Volume 14 Issue 3

A modified charcoal kiln was developed for both thermal therapy and charcoal production. The design of a modified kiln for thermal therapy focused on safety and cleanliness, plus the production of good quality charcoal. Two entrances in the kiln were designed for convenient charcoal production and thermal therapy. A barrier wall designed for noxious gases was installed between the adjoining charcoal kilns for safe thermal therapy. Additionally, a fine dust collector was installed to remove the fine dust generated during charcoal production. To verify the safety of the kiln, fine dust and harmful gases, such as carbon monoxide (CO), carbon dioxide (CO2), nitrogen dioxide (NO2), and radon (Rn), were measured after the charring process. The quality of the charcoal produced in the thermal therapy kiln was also examined. To evaluate charcoal quality, some physical properties and results from a proximate analysis were evaluated using Korean standards. The measurements of harmful substances and fine dust in the modified charcoal kiln met the criterion of the Ministry of Environment Clean Air Conservation Act in Korea. In addition, there were no noticeable differences in the monthly charcoal characteristics prepared from the thermal therapy kiln, and the charcoal characteristics also met the reference values of the Korea Forest Service.

Magnesium-cemented straw composites (MCSC), as an environmentally friendly and energy-conserving material, have an enormous potential to achieve favorable properties, especially for bending strength. In this study, rice straw powder, fly ash, and magnesia cement (MC) were mixed to prepare MCSC. An optimization formula for composites was found to promote the bending strength by 490% from 0.28 MPa (empty sample) to 13.89 MPa (composites). From the variance results, the molar ratio of MgO/MgCl2 (M value) and addition of rice straw (As) noticeably impacted the compressive and bending strengths. The optimum schemes were:10% (weight ratio) for rice straw, 10% for fly ash (Af), 5 for M value, 12 to 15 for H value (the molar ratio of H2O/MgCl2), 20-mesh of straw powder (Ms), and 28 days for the curing time (T). Considering the different use of MCSC, if the weight vector was 0.7 (compressive strength) and 0.3 (bending strength), the optimized formula was M5H25Ms20T15daysAs10%Af10%. If the weight vector was 0.3 (compressive strength) and 0.7 (bending strength), the optimized formula was M5H10Ms20T3daysAs10%Af10%.

Peatlands require soil improvement to be suitable for cultivation. Creating eco-friendly and cost-effective carbon sinks in peatlands originated from peat production has several benefits. For this purpose various valuable biomass can be used by utilizing industrial by-products also as soil conditioners and fertilizers. For example, the addition of such materials has potential to transform peat bogs, which otherwise would slowly release methane, into productive cultivated areas. The rehabilitation of peat bogs from unused land into various agricultural and forestry areas is also a viable business activity. The examined industrial by-products could have many agricultural applications in non-food potato production, wherein monoculture causes problems such as condensed soil, lost humus or soil organic matter, and reduced nutrient retention capacity, leading to increased leaching of nutrients and negative impacts on the environment. Five industrial by-products were examined in this study as soil conditioners and fertilizers: fiber sludge, biocarbon, hygienic biodigestate, paper mill sludge, and gypsum waste. Based on the results of a nutrient content analysis, hygienic biodigestate and fiber sludge were the most effective fertilizers.

The suitability of using milled sunflower husks as a wood substitute for producing medium-density particleboard was investigated. Additionally, the impact of the adhesive type and the amount used on the properties of the panels were evaluated. Urea-formaldehyde (UF) in three commercial variants (UCL, U96, and AG), phenol-formaldehyde (PF), modified melamine urea-formaldehyde (VM), and polymeric diphenylmethane diisocyanate (pMDI), as well as mixtures of VM/AG and of PF/pMDI, were used to manufacture the panels. The adhesive content was varied between 3% and 6% for pMDI, and from 9% and 12% for the other adhesives. Higher thickness swelling (TS) and water absorption (WA) values were observed with the UF panels compared with the PF and pMDI panels. The lowest mechanical strength properties were observed for the UF panels, with the commercial variants ranking (from highest to lowest): UCL > VM/AG > U96. Increasing the adhesive content level resulted in better dimensional stabilities and mechanical properties for the pMDI and PF panels, which met some of the performance requirements for interior uses prescribed by the relevant standard.

Due to environmental concerns and the proposed global policies for reducing carbon emissions, lignocellulosic biomass is an attractive renewable feedstock for biofuel and biochemical production. Wood residues from the plywood industry have a lignin content as high as 30.7% ± 0.1%. Diluted acid pretreatment followed by enzymatic hydrolysis is often employed to release sugar from lignocellulosic biomass. A high lignin content limits the accessibility of cellulose. Lignin also binds with enzymes, which reduces the enzymatic hydrolysis efficiency. In this study, different concentrations of polyethylene glycol (PEG) 6000 were used as an additive to inhibit the detrimental effects caused by lignin. The optimal dosage was 1 g/L, which increased the glucose production to 35.8% and 26.6% for solid-to-liquid ratios of 2% and 20%, respectively. The results suggest that PEG 6000 is a suitable potential additive for increasing the bioethanol production from plywood residue in upscale operations.

Rice husk flake (RHF) engineered wood panels were manufactured from unmodified rice husk flake in its original form and epoxy adhesive. One of the main objectives for using the original form of RHF was to minimize the manufacturing cost and processing time for treating the flake. Two types of short randomized reinforcements namely carbon fiber (CF) and glass fiber (GF) were employed to enhance the mechanical properties. The optimal compression pressure for the manufacturing process was 120 kgf/cm2. The short randomized CF and GF reinforcements were employed and investigated. An outstanding enhancement in mechanical performances was observed. At the given short fiber content, the CF showed superiority as reinforcement to the GF. The adhesive exhaustion was evidenced when the reinforcement loading exceed 40 wt%. In the combined CF/GF short fibers at constant 40 wt% loading, the mechanical performance was reduced by increasing the GF portion.

Thermosetting epoxies are low-density polymers with excellent adhesion, mechanical properties, and resistance to environmental degradation. They are widely used as molds and castings for manufacturing, protective coatings, and reinforcement material for aircraft. However, polymer brittleness is a major disadvantage preventing its widespread application. The addition of filler materials such as nanoparticles has attracted considerable attention. Using reinforcement materials for biocomposite derived from a natural, renewable and sustainable material will lower the manufacturing cost for epoxy composites. This study investigated the physical and mechanical properties of epoxy composites reinforced with amorphous and crystalline silica. The amorphous and crystalline silica were obtained by the precipitation method from the carbonization of rice husk at 700 °C and 1000 °C for 6 h, separately. The epoxy resin was mixed with 5 wt%, 10 wt%, and 15 wt% concentrations (by weight) of amorphous and crystalline silica, separately. Silica 10 nm to 30 nm in size was obtained, as observed by scanning electron microscopy (SEM). The epoxy nano-crystalline silica composite had a significantly lower thickness swelling value compared to the epoxy nano-amorphous silica composite. However, the epoxy nano-crystalline silica composite had significantly better mechanical properties.

The effects of lysozyme (LZM) and freeze-thaw conditioning, alone or in combination, on sludge dewatering performance were comparatively investigated. After the optimization of the dewatering conditions using response surface methodology (RSM), the co-conditioning exhibited obvious superiority to the separate conditioning in improving the dewaterability of municipal sludge, with the capillary suction time (CST) and the water content (W) of the dewatered sludge reduced to 12 ± 0.5 s and 52.0% ± 0.4% from 61.8 s and 73.0%, respectively. The co-conditioning appeared not only to destroy the structure of extracellular polymeric substance (EPS) and microbial cell wall by virtue of enzymatic conditioning, but it formed larger particles and compact sludge floc structure with the help of freeze-thaw conditioning. Additionally, the bound water content of sludge decreased by 47.5% after co-conditioning, consistent with the enhancement in sludge dewaterability. All the results showed that LZM in combination with freeze-thaw conditioning had a great potential in sludge reduction, providing more opportunity of resource utilization for the dewatered sludge.

Numerous dyes and fluorescent compounds, as reported in the literature, exhibit specificity in the staining of materials associated with lignocellulosic fibers and their chemical components, including cellulose, hemicellulose, and lignin. Such effects long have provided analysts with convenient ways to identify cellulosic fiber types, products of different pulping methods, degrees of mechanical refining, estimates of accessibility to enzymes, and localization of chemical components within microscopic sections of cellulosic material. Analytical staining procedures allow for the facile estimation or quantification using simple methods such as light microscopy or UV-vis spectroscopy. More recent developments related to confocal laser micrometry, using fluorescent probes, has opened new dimensions in staining technology. The present review seeks to answer whether the affinity of certain colored compounds to certain cellulose-related domains can improve our understanding of those stained materials – either in terms of their fine-scale porous structure or their ability to accommodate certain colored compounds having suitable solubility characteristics. It is proposed here that successful staining ought to be viewed as being a three-dimensional phenomenon that depends on both the physical dimensions of the colored compounds and also on functional groups that influence their interactions with different components of lignocellulosic materials. Published information about the mechanisms of staining action as well as characteristics of different stain types is reviewed.

Adhesives, flame-retardant chemicals, and paints are used in engineered wood products (EWPs) to increase some of the properties of wood. Most of the engineered wood composites, including plywood, particleboard, and fiberboard, used as furniture components contain formaldehyde resins as an adhesive. The International Agency for Research on Cancer (IARC) added formaldehyde to the list of human carcinogens (Group 1) in 2004. Flame-retardant chemicals are semi-volatile organic compounds that can migrate from the products to the air. There are developmental neurotoxic effects from flame-retardant additives, among which polybrominated diphenyl ethers (PBDEs) are commonly used in EWPs. The flexibility and durability of plastics are increased using phthalates, which are a class of synthetic chemicals, by adding them to the polyvinyl chloride (PVC) that is used in the wood-plastic composites (WPC). Formaldehyde, PBDEs, and phthalates are toxicants that are commonly present in value-added furniture products. This review summarized the toxic effects of these chemicals from the aspect of human health and from the perspective of green products.