve fit.

  • Researchpp 5128-5139Xu, M., Zhang, Q., Xing, L., and Pu, J. (2017). "Novel medium-density fibreboard produced by ultrasonic-assisted pulp with superhydrophobic and flame-resistant properties," BioRes. 12(3), 5128-5139.AbstractArticlePDF

    A novel medium-density fibreboard produced by an ultrasonic-assisted wheat straw pulp (UWP) was obtained without adhesives. It was then coated with a superhydrophobic sol solution integrated with an in vitro addition of two fire retardants (polyhedral methyl-silsesquioxane and ammonium polyphosphate) during the process of sol-gel reaction involving the two silane precursors tetraethyl orthosilicate (TEOS) and tridecafluorooctyltriethoxysilane (FAS). The coated UWP medium-density fibreboard (UPB) had good strength properties and possessed excellent hydrophobicity (water contact angle (WCA) above 150°), and flame-resistant properties (limiting oxygen index (LOI) improved by 5% compared with the original sample with a LOI of 18%). Meanwhile, the fibreboard also exhibited outstanding anti-permeability towards water (kept constant WCA for more than 1 h).

  • Researchpp 5140-5154Vančo, M., Mazán, A., Barcík, S., Rajko, L., Koleda, P., Vyhnáliková, Z., and Safin, R. R. (2017). "Impact of selected technological, technical, and material factors on the quality of machined surface at face milling of thermally modified pine wood," BioRes. 12(3), 5140-5154.AbstractArticlePDF

    The impact of technical and technological parameters on the quality of machining during milling of thermally modified pine wood (Pinus sylvestris L.) was studied. Experiments were conducted to evaluate the effects of tools (α = 30°, β = 45°, γ = 15°, 20°, and 30°), material (natural material, thermally treated at 160 °C, 180 °C, 210 °C, and 240 °C), and technological factors, such as cutting speed (20 m.min-1, 40 m.min-1, and 60 m.min-1) and feed rate (6 m.min-1, 10 m.min-1, and 15 m·min-1) on the quality of the machined surface (standard deviation of surface Ra). The roughness measurements were realized by a non-contact method using a laser. This paper aimed to highlight which one of the technological or tool factors had the greatest impact on the quality of the surface of heat-treated wood in face milling. The importance of the parameters impact on surface quality was in the following order: rake angle, feed rate, thermal treatment, and cutting speed.

  • Researchpp 5155-5173Malá, D., Sedliačiková, M., Kaščáková, A., Benčiková, D., Vavrová, K., and Bikár, M. (2017). "Green logistics in Slovak small and medium wood-processing enterprises," BioRes. 12(3), 5155-5173.AbstractArticlePDF

    Current approaches in logistics are focused on sustainable development of enterprises and society. Small and medium enterprises (SMEs), in this case wood-processing enterprises, can achieve this goal by implementing green logistics strategies in business practice. The main objective of this paper is to propose an algorithm for the implementation of green logistics activities in wood-processing SMEs, through a survey aimed at analyzing the accelerators and barriers to implementation in business practice. The research has been evaluated via methods of testing the statistical hypothesis (binomial test, Chi-squared, Friedman test, Wilcoxon test), methods of descriptive statistics, and data visualization. The survey found that one of the most significant determinants for implementing green logistics activities in a wood-processing enterprise is a decrease in cost. Based on the performed analysis, a model for the implementation of green logistics activities for wood-processing SMEs was proposed that includes appropriate activities that ensure the sustainable development of wood-processing SMEs in Slovakia.

  • Researchpp 5174-5195Cai, Q., Xu, J., Zhang, S., and Wang, S. (2017). "Aromatic hydrocarbon generation from a simulated bio-oil fraction by dual-stage hydrogenation-cracking: Hydrogen supply and transfer behaviors," BioRes. 12(3), 5174-5195.AbstractArticlePDF

    The improvement of the hydrogen-poor composition of bio-oil is important for its cracking to produce aromatic hydrocarbons. In this work, a mild hydrogenation pre-treatment and methanol cocracking were combined to implement proper hydrogen supplementation for cracking. Acetic acid (HAc), hydroxypropanone (HPO), and cyclopentanone (CPO) were selected as model compounds and mixed to prepare a simulated distilled fraction (SDF) of bio-oil. The hydrogen supply and transfer behaviours in hydrogenation-cracking were investigated. For the conversion of individual components: HAc was difficult to be hydrogenated, and therefore in the cracking stage, the conversion and oil phase yield were low; ketones were successfully hydrogenated to alcohols, and thus high aromatic hydrocarbon yields were achieved. Hydrogenation-cracking of SDF showed that the inferior performance of HAc was improved by an internal hydrogen transfer, namely the alcohols produced from ketones supplied hydrogen for HAc conversion. However, because of the high HAc content in SDF, this hydrogen supplement was not sufficient. Therefore, methanol (MeOH) was used as the coreactant for secondary hydrogen supply. The integral efficient conversion of SDF and MeOH to aromatic hydrocarbons was achieved when the MeOH blending ratio was 30%. Finally, a reaction mechanism of hydrogenation-cocracking was proposed.

  • Researchpp 5196-5211Yasin, S., Curti, M., Rovero, G., Behary, N., Perwuelz, A., Giraud, S., Migliavacca, G., Chen, G., and Guan, J. (2017). "An alternative for the end-of-life phase of flame retardant textile products: Degradation of flame retardant and preliminary settings of energy valorization by gasification," BioRes. 12(3), 5196-5211.AbstractPDF

    It is well established that current flame retardant (FR) products at disposal generate various ecological hazards. Irrespective of their environmental impacts, the FR market is growing and is estimated to reach 2.8 million tons globally in 2018. In the textile domain, FRs are incorporated into baby clothing, pushchairs, car seats, etc. When disposed, these FR textile products end up in a landfill or are incinerated. These disposal processes are unsustainable. With landfilling, there is a huge chance of the FR product leaching into the environment. Similarly, FRs decrease energetic yields in the incineration process due to incomplete combustion. To cope with such issues, degradation and elimination of the FR product from the textile products before disposal could be a sustainable alternative. This study dealt with the preliminary degradation of flame retardant from the cotton textiles and its thermal characterization. Energy valorization by gasification is considered beneficial opposed to incineration with overall low energy recovery. The initial optimum gasification conditions including FR-treated cotton as a feeding material and potential outcomes of FR-treated cotton after degradation were characterized.

  • Researchpp 5212-5222Saeed, H. A. M., Liu, Y., Lucian, L. A., and Chen, H. (2017). "Evaluation of Sudanese sorghum and bagasse as a pulp and paper feedstock," BioRes. 12(3), 5212-5222.AbstractPDF
    The suitability of specific Sudanese agrowastes, sorghum straw, bagasse, and their 50% blend, were investigated for pulp and papermaking initiatives. A chemical analysis of sorghum straw and bagasse revealed levels of cellulose, lignin, hemicellulose, and ash for sorghum straw and bagasse that signalled a suitable relation to traditional wood feedstocks for pulping and papermaking applications. Moreover, the pulp yield and viscosity of sorghum straw were lower and higher, respectively, compared with the bagasse and the blend. More specifically, the papers obtained from bagasse showed better physical properties (tensile strength, tearing index, bursting index, and folding) compared to those of sorghum straw and the blend. The surface morphologies of the papers were analysed using scanning electron microscopy (SEM), which showed that the fibres had a long, swollen, compact, and closely packed arrangement and were more homogeneous and well-blended for the bagasse compared with the pure sorghum straw and the 50% blend.
  • Researchpp 5223-5235Santanaraj, J., Sajab, M. S., Mohammad, A. W., Harun, S., Chia, C. H., Zakaria, S., and Kaco, H. (2017). "Enhanced delignification of oil palm empty fruit bunch fibers with in situ Fenton-oxidation," BioRes. 12(3), 5223-5235.AbstractPDF
    The degradation of lignin in oil palm empty fruit bunch (EFB) fibers by a low concentration of H2O2 was observed with the assistance of Fenton oxidation with Fe(III), Fe(0), and Fe3O4 as a catalyst. To escalate the oxidation activity toward lignin in the EFB fibers, the uptake of the Fenton reagent on the EFB fibers for in situ Fenton oxidation was optimized with fitted Langmuir and Freundlich adsorption models. The efficiency of assisted Fenton reagents was monitored through controlled parameters of H2O2 concentration, retention time, and increment of Fenton reagents. The delignification was observed with up to 71.2% of lignin degradation compared to 47.2% without the use of the Fenton reagents. The characteristics of EFB fibers after the oxidation process were changed based on the observation of morphological and chemical properties. The oxidation concurrently dislodged part of the silica bodies and disrupted specific functional groups and the crystallinity of the EFB fibers.
  • Researchpp 5236-5248Yun, N., and He, B. (2017). "Photo-induced yellowing of Mg(OH)2-based peroxide bleached deinked pulp," BioRes. 12(3), 5236-5248.AbstractArticlePDF

    The effects of ultraviolet (UV) irradiation on the changes in color and chemical structure of the surfaces of unbleached, PNaOH-, and PMg(OH)2- bleached deinked pulp (DIP) were studied by attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy. The analysis of color changes in pulp surfaces during the photo yellowing was performed by measuring the brightness loss, post color (PC) number, and CIELAB parameters (L*, a*, b*, and ΔE*). The results showed that the pulp brightness loss, PC number, and chromatic aberration had a linear relationship with b*. During the UV irradiation, the pulp brightness loss, PC number, and chromatic aberration (ΔE*) increased quickly, and then the changes slowed down. After being irradiated with UV for 360 min, the band intensity of the pulps at 1729 cm-1 increased distinctively and a new band at 1674 cm-1 appeared. This indicated that p-quinone groups were produced during the irradiation process, thus resulting in paper yellowing. The band intensity at 1674 cm-1 of PMg(OH)2-bleached pulp was lower than that of PNaOH-bleached pulp, which indicated that the brightness stability of PMg(OH)2 pulp was better than that of PNaOH pulp.

  • Researchpp 5249-5263Zhou, W., Gong, Z., Zhang, L., Liu, Y., Yan, J., and Zhao, M. (2017). "Feasibility of lipid production from waste paper by the oleaginous yeast Cryptococcus curvatus," BioRes. 12(3), 5249-5263.AbstractArticlePDF

    Waste paper was studied as a potential source for lipid production using the oleaginous yeast Cryptococcus curvatus for the first time. Three common types of waste paper, office paper, newspaper, and cardboard, were directly hydrolyzed by an enzyme cocktail to generate sugar-rich and nitrogen-limited hydrolysates. When these hydrolysates were used without any auxiliary nutrients by C. curvatus, the lipid content and lipid yield were higher than 50% and 200 mg/g, respectively. The nitrogen-rich enzyme cocktail exerted no negative effects on lipid production. Moreover, the integrated processes of enzymatic hydrolysis and lipid fermentation achieved comparable lipid yield to the separate hydrolysis and lipid production process. The resulting lipid samples had similar fatty acid compositional profiles to those of vegetable oils, which suggested their potential for biodiesel production. These findings strongly supported waste paper as appealing substrates for lipid production via oleaginous yeast, which provided cost-effective waste paper-to-lipids routes for sustainable biodiesel production.

  • Researchpp 5264-5278Nathan, V. K., Esther Rani, M., Rathinasamy, G., and Narayanan Dhiraviam, K. (2017). "Low molecular weight xylanase from Trichoderma viride VKF3 for bio-bleaching of newspaper pulp," BioRes. 12(3), 5264-5278.AbstractArticlePDF
    Xylanase is a major enzyme used in the paper and pulp industries for bio-bleaching applications. There are possibilities for xylanase with better properties suitable for industrial applications. This paper focused on a potential xylanolytic fungus, Trichoderma viride VKF-3, obtained from a mangrove soil sample. Optimum conditions for xylanase production were tested by culturing T. viride VKF3 under varying carbon and nitrogen sources, medium pH, and incubation temperature. The isolate T. viride VKF3 achieved a maximum of 3.045 IU/mL of xylanase activity by utilizing coconut oil cake as a substrate. During purification, 84% yield was obtained with 40% ammonium sulphate. The enzyme activity was confirmed through zymogram analysis, and a band was observed at 14 kDa. The xylanase facilitated maximum hexenuronic acid release with a 30% enzyme dosage following 4 h of incubation. Moreover, the Kappa number tended to decrease with increased enzyme dosage and incubation time. There was a Δ brightness of 11% following 4 h of enzymatic treatment. Strength properties, such as the tensile, burst indices, and folding endurance, was improved during the xylanase assisted deinking of pulp. Hence, the present xylanase was found to be suitable for the bio-bleaching of newspaper waste via an eco-friendly process.
  • Researchpp 5279-5295Dogu, D., Tuncer, F. D., Bakir, D., and Candan, Z. (2017). "Characterizing microscopic changes of paulownia wood under thermal compression," BioRes. 12(3), 5279-5295.AbstractPDF

    This study evaluates the microscopic changes of paulownia solid wood panels subjected to thermal compression via characterizing the changes in wood microstructure. The panels, with dimensions of 500 mm × 100 mm × 20 mm, were hot-pressed in a tangential direction by using a laboratory-type hot press at a temperature of either 150 °C or 170 °C and a pressure of 2 MPa for 45 min. Microscopic investigations conducted by light microscopy showed that slightly more damage occurred in the samples compressed at 170 °C and 2 MPa than at 150 °C and 2 MPa, and that the distribution of deformation in the panels was not uniform in the growth rings of the two treatment groups. The cell collapse was not observed in the microstructure of paulownia wood after the thermal compression. Cell shapes and their arrangement in the growth ring alongside loading direction were interpreted as effective factors governing the non-uniform distribution of damage and the lack of cell collapse in the microstructure.

  • Researchpp 5296-5307Yu, L., Cai, J., Li, H., Lu, F., Qin, D., and Fei, B. (2017). "Effects of boric acid and/or borax treatments on the fire resistance of bamboo filament," BioRes. 12(3), 5296-5307.AbstractPDF

    Bamboo filament, a material often used for indoor decoration, should be treated with flame retardants for safe use. This study evaluated the effects of different boron fire retardants on the heat release and smoke release of bamboo filaments and untreated samples via a cone analysis. A thermogravimetric analyzer (TA) instrument was used to investigate the fire retardant mechanisms of the different boron compounds. The results showed that compared to the untreated samples, fire retardants that contained boric acid or borax effectively reduced the heat and smoke release from the bamboo filament. The effects of the different ingredients in the fire retardant on the combustion process were quite different. During the combustion process, borax displayed better performance for restraining the heat release rate than boric acid, while for the total amount of heat release and the smoke suspension performance, the result was the converse. The excellent synergistic effect could be obtained by a mixture that contained a reasonable proportion of boric acid and borax (Boric Acid:Borax = 1:1). In the pyrolysis process, boric acid had stronger catalytic dehydration, while the mass loss in the treated samples with boric acid or higher proportions of boric acid was less than the loss in the borax-treated samples.

  • Researchpp 5308-5320Duan, D., Zhao, Y., Fan, L., Dai, L., Lv, J., Ruan, R., Wang, Y., and Liu, Y. (2017). "Low-power microwave radiation-assisted depolymerization of ethanol organosolv lignin in ethanol/formic acid mixtures," BioRes. 12(3), 5308-5320.AbstractPDF

    Ethanol organosolv lignin separated from bamboo was depolymerized by low-power microwave radiation (~80 W) using ethanol as a swelling agent and formic acid as a hydrogen donor solvent. After increasing the temperature from 100 to 200 °C, the total amount of phenolic compounds in the products increased from 8.1% to 40.8%, and both the weight average molecular weight (Mw) and number average molecular weight (Mn) of the products from the lignin depolymerization decreased. With extended reaction time from 20 to 60 min, the total amount of phenolic compounds and molecular weight did not remarkably change. In addition, Fourier transform infrared (FT-IR) spectroscopy showed that oxidative fracture was the primary way that lignin depolymerized. The severity factor played an important role in converting lignin into small molecular substances, and the evaluation showed that the microwave temperature was more influential on the lignin depolymerization than the reaction time. Because depolymerization and repolymerization of fragments both occurred during the microwave radiation process, it is critical to inhibit repolymerization of degraded fragments for the efficient degradation of lignin. This study not only provides a theoretical basis for studying the mechanism of microwave-assisted lignin degradation but is also important for the determination of a cost-effective lignin depolymerization method.

  • Researchpp 5321-5342Aliberti, A., Ventorino, V., Robertiello, A., Galasso, M., Blaiotta, G., Comite, E., Faraco, V., and Pepe, O. (2017). "Effect of cellulase, substrate concentrations, and configuration processes on cellulosic ethanol production from pretreated Arundo donax," BioRes. 12(3), 5321-5342.AbstractPDF

    Arundo donax was used to investigate the effect of the enzyme and substrate concentrations on hydrolysis, pre-hydrolysis and simultaneous saccharification and fermentation (PSSF), in comparison to simultaneous saccharification and fermentation (SSF). Hydrolysis was performed at 37 and 50 °C. At the highest biomass (10%) and enzyme (69.6 FPU/g cellulose) loadings, the highest glucose concentration (32.4 g/L) was obtained (at 50 °C). SSF resulted in a cellulose conversion (91.9%) and an ethanol concentration (19.8 g/L) higher than what was obtained using PSSF at 37 °C (86.9% and 18.8 g/L, respectively) and PSSF at 50 °C (81.6% and 17.7 g/L, respectively). A positive correlation between the cellulase concentration, cellulose conversion, and ethanol content was observed. In PSSF, the increase in the solids loadings caused a reduction in the % cellulose conversion, but the ethanol concentration in PSSF and SSF increased. SSF appeared to be the most advantageous process for bioethanol production from A. donax.

  • Researchpp 5343-5357Zhang, X., Jin, C., Jiang, Y., Liu, G., Wu, G., and Kong, Z. (2017). "A novel gallic acid-grafted-lignin biosorbent for the selected removal of lead ions from aqueous solutions," BioRes. 12(3), 5343-5357.AbstractPDF

    The low content of phenolic groups limits the application of lignin-based materials as biosorbents for the removal of metal ions. In this work, a novel gallic acid-grafted-lignin (GAL, 4.43 mmol/g hydroxyl group) biosorbent was designed by introducing gallic acid moieties to replace the hydroxyl groups of lignin. These grafted polyphenolic groups provide additional sites for the adsorption of metal ions. The structure of GAL was characterized by FT-IR, 31P NMR, and 13C NMR spectroscopy. The adsorption properties of GAL for Pb(II) ions were investigated under batch conditions. Kinetic and isothermal adsorption processes could be well-described by the pseudo-second order kinetic model and Langmuir isothermal model, respectively. The grafting of polyphenolic groups onto lignin increased the maximum adsorption capacity of the adsorbent for Pb(II) (119.1 mg/g). The adsorption thermodynamics indicated that the adsorption process was endothermic and spontaneous. In addition, GAL could selectively adsorb Pb(II) with a selectivity coefficient (k) at 1.89 in the presence of coexisting metal ions from aqueous solution. The high adsorption capacity and selectivity for Pb(II) by GAL, together with its environmental compatibility, enable this material to act as a promising biosorbent for removing heavy metal ions from polluted water.

  • Researchpp 5358-5368Genc, G., and Koruk, H. (2017). "Identification of the dynamic characteristics of luffa fiber reinforced bio-composite plates," BioRes. 12(3), 5358-5368.AbstractPDF

    Luffa cylindrica plant fiber is a new biodegradable engineering material. However, the dynamic behaviors of these new green materials or their composites should be explored to consider them for practical applications. The dynamic characteristics including modal behavior and the elastic and sound isolation properties of luffa-based bio-composite plates were explored in this study. Structural frequency response function measurements were conducted using a few luffa bio-composite plates to identify their modal behavior. The modal frequencies and loss factors of the luffa bio-composite plates were identified by analyzing the frequency response function measurements using a few modal analysis methods such as half-power, circle-fit, and line-fit. The same luffa bio-composite structures were modelled using a finite element formulation with damping capability, and the elastic moduli of the composite plates were identified. In addition, the transmission loss levels of the same luffa composite samples were measured using the impedance tube method. The results showed that luffa composite structures have considerably high stiffness (elasticity modulus: 2.5 GPa), damping levels (loss factor: 2.6%), and transmission loss level (25 to 30 dB for a 1 cm thickness), and their mechanical properties are promising as an alternative disposable material for noise and vibration control engineering applications.

  • Researchpp 5369-5382Wu, J., Wang, M., and Guo, H. (2017). “Synergistic flame retardant effects of different zeolites on intumescent fire retardant coating for wood,” BioRes. 12(3), 5369-5382.AbstractPDF

    To investigate the fire-retardant properties of intumescent fire-retardant coatings of wood modified by different zeolites, tests were conducted by a cone calorimeter with poplar samples whose surfaces were covered by an intumescent fire-retardant coating modified by 3A, 4A, 5A, 13X zeolites, respectively. Results indicated that the ignition time (TTI) of the intumescent fire-retardant coating modified by 3A zeolite was prolonged 120 s, while the total smoke production (TSP) increased 60.1% as compared with the untreated group. The intumescent fire-retardant coating modified by the 13X zeolite had a smaller smoke production rate (SPR) and was the last to reach the peak-SPR. Its TSP remained in a very low state until 410 s and decreased 25%. Thus, 3A zeolite and 13X zeolite were of complementarily synergistic effects on improving the fire-retardant properties of an intumescent fire-retardant coating for wood. This paper suggested the alternative types of zeolites for flame-retardant coatings.

  • Researchpp 5383-5394Ramos, D., Salvadó, J., and Fernando, F. (2017). “High mechanical performance boards made from fibers of Arundo donax without added adhesives,” BioRes. 12(3), 5383-5394.AbstractPDF

    Arundo donax is a cane species with high growing productivity, and it is becoming an important source of biomass. The main objective of this study was to obtain fibreboards with high mechanical performance from A. donax without any added adhesive. Boards made without adhesive are free from formaldehyde emissions and consume no fossil resources. The characteristics of the obtained boards depended on the original material, steam explosion pre-treatments, and forming conditions (pressure, temperature, and pressing time). Production parameters were optimized. The effect of forming pressure on the physical and mechanical properties density, elastic modulus (MOE), modulus of rupture (MOR), tensile strength perpendicular to the faces (IB), thickness swelling, and water absorption of the obtained boards was studied. The European Norms (EN) methodologies were used to test the board specifications. Density, MOE, and MOR were modelled by a double reciprocal function. TS and WA were modelled with a reciprocal function in X. The boards obtained met and sometimes exceeded the requirements of these standards for the most demanding structural use.

  • Researchpp 5395-5406Ji, X., Zhang, Z., Chen, J., Yang, G., Chen, H., and Lucia, L. A. (2017). "Synthesis and characterization of alkali lignin-based hydrogels from ionic liquids," BioRes. 12(3), 5395-5406.AbstractPDF

    Hydrogels from alkali lignin were prepared and shown to display unique swelling. Variable lignin contents (6.25%, 10.00%, 12.50%, and 14.29%) were successfully grafted with both N,N’-methylenebisacrylamide (MBA) and acrylamide (AM). Ionic liquids such as 1-ethyl-3-methylimidazolium acetate ([Emim]Ac) were used to avoid harsh, unfriendly solvents. All materials were characterized using X-ray diffraction (XRD) FT-IR spectroscopy, scanning electron microscope (SEM), thermogravimetric analysis (TGA), and swellability. The swelling behaviors of the hydrogels were noticeably influenced by their lignin content. The degree of equilibrium swelling (the maximum swelling degree) decreased with increasing content of lignin. The highest swelling degree (1,650%) was obtained at 6.25 wt% lignin. Kinetics revealed that the swelling behaviors of hydrogels were well-fitted by the Schott model.

  • Researchpp 5407-5416Liu, R., Chen, Z., Ren, H., and Duan, E. (2017). "Synthesis and properties of non-aromatic ionic liquids and their role in cellulose dissolution," BioRes. 12(3), 5407-5416.AbstractPDF

    The dissolution of cellulose is an important pretreatment method required for some of its catalytic conversion processes. Morpholinium-based ionic liquids (ILs) are challenging solvent choices available for “greener” and “cheaper” dissolution of cellulose. In this study, morpholinium-based ILs were prepared, and their influencing factors were experimentally investigated. The unique bipolar chemical structure derived from oxygen (electron-rich center) and nitrogen (electron-poor center) considerably enhanced the Hammett acidity function (H0) of task-ILs. N-Methyl-N-allyl-morpholinium acetate IL showed the highest H0 (2.324) and polarizability power (1.096). The anion of ILs determined the hydrogen bond basicity (β). The acetate anion contributed to β (0.88) values. As to fluid properties, the morpholinium-based ILs exhibited much lower viscosity. The properties of ILs improved the dissolution efficiency. The cellulose was directly dissolved in morpholinium-based Ils, and no other derivatives were formed. The cations and the anions of ILs studied reacted with oxygen and hydrogen atoms on the hydroxyl groups of cellulose, respectively.

  • Researchpp 5417-5427Seo, H. J., Hwang, W., and Lee, M. C. (2017). "Fire properties of Pinus densiflora utilizing fire-retardant chemicals based on borated and phosphorus (I) – combustion characteristics," BioRes. 12(3), 5417-5427.AbstractPDF

    The combustion and thermal characteristics of fire retardant-treated pine (Pinus densiflora) were evaluated according to the KS F ISO 5660-1 (2003) standard, using a cone calorimeter. The specimens were treated with fire-retardant chemical compounds using pressure-impregnation equipment to reliably impregnate the compounds inside the wood. The heat release rate value of the fire retardant-treated wood specimens showed that the heat release time was delayed. A reduction of the total heat release value can indicate that fire was prevented from igniting in the materials during combustion. The microstructures of natural specimen and treated fire-retardant chemical compounds specimen were determined by scanning electron microscopy. It also confirmed that the pressure-impregnation processing method was effective in comparison to the other treatment methods.

  • Researchpp 5428-5448Ramos-Carmona, S., Delgado-Balcázar, S., and Perez, J. F. (2017). "Physicochemical characterization of torrefied wood biomass under air as oxidizing atmosphere," BioRes. 12(3), 5428-5448.AbstractPDF

    The effects of torrefaction under an oxidizing atmosphere on the physicochemical properties of patula pine wood chips were studied. Raw and torrefied pine were characterized to evaluate the effect of temperature and residence time on biofuel properties, such as bulk density, equivalent Hardgrove grindability index (HGIeq), ultimate and proximate analyses, heating value, and fuel value index (FVI). In contrast, the torrefaction process was characterized by mass and energy yields, and by the energy-mass co-benefit index (EMCI). Torrefaction was performed in a rotary kiln at temperatures between 180 °C and 240 °C during residence times between 30 min and 120 min. The torrefaction process under an oxidizing atmosphere tended to increase the fixed carbon/volatile matter ratio (from 0.19 to 2.5), while the H/C and O/C atomic ratios decreased 73% and 55%, respectively. The best properties of wood reached in the experimental plan were obtained at 210 °C during 75 min. For this torrefaction condition, energy yield, FVI, and EMCI were 85.91%, 1.91 MJ/cm3, and 4.41%, respectively. Additionally, the lower heating value for torrefied pine (18.65 MJ/kg) was higher than for the raw material (17.76 MJ/kg), and the HGIeq was 17% greater, which resulted in a better grindability behavior.

  • Researchpp 5449-5461Valášek, P., Müller, M., and Šleger, V. (2017). "Influence of plasma treatment on mechanical properties of cellulose-based fibres and their interfacial interaction in composite systems," BioRes. 12(3), 5449-5461.AbstractPDF
    The use of natural reinforcements is growing in current material engineering due to their satisfactory mechanical properties such as availability, price, and environmental aspects. Synthetic fibres are more often replaced by natural ones in many applications. The interfacial interactions of matrices are key factors that limit the use of natural fibres. The matrix interactions of natural fibres can be optimized by surface treatments, such as plasma treatment. This paper examined the possibility of using plasma to treat natural fibres. The basic mechanical characteristics of the fibres were changed by this treatment. Changes in the surface structures and the subsequent interaction with polymeric matrices with epoxy resins were evaluated by scanning electron microscopy. The plasma treatments of fibres did not decrease the tensile strength but did optimize their surface structures.
  • Researchpp 5462-5486Zhang, Z. C., Li, J. H., and Wang, F. (2017). "Kinetics of cellulase saccharification of corn stover after pretreatment by lignin peroxidase and H2O2," BioRes. 12(3), 5462-5486.AbstractPDF

    The kinetics of cellulase saccharification of corn stover (CS) after pretreatment by lignin peroxidase (LiP) and H2O2 was modeled in this work. The Impeded Michaelis model was applied in fitting all experimental data. The model gave the initial activity and accessibility of the enzyme on the substrate (Kobs,0) and the gradual loss of enzyme activity (Ki). The maximum Ytrs (55.56%) was obtained at pH 4.7, 48.6 °C, a 1.5% cellulase, and 12.4:1 water-to-material ratio. The binary quadratic model provide a good fit of the data on Ytrs and of the model parameters Kobs,0 and Ki. The results showed that Ytrs was positively correlated with Kobs,0 and negatively correlated with Ki. This study laid a foundation for improving the cellulase saccharification efficiency of lignocellulosic biomass after pretreatment by H2O2 and LiP.

  • Reviewpp to be addedChin, K., Ibrahim, S., Hakeem, K., H’ng, P., Lee, S., and Mohd Lila, M. (2017). “Bioenergy production from bamboo: Potential source from Malaysia’s perspective,” BioRes. 12(3), Page numbers to be added.AbstractPDF
    Global energy sectors are facing the crucial challenge of sustainability and diversification of energy resources. Seeking renewable resources with a sustainable supply is therefore a matter of the utmost concern. In this respect, bamboo, a renewable lignocellulosic material and non-food biomass, has great potential to be utilized to produce energy. Several studies have been conducted on a wide range of bamboo species and the results have shown that bamboo could potentially be used as a suitable fuel because it shares desirable fuel characteristics present in other woody biomass. Bamboo can be used as an energy source by converting it into solid, liquid, and gaseous fuels. However, to utilize bamboo as a high promise energy crop resource for biofuels, a secure and stable supply is required. Therefore, additional information on the availability, cultivation, and harvesting operations of bamboo is vital to ensure the practicability of the idea. The objective of this review is to highlight the potential of bamboo as an alternative source of bioenergy production, particularly in a Malaysian context, with emphasis on the concepts, pretreatment, and conversion technologies.
  • Researchpp 5487-5501Bailón-Salas, A., Ordaz-Díaz, L., Valle-Cervantes, S., Lopez-Miranda, J., Urtiz-Estrada, N., Páez-Lerma, J., de León-Mata, G., and Rojas-Contreras, J. (2017). "Bacterial diversity in two aerated lagoons of a pulp and paper effluent and their interaction with a commercial inoculum using PCR-DGGE," BioRes. 12(3), 5487-5501.AbstractPDF
    Aerated lagoons are a main unit operation for wastewater treatment in the paper industry. Many such operations involve inoculation with bacterial formulations in which in situ effectiveness has not been proven; this can be translated into low efficiency in treatment and unnecessary investments. Lack of knowledge of bacterial biodiversity present in a lagoon limits the capacity to exploit the maximum degradation. To overcome such problems, various methods to identify and study these microorganisms have been developed. In this study, a PCR-DGGE analysis was performed to estimate the bacterial diversity and to verify the presence of bacteria present in a commercial inoculum in two aerated lagoons of a pulp and paper effluent. Phylogenetic affiliation of predominant member’s correspondent to γ- and β-proteobacteria and Firmicutes were found. The dominant bacteria present in lagoon 2 belonged to the following genus Microbacterium sp. Rhodocyclaceae sp., Eubacterium sp. and B. subtilis. In lagoon 1 the dominant genus included Microbacterium sp., Rhodocyclaceae sp. Tepidimonas sp., Acetanaerobacterium sp., and Flavobacteria sp. The two characterized lagoons were not similar to the commercial inoculum. In addition, non-dominant bacteria (less relative intensity) were composed mostly of bacteria of the commercial inoculum.
  • Researchpp 5502-5511Shi, Y., Xie, J., Kou, J., Kong, R., Sun, N., and Bai, M. (2017). "Decomposition study of methyl α-D-glucopyranoside (MGPα) and lignin model compounds for better glucose yield during sulfurous acid treatment," BioRes. 12(3), 5502-5511.AbstractPDF

    From the perspective of bio-refinery, sulfurous acid (H2SO3) treatment of lignocellulosic biomass is attractive because of its ability to act both as an acid catalyst and as a sulfonation agent. Therefore, its capability to hydrolyze polysaccharides (especially glucan) into monosaccharides was compared with two other acids, hydrochloric and sulfuric acids. The decomposition of methyl α-D-glucopyranoside (MGPα) in these three acids, hydrochloric, sulfuric, and sulfurous acids were studied. In addition, p-creosol and vanillyl alcohol were introduced to check whether it is possible to convert polysaccharides (such as hemicelluloses) into monosaccharides during the sulfurous acid treatment. The results showed that the decomposition of MGPα is much slower in H2SO3 than in HCl and H2SO4. The ligninsulfonic acid resulting from the lignin sulfonation reaction can be expected to improve the efficiency of hydrolysis of polysaccharides into monosaccharides during sulfurous acid treatment. Moreover, a higher actual yield of glucose was obtained in this case than in the other two acids.

  • Researchpp 5512-5524Urbaniak, M., Goluch-Goreczna, R., and Bledzki, A. (2017). "Natural cork agglomerate as an ecological alternative in constructional sandwich composites," BioRes. 12(3), 5512-5524.AbstractPDF

    The investigations presented in this article include a comparative study of static and fatigue four-point flexural tests performed for sandwich composites. The investigated composites consisted of a glass-epoxy laminate as a cladding material and core materials, such as synthetic foams and natural cork agglomerates, in different densities. The sandwich composites were prepared with the vacuum bagging method using the same resin, reinforcement, and additives. Although using cork agglomerate in sandwich composites instead of synthetic foam resulted in a decrease of the static flexural strength in such composites, it increased their resistance to fatigue cycles considerably and benefitted their eco-friendly image. However, only the reproducibility of all the factors in the production process and testing of composites allows a direct comparison of their test results to be made.

  • Reviewpp to be addedRadics, R. I., Gonzalez, R., Bilek, E. M., and Kelley, S. S. (2017). "Systematic review of torrefied wood economics," BioRes. 12(3), Pg #s to be added.AbstractPDF

    This literature review aims to provide a systematic analysis of studies on the financial aspects of producing torrefied biomass and torrefied pellets. There are substantial differences in the specific technologies, operating conditions, scale of the demonstration, and properties of biomass feedstock. There is a lack of reports that consider the entire supply chain, which is required for an understanding of the high-cost steps. To obtain a robust view of the torrefaction processes’ financial prospects the authors have used both peer-reviewed and non-peer-reviewed papers that allowed the researchers to include thirty-one papers in this analysis. All these studies establish that the prices of the biomass and the final torrefied product are critical. The product yield and caloric content, which are related to pricing, were also key financial drivers. The lower freight costs due to high-energy density of the torrefied pellets was recognized and calculated, but some other benefits were not quantified. There is a need for a detailed and flexible torrefaction financial model that includes variations in financial assumptions and biomass properties. Given the uncertainty around many specific steps, there is value in including stochastic tools in these financial analyses.

  • Researchpp 5525-5538Grič, M., Joščák, P., Tarvainen, I., Ryönänkoski, H., Lagaňa, R., Langová, N., and Andor, T. (2017). "Mechanical properties of furniture self-locking frame joints," BioRes. 12(3), 5525-5538.AbstractPDF
    The load carrying capacity, stiffness, and strain fields of 18 mm thick and half lap 30 mm thick L-shaped furniture self-locking frame joints made of a Finnish birch plywood and a birch battenboard were determined. The joints were tested under tensile and compression bending. On the basis of the experimental information, finite element analysis models were verified. The data showed that the joints made of birch plywood reached a higher load carrying capacity and stiffness than the joints made of the birch battenboard with the same thickness. The Half lap joint (H L J) made of the Finnish plywood reached the ultimate load carrying capacity and the ultimate stiffness under both the compression bending and the tensile bending. The finite element analysis models of the joints can be used for estimating the mechanical properties of the self-locking joints with different tenon shapes made of the materials used in this paper.
  • Researchpp 5539-5549Gu, L., Li, Y., Yang, Y., Wang, Z., and Jin, Y. (2017). "Preparation and adsorption performance of cellulose-graft-polycaprolactone/polycaprolactone porous material," BioRes. 12(3), 5539-5549.AbstractPDF

    Cellulose-graft-polycaprolactone/polycaprolactone (cell-g-PCL/PCL) was formed by grafting cotton linter pulp with caprolactone via ring-opening polymerization catalyzed by Ti(O-n-Bu)4. The cell-g-PCL/PCL and polycaprolactone (PCL) were used to prepare porous materials (PMs) using solvent exchange and freeze-drying procedures. The obtained PMs were characterized by their porosity, tensile strength, and thermal stability via thermal gravimetric analysis and scanning electron microscopy. The preparation conditions of the cell-g-PCL/PCL PM were optimized based on the characterization results. Compared with PCL PM, cell-g-PCL/PCL PM showed higher porosity and better thermal stability. The adsorptivity of cell-g-PCL/PCL PM for the organic pollutant chlorobenzene was greatly improved compared with that of PCL PM. The adsorption processes of both PMs fit well with the Lagergren pseudo-first-order and pseudo-second-order kinetic models. The results of isothermal adsorption simulation indicated that cell-g-PCL/PCL PM and PCL PM fit better with the Langmuir model and Freundlich model, respectively.

  • Researchpp 5550-5568Kim, N. K., and Rie, D. H. (2017). "A study on fire risk reduction of porous combustible storage," BioRes. 12(3), 5550-5568.AbstractPDF

    As biomass has become increasingly important, wood pellets are becoming more widely used, and the storage of wood flour, which is the raw material of wood pellets, has become inevitable. The purpose of this study was to reduce the economic losses from fires during storage of porous combustible materials. To achieve this purpose, the authors analyzed and compared the wood flour loss rate between the use of water and the use of wetting agents to extinguish a deep-seated fire through a scale model experiment. To do this, the authors measured the penetration amount of the water and dilute solutions of wetting agent, the weight change of the wood flour holder, and the emissions on a real time basis when that spray amount was the same. Furthermore, the authors analyzed the calorific value and combustion gas to examine the reusability of the wood flour with the added wetting agent. This study quantitatively demonstrated that the active use of wetting agents in wood flour storage fires dramatically reduced the fire loss rate of raw materials and resulted in early fire extinguishing, which minimizes companies’ economic loss.

  • Researchpp 5569-5582Merhar, M., Gornik Bučar, D., and Pepelnjak, T. (2017). "Dynamic behaviour analysis of a commercial roll-tensioned circular sawblade," BioRes. 12(3), 5569-5582.AbstractPDF

    A commercial woodcutting circular sawblade was analysed in this work. The lateral stiffness on the periphery was measured, and the natural frequencies were determined by modal analyses. The sawblade was modelled by the finite element method, where the influence of the internal stresses caused by roll-tensioning of the sawblade was considered. The roll-tensioning force was determined based on the measurement of the sawblade rolling profile, where it was established that the sawblade had been rolled with a force of 7800 N. The analysis showed that at the aforementioned force, the lateral stiffness was a maximum; here, the calculated and measured stiffnesses were 81 and 60 N/mm, respectively. The calculated natural frequencies agree well with the measured ones, where in the most important vibrational modes there is only a 7% difference. The maximum rotational speed for the sawblade was determined to be 85% of the critical speed. Because the sawblade was clamped with a ratio of clamping of only 0.25, the maximum rotational speed was amounted to 6630 rpm. Increasing the rolling force would increase the critical speed but greatly reduce the lateral stiffness.

  • Researchpp 5583-5600Ouyang, H., Wang, L., Peng, W., and Deng, H. (2017). "Fungus-assisted acetic acid pre-treatment of Eucommia ulmoides Oliver seed shells for enhancement of enzymatic hydrolysis," BioRes. 12(3), 5583-5600.AbstractPDF

    The potential of nine fungal strains for pre-treating Eucommia ulmoides Oliver seed shells (EUOSSs) was investigated. Phanerochaete chrysosporium Burds. was found to be the best fungal strain for pre-treating EUOSSs. After co-pre-treatment with acetic acid and P. chrysosporium Burds., which was cultivated in a solid state with an approximately 74% moisture content at 28 °C for 28 d, the weight loss of the EUOSSs was 51.9%. Because of the cooperative efficiency of the biochemical pre-treatment, an enzymatic digestibility value of 86.6% was achieved. The high digestibility value was attributed to the synergism between the acetic acid and fungal treatments, which led to improved enzymatic accessibility of the EUOSSs. As an environmentally friendly processing method, fungal pre-treatment can save a great amount of energy and, in combination with an acetic acid treatment, is more efficient at improving the rate of sugar transformation.

  • Researchpp 5601-5616Chen, X., Han, Y., Zhang, C., Feng, G., Zhao, M., Yue, R., Li, Y., Jiang, L., Zhang, L., Li, J., and Li, S. (2017). "Alkaline pretreatment of banana stems for methane generation: Effects of temperature and physicochemical changes," BioRes. 12(3), 5601-5616.AbstractPDF
    The effects of NaOH pretreatment temperature on the physicochemical characteristics and methane production of anaerobically digested banana stems were investigated in this paper. With the increase of pretreatment temperature from 0 °C to 100 °C, the chemical oxygen demand (COD) of the soak liquid in the treated biomass approximately linearly increased from 5.9 g/L for the untreated stems to 34.0 g/L. A weight loss of 5.1% was observed for the untreated material, while it was up to 31.2% for the sample treated at 100 °C. The removal of lignin and hemicellulose accounted for the majority of the weight loss. The removal rates of lignin and hemicellulose increased from 15.0% to 41.6% and 1.9% to 23.6% when the treatment temperature increased from 0 °C to 100 °C, respectively. Moreover, the crystalline index (CI) of the banana stems also increased with rising temperature, resulting from the dissolution of amorphous cellulose with increasingly harsher alkaline environments. The optimal pretreatment temperature for banana stems was confirmed at 50 °C. In these conditions, methane was produced via anaerobic digestion with 239.9 mL/g total solid (TS) yield, which represented an increase of 66.7% over untreated banana stems.
  • Researchpp 5617-5631Mahgoub, K. B., Hassan, S., Sulaiman, S. A., Mamat, R., Abdullah, A. A., and Hagos, F. Y. (2017). "Combustion and performance of syngas dual fueling in a CI engine with blended biodiesel as pilot fuel," BioRes. 12(3), 5617-5631.AbstractPDF

    Simulated syngas produced from biomass gasification was evaluated in a compression ignition (CI) engine under a dual fueling mode. Syngas is an economical solution with a carbon-neutral system that could replace petroleum diesel fuel. Syngas can be introduced into CI engines through a dual fueling process. However, syngas dual fueling combustion is very complicated because it consists of several combustion phases. In addition, CI engines operating under the syngas dual fueling mode suffer from low performance. Therefore, this study examined the performance of syngas dual fueling in a CI engine with blended biodiesel as pilot fuel. Two types of simulated syngas, namely typical syngas and high hydrogen syngas, were considered. The simulated high hydrogen syngas was assumed to be the product of biomass gasification with introduction of a carbon dioxide adsorption. The effect of carbon dioxide removal from syngas on the performance of syngas dual fueling in a CI engine at constant engine speed, half load, and different pilot fuel substitution rates was investigated. The combustion characteristics showed a maximum pilot fuel substitution of up to 47% with simulated syngas. Better engine performance was achieved with the simulated typical syngas in terms of brake specific energy consumption and brake thermal efficiency.

  • Researchpp 5632-5648Hutterer, C., Fackler, K., Schild, G., Ibl, V., and Potthast, A. (2017). "Xylan localization on pulp and viscose fiber surfaces," BioRes. 12(3), 5632-5648.AbstractPDF

    A method for the immunological visualization of plant polysaccharides in native plant tissues was adopted for the histological investigation of xylan on kraft pulp and xylan-enriched viscose fibers. The method consisted of the selective labeling of xylan structures through the binding of specific monoclonal primary antibodies and fluorescein isothiocyanate (FITC)-carrying secondary antibodies. This indirect immunolabeling method was adapted for pulp and viscose fibers through the blockage of unspecific binding sites with bovine serum albumin (BSA), which allowed a selective localization of xylan. The combination of this technique with high resolution confocal laser scanning microscopy (CLSM) rendered a parallel detection of morphological changes of pulp fibers alongside various processing steps possible. Within this study, kraft pulps from birch, beech, and eucalyptus were investigated throughout a purification process that enabled an upgrade from paper pulps to dissolving pulps by caustic hemicellulose extraction and xylan-enriched viscose fibers. The method demonstrated its potential for gaining novel insights into pulp purification, as well as fiber modification through the application of an immunolabeling method.

  • Researchpp 5649-5663Imran, M., Anwar, Z., Zafar, M., Irshad, M., and Iqbal, T. (2017). "Hyper-productivity, characterization, and exploitation of a cellulase complex from a novel isolate of Aspergillus tubingenesis S2 using lignocellulose-based material," BioRes. 12(3), 5649-5663.AbstractPDF

    The hyper-production potential of a cellulase complex from a local strain of Aspergillus tubingensis S2, indigenously isolated from rotten tomato, was investigated. A total of nine fungal species of Aspergillus and Trichoderma were isolated and confirmed through triple-phase screening via 18S ribosomal DNA sequencing and construction of a phylogenetic tree. Congo red testing and the zone of clearance method were used to confirm the cellulase production from A. tubingenesis S2 isolate. A. tubingenesis S2 revealed maximum cellulase production (78 µg/mL/min) and was selected for further study. The optimum fermentative conditions, including the incubation period, pH, and temperature values, were determined to be 96 h, pH 4.8, and 40 °C, respectively, for obtaining the cellulase activity of 86.4±2.1 µg/mL/min. The cellulase was 5.14-fold purified by ammonium sulfate fractionation and gel permeation chromatography. Characterization revealed that maximum activity (130.5 µg/mL/min and 133.5 µg/mL/min) was achieved at 4.5 pH and 40 °C, respectively. A monomeric protein with an apparent molecular weight of 76 kDa was evident after sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Cellulase revealed maximal activity with 40-mesh size corn stover as compared with 20-mesh size corn stover and 80-mesh size corn stover after 36 h of incubation at 40 °C.