Journal of Material Cycles and Waste Management最新文献

The adequacy of the number of samples extracted using the central limit theorem (CLT) was evaluated for 11 excavation waste items at the S landfill site in the Seoul metropolitan area of Korea. The relative error range, which is the error-capable range for the estimated average value for each analyzed item, was the largest at 22.2% hemicellulose, 19.9% sulfur, and 14.7% cellulose, and the smallest at 3.4% combustibility. At the 95% reliability level and 10% relative error range, the number of samples of N, S, hemicellulose, and cellulose was insufficient, and at the 5% relative error range, the number of samples was insufficient for all items, except for moisture and combustibility. It was determined that it would be practically impossible to secure excavated samples below 3% error range. The results of this study show that CLT is useful for evaluating the reliability of the results of landfill collection sample analysis and determining the appropriate number of samples.

The recycling of end-of-life automobiles has become one of the most important issues facing various countries. At present, the main approach to processing these automobiles involves recycling, which, after dismantling and crushing, creates residual materials known as automotive shredder residue (ASR). ASR is mainly recycled through incineration or landfill disposal, which can cause environmental pollution and waste of resources. Pyrolysis, an emerging ASR treatment method, is widely considered an ideal alternative. While traditional electric pyrolysis has the advantages of high energy consumption and low heating rate, microwave pyrolysis offers higher heating coefficient, lower energy consumption, and greater environmental protection. Therefore, based on the microwave pyrolysis technology, this work investigates the thermal analysis kinetics and pyrolysis of whole components of ASR. The results revealed that the average activation energy of ASR reached 93.476 kJ/mol, as calculated using the Flynn–Wall–Ozawa (FWO) method, and the reaction model was close to the diffusion-control model. Furthermore, the residence time and heating temperature have a great influence on the product composition and yield and affect the occurrence of secondary reactions, and the microwave power influences the rate of ASR cracking and the rate of energy transfer of the products, in which the microwave power has the greatest influence on the gaseous products. The H₂ content increased from 1.097 to 2.565 wt.%, while the methane content increased from 0.781 to 2.687 wt.%. Moreover, the yield of aromatic hydrocarbons in the liquid product increased with the increase of residence time, and the aromatic hydrocarbon product content increased from 31.67 to 44.39 wt.%. Finally, the increase in heating temperature decreased the yield of aromatic hydrocarbons in liquid products, while the increase of microwave power initially decreased and then increased the yield of aromatic hydrocarbons in liquid products. The findings of this work provide theoretical and experimental references for ASR microwave pyrolysis.

Currently, the footwear industry faces a great environmental problem, since its production system generates large volumes of chrome-tanned leather scrap. Given this scenario, it seeks to promote the circular economy in this area with the aim of minimizing the final disposal of waste in landfills through proposals for the reuse of this material. This work aims to study the incorporation of leather waste from the footwear industry in the production of particleboards. Based on the obtained results, the boards with up to 20 wt% leather showed a decrease of around 15 and 30% in the MOR and MOE, respectively. On the other hand, the water swelling tests show that leather presented better dimensional stability than wood, and its incorporation reduces the thickness swelling of the panels. The water resistance of the wood/leather boards is given mainly by the average pore diameter, where the pores of the leather were 500% larger than those of the wood. Finally, according to the thermal properties leather showed better thermal stability than wood, since the mass loss at 400 °C was 55% for leather and 80% for wood. However, the incorporation of leather up to 20% did not enhance the fireproof properties of the panels. Therefore, the incorporation of low leather content to particleboards could be considered as a sustainable alternative for a residue with high environmental impact.

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In this study, we focused on the chemical recovery of carbon fibres from epoxy matrix composite wastes. First, we laminated and cured composite panels from carbon fibre-reinforced prepregs (CFRP) and then aged them under controlled circumstances to simulate their lifespan. Fibre recovery was then carried out by hydrogen peroxide (H₂O₂) at 6 bar and between 60 and 150 °C. We chose this material because it results in a rapid, cost-efficient, and environmentally friendly process. Besides, we expected it would allow the removal of the polymer matrix without fragmenting the fibres. We aimed to investigate the matrix decomposition in H₂O₂, the purity of the obtained fibres and the retention of their mechanical properties. The purity and the structure of the obtained carbon fibres were then characterised by using scanning electronic microscopy (SEM), X-ray diffraction (XRD), thermogravimetry (TGA), infrared spectroscopy (IR), and X-ray photoelectron spectroscopy (XPS). We found that H₂O₂ was effective in recovering carbon fibres, especially at 150 °C. The mechanical results showed that the retention of the modulus was complete, while the tensile strength and elongation at break decreased by 35% due to microstructural damages. The fibres still have better properties than glass or basalt fibres; therefore, good-quality composites can be made using them.

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This study looked at the effects of different extraction protocols on the biochemical properties of compost extract (CE) and its effect on the growth of Dahlia pinnata Cav. (dahlia), Consolida ajacis (L.) Schur (delphinium), and Centaurea cyanus L. (cornflower). Composted green waste (CGW) extract was prepared at compost-to-water ratios of 8:1, 8:2, 8:3, and 8:4, employing preservation methods of sterilization and refrigeration, or direct refrigeration. Sterilized CE with compost-to-water ratio of 8:3 exhibited superior biochemical properties (pH value, electrical conductivity, nutrient contents, and enzyme activities). The stem width, root length, flower number, root-shoot ratio, and total chlorophyll contents of dahlia cultivated in the optimal CE significantly increased by 33%, 44%, 115%, 110%, and 28%, respectively; the stem width, root length, flower number, root-shoot ratio, and total chlorophyll content of delphinium in the optimal CE greatly increased by 39%, 25%, 76%, 31%, and 31%, respectively; the stem width, root length, flower number, root-shoot ratio, and total chlorophyll content of cornflower in the optimal CE remarkably increased by 29%, 27%, 108%, 44%, and 17%, respectively. Therefore, the results indicated that CE at a compost-to-water ratio of 8:3, coupled with sterilization and refrigeration effectively promoted plant growth, offering a superior alternative to CGW.

Glass fibre composites have become widely used in many applications, notably in wind turbine rotors. Fluidised bed valorization has demonstrated glass fibre recycling from waste composites, enabling reuse in traditional composite manufacturing technologies. This paper intendeds to inform long-term strategies for glass fibre composite waste by identify operating conditions that can optimise environmental and economic metrics for fluidised bed valorization. Experimentally derived operating parameters were integrated into energy models for a commercial-scale recycling process. An environmental assessment was conducted to compare the global warming potential of recycled glass fibres with that of virgin materials. In addition, a technoeconomic analysis was performed to assess the viability of the recycling technology at scale. The findings indicate that recycled glass fibre can achieve a global warming potential of less than 2 kg CO2e. per kg, contributing to a net reduction in greenhouse gas emissions when replacing virgin glass fibre. Furthermore, the economic analysis showed that a recycling facility with a capacity of just 10 kt per year could produce recycled glass fibre at a cost of $0.61/kg, significantly lower than the cost of virgin glass fibre. Overall, fluidised bed valorization presents an environmentally and economically sustainable solution for managing glass fibre composite waste.

The pyrolysis of waste tires offers an environmentally friendly solution to the global tire waste problem. Pyrolytic carbon black (PCB) is an important by-product that can be reintroduced into industrial processes. This study aimed to improve the commercial viability of PCB by reducing its ash content. Pyrolysis was optimized at 420 °C for 4 h with a nitrogen flow rate of 1 L min^-1. Demineralization, crucial for minimizing ash, was carried out using acid and alkali treatments (H₂SO₄, HNO₃, HCl, NaOH). Two demineralization strategies were tested, one using fresh acid for three cycles and the other reusing the solution. The most effective method used 1 M HNO₃ at 80 °C for 1 h, reducing the ash content to 1.7%. The demineralized PCB (PCBd) had improved properties, including a BET surface area of 74 m²  g^-1, an iodine number of 57 mg g^-1, and a particle size distribution up to 140 nm, comparable to commercial carbon blacks. These results highlight the potential of PCBd as a sustainable alternative for tire management and material production.

This study explores the effects of a policy intervention designed to simplify the standards for plastic waste separation on collection volume and the quality of recyclables. We employ a causal impact analysis based on a Bayesian structural time-series approach to estimate the effects of simplifying the municipal solid waste-separation process for plastic waste in Japan. We find that simplifying plastic waste-separation standards increases plastic packaging waste-collection volume. This effect seems to be largely driven by behavioral changes such as decreased time spent on waste separation. We also find that simplifying home separation increases the percentage of contaminated plastic packaging waste collected for recycling and other materials not subject to collection in the post-collection period. Several robustness and falsification tests corroborated these results. Our results highlight the importance of considering the trade-off between the quantity and quality of recyclables when designing plastic waste recycling policies.

In line with circular economy principles, particularly the concept of “closing the loop”, this study examines the basic physicochemical and short-term mechanical viability of revalorization of waste road materials, specifically recycled sediments (RSD), for secondary use as subbase materials. Geotechnical and environmental characteristics of RSD were analyzed to assess its material evolution in comparison to raw sediments (SD) and to explore its environmental potential under varying pH conditions, applied with the intention of simulating diverse treatment and environmental scenarios. This analysis aimed to provide insight into the differing outcomes of SD valorization and RSD revalorization across the different road types of uses (paved road construction, covered embankments, and unpaved/uncapped road construction). RSD demonstrates enhanced short-term mechanical properties, with higher Immediate California Bearing Ratio (I-CBR) than SD for road use. However, the environmental assessment reveals potential contamination constraints. This research showed that the recycled road material or recycled sediments exhibits enhanced mechanical properties, indicating an increased potential for revalorization despite certain additional environmental constraints.

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