Journal of Material Cycles and Waste Management最新文献

The goal of this paper is to conduct an environmental analysis of a municipal solid waste management system in a midsized region of Southeast Brazil with two million inhabitants. While the current municipal solid waste management system has already eradicated dumps, it landfills practically all its waste, with < 2% open composting and recycling. Therefore, alternatives such as closed composting (CC), anaerobic digestion (AD) with electricity or biomethane production, and incineration are proposed via scenarios in which legal requirements are observed and diversion targets are set. Life cycle assessment (LCA) was performed using EASETECH, a specific software for municipal solid waste (MSW) management systems. The results show that the high diversions scenario (70% recyclables/biowaste) with upgraded biomethane from AD and recycling had 76% greater environmental savings than the similar scenario with the new Brazilian diversion targets (25.8% recyclables, 18.1% biowaste). CC performed much worse than AD, with 80% less savings, although it was marginally better than open composting, with a 95% difference in savings. Despite the benefits of incineration, these scenarios were penalized for their toxicity. Recycling is always recommended if feasible.

Rare earth elements (REEs) such as yttrium, europium, and terbium are extracted from minerals like bastnäsite and monazite through complex, energy-intensive processes. Recycling these elements is crucial for reducing environmental impact, conserving resources, and ensuring a stable supply. This manuscript explores the selective separation of Y and Eu from a solution using various solvent extraction agents (Cyanex 272, 572, 923, D2EHPA, and Aliquat 336). Initially, the phosphor powder with a particle size of less than 45 µm was dissolved in a 4 M HNO3 solution, followed by Ca precipitation using Na2SO4. Solvent extraction was then carried out with D2EHPA, which enabled a higher separation efficiency of Y and Eu. The pH, concentration, time, and O: A effects on both the loading and stripping stages were investigated. For the stripping step, the effect of the stripping agent (HCl, HNO₃) on the selective recovery of Y (> 99% purity) or Y–Eu oxides was examined. At the pH value of 0.05, 20% ligand concentration, and 1:1 O: A ratio for 10 min, 88.50% of Y was selectively transferred to the organic phase (D2EHPA) in one step, leaving a considerable amount of Eu remained in the raffinate. After solvent extraction, the effects of temperature, time, stoichiometric ratio, and pH were investigated for precipitation. For precipitation, using oxalic acid at twice the stoichiometric ratio at 50 °C, 99.45% of Y and 98.82% of Eu were precipitated in 120 min as REE oxalates. The precipitated oxalates were calcined, at 500–1100 ℃ for 2–8 h. With a calcination process conducted at 800 ℃ for 2 h, all the REE oxalates were converted to REE oxide form. It was observed that without solvent extraction, a Y–Eu oxide containing 90.64% Y and 6.92% Eu was produced, whereas, after D2EHPA extraction, Y oxide with 99.17% purity was obtained.

Pulp mill sludge is a challenging by-product in wastewater treatment plants (WWTP), due to high moisture content, and poor dewatering characteristics. Solar drying was identified as an appropriate pre-treatment to reduce sludge moisture and enhance its energy efficiency for combustion purposes. Brazil is the world’s second-largest pulp producer, and its high intensity of annual solar irradiation makes it a prime candidate for the application of solar sludge drying technology. This study evaluates the main characteristics of primary sludge (PS) from pulp mills at 65% and 95% moisture content. An active passive solar dryer, followed by ASPEN Plus software simulation was used to evaluate drying properties and combustion potential. CO₂ emission impact was explored, and the environmental effects of primary sludge combustion after solar drying were estimated. As indicated by the findings, the sludge commenced with a solids concentration of 21%, eventually reaching 95.5%, thereby enhancing its suitability for combustion. From the simulation, a heat rate expenditure in sludge combustion reported 24672 kW and 16295 kW for a solids content of 65% and 95%, respectively. Therefore, employing solar drying before the sludge incineration is crucial for minimizing energy consumption during combustion. Additionally, solar energy being cost-free, offers an opportunity to alleviate environmental harm.

The Philippine government launched its Public Utility Vehicle Modernization Program last 2017 to modernize the country’s public transportation system. Part of this program is a sustainable scrappage scheme to handle about 200,000 jeepneys when they are eventually replaced by modern transportation units. In order to provide a technical basis for this scheme, a university-based research team dismantled a typical public utility jeepney. After weighing and classifying the different parts, the jeepney was found to be composed of about 80.44% by weight of ferrous metal alloys while the balance consisted of aluminum, copper, rubber, plastic, wood and oil-based fluids. The jeepney’s recyclability index of 92.50% and the recoverability index of 93.48% were determined for the first time using the International Organization for Standardization (ISO) 22,628 criteria. Using the available junkshop prices, the jeepney’s estimated scrappage value of about Php30,000 was assumed when the preliminary feasibility study of a proposed scrappage facility with a capacity of 15,600 units per year was conducted.

Red mud, an alkaline waste from bauxite refining, takes up land and poses environmental risks from its storage. This study examines red mud treatment, assessing blast furnace slag (GGBS), silica fume (SF), and sodium hydroxide (SH) for solidification. Tests show a mix of 79% red mud, 15% GGBS, 3% SF, and 3% SH yields a 28-day compressive strength of 13.12 MPa, suitable for industrial materials. Solidified red mud’s resistivity rises and permeability drops over time, enhancing impermeability and compactness. Durability tests through seven wet-dry and freeze–thaw cycles show solidified red mud’s excellent durability, with mass loss below 2% and compressive strength over 9.67 MPa. Scanning Electron Microscopy and Energy Dispersive Spectroscopy show solidified red mud is filled with Calcium-Alumino-Silicate-Hydrate gel and ettringite crystals, reducing porosity and improving particle bonding. X-ray diffraction and Mercury Intrusion Porosimetry tests confirm their even distribution within the mud. Environmental analysis shows solidified red mud reduces heavy-metal leaching and stabilizes radioactive nuclides. Life-cycle assessment indicates it cuts carbon footprint by about 45.23% compared to traditional cement, highlighting sustainability and economic advantages. In summary, the study validates that GGBS, SF, and SH enhance red mud’s environmental performance, offering new paths for sustainable industrial waste utilization.

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Desulphurization gypsum (DG) is the by-product of wet desulphurization of flue gas in power plant, with a large yields and low resource utilization rate. However, it is rich in CaSO₄·2H₂O. This work reused the DG for the activation of steel slag (SS)-alkalied-granulated blast furnace slag (GBFS) and produced a DG–SS–GBFS-based geopolymer. The compressive strength, dehydrated polymeric products and their generation and micromorphology, and pozzolanic activity were studied. Results show that the DG–SS–GBFS-based geopolymer produced with 15 wt.% DG, 51 wt.% SS and 34 wt.% GBFS is 1.20 MPa and 14.66 MPa at 3 and 28 days, which is increased by 990.91% and 18.13% compared to that without DG; this increase is attributed to the fibrous AFt formed in the DG–SS–GBFS-based geopolymer. Also, the C-A-S-H gel and Ht phase were generated. The produced geopolymer’s pozzolanic activity is 84.19% (> 65.00% in accordance with GB/T 2847–2005 “Pozzolanic materials of Portland cement”) at 28 days, and no more than 30 wt.% of the DG–SS–GBFS-based geopolymer can be applied to the production of 42.5-grade composite cement specified in the GB 175–2020 “common Portland cement”. This work contributes to the reuse of DG on a large scale, which fits well with the concept of cleaner production.

The impact of salinity levels (0 g/L,5 g/L,10 g/L,15 g/L,20 g/L, and 25 g/L) on the production of combustible gases from anaerobic fermentation of fruit pomace waste with thermal pretreatment. The underlying mechanisms behind this effect are also be analyzed. The experimental findings reveal that the production of gas from anaerobic fermentation of fruit pomace waste is significantly inhibited under high salt conditions (NaCl ≥ 5 g/L). Specifically, the gas production of the experimental groups with salinity ranging from 15 g/L to 25 g/L is about 79% of that observed in the blank group (without adding NaCl). In addition, high salinity also delays the start of fermentation. Consistent with the experimental data, the Gompertz model simulations reveal that increasing the salt concentration prolongs the fermentation period. Notably, the experimental group with salt concentration of 20–25 g/L is subjected to an 11-h delay, yet this prolongation does not disrupt the 24-h fermentation completion cycle. The high salinity inhibits the total amount of hydrogen in the fruit pomace waste gas production, but it has little effect on the proportion of hydrogen in the gas production. Salinity affects the production of various volatile fatty acids, including acetic, propionic, and butyric acids, without altering the overall composition of short-chain fatty acids. The study shows that high salinity inhibits the consumption of organic matter during the fermentation process of fruit waste, reduce the production of H₂, and notably delays in the onset of fermentation.

Rare earth elements (REEs) and cobalt (Co) are listed as critical raw materials because of their importance in global industrial production growth, high supply risk, and economic significance. The recovery of Co and REEs from secondary resources is therefore proposed as a key countermeasure to address this concern. In this study, a straightforward process that integrates acid baking and water leaching is proposed for the recovery of samarium (Sm) and Co from scrap SmCo magnets. Firstly, the chemical composition of SmCo magnets is revealed by ICP-OES and XRF. The Taguchi experimental design technique is employed to optimize nitric acid baking and water leaching. Based on the thermal decomposition behavior of Co, Fe, and Sm, the acid baking temperature is studied for the conversion of metal nitrates, excluding REEs nitrates, into metal oxides. The optimal conditions for acid baking and water leaching are identified, and a reactor for the pilot-scale acid baking process is proposed. The optimum parameters are tested with the proposed reactor.

The development of techniques to reduce stress in the aquaculture industry is essential for the good growth, low mortality, and high flesh quality of farmed fish. Shochu is a traditional Japanese alcoholic beverage, and the disposal of large amounts of Shochu lees waste has been a problem. As Shochu lees contain low-molecular-weight compounds, which are thought to have health benefits, the lactic acid-fermented by-product of Shochu distillery (FBPSD) was tested to estimate its anti-stress effects in neuropeptide Y-knockout zebrafish (NPY-KO), which exhibit high anxiety and low sociability, as a farmed fish model.

In the Black-White preference test, NPY-KO preferred the black area over the white area due to fear, whereas NPY-KO fed the FBPSD showed a higher preference for the white area with more swimming distance than the control group. In the 3-chambers test, NPY-KO showed low sociability with the unfamiliar zebrafish group, whereas FBPSD-fed NPY-KO showed high sociability with the group. The mRNA level of isotocin, the homologue of human oxytocin, was significantly increased in the brains of FBPSD-fed zebrafish. The oxytocin receptor antagonists L-368,899 attenuated the effects of FBPSD in the 3-chambers test. These results suggest that FBPSD attenuates anxiety in NPY-KO zebrafish by activating isotocin neurons.

This study aimed to identify the benefits and challenges of clothing reuse, both in terms of fashion companies collecting unwanted clothing and consumer attitudes, focusing on Japanese fashion companies and consumers To achieve the goal, this study conducts a survey to gain an overview on the supply chain of fashion brands carrying out a take-back program in Japan. This study also conducted a questionnaire survey to gage consumers’ awareness and purchasing decisions regarding second-hand clothes and to clarify the annual CO₂ emissions generated by different clothing maintenance habits among second-hand clothes consumers. Business review results revealed that large companies only take back their products for reuse or recycling to control product quality. The questionnaire survey results revealed the primary motivations for purchasing second-hand clothes were financial advantages and the desire for fashionable styles. The environmental impact assessment results indicated that purchasing a second-hand shirt in the context of a circular economy produces 6.71 kg-CO₂ less than buying a newly produced shirt within a linear economy (9.23 kg-CO₂). Additionally, based on the questionnaire results, this study unveiled how laundry habits affect CO₂ emissions during the garment use phase.