Research Articles

Tar is an undesirable product of biomass gasification. Tar analysis is a challenging task because it is a complex mixture. The objectives of this study are to identify and quantify the major tar compounds in raw producer gas and deposits from a 10 kW downdraft gasifier using cedar pellets. Gas chromatography-mass spectrometry (GC-MS) was used to analyze the 16 tar samples from raw producer gas under varying airflow rates and four tar samples from the deposit inside the suction pump after long-term operation. The results showed that tar in raw producer gas and tar deposits consisted of about 46 and 28 major chemical compounds, respectively. Tar in raw producer gas was found to contain three main groups of substances, including acids/ketones with 32.1 wt%, heterocyclics with 30.0 wt%, and light poly-aromatic hydrocarbons (light PAHs) with 31.8 wt%. Heterocyclic and light PAH compounds dominated in tar deposits and accounted for 58.6 wt% and 36.2 wt%, respectively. It was observed that the tar condensation problem was dominated by the components and the molecular weight of tar compositions instead of the tar concentration. These findings are useful for optimizing the gasification process and developing the gas cleaning system for a small downdraft gasifier.

Lignin precursors of coniferin and syringin were synthesized and used to prepare guaiacyl-type and guaiacyl-syringyl-type oligomeric compounds (designated here as dehydrogenation polymers DHP-G, DHP-GS) via bulk method. The carbon 13 nuclear magnetic resonance spectroscopy (13C-NMR) spectra indicated that both DHPs contained typical lignin substructures. The DHPs were extracted sequentially with petroleum ether, ether, ethanol, and acetone to obtain eight fractions (F11 to F14 and F21 to F24). The 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide (MTT) experimental results showed that the growth of cervical cancer cells was inhibited by the two ether-soluble fractions F12 and F22, with semi-inhibitory concentration (IC50) values of 81.60 ± 9.30 and 103.24 ± 14.09 μg/mL, respectively. The bioactive compounds in F12 and F22 were separated by a preparative chromatography method. Ten bioactive compounds (G1 to G5 and GS1 to GS5) were obtained. Mass spectroscopy analysis revealed the following chemical structures: G1, β-5 G-type dimer; G2, (β-5)(β-5) G-type trimer; GS1, β-5 GS-type dimer; and GS2, (β-O-4)(β-5) GS-type trimer. The compounds had inhibitory effects on cervical cancer cells. The syringyl aromatic ring decreased the anticancer activity of DHP, and the β-O-4 linkages did not contribute to the anticancer activity. It was also found that the carboxyl groups contributed to the anticancer activity of DHP.

The effect of waste tar from particle board factories was investigated relative to some physical and biological resistance properties of Scots pine (Pinus sylvestris) and beech (Fagus orientalis) woods. Solutions were prepared by dissolving waste tar in ethanol:toluene (1v:1v) in concentrations of 5%, 10%, 15%, and 20%. These solutions were forced deep into the Scots pine and beech woods under vacuum and pressure (deep treatment, DT). In addition, surface coating (SC) was applied by spreading 96% waste tar on the wood surfaces after treatment. Deep-treated and surface-coated (DT+SC) wood samples were exposed to the wood-decay fungi Trametes versicolor L. and Neolentinus lepideus Fr. for 12 weeks. At the same time, sample blocks were tested against wood-destroying house borer (Hylotrupes bajulus) larvae for 16 weeks. Total phenolic content, water uptake, water-repellent efficiency, and surface contact angle were tested. Although a mean mass loss resulting from T. versicolor of 31.1% was seen in the Scots pine control samples, only 3.87% mass loss was found with a concentration of 20% (DT + SC). The H. bajulus larvae mortality rate was 80% in the Scots pine wood samples deep-treated with 20% waste tar.

Polyaniline (PANI) is a conductive polymer that allows cellulose aerogels to achieve high electrical conductivity. However, aerogels containing PANI alone display a low mechanical stability. Graphene nanosheets (GNS) display high conductivity and mechanical strength but are prone to agglomeration, hindering their electroactive sites. To avoid shortcomings of the individual components, a composite aerogel was prepared via addition of graphene nanosheets (GNS) and PANI to a suspension of cellulose nanofibril (CNF). Transmission electron microscopy and scanning electron microscopy were used to analyze the structural morphology of the CNF/GNS/PANI aerogel. The electrochemical properties were analyzed using a four-probe conductivity meter, cyclic voltammetry, galvanostatic charge-discharge tests, and electrochemical impedance spectroscopy. A 2:2:1 ratio of CNF/GNS/PANI provided optimal structural and electrochemical results. Incorporation of PANI through in-situ polymerization for 6 h resulted in uniform mixing of the three components. The CNF/GNS/PANI composite aerogel displayed a high electrical conductivity with a specific capacitance of 375 Fg-1 at a current density of 0.2 Ag-1. As a base binder and dispersant, CNF made use of PANI as a conductive medium and of GNS as a conductive reinforcing medium to form a flexible nanocellulose composite conductive material with increased stability and improved performance.

Wood drying is an important stage in the woodworking process. After drying, wood is subject to a re-sawing process, for which a high quality surface, low material loss, and high efficiency are often required. In this paper, forecasted values were presented of cutting power for the re-sawing process of pine and beech wood that were dried with four different methods. Forecasting of cutting power for an industrial band saw machine that works daily in a Polish sawmill was determined. Values of cutting power were forecasted for a full range of feed speeds of the analyzed band saw machine. The achieved results allowed the observation of noticeable changes in the forecasted cutting power for a given sawing process as a function of the wood drying method applied. Significant changes were observed for pine wood, especially between air-dried pine wood and wood dried with warm air-steam mixture, and between pine wood dried in a conventional kiln and with warm air-steam mixture.

The increase in activities in the wood-based industries has contributed greatly to deforestation, and this has consequently led to the development of new materials to substitute for the felling of trees. In this study, red Ironwood (Lophira alata) chips and cassava starch were used for the production of particleboard. Chip sizes of 0.85 and 1.7 mm and the dosage and types of binders (cassava starch, urea formaldehyde, and glutaraldehyde-modified cassava starch) were the variables. The ratio of wood chips to the binders was 1.0:1.5. The boards were formed in rectangular moulds. Water absorption, thickness swelling, flexural tests, and material characterisation (scanning electron microscopy) were performed. The data were subjected to analysis of variance. The panels produced with modified cassava starch had the best mechanical properties with the modulus of elasticity ranging from 5.9 to 32.3 N/mm2 but had a higher thickness swelling values ranging from 3 to 59.4%. There was a significant difference (p < 0.01) between the boards manufactured using plain starch and modified starch. These results showed that modified cassava starch is a better binding agent than plain cassava starch in terms of panel MOR and MOE. The developed particleboard can be used for indoor paneling, partitioning, and ceilings.

Musa acuminata (Cavendish) unripe peel is a waste product of limited value that is generated in large quantities. Therefore, the conversion of this by-product into a more useful product is necessary. This study aimed to optimize the ultrasound-assisted extraction (UAE) parameters, including extraction temperature, extraction time, preincubation time, and solid to solvent concentration from an unripe banana peel using response surface methodology (RSM). The UAE parameters affected the recovery of yield, total tannin content, and flavonoid content with antioxidant activities. The optimum extraction temperature was 60 °C with an optimum extraction time of 30.0 min. Additional optimum conditions included 25.0 min for the preincubation time and 5.03% solid to solvent concentration. The optimum yield processing parameter of crude extract of unripe peel was 14.9% and the total tannin content was 119.2 mg TAE per g of the sample. Furthermore, the content of flavonoid was 29.0 mg RE per g of the sample and the DPPH and ABTS scavenging activity was 80.8% and 84.7%, respectively. The results from this study can be used for further isolation and purification of tannin from unripe banana peel. Further explorations could lead to the possible application of bio-based polymer in packaging materials.

Wood-plastic composites (WPCs) have become one of the most remarkable materials for construction in recent years. Along with high resistance against biological threats, the high mechanical properties are also desired from WPCs as well. In this study, polypropylene (PP) and polyethylene (HDPE) based flat-pressed WPC specimens were reinforced with woven fiber fabric to gain higher mechanical properties. Woven fabrics were located 20% (w/w) below for both surfaces. Carbon fiber and glass fiber woven fabrics, known to have high mechanical properties, were preferred to improve screw withdrawal resistance (SWR) of WPC. Specimens were produced with different wood flour contents (40, 50, and 60%). Results indicated that the increase of SWR reached up to 83%. The highest increase was obtained from carbon fiber for PP, while it was glass fiber for HDPE fabric. The coupling agents had a positive effect on SWR. This study also showed that PE based WPCs had higher SWR compared to PP based ones. Moreover, as wood flour content increased, SWR decreased. The surface roughness of WPCs was also investigated. Contrary to SWR, the wood flour content positively affected the surface roughness; i.e., as wood content increased, surface roughness of WPCs increased. The structure of specimens were also examined using SEM.

A method was developed to reduce isothiazolinone (MCI/MI) leaching from treated bamboo, thereby extending the service life of bamboo. In this study, the self-healing coatings were prepared by incorporating 10 to 12 wt% microcapsules of urea-formaldehyde resin (UF)/tung oil into conventional polyurethane varnish and acrylate varnish. In the leaching test, the self-healing coatings outperformed the control coatings. Compared with the control coatings, the average leaching rates coated by the polyurethane and acrylate self-healing coatings were reduced by 6.22% and 6.29%, respectively. In impact damage and adhesion strength tests, the ability of the self-healing coatings to withstand damage was close to the control coatings. The results indicated that self-healing coating is a feasible method to reduce the leaching of MCI/MI from treated bamboo.

Kenaf (KNF) was treated at room temperature with the amino acid lysine. The surface treatment of KNF using lysine was studied for the first time on prepared composites with linear low-density polyethylene, poly(vinyl alcohol), and kenaf. The LLDPE/PVOH/KNF composites with different loadings of lysine-treated and untreated KNF were studied at levels of 10, 20, and 40 parts per hundred resin (phr). The melt mixing of all the composites were prepared by using an internal mixer for 10 min at a temperature and rotor speed of 150 °C and 50 rpm, respectively. The results showed that tensile strength and tensile modulus were improved for the lysine-treated KNF composites compared to the untreated KNF composites. Fourier transform infrared (FTIR) spectroscopy revealed the presence of protonated amino (NH3+) and carboxylate (COO-) groups in the LLDPE/PVOH/KNF composites after the lysine treatment. Scanning electron microscopy analysis showed good adhesion between the lysine treated KNF and the LLDPE/PVOH matrices. Thermogravimetric analysis (TGA) showed that the lysine treated KNF composites possessed a higher thermal stability than the untreated KNF composites.