Volume 13 Issue 4

Properties were evaluated for heat-treated yellow poplar (Liriodendron tulipifera), eastern redcedar (Juniperus virginiana), and southern pine (Pinus echinata) samples. Differences in discoloration, surface roughness, and hardness of the samples as a function of heat exposure were tested at temperature levels of 130 °C, 160 °C, and 190 °C. The experiments were carried out on defect-free eastern redcedar, yellow poplar, and southern pine samples with dimensions of 50 cm by 4 cm by 2 cm (longitudinal, radial, tangential) supplied by a local sawmill. A total of 80 samples, 20 for each temperature level, were used for the tests. Based on the findings, it appears that eastern redcedar specimens had the least discoloration values as compared to those of two other types of wood. In all cases, hardness values of the samples showed adverse influence of heat exposure. It seems that as temperature level increased, the surface quality of the samples from all three species was enhanced. All types of samples had significant discoloration as a result of heat treatment, and such findings were more prominent in the case of both pine and yellow poplar specimens. Overall hardness characteristics of the samples were adversely influenced due to heat exposure.

This study aimed to screen high-performance flocculant-producing bacteria for flocculating suspended matter in wheat distillery wastewater. After the preliminary and secondary screening, a high-performance flocculant-producing bacteria strain was screened from the activated sludge of wheat distillery wastewater. Single factor and orthogonal experiments were used to optimize the culture and flocculent conditions for the flocculant-producing bacteria. A superior strain of Klebsiella M1 was screened and identified by 16S rDNA. The initial flocculating degree was up to 72%. Based on single-factor tests, the optimum flocculent conditions were a resting time of 30 min, 8%(v/v) culture medium dosage, and 3%(v/v) CaCl2. The optimum culture conditions were an incubation temperature of 30 °C for 48 h at pH 4.5 and rotation speed of 150 rpm. Under the optimum conditions, the flocculating degree was up to 82%. The best fermentation medium components were 15 g/L glucose, 2 g/L peptone, 1 g/L KH2PO4, and 2.5 g/L K2HPO4. A high flocculating degree was also achieved with the low-cost medium. The Klebsiella M1 bacteria strain can be used as a good bioflocculant produced bacteria for wheat distillery wastewater.

This study investigated the possibility of using chips obtained from annual plants as substitutes for pine chips in the external layers of boards intended for the building and furniture industries. The tested materials included rape, rye, triticale, reed, and corn straw, as well as pine chips. Three-layer boards were produced with the core layer made from pine chips and the external layers from different annual plants. The chips were glued with 4% polymeric diphenylmethane diisocyanate (pDMI) for all layers. The boards were tested for their modulus of rigidity, modulus of elasticity, internal bond, swelling, water absorption, and strength after being subjected to the cooking test. The results showed that in specific conditions, all annual plants may serve as partial substitutes for pine chips in the external layers of particleboards. The presence of these materials was particularly favorable for the modulus of elasticity. Corn straw was the most useful, as the boards supplemented with the material met the requirements of the EN 312 (2010) standard in terms of mechanical properties and water resistance for P5 boards and therefore it can be used in the building industry.

Hydrogen production from enzymatic hydrolysates of Agave lechuguilla pretreated by autohydrolysis was assessed in this work. The pretreatment was carried out in a high-pressure reactor using a solid/liquid ratio of 1:6 (w/v) at 190 °C for 30 min at 200 rpm. The pretreated solids were enzymatically hydrolyzed and then were digested with a treated mixed consortium under specified conditions with a Taguchi (L₉(3⁴)) experimental array. The results showed that the xylan was 65.2% solubilized during pretreatment, and the glucan preserved was 77.5% hydrolyzed, obtaining a hydrolysate with 55 g/L of glucose. The production of hydrogen after anaerobic digestion of hydrolysates was significantly influenced mainly by the temperature (80.6%) and glucose concentration (15.1%). The best conditions were 40 ºC, glucose 20 g/L, inoculum 5% (v/v), and initial pH 7. Under optimal conditions, the hydrogen yield achieved was 3.48 mol H₂/mol glucose consumed at 120 h.

Effects of cellulose micro/nanofibrils were investigated relative to the strength and drainability of security paper made from cotton lint mixed pulp. Six types of cellulose micro/nanofibrils were made from bleached softwood kraft pulp (SwBKP) and bleached hardwood kraft pulp (HwBKP) using refining and micro-grinding processes, respectively. After their main properties were measured, handsheets were produced by adding micro/nanofibrils into a cotton pulp furnish, and the physical properties of the sheets were measured. The cotton pulp furnish drainage rate was also analyzed with respect to the dosage and the fibrillation degree of the cellulose micro/ nanofibrils. The cellulose micro/nanofibrils made from SwBKP resulted in higher viscosity, lower particle size, and higher zeta-potential than those made from HwBKP. The nanofibrils made from SwBKP were the most effective for enhancing the tensile strength, folding endurance, and sheet density of the security papers made from cotton lint mixed pulp. However, the cellulose micro/nanofibrils made from SwBKP could be limited as a paper additive in papermaking due to its high drainage resistance. Because the cellulose micro/nanofibrils made from HwBKP also reduced the drainage rate, the dosage and the fibrillation degree should be controlled by simultaneously considering the paper strength and drainage.

A new method was developed to characterize the cellulose fiber (hardwood dissolving pulp) size distribution after 50 wt% sulfuric acid hydrolysis at different hydrolysis temperatures with exponential and Rosin-Rammler (R-R) laws. The results show that the two above laws can be effective to explain the cellulose hydrolysis process. The exponential and the R-R laws were found to be well fitted to the sulfuric acid hydrolyzed cellulose fiber length distribution. The cumulative number distribution from Fiber Tester was shown to fit the exponential distribution well, while the cumulative mass distribution obtained from the acid hydrolysis was found to be suitable to the R-R law via an approximation process. The results from SEM analyses also supported the above conclusions. This approach can be used to characterize the cellulosic fiber properties before a further process of biorefinery, nanocellulose preparation, or other application of lignocellulosic fibers.

Sulfuric acid lignin (SAL), one of the major biorefinery industry residues from the acid saccharification process on lignocellulosic materials for bio-fuel generation, is becoming a major problem for the sustainable development of the bio-refinery industry. Meanwhile, the recalcitrant and highly complex structure of SAL makes it insoluble in water and other organic solvents, resulting in a low reactivity. This study investigated the effects of hydrothermal reactions on SAL to enhance its solubility and reactivity. A hydrothermal reaction was first conducted on SAL from Cryptomeria japonica to obtain a completely water-soluble lignin. Fourier transform infrared spectroscopy, gel permeation chromatography, gas chromatography, and nuclear magnetic resonance (NMR) analyses revealed that the hydrothermal reaction of the SAL caused depolymerisation, demethylation, and the introduction of phenolic hydroxyls. Furthermore, another experiment was conducted on synthesizing a lignin polymer model compound (DHP) with 13C-labelled on the aromatic ring, followed by hydrothermal reaction and acetylation. Detailed structural information of DHP under hydrothermal reaction was obtained by solid-state cross polarization magic angle spinning NMR analysis. Reactivity of the hydrothermally treated SAL was enhanced by the hydrothermal reaction through the reversed increasing of the phenolic hydroxyl/aliphatic hydroxyl ratio in the condensed lignin units.

Rhizophora spp. are grown for wood charcoal production in many tropical estuaries and coastal areas. However, a lack of species-level information stands in the way of promoting this resource for sustainable practices. The present study investigated management practices and aboveground biomass (AGB) production patterns of Rhizophora apiculata plantations in the Yeesarn area of Samut Songkhram Province, Central Thailand. Interviews of farmers and a field survey were main instruments for collecting and analyzing of the data. It was found that farmers collect mature propagules locally and use traditional knowledge for maintenance of the plantation including site preparation and planting. Beating-up and weeding are the main operations applied in establishing a plantation; otherwise, little effort is directed towards post-planting maintenance. The plantation was reforested in a harvesting rotation of 8 to 15 years. Observed stand growth in terms of annual turnover rate (ATR) of height and diameter was highest in a 12-year old plantation; 0.82 m/year and 0.46 cm/year, respectively. Highest AGB production, stem wood volume (SWV), and commercial wood volume (CWV) were observed in a 14-year old plantation; 201.95 tonnes/ha, 181.49 m³/ha, and 178.98 m³/ha, respectively. Growth and productivity patterns indicate that the plantation has a high yield potential in terms of wood biomass production.

Glucose and xylose are the dominant hydrolysis products of lignocellulose, and they can be used as a potential substrate for biogas generation. To reveal the acid hydrolysis metabolism and enhance the methane production, mild acid hydrolysis of rice straw was conducted to obtain hydrolysates with different glucose to xylose ratios. The methane production and microbial metabolism process using mixed sugars and hydrolysates were investigated. The results showed that the cellulose and hemicellulose in the rice straw were converted to the desired sugars by controlling the acid hydrolysis conditions. The glucose to xylose ratios tested were 70:30, 60:40, 50:50, 40:60, and 30:70. The anaerobic digestion process had the highest methane yield with the 40:60 glucose to xylose ratio in the mixed sugars and hydrolysate, which were 334.1 mL/g and 318.2 mL/g based on the chemical oxygen demand (COD), respectively. The metabolic process with the 40:60 glucose to xylose ratio had good butyrate type fermentation and a high COD removal rate. The corresponding acid hydrolysis conditions were 1% HCl and a 7.5% solid loading at 60 °C for 48 h. Therefore, the mild acid hydrolysis conditions can adjust the glucose to xylose ratio in the hydrolysate for high methane production.

Water-soluble amphoteric polyacrylamide (AmPAM) has been widely used in papermaking as one of the agents for the improvement of dry strength. In this investigation, AmPAM was used, solely or with the combination of cationic starch (CS), for the strength improvement of paper sheets made from kraft hardwood fiber (KHW) and recycled old corrugated container (OCC) fiber. The results showed that AmPAM achieved better performance than CS as the dry strength additive of paper on the condition of the same dosage, especially for secondary fibers. AmPAM improved the breaking length of paper sheets made from virgin KHW by 25%, while by 80% for OCC, when at the dosage of 0.5% (wt% to mass of oven dried pulp). When AmPAM was applied with the combination of CS, a negative synergism was observed. Besides strength improvement, there were many additional benefits obtained from adding AmPAM, especially in the absence of cationic starch, e.g. decreased slurry conductivity, decreased beating degree, and increased retention. In this aspect, AmPAM is an efficient, multi-beneficial dry strength agent for the papermaking process, especially for secondary fibers.