Research Articles

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.

An efficient and selective process for the conversion of carbohydrates to 5-hydroxymethylfurfural (HMF) was applied over a novel phosphated TiO₂-SiO₂ (P-TiO₂-SiO₂) catalyst. The catalyst, synthesized by a facile sol-gel technique, was characterized by X-ray diffraction (XRD), N₂ sorption, NH₃ temperature-programmed-desorption, and Fourier transform infrared spectroscopy (FT-IR) study of the pyridine adsorbed. The highest HMF yield of 63.0 mol% was achieved at 170 °C for 90 min over P-TiO₂-SiO₂ catalyst in a tetrahydrofuran (THF)/H₂O-NaCl system. The P-TiO₂-SiO₂ catalyst showed a predominant catalytic performance in the synthesis of HMF, a result of its moderate acid density and suitable Brønsted/Lewis (B/L) acid ratio. Additionally, the catalyst was shown to be efficient in the conversion of more complex cellulose with the high HMF yield of 56.0 mol%. More importantly, this mesoporous catalyst exhibited high stability and recyclability, making it a promising choice for the future production of HMF.

The efficacy of five different nanoparticles (zinc-oxide, zinc-borate, silver, copper, and copper-borate) were evaluated after application at different concentrations for protection against Coniophora puteana and Coriolus versicolor. Tests were performed with two different wood species (beech and pine sapwood). Furthermore, tests were done to investigate the resistance of the nanoparticles to leaching. Overall, the results of the efficiency of the investigated nanoparticles against the brown and white rot fungi were diverse. One of the investigated fungi showed a tolerance to the nanoparticles in some cases (zinc-oxide, silver nanocubes, and copper). The most effective nanoparticle treatments were those containing borate. However, only the zinc-oxide, copper, and silver nanoparticles showed a high resistance to leaching. Unfortunately, zinc-borate and copper-borate showed a low resistance to leaching, as the treated samples showed a similar decay compared with that of the control. Thus, only the zinc-oxide at the highest investigated concentration (5% m/m) provided effective protection after leaching for both of the investigated fungi. Also, the copper nanoparticles showed potential as an effective treatment at higher concentrations.