Recycling Rate Research Articles

Research on Education for Sustainable Development with Design-Based Research by Employing Industry 4.0 Technologies for the Issue of Single-Use Plastic Waste in Taiwan

The social impacts of prevailing circular economy (CE) strategies remain under-researched despite the considerable attention that CE has received from scholars and in industry. Existing CE indicators primarily focus on business models from a decision-making standpoint, overlooking consumer engagement and alternative solutions. Boasting one of the highest recycling rates globally, Taiwan faces challenges in optimizing collected resources. This study delves into recycling plastic waste by integrating consumer behavior within CE strategies, leveraging open-source resources and additive manufacturing technologies to align with the United Nations Agenda 2030, particularly Sustainable Development Goals (SDGs) 4 (Quality Education), 12 (Responsible Consumption and Production), and 13 (Climate Action). These resources facilitate the transformation of plastic waste into reusable materials. Employing an exploratory and participatory action research approach, this research uses the Precious Plastic Universe (PPU) database to identify potential resources from post-consumer polymer waste. Subsequently, it explores tools for converting collected waste into usable polymers. Lastly, the study investigates integrating collected polymer waste into student design projects to enhance creativity and problem-solving skills for sustainable development, employing additive manufacturing tools at the National Taiwan Normal University Department of Design. Thematic analysis of the data revealed several recurring patterns, including the role of consumer behavior in plastic waste generation, the development of creativity and problem-solving skills among students, and the challenges of working with recycled materials. These themes were observed in quantitative data (collected single-use polymers) and qualitative insights from student observations and interviews. Through thematic analysis, the study highlights key factors contributing to successful CE integration, providing a model for future educational and industrial applications of sustainable design.

Recycling Li-Ion Batteries via the Re-Synthesis Route: Improving the Process Sustainability by Using Lithium Iron Phosphate (LFP) Scraps as Reducing Agents in the Leaching Operation

The development of hydrometallurgical recycling processes for lithium-ion batteries is challenged by the heterogeneity of the electrode powders recovered from end-of-life batteries via physical methods. These electrode materials, known as black mass, vary in composition, containing differing amounts of nickel, manganese, and cobalt (NMC), as well as other chemicals, such as lithium iron phosphate (LFP). This study presents the results of the hydrometallurgical treatment of mixed NMC and LFP black masses aimed at creating flexible recycling processes. This approach leverages the reducing power of LFP to optimize the leach liquor composition for re-synthesizing NMC precursors. In particular, the leaching conditions were optimized based on the LFP content in the solid feed to maximize the extraction of key metals (Ni, Mn, Co, and Li). The leaching solid residue, graphite, was treated and characterized as a secondary raw material for new anode preparation. Iron phosphate was recovered by increasing the pH of the leach liquor, and the NMC precursors were obtained via coprecipitation. This process achieved a recycling rate of 51%, based on the black mass input and the mass of recovered elements in the output products. Additionally, substituting LFP scraps as the reducing agent in place of H2O2 reduced the recycling process’s environmental impact by avoiding 1.7 tons of CO2-equivalent emissions per ton of NMC black mass.

Improving the decision-making for sustainable demolition waste management by combining a BIM-based life cycle sustainability assessment framework and hybrid MCDA approach.

Increasing efforts have been devoted to promoting sustainable demolition waste management (DWM) from a life cycle-thinking perspective. To this end, facilitating sustainability-oriented decision-making for DWM planning requires a sustainability assessment framework for assessing multifaceted criteria. This study develops a building information modelling (BIM)-based DWM sustainability assessment approach to facilitate the life cycle assessment (LCA) and decision-making by coupling the enriched Industry Foundation Classes model with hybrid multi-criteria decision-aiding (MCDA) methods using Dynamo visual scripting. To streamline the data-intensive LCA process, this study enriched the BIM properties and accommodated them into the LCA data template to enhance data interoperability, thus achieving seamless data transfer. Moreover, hybrid MCDA methods are integrated into the decision-making workflow for DWM scenario ranking. A pilot study is employed to verify the applicability of the decision-aiding framework. The results unveil that the sustainability score ascended with the recycling rate. The optimal DWM alternative with the highest recycling rate yields the highest sustainability score at 91.63. Conversely, a DWM alternative reflecting the 'status quo' in China's recycling industry has the lowest score at 8.37, significantly lower than the baseline scenario with a 50% recycling rate. It is worth noting that the 'growth curve' of the sustainability score continuously flattens as the target recycling rate escalates. The increment in recycling rate from the 'Australian standard' scenario to the optimal scenario is 18.4%, whereas the sustainability score merely increases by 2.3%, signalling that the former scenario arrived at an optimum point for maximising the cost-efficiency of DWM under the predefined framework and contexts.

Development of a deep learning-based object recognition system for pre-stage separation to improve the recycling rate of major general-purpose plastics

ABSTRACT The generation of plastic waste has been increasing annually, necessitating various recycling methods. Among these, material recycling with low carbon emissions should be prioritized. This study aims to enhance the material recycling rate by developing a separation system using deep learning-based object recognition. To improve labeling efficiency, image data were acquired for each material type, and the performance of different labeling methods was evaluated. The average precision (AP) values for the single-material learning model using hybrid labeling (manual + automatic) were 0.947 for PET, 0.951 for PP, 0.892 for PE, and 0.896 for PS, demonstrating superior performance compared to other methods. An integrated learning model was also developed for composite materials, achieving AP values of 0.972 for PET, 0.976 for PP, 0.963 for PE, and 0.961 for PS. These results demonstrate the model’s strong applicability for plastic waste recognition.

Increasing the Recycling of PVC Flooring Requires Phthalate Removal for Ensuring Consumers' Safety: A Cross-Checked Substance Flow Analysis of Plasticizers for Switzerland.

As our planet grapples with the severe repercussions of plastic pollution, mechanical recycling has been proposed as a potential remedy. However, increasing mechanical recycling may have unintended negative consequences. For example, recycling of PVC flooring containing hazardous plasticizers that were used in the past may lead to continued exposure. Here we propose measures to increase recycling while circumventing adverse health impacts caused by legacy additives. For this, we conduct a dynamic substance flow analysis for Switzerland and the time period from 1950 to 2100, focusing on three plasticizers: di(2-ethylhexyl) phthalate (DEHP), diisononyl phthalate (DiNP), and di(2-ethylhexyl) terephthalate (DEHT). We quantify the uncertainty of results, check their plausibility against measured concentrations in samples representative for the Swiss market, and compare them with modeled substance flows in Germany. Based on the cross-checked model, future average concentrations of DEHP in PVC flooring on the Swiss market are expected to be above the legal limit of 0.1 wt % for several decades if increased recycling rates are implemented without additional measures. Phasing out the potentially concerning DiNP, too, and preventing phthalates from entering recycling would lower their average market concentrations to values below 0.1 wt % and enable increasing recycling rates without compromising product safety. Analogous measures could help achieve this goal across other European countries and product groups.

Enhancing the recyclability of ELV plastic bumpers: Characterization of molecular, morphological, rheological, mechanical properties and ageing degradation

While the automotive industry has traditionally prioritized metal recycling, the increasing use of plastics in vehicles underlines the need for sustainable management of these materials. Recycling rates of plastics from end-of-life vehicles (ELVs) in Europe are low, but recent EU legislation requires 25 % of the plastics in new vehicles to be recycled, forcing innovative designs and strategies to enhance the recovery and quality of recycled resins. This study focuses on post-consumer bumpers, a significant recoverable component of ELVs, by assessing their molecular, morphological, rheological, and mechanical properties to investigate their homogeneity and quality from various sources to assess their suitability for recycling. Since the aging of these materials, caused by thermo-oxidative and thermo-mechanical degradation processes, can compromise the quality of recycled bumpers, we propose a blend of recycled PP from different bumper cars with virgin resin, representing a realistic scenario where the post-consumer ELV bumpers are collected. Interestingly, this blend, which can replace up to 50 % of the virgin resin without additional compatibilizers or additives, mitigates the degradation effects. Furthermore, the study evaluates the degradation resistance of these blends through multiple extrusion cycles and accelerated weathering tests in a temperature-controlled UV chamber to ascertain the number of cycles the material can tolerate without significant quality degradation, and to determine its suitability for long-term applications. Our results not only support the feasibility of using recycled PP for automotive components but also contribute to meeting the EU's recycling targets. This research highlights the potential for significant advances in the circularity of automotive plastics, providing a sustainable pathway for integrating recycled materials into new vehicle production.

Causes for overestimation of the moisture recycling in an alpine meadow ecosystem of the Shule River Basin, Tibetan Plateau, China

Terrestrial moisture recycling is an essential hydrological component and a significant source of the atmosphere’s humidity budget in arid and semi-arid inland regions. Investigations on moisture recycling using the stable hydrogen and oxygen isotopes is currently a focal point in hydrologic research. However, the direct quantification of recycling ratio based on isotopic composition of evapotranspiration vapor is lacking. So, this causes challenges to compare studies, based in the same region and time period but with different methodologies. In this study, we measured the isotopic compositions of evapotranspiration vapor (δ18OET/δDET) from June to September 2018 in an alpine meadow ecosystem at the Shule River Basin by combining the Keeling plot model and in-situ chamber measurement. Using this data, the moisture recycled rate (mrr) was assessed based on the two-component (Model A) and three-component isotopic mixing models (Model B), respectively. Based on Model A and δ18OET, the analysis revealed that the mean recycled rate for the entire observation period was 35 %, while it was 26 % during the westerly period (the months dominated by the north branch of prevailing westerlies) and 44 % during the monsoon period (when subtropical moisture from the Indian monsoon penetrated the region). The recycled rate based on Model A and δDET was slightly larger with a mean value of 41 % during the entire observation period. The recycled rate based on Model B was also significantly higher in comparison with Model A, while the causes for this difference could be the assumption of substituting xylem water for transpiration vapor and the plant water source δD offset. The contribution of recycled moisture was notable lower for heavy rainfall comparing with light rainfall. Our findings provided a new perspective for the investigations of alpine meadow ecosystem hydrological processes.

Does the material recycling rate matter in the effect of the generated waste on environmental pollution? Panel smooth transition regression approach

This study examined the effect of material recycling on the relationship between the waste amount and environmental pollution in EU-15 countries for the 1995-2019 period through panel smooth regression analysis by using the material recycling rate as the threshold variable. Based on the analysis results, the material recycling rate threshold level was estimated as 11.79. In these countries, if the material recycling rate is below the threshold level, the rise in the waste amount will increase environmental pollution. If the material recycling rate is above the threshold value, the rise in the waste amount will still increase environmental pollution, but the pollution increase rate will decrease. With the increase in the waste amount in the long term, environmental pollution can only be reduced by raising the material recycling rate. For the reduction of environmental pollution, which is one of the most prioritized issues in Europe in recent years, policy makers should take measures to increase the material recycling rate by taking the results of this study into consideration and pay attention to the implementation of these measures.

Review of Plastic Waste Recycling: Advances, Challenges, and Future Perspectives

Plastic waste recycling is pivotal for sustainable waste management, offering solutions to mitigate environmental impacts and conserve resources. This thesis reviews technological advancements, challenges, and future prospects in recycling various plastic types. It begins with an overview of plastic pollution’s global impact and the imperative to manage plastic waste responsibly amidst rising production. Recycling processes are explored, detailing collection, sorting, cleaning, and reshaping methods that extend plastic life cycles while reducing energy consumption and greenhouse gas emissions. The review highlights challenges such as plastic type variability, recycling infrastructure limitations, and market demand discrepancies, affecting recycling effectiveness. Technological advances, including mechanical and chemical recycling innovations, are analyzed for their potential to improve plastic recycling rates. Economic and environmental implications underscore the benefits of effective recycling, contributing to a circular economy and minimizing landfill waste. Future directions advocate for enhanced recycling technologies, standardized labeling, and policy interventions like extended producer responsibility schemes. By addressing these facets, stakeholders can collaboratively advance sustainable plastic waste management globally, fostering a future where environmental stewardship aligns with economic viability.

RECYCLING OF PLASTIC WASTE BY THE PYROLYSIS METHOD

Chemical recycling of plastic waste can be a useful complement to mechanical recycling to achieve the required rate of plastics recycling and create a climate-neutral and resource-saving circular economy. Various mixed plastic wastes to be recycled in the future are investigated under fully uniform intermediate pyrolysis conditions characterized by moderate heating rates and pyrolysis temperatures. The distribution of the product and the selected properties of the product are determined, and the mass and energy balance of the process is obtained. Product yield and composition are highly dependent on pyrolyzed residues. All results indicate that pyrolysis is a suitable process for obtaining chemical feedstocks from various complex mixed plastic wastes. The main mass and energy balances for chemical recycling of mixed plastic waste by pyrolysis method were determined. Products for recycling raw materials can be obtained from all investigated plastic waste. Product quality often depends on raw materials. The energy requirement for heating, melting, pyrolysis and evaporation is about 5% of the calorific value of the raw material. It has been demonstrated that 50 to 75% of the raw carbon can be recovered in the condensate and reintroduced into the value chain in the chemical industry.

Sustainability and circularity assessment of biomass-based energy supply chain

Climate change and other environmental consequences of socio-economic activities require a more sustainable and circular growth. At the same time, the limitation of the earth resource demands industries to improve resource efficiency and increase the rate of recycling of materials. There are several sustainable and circular alternatives that the industries may adopt. However, the question is that among these alternatives, which one should be selected for implementation for the highest sustainable and circular benefits. This study introduces a novel tool for assessing the sustainability and circularity of biomass-based energy supply chains, integrating multi-criteria decision-making methods with life cycle thinking approach. It evaluates five alternatives using a sustainability and circularity indicators, offering new insights into the deloyment of circular business models at companies in biomass-based energy supply chain. The tool is also applied to a specific rice straw supply chain in Italy, to assess the sustainability and circularity of five alternatives and outrank them. The results indicated that not all the alternatives are better in terms of supporting sustainable development and circular economy, compared to the baseline business model. In this supply chain, the extended lifetime for digestate from the aerobic digestion plant is the most ‘sustainable and circular’ alternative, while the capture of carbon dioxide from the same plant and its use for microalgae cultivation is the least ‘sustainable and circular’ alternative. A sensitivity analysis was conducted on different weighting sets during the assessment. It indicated that the priority of the decision makers can slightly change the outrank of the alternatives and the magnitude of the outranks.

Optimization of PET depolymerization for enhanced terephthalic acid recovery from commercial PET and post consumer PET-bottles via low-temperature alkaline hydrolysis

The increasing demand for plastic has resulted in a surge in plastic waste production. Polyethylene terephthalate (PET), commonly used in beverage bottle manufacturing, is only partially recycled, with an estimated recycling rate of just 28.4% in 2019. This accumulation of plastic waste is harmful to the environment and living organisms, necessitating effective recycling methods for PET waste. One promising method is alkaline hydrolysis using NaOH, which can break down PET into its monomer components, terephthalic acid (TPA) and ethylene glycol (EG). This process not only recycles PET efficiently but also manages contaminants effectively, producing high-quality TPA, supporting the development of a circular economy. This study looks into PET depolymerization via alkaline hydrolysis at low temperature by investigating effects of various factors: pH levels, water to ethanol ratio, NaOH concentration, NaOH to PET ratio, reaction time, PET size, reusability of unreacted PET, air plasma pretreatment of PET, and different kinds of PET. Promisingly, PET conversion rates of over 90% and a TPA purity of 99.6% were achieved in this study highlighting the efficacy of alkaline hydrolysis in depolymerizing post-consumer PET waste. Ultimately, this research advances sustainable plastic waste management and supports the integration of PET into a circular economy framework.

Unveiling the Age Factor: The Influence of Cabinet Members’ Age on Waste Electrical and Electronic Equipment Recycling Rates in European Nations

Unveiling the Age Factor: The Influence of Cabinet Members’ Age on Waste Electrical and Electronic Equipment Recycling Rates in European Nations

Design of novel high entropy alloys based on the end-of-life recycling rate and element lifetime for cryogenic applications

The equiatomic face-centred cubic (FCC) CoNiCrFeMn alloy, known as the Cantor alloy, is renowned for its high ductility under extreme conditions, such as cryogenic temperatures. Despite this, it suffers from low hardness and yield strength (YS) and includes elements with significant supply concerns. This study introduces novel non-equiatomic CoNiCrFeMn alloys, designed using machine learning (ML)-assisted-high-throughput atomistic simulations to enhance sustainability and mechanical properties such as hardness and YS while maintaining the alloy's single-phase FCC structure. We incorporated two critical sustainability indicators, end-of-life recycling rate (EOL−RR) and lifetime (τ), to guide the alloy design process. Mean-flow stress (MFS), measured from the yield point to 15% strain during tensile tests, was used to assess and predict the mechanical properties. Two alloys, with cobalt contents of 12.5% and 21.5%, were developed and analysed. The Co12.5 alloy showed better sustainability (44% improvement in τ with almost the same mechanical properties), while the Co21.5 alloy exhibited better mechanical properties (20% improvement in MFS with almost the same sustainability) as the equiatomic system. Their stable FCC microstructures were confirmed through CALPHAD modelling and X-ray diffraction (XRD) analysis of vacuum arc melted, as-cast samples. The results highlight the potential of integrating sustainability metrics into high-performance alloy design.

Do green parties affect local waste management policies?

We explore whether mayors supported by pro-environmental parties enhance local environmental outcomes compared to their non-environmental counterparts. We study close elections within a regression discontinuity design and find a notable rise in recycling rates in Italian municipalities governed by pro-environmental coalitions. This uptick becomes far less pronounced when adopting broader criteria to define green mayoral candidates. Crucially, the enhanced recycling rates are not realized through augmented budgets for environmental initiatives or waste collection, but rather are primarily attributed to the implementation of local policies, such as on-call waste collection and the establishment of waste collection centers.

Modeling Aluminum Stocks and Flows in China until 2050 Using a Bottom-Up Approach: Business-As-Usual Scenario Analysis

Aluminum metal is used in a wide range of applications such as construction, transportation, power, and aerospace. Previous studies have mainly used a top-down approach to explore future aluminum stocks and flows in China. In this study, we developed a dynamic material flow analysis model using a bottom-up approach to simulate aluminum flows and stocks in China until 2050, based on current government and sector policies. The results show that China’s aluminum stocks will be nearly saturated by 2050, with a total and per capita of 591 million tons (Mt) and 449 kg/per, respectively. The domestic demand for aluminum will grow until 2030 and will remain relatively stable thereafter at around 28–30 Mt. Construction and transport are the two sectors with the highest demand for aluminum, accounting for over 60% of the total aluminum demand. The domestic aluminum scrap will increase almost sevenfold, from 2.7 Mt to 20.0 Mt between 2020 and 2050. However, even assuming a 90% recycling rate, secondary aluminum will at best meet around 70% of demand by 2050. To realize sustainable development in China’s aluminum industry, extending the life of aluminum products and increasing aluminum scrap recycling are sensible measures.

Display of Bacterial Exochitanase on Bacillus subtilis Spores Improved Enzyme Stability and Recyclability.

Chitin is the second most prevalent polysaccharide found in nature, following cellulose. Amino-oligosaccharides, the byproducts of chitin degradation, exhibit favorable biological properties and potential for various uses. Chitinases play a crucial function in the breakdown of chitin, and their exceptionally effective production has garnered significant interest. Here, in this study, the exochitinase PbChiA, obtained from Paenibacillus barengoltzii, was recombinantly produced and immobilized using the CotG surface protein of Bacillus subtilis WB800N. The resulting strain Bacillus subtilis WB800N pHS-CotG-Chi exhibited exceptional heat stability and efficacy across various pH levels. The chitinolytic activity of the enzyme, which had been isolated and immobilized on the spore surface, was measured to be approximately 16.06 U/mL. Including Ni2+, Zn+2, and K+, and EDTA at various concentration levels in the reaction system, has significantly enhanced the activity of the immobilized enzyme. The immobilized exochitinase demonstrated a notable rate of recycling, as the recombinant spores sustained a relative enzyme activity of more than 70% after three cycles and 62.7% after four cycles. These findings established a basis for additional investigation into the role and practical use of the immobilized bacterial exochitinase in industry.

Closed-loop circular economy in ‘upcycled’ acrylonitrile–butadiene–styrene vitrimer

Today, the issue of plastic waste pollution has reached unprecedented levels. The increasing production of plastics, combined with a decreasing rate of recycling, has significantly worsened this problem in recent years. While a wide range of plastics are manufactured, thermoplastics are a type that can be recycled relatively easily. However, recycled thermoplastics often have lower mechanical properties compared to new ones. Considering this challenge, making thermoplastics recyclable could revolutionize the recycling process and represent a major advancement towards establishing a circular economy for plastics. In this study, virgin acrylonitrile–butadiene–styrene (ABS) was transformed into a vitrimer through reactive melt extrusion using a bio-derived crosslinker containing dynamic imine linkages. This crosslinker results in a dynamic network, in the melt, as observed from the higher gel fraction and imparts recyclability to the resulting ABS vitrimer, which exhibits higher yield strength (by 15 %) and Young’s modulus (by 19 %). Remarkably, the mechanical and thermal properties of the vitrimer remain largely unchanged even after undergoing five cycles of reprocessing. In addition, the resulting vitrimer is dimensionally stable as inferred from creep studies and shows rapid stress relaxation at higher temperature following Arrhenius behaviour. The electron paramagnetic resonance (EPR) spectra were captured at room temperature for both ABS and its vitrimer. The difference in singlet band intensities in the spectra begins to suggest that the vitrimer is more stable post multiple recycling. While this research focused on virgin ABS, the approach outlined in the study has the potential to be applied to post-consumer recycled (PCR) ABS. This could introduce recyclability to PCR ABS and pave the way for a closed-loop circular economy for ABS plastics.

Economic viability requires higher recycling rates for imported plastic waste than expected

The environmental impact of traded plastic waste hinges on how it is treated. Existing studies often use domestic or scenario-based recycling rates for imported plastic waste, which is problematic due to differences in recyclability and the fact that importers pay for it. We estimate the minimum required recycling rate (RRR) needed to break even financially by analysing import prices, recycling costs, and the value of recycled plastics across 22 leading importing countries and four plastic waste types during 2013–2022. Here we show that at least 63% of imported plastic waste must be recycled, surpassing the average domestic recycling rate of 23% by 40 percentage points. This discrepancy suggests that recycled plastics volumes from the global North-to-South trade may be underestimated. The country-specific RRR provided could enhance research and policy efforts to better quantify and mitigate the environmental impact of plastic waste trade.

Driving EU sustainability: Promoting the circular economy through municipal waste efficiency

The need to balance ecosystems and ensure the well-being of all people underlines the urgency of closing product life cycles. In recent years, the circular economy (CE) has emerged as one of the most relevant factors in achieving the Sustainable Development Goals. This paper presents a systematic literature review (SLR) of waste management efficiency at the European level. Furthermore, it presents a standard data envelopment analysis (DEA) of 27 European countries over the period 2017–2021, focused on municipal waste. Three models (i.e., economic, technical, sustainable) are proposed to optimise the rates of municipal waste recycling and circular material use.The SLR, based on an initial set of 216 articles that was subsequently refined through double screening to 31, highlights the strategic role of the waste management, recycling and municipal solid waste triangle. The results of the DEA indicate stronger synergy between technical and sustainability dimensions than between economic and sustainability components. Moreover, they highlight fragmented performance in Europe, with distinct clusters of countries emerging as top performers in each of the three models, and the Netherlands, Slovenia, France, Italy, Germany and Sweden demonstrating superior performance for both CE outcomes and sustainable performance. Overall, the results emphasise the strategic role played by technology in facilitating an efficient circular model of municipal waste management to minimise landfilling and other environmentally detrimental practices, thereby stimulating the development of sustainable communities for optimised waste management, in line with broader sustainability objectives.