Journal of advanced manufacturing and processing最新文献

The preconsumer textile waste in the manufacturing country dominates the circularity in the textile and apparel industries. Bangladesh, the world's second largest exporter of apparel, produces a tremendous amount of preconsumer waste while manufacturing yarn, fabric, dyed fabric, and apparel in the whole textile production chain. The sheer number of workers, traders, local manufacturers, exporters, and other formal and informal channels makes this waste management sector important. In addition, the value addition of this waste in the local and export markets is increasingly significant. This study aims to determine and fill the knowledge gap on current circularity practices of nonhazardous textile solid waste in Bangladesh, drawing experience from an end-market for textile solid waste. One distinct textile waste cluster, Mirpur, was selected. Based on field surveys and interviews, it is found that approximately 76% of textile solid waste is reused, 11% is used for making recycled yarn, and another 11% is used as fuel for boilers and geotextile for road construction activities, and 2% is wasted as fabric dust. The cost of selling textile solid waste ranges from USD 0.1 to USD 0.95, depending on the type of waste. Overall, the Mirpur cluster processes around 600–800 tons of textile solid waste per month and employs around 800–1000 staff, of whom 95% are women. It shows an informal circular textile waste economy where nothing is wasted, and everything is utilized, creating new markets, products, businesses, and employment. However, such practices lack regulatory oversight and monitoring, which could be transformed into a formally functioning circular economy.

The study investigates the fabrication and characterization of titanium dioxide (TiO₂) nanotubes synthesized via a two-electrode anodization process, with a focus on their application in solar-driven water splitting for sustainable hydrogen production. TiO₂ nanotubes were fabricated on titanium foils by anodizing in a 0.5% M ammonium fluoride (NH₄F) solution in ethylene glycol, using a range of applied voltages (12, 20, and 30 V) for a duration of 2 h. The resultant TiO₂ nanotubes exhibited an average diameter of 85 nm and an average length of 1.4 μm, demonstrating a highly ordered and uniform structure, as observed via field emission scanning electron microscopy (FESEM). The crystallinity and phase composition of the TiO₂ nanotubes were investigated through X-ray diffraction (XRD), which revealed that the nanotubes predominantly retained the anatase phase, known for its high photocatalytic efficiency. Optical properties were further examined using UV–Vis absorption spectroscopy, which indicated a characteristic absorption edge around 380 nm, corresponding to a bandgap of 3.2 eV. This suggests that the material predominantly absorbs ultraviolet (UV) light, limiting its use under natural sunlight. However, these properties indicate the potential for further enhancement through techniques such as doping or cocatalyst integration to improve visible light absorption and overall photocatalytic efficiency. The findings demonstrate that TiO₂ nanotubes, with their high surface area and well-defined structure, exhibit favorable characteristics for photocatalytic water splitting. This work highlights the efficiency of the anodization technique in fabricating TiO₂ nanotubes with desirable properties for solar hydrogen production. The results suggest that future work aimed at optimizing the material through doping or the integration of cocatalysts could further enhance its performance in solar-driven water splitting, contributing to the development of sustainable energy solutions.

The recently released Circularity Gap Report 2023 by the Circle Economy Foundation states that the circularity score for the global economy is declining. The US Environmental Protection Agency (EPA) tracked municipal solid waste from 1960 to 2018 and found that 50% of the waste was destined for landfills. EPA estimates that US industry is responsible for 2.7 Gt of solid nonhazardous waste annually in the US mostly linear economy model. The circular economy framework aims to decouple economic value generation from the extraction of virgin materials from nature. The linear model of material extraction and disposal at the end of life is highly unsustainable. Manufacturing companies are adopting ambitious waste reduction targets to achieve sustainability. Through the Better Plants program, US DOE has established the Waste Reduction Network, which offers technical assistance to partners to achieve their ambitious waste reduction goals. Basic requirements of establishing a target include identifying a baseline, quantifying waste performance, and measuring progress over time. One problem faced by industry is unstandardized metrics for quantifying waste performance that may not be well suited to demonstrate progress. This paper studies traditional methods used to measure waste performance and highlights advantages, disadvantages, and limitations of each method. It also examines the suitability of applying the methods in different manufacturing circumstances. Finally, the paper presents a case study of a large manufacturer that faced inconsistencies in its tracked measurement metric. A solution was proposed and implemented to alter the methodology to enable more accurate waste performance tracking against a baseline.

Plastics are one of the most widely consumed materials around the world, and its impact on our ecosystems is undeniable. Initiatives to reduce plastic waste have gained momentum in recent years, but the focus areas of such initiatives do not always align with significant positive impacts. This presentation demonstrates a material flow analysis (MFA) aimed at quantifying the global flow of plastics, from production to end of life, ultimately identifying where plastic reduction efforts can be most impactful. On a global scale, specific data on plastic production and material flow is lacking, so calculations relied heavily on data published in the United Nations' Mapping Global Plastics Report, based on the year 2015. The MFA was conducted with emphasis on end of life and flows lost to the environment, including macro- and microplastics. Across the global MFA, results show packaging was the largest individual industry consumer of plastics. Categories designated as “other” should be investigated further due to their substantial presence in the material flow. Plastics lost to the environment made up about 2% of the total mass, but that 2% equated to over 8 million metric tons. These lost plastics stem from various sources, making the issue difficult to tackle, but addressing this loss is important, nonetheless. Reducing demand for plastic production through decreased use is an obvious approach to minimizing waste and pollution, and this study provides insight about which plastics pose the greatest threat while also identifying current data gaps, ultimately guiding where future efforts should be focused.

Many actions are underway at global, national, and local levels to address the plastic waste problem and transition toward a circular economy of plastics. Studies evaluating environmental and socioeconomic impacts of such a transition are lacking. The purpose of this study is to conduct a national systems analysis of polyethylene terephthalate (PET) packaging supply chains in the United States. Material flow data was combined with environmental and socioeconomic indicators to evaluate and compare the sustainability of the linear PET packaging supply chain, current (2019) supply chain, and possible future circular supply chain options in the United States. Environmentally optimal circular US PET packaging material flows showed 31% and 38% savings of GHG emissions and energy demand, respectively, with a circularity of 77% when compared with a linear supply chain. Additionally, the environmentally optimal system showed higher employment (29%) and wages (31%) than a linear system, but with a 5% decrease in revenue generation. A socioeconomically optimal circular PET supply chain showed increased employment (by 52%), wages (by 67%), and revenues (by 1%), with a circularity of 59% when compared with the linear system. However, it showed 14% higher GHG emissions than a linear system, indicating a trade-off between environmentally and socioeconomically optimal circular PET packaging systems. Overall, linear-to-circular material flow transition may not necessarily lead to increased revenues and decreased environmental impacts of the entire system, but it does benefit society due to increased employment and wages. Future systems analysis work should focus on improving data quality for environmental and socioeconomic dimensions.