2022, Vol. 7, No. 4

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Review Article
Production of solid fuels by hydrothermal treatment of wastes of biomass, plastic, and biomass/plastic mixtures: A review
Qingxin Zheng, Zixian Li, Masaru Watanabe
2022, 7(4): 221-244. doi: 10.1016/j.jobab.2022.09.004
Traditional disposal methods of biomass and plastic waste, such as landfill, combustion, and compost, no longer meet the requirements of carbon reduction, carbon neutrality, and sustainable society due to low utilization efficiency and severe pollution. As a green, efficient and environmentally-friendly method, hydrothermal technology has been paid much attention to and has already been applied to recycle or reuse various plastic and biomass wastes. No matter for the single or mixed type of waste, it is expected to achieve efficient recycling and obtain value-added products through the hydrothermal process. This review summarized the basic knowledge of hydrothermal technology and the possible reaction mechanism of biomass and plastics under hydrothermal conditions and listed the previous reports on the application of hydrothermal technology for converting wastes of biomass, plastic, and biomass/plastic mixtures to solid fuels. Moreover, regarding the future of hydrothermal technology, four points related to reaction mechanism, synergistic effect, catalysis, and scaled-up application, were provided for consideration.
Review Artcile
Nanocellulose and its derived composite electrodes toward supercapacitors: Fabrication, properties, and challenges
Junlei Xiao, Huiling Li, Hua Zhang, Shuijian He, Qian Zhang, Kunming Liu, Shaohua Jiang, Gaigai Duan, Kai Zhang
2022, 7(4): 245-269. doi: 10.1016/j.jobab.2022.05.003
With the increasing demand for sustainable energy storage systems, the development of various advanced materials from a renewable source is imminent. Owing to the advantages of high specific surface area, unique nanostructure, modifiability, and excellent mechanical strength, nanocellulose integrated with other conductive materials, such as nanocarbons, conducting polymers, and metal oxides, has been emerged as promising candidate materials for green and renewable energy storage devices. Besides, nanocellulose-derived carbon materials with good electrical conductivity and tunable microstructures can be fabricated via simple carbonization, which has been widely used as supercapacitor electrode materials. Herein, we present a comprehensive review that focuses on the development of nanocellulose materials for sustainable energy storage, particularly on supercapacitors. The fabrication strategies of nanocellulose-derived hybrid materials are first presented and summarized, followed by highlighting the use of natural nanocellulose for constructing composite electrode materials including two-dimension film electrodes, and three-dimension aerogel electrodes for supercapacitors. In addition, the possible limitations and potentials of nanocellulose in supercapacitors are outlooked.
Research Artcile
Microwave torrefaction of empty fruit bunch pellet: Simulation and validation of electric field and temperature distribution
Peter Nai Yuh Yek, Sieng Huat Kong, Ming Chiat Law, Changlei Xia, Rock Keey Liew, Teck Sung Sie, Jun Wei Lim, Su Shiung Lam
2022, 7(4): 270-277. doi: 10.1016/j.jobab.2022.09.002
Microwave simulation is significant in identifying a reactor design allowing the biomass to be heated and processed evenly. This study integrated the radio frequency and transient heat transfer modules to simulate the microwave distribution and investigated the performance of microwave heating in the cavity. The simulation results were compared with the experimental findings using the finite element analysis software of COMSOL MULTIPHYSICS to predict the temperature profile and electric field of microwave in the biomass (empty fruit bunch pellets). The higher temperature distribution was observed at the bottom and centre section of the empty fruit bunch pellet bed in the reactor, showing the uniqueness of microwave heating. According to the simulation results, the temperature profile obtained through the specific cavity geometry and dielectric properties agreed with the experimental temperature profile. The simulated temperature profile demonstrated a logarithmic increase of 120 ℃/min at the first 50 s followed by 50 ℃/min until 350 s. The experimental temperature profile showed three different heating rates before reaching 300 ℃, including 78.3 ℃/min (50–120 ℃), 30.6 ℃/min (121–250 ℃), and 105 ℃/min (250–300 ℃). The results of this study might contribute to the improvement of microwave heating in biomass torrefaction.
Alternative wood treatment with blends of linseed oil, alcohols and pyrolysis oil
Jost Ruwoldt, Kai Toven
2022, 7(4): 278-287. doi: 10.1016/j.jobab.2022.07.002
Linseed oil is a common wood treatment agent, which is often blended with naphthenic oil during its application. In this study, we developed new types of linseed oil blends, where the naphthenic oil was substituted with alcohols and pyrolysis oil. As miscibility tests revealed, linseed oil can be blended indefinitely with primary alcohols containing three carbon atoms or more. In addition, kinetic stability of three-component-mixtures was found, which comprised linseed oil, alcohol and pyrolysis oil. The developed blends were further tested for their viscosity and rate of solvent evaporation. At last, trial impregnations of wood were done to test this new treatment agent. The uptake of treatment oil and the effect on water repellency varied, and substituting white spirit with propanol and pyrolysis oil showed potential. The latter were miscible with 50% (wt) linseed oil at concentrations of 37.5% 1- or 2-propanol and 12.5% pyrolysis oil. Compared with the reference case, treatment with this agent markedly decreased the water-uptake of the wood. Our study hence attributes great potential to the newly developed linseed oil blends, which may introduce additional product characteristics and generate value to byproducts via pyrolysis.
Evaluation of ligninolytic activity in spent mushroom substrate from four cultivated mushrooms
Ana Marión Pérez-Chávez, María Melisa Alberti, Edgardo Albertó
2022, 7(4): 288-294. doi: 10.1016/j.jobab.2022.09.001
Spent mushroom substrate (SMS) is an abundant residue generated by the mushroom industry, which is mostly discarded. In this study, the SMS of four cultivated mushrooms were evaluated as potential sources of ligninolytic enzymes. Pleurotus ostreatus, P. eryngii, P. djamor and Ganoderma lucidum were cultivated in two different substrates to determine growth, mushroom yields and ligninolytic activity of laccase (Lac) and manganese peroxidase (MnP). Maximum activities in the SMS were 3.731 U/g Lac and 0.191 U/g MnP, both for P. eryngii. Colonized mushroom substrates were also analyzed, and higher activities were found in almost all samples. A correlation test between mushroom yields and ligninolytic activities of each culture was made, and we found that high enzymatic activity in the substrate did not result in high mushroom productivity or vice versa. The SMS was a good source of ligninolytic enzymes. Enzymatic activity depended on the mushroom species and its affinity to the substrate, and it was not influenced by the mushroom yields. Production of mushrooms in diverse lignocellulosic substrates is gaining interest, and obtaining ligninolytic enzymes from residual SMS is an excellent alternative in the circular economy concept.
Preparation and properties of hydrophobic and transparent wood
Linhu Ding, Xiaoshuai Han, Lian Chen, Shaohua Jiang
2022, 7(4): 295-305. doi: 10.1016/j.jobab.2022.02.001
Natural wood (NW) was treated with sodium chlorite to obtain delignified wood (DW) in this study, then epoxy was impregnated to get transparent wood (TW), and finally the TW was coated with perfluorodecyltriethoxysilane (FAS) to acquire hydrophobic and transparent wood (HTW). The hydroxyl group generated by the hydrolysis of the FAS and the hydroxyl group of the epoxy underwent a dehydration condensation reaction to generate a Si–O–C bond, while the FAS molecules were also dehydrated and condensed to form a Si–O–Si bond according to Fourier transform infrared (FT-IR) spectroscopy and X-ray photoelectron spectroscopy (XPS). Therefore, the mechanical property and thermal stability of the HTW were better than the TW based on their tensile tests and thermogravimetric analysis (TGA). Due to the large reduction of hydroxyl in epoxy, the hydrophobicity of the HTW was greatly improved compared with the TW, and their contact angles were 113° and 77°, respectively. The results of scanning electron microscopy (SEM) showed that epoxy was filled in the voids of wood. In addition, the coating of the FAS did not obviously reduce the transmittance, and the transmittance of the TW and HTW was 69% and 67% at 750 nm. All in all, the HTW has potential for application in transparent decoration.
Physico-mechanical characteristics of bast fibres of Sesamum indicum and Sesamum radiatum for bioprospecting
Ancy S Watson, Suhara Beevy S
2022, 7(4): 306-319. doi: 10.1016/j.jobab.2022.07.003
Natural fibres are renewable, inexpensive and biodegradable sources of sustainable materials from plants or animals. Bast fibres, as the notable natural fibres, are gathered from the outer cell layers of the stem of plant. Mature and young bast fibres from two species of Sesamum, namely Sesamum indicum L. and S. radiatum Schumach. & Thonn. were extracted through traditional water retting technique and analyzed for their physical, mechanical and chemical attributes. Anatomical studies revealed polygon shaped phloem (bast fibre) cells with small lumen were similar to jute, in terms of architecture, and bagasse, in terms of lumen size. Upon extraction and subsequent drying, the young stems of S. radiatum were found to yield more bast fibres by mass compared with the rest of the Sesamum samples, that was, 0.59 g (dry weight) of bast fibres from 100 g (fresh weight) of stem. According to stereo microscopic images, the mature S. radiatum fibres had rougher edges than the rest. Both S. indicum and S. radiatum fibre surfaces also seemed to have pores, according to scanning electron microscopy (SEM) images. The porosity appeared to get more pronounced as the plants got older. The Sesamum bast fibres were also found to be extremely hydrophilic with a high-water retention value. The fibres obtained from S. radiatum were determined to be suitable for the textile industry due to their light colour, ideal diameter and length, and water-holding capacity that matched the requirements of fabric manufacturing. Even in the absence of a mordant, the mature fibres showed a significant degree and evenness of Alizarin dye attachment, which might be correlated to the increase in fibre surface roughness with fibre maturity. These fibres were also discovered to be comparable with jute in terms of phloem cell shape (polygonal), diameter (13–15 m), tenacity (12.86–32.54 gf/(g·km–1)), and linear density (2.5–3.3 g/km). It suggested that they might find industrial applications if further research were to be done.
Dynamical mechanical behaviors of rubber-filled wood fiber composites with urea formaldehyde resin
Feiyu Tian, Xinwu Xu
2022, 7(4): 320-327. doi: 10.1016/j.jobab.2022.05.004
Wood composites glued with thermosetting synthetic resins tend to show inadequate damping performance caused by the cured resinous matrix. Waste rubber maintains prominent elasticity and is feasible to be an optional modifier. To that end, composite panels of granulated tire rubber (GTR) powders and thermal-mechanically pulped wood fibers were fabricated in this study. Urea formaldehyde (UF) resin was applied as the bonding agent (10% based on wood/rubber total weight). Dynamical mechanical analysis (DMA) was conducted to disclose the thermo-mechanical behaviors of the rubber-filled wood fiber composites. Influence of two technical parameters, i.e., GTR powder size (0.55–1.09 mm) and addition content (10%, 20% and 30% based on wood/rubber total weight), was specifically discussed. The results showed that storage modulus (E') of the rubber-filled composite decreased while loss factor (tan δ) increased monotonously along with elevated temperature. A steady "plateau" region among 110–170 ℃ was found where both E' and tan δ keep constant. Accordingly, tan δ showed two peak values at 103–108 and 231–233 ℃ due to glass transition of lignin and thermal degradation of hemicellulose, respectively. Addition of rubber fillers resulted in lower bending and internal bonding strengths as well as storage modulus values. When the temperature was above 183 ℃, all the rubber-filled composites showed higher tan δ values than the control. The findings above fully demonstrate the improved damping performance of the UF-bonded wood fiber composites on account of rubber component. Further work is still needed to optimize the rubber/fiber interfacial bonding strength.
Composition analysis and antimicrobial activity of essential oil from leaves of Laurus nobilis grown in Oman
Siham Saleh Al-Abri, Sadri Abdullah Said, Salem Said Al Touby, Mohammed Amzad Hossain, Jamal Nasser Al-Sabahi
2022, 7(4): 328-334. doi: 10.1016/j.jobab.2022.09.003
Traditionally, Laurus nobilis is used for the treatment of earaches and skin rashes as well as rheumatism. The most common technique to isolate the oil is hydro-distillation and steam-distillation. The investigation presented in this paper was aimed to unravel the antimicrobial activity and chemical composition of essential oil in the leaves of L. nobilis grown in Oman. The essential oil was extracted from the leave of the selected plant species by hydro distillation using Clevenger type apparatus. The antimicrobial assay was done by disc diffusion methods against three bacterial strains, Staphylococcus aureus, Pseudomonas aeruginosa and Escherichia coli, and one fungal strain: Candida albicans. The isolated essential oil was analyzed by gas chromatography-mass spectrometry (GC-MS). The percentage yield of the essential oil was 0.064% (w/w). The essential oil was found actively against the applied bacterial and fungal strains. The highest activity was found against S. aureus and the lowest was against E. coli, and the order was S. aureus > P. aeruginosa > E. coli. The essential oil was also active against the fungus C. albicans. The range of inhibition zones was 6–14 mm. The results of GC-MS analysis showed (E)-β-caryophyllene to be the major component about 59.62%. Other major components included α-selinene (14.03%), α-humulene (8.65%), β-selinene (4.99%), and α-pinene (4.98%). In addition, several minor components were found in the essential oil of L. nobilis. Based on the experimental results, it showed that the plant species that grown in Oman were a potential source of therapeutic agents. In conclusion, the essential oil and the plant could be used as natural and potential therapeutic agents to treat earaches, skin rashes, and rheumatism.