Research Articles

The influence of particle size and an alkaline pretreatment on the anaerobic digestion of corn stover was studied. Four particle sizes, 0.075 to 0.25, 0.25 to 1.0, 1.0 to 5.0, and 5.0 to 20.0 mm, were used. The highest and lowest methane yields were obtained from untreated corn stover at particle sizes of 0.25 to 1.0 and 5.0 to 20.0 mm, respectively. 4% NaOH and 2% Ca(OH)2 (combined alkaline pretreatment, CAP) were then used together to pretreat corn stover at these two particle sizes, compared with 6% NaOH pretreatment (single alkaline pretreatment, SAP). The cumulative methane yields from particle sizes 0.25 to 1.0 mm after CAP, 0.25 to 1.0 mm after SAP, 5.0 to 20.0 mm after CAP, and 5.0 to 20.0 mm after SAP were 286.9, 287.0, 268.7, and 272.6 mLg^-1 VS, respectively. The particle size barely influenced the final cumulative methane yield of alkali-treated corn stover. Moreover, the cumulative methane yield of the corn stover after CAP was comparable with that of the corn stover after the SAP under the same conditions. These results provide us with a promising substitute of NaOH pretreatment for corn stover bioconversion in the future.

Bleached simao pine kraft pulp was treated with Aspergillus niger crude cellulase produced by submerged fermentation using the pulp as the carbon source. The effects of the cellulase on the pulp beatability and mechanical properties were studied. Fourier transform infrared spectroscopy (FT-IR) was performed to study the effect of cellulase treatment on the cellulose crystallinity index. The fiber morphology difference before and after treatment was also revealed by atomic force microscope observation. Compared to the control pulp, the beating time of the cellulase-treated pulp with the dosage of 7 u/g could be reduced from 360 s to 260 s under the same beating degree of 48 °SR, which indicates a savings of about 28% beating energy consumption. The cellulase treatment had negative impacts on the pulp’s mechanical properties. The cellulase preferentially adsorbed on the fine surface. The cellulose amorphous region was easier to treat with cellulase than the crystalline region. Atomic force microscope images demonstrated that the primary wall of fibers was peeled off and the S1 layer of fibers came to the surface after the cellulase treatment.

This study evaluated the properties of fluting paper made with a blend of unbleached bagasse soda pulp (340 mL CSF freeness) and OCC pulp (250 to 300 mL CSF freeness) of 0:100, 10:90, 30:70, 50:50, 70:30, and 90:10 ratios by weight, respectively. Some handsheets at 120 g/m2 basis weight were made. Strength characteristics such as tear index, tensile index, air resistance, double folds, burst index, and Concora medium test (CMT) were measured according to TAPPI and ISO standards and compared to each other. Inferior handsheet properties were observed when using 100% recycled fibers. Results further showed that addition of 10 to 30% bagasse pulp to OCC pulp did not significantly enhance the sheet strength of the product compared with the control sample (100% OCC pulp). However, it was found that addition of 70% or more of virgin pulp to the OCC pulp resulted in a substantial increase in the strength properties, except for the tear index. The modification of the fibers was visually evaluated by Scanning Electron Microscope (SEM). Overall, the results showed that flexible virgin bagasse fibers can be used as a lignocellulosic fiber for making fluting paper in combination with recycled OCC fibers.

Novolak-type resins were produced via liquefaction of oil palm empty fruit bunch (EFB) fibres with various liquefaction and resinification parameters such as temperature, time, catalyst concentration, and phenol-to-EFB ratios, and investigated in terms of flow properties (melt viscosity and melt flow rate) of the phenolated EFB (PEFB) and resinified PEFB (RPEFB). The results showed that the phenol/EFB ratio was the most effectual parameter in the variation of melt viscosity and melt flow rate (MFR) of PEFB. The melt flow rate of the PEFB was tremendously lower than that of the commercial novolak resin. The results showed that the activation energy for flow, which was obtained using the Arrhenius equation, increased when the liquefaction temperature increased. The results also demonstrated that the molten PEFB showed a shear thinning or pseudo-plastic behavior.

A direct synthesis of methyl levulinate from the degradation of paper sludge in a methanol medium at moderate temperatures ≤ 230 °C) was performed using low-concentration sulfuric acid (≤ 0.05 mol/L) as the catalyst. Response surface methodology with a four-factor, five-level central composite rotatable design was employed to optimize the process conditions for . The yields of methyl levulinate and dimethyl ether as a function of the process variables were fitted to second-order polynomial models through application of multiple regression analyses. A good agreement between the experimental and modeled data was obtained. When the controlled yield of dimethyl ether was less than 20%, a maximum methyl levulinate yield of 54.8% was achieved, corresponding to 27.7% (w/w) overall yield for dry paper sludge. The findings indicated that paper sludge can act as a potential biomass material for upgrading and converting into high value-added chemicals.

The wood pellet industry has been in a growing trend worldwide. The Southern U.S. has been proposed as a good location to further develop wood pellet industries geared toward the supply of international markets. This research looks into the current status of the wood pellet industry of the region in terms of consumption of biomass, installed capacity, and production levels of wood pellets. It assesses the known future developments for the region (Virginia, North Carolina, South Carolina, Georgia, and Florida). The study also includes an analysis of major ports within the region. Currently, companies within the region have a total production capacity of over 4.7 million tons of pellets, while the current production levels are estimated at 3.1 million tons. Research indicates that at least 20 facilities within the region will be opening their operations, and the expected capacity of the wood pellet industry will then be over 5 million tons of pellets per year. The biomass requirement for the production of these pellets was determined, and the current production level requires over 11 million tons of green biomass (55% moisture content). Future developments may require over 13 million tons, making the industry total over 24 million tons in coming years.

TEMPO oxidation was performed on never-dried bleached softwood kraft pulp fibres to study the influence of reaction temperature and the dosage of sodium hypochlorite in the oxidation treatment. It was found that oxidation at a high temperature shortened oxidation time, but it also resulted in more extensive degradation of the pulp. Harsh reaction conditions (high temperature and high dosage of sodium hypochlorite) enabled the rapid disintegration of pulp fibres with a low energy demand. The freeze-dried disintegrated pulp fibres had a high absorption capacity of saline liquid, 40 to 80 g/g, and retained 9 to 14 g saline liquid/g material in a standard centrifuge retention test. Four different models were investigated to describe the kinetics of TEMPO oxidation of pulp fibres. However, none of the models could adequately describe all the mechanisms involved in this reaction system. The results showed that the diffusion of hypochlorite ions was sufficiently fast compared to the chemical reactions. In contrast, the concentration of the catalytic compounds, NaBr and TEMPO, both had a strong influence on the reaction rate. Results show that the reactions have different phases, possibly with different rate-determining steps. It remains to be determined which reaction steps correspond to the different phases.

The possibility of using cellulose from kenaf as reinforcing fibres in lithium-conducting composite polymer electrolytes based on 49% poly(methyl methacrylate)-grafted natural rubber and LiCF3SO3 has been explored. Cellulose was extracted from kenaf bast fibres by a two-step chemical treatment, specifically an alkali treatment and a bleaching process. High-performance composite polymer electrolytes were prepared by solution casting with various compositions of cellulose (0-10 wt%). Scanning electron microscopy was used for morphological studies of the kenaf fibres at each stage of treatment. The morphology of the electrolytes showed a good dispersion of the cellulose fibres. Infrared spectroscopy showed significant interactions between Li+ ions from the salt and the C=O and C-O-C groups of methyl methacrylate. X-ray diffraction analysis showed that the crystallinity of the polymer host increased upon addition of cellulose and decreased upon addition of salt. Composite electrolytes with 4 wt% cellulose exhibited the best mechanical performance with 10.9 MPa and 995 MPa for tensile strength and Young’s modulus, respectively. The electrolyte films were analyzed by electrochemical impedance spectroscopy and the optimum value of ionic conductivity of SPE with cellulose was 5.3×10-7 Scm^-1. The addition of cellulose involved a weak decrease of the conductivity, which might be due to interactions between cellulose, polymer, and LiCF3SO3. The incorporation of cellulose fibres in polymer electrolytes provides a high reinforcing effect at an acceptable level of ionic conductivity.

The effect of biochar amendment of a multi-element contaminated soil on the transfer and accumulation of Cd, Zn, Pb, and As in wheat was investigated in this study. Addition of biochars from rice residues (straw, husk, and bran) significantly decreased shoot Cd, Zn, and Pb concentrations by up to 71%, 37%, and 60%, respectively, but increased As by up to 199%. Biochar additions decreased the NH4NO3-extractable concentrations of Cd, Zn, and Pb in soil by 23 to 81%, 29 to 94%, and 31 to 92%, respectively, especially straw-char treatment, though biochar treatment increased the concentration of As by 64 to 2650%. A decrease in biochar particle size generally favored the immobilization of Cd, Zn, and Pb in soil and reductions in their accumulation in wheat shoot, but this was reversed for As. Increases of up to 21%, 70%, 59%, and 40% in shoot biomass, root length, and shoot P and K levels, respectively, of wheat seedlings were caused by biochar amendments. Biochar has the potential to reduce accumulations of Cd, Zn, and Pb in wheat shoot and improve its growth.

Microcrack behaviors in black and red heartwoods of Cryptomeria japonica were compared in this study. Black and red heartwoods have extremely different green moisture contents but similar wood structure. Small heartwood samples were prepared from these two types of green wood. Moisture contents of black and red heartwood were 201.5% and 51.3%, respectively. The samples were dried at 50 °C in a controlled-environment chamber with a relative humidity below 5%. The propagation of microcracks was continuously observed using a confocal laser scanning microscope while the samples dried. The electrical resistivity of the surface was also measured to assess surface moisture content. Results showed that the transformation of the microcracks was similar between black and red heartwoods. However, the appearance of microcracks in the black heartwood was delayed, whereas the microcracks appeared in red heartwood immediately after drying. These suggested that in-situ observation is essential for distinguishing when microcracks emerged. It was also suggested the green moisture content of heartwood has a major effect on the occurrence of microcracks. Drying conditions must be adjusted to account for the moisture content of green heartwood, even for specimens of the same species that have the same anatomical structure.