Circular Economy最新文献

Plastic recycling is a critical aspect of achieving a circular economy, aiming to reduce fossil fuel dependency, greenhouse gas emissions, and biodiversity impacts from uncontrolled disposal routes. The study outlines the evolving landscape of plastic recycling in the European Union (EU), addresses challenges, and emphasizes the need for innovative approaches to achieve circular economy goals. This paper delves into the innovative approaches and strategies employed by the PHOENIX project, a multidisciplinary project funded by the Cariplo Foundation, which focuses on plasmix – a complex mixture of plastics often excluded from recycling due to its heterogeneous composition. The authors utilize a systemic design approach, integrating survey results, interviews, literature reviews, and case studies to provide a comprehensive understanding of plasmix and propose novel solutions. Key findings include the application of design from recycling, systemic design strategies, and the utilization of plasmix in new product developments. It presents survey insights and stakeholder perspectives, and introduces systemic strategies applied in the project. The study concludes with valuable considerations for future research and underscores the significance of such initiatives in reshaping the plastic recycling paradigm.

The recycling of waste printed circuit boards (WPCBs) generates nonmetallic fractions (NMFs); due to the complex components of NMFs and the limited nature of economic benefits of treating NMFs, treatment of NMFs is challenging. In this study, two types of NMFs—dry-NMFs (D-NMFs) and wet-NMFs (W-NMFs)—derived from the dry and wet separation processes of WPCBs, respectively, were investigated. These NMFs were used as fillers to reinforce the polyethylene (PE) matrix, and their effects on the composite properties were examined. Thermal property studies revealed that incorporating both types of NMFs improved the thermal stability of the prepared composite samples. When neat PE was filled with 15 wt% of D-NMFs and W-NMFs, the final decomposition temperature (T_f) increased from 475 to 482 and 487 °C, respectively. Mechanical property studies revealed that the addition of NMFs to the composite sample, particularly that of W-NMFs, enhanced the stiffness of the prepared samples, although at the expense of some reduction in their toughness values. The tensile strength, tensile modulus, flexural strength, and flexural modulus values increased from 9.41, 121.80, 5.89, and 99.15 MPa for neat PE to 11.15, 521.82, 17.94, and 597.29 MPa, respectively, for composites containing 25 wt% of W-NMFs. Furthermore, the introduction of shellfish wastes in the NMF/PE blend, especially that of clam shell, further enhanced the overall properties of the composite. After adding 8 wt% of clam shell with 15 wt% W-NMFs, the T_f increased from 487 to 498 °C. The tensile strength, tensile modulus, flexural strength, and flexural modulus values increased from 11.37, 355.13, 16.06, and 443.31 MPa for neat PE to 12.26, 466.73, 18.71, and 568.46 MPa, respectively, for the composite prepared with clam shell. Thus, this study contributes to the WPCB recycling literature and promotes circular economy development.

The treatment and utilisation of agricultural and rural solid wastes are important initiatives to advance high-quality agricultural development and improve rural living environment in a concerted manner. We identified the general background and need of agricultural andrural solid wastes in China, and elucidated the main sources and classified the agricultural and rural solid wastes; we grouped the wastes according to their source, value, components, and form, and described the basic characteristics of agricultural and rural solid wastes, namely, diversity, spatio-temporal fluctuations, and consistency of collection. Based on this, the technical pathways of agricultural and rural solid waste co-processing were systematically summarised for a circular economy based on the construction concept of ‘zero-waste city’ in China, including conversion to fertilisers and energy, value enhancement, and volume reduction. Three main models were developed, namely, the mixed fermentation of agricultural and rural solid wastes for fertiliser production, mixed pyrolysis/gasification/incineration for energy production, and urban-rural integrated waste treatment. Subsequently, we systematically analysed the main framework, fundamental characteristics, and applicable scenarios of the three models. We established the foundations and strategies for the co-processing and efficient utilisation of agricultural and rural solid wastes.

Coal-fired power generation resulted in a shortage of conventional fossil fuels and an increase in greenhouse gas emissions. The co-firing of coal and biomass waste in coal-fired boilers was a promising strategy to supplement the energy source and reduce greenhouse gases. However, the co-firing mechanism and potential problems were not well understood. Therefore, the differences between coal and biomass in properties such as proximate and ultimate composition, components in ash and the calorific value were first discussed. Next, compared with the combustion of coal alone, this review analyzed the discrepancies and corresponding issues of co-firing in combustion behaviors and products such as ash and gaseous pollutants. Finally, this review outlined how operational conditions could affect the co-firing performance.

Despite progress in plastic waste recycling technologies, global plastic waste recycling rates remain disappointing. This issue not only suggests an underutilization of existing recycling technologies but also hinders resource utilization, the circular economy, and sustainable manufacturing. Several studies have proposed to address this issue, such as by evaluating the efficiency of recycling technologies based on the volume of recycled waste. However, such single-indicator methods often overlook other critical factors and, thus, may not provide holistic assessments. Additionally, existing methods for evaluating or comparing different recycling technologies are often complex and time-consuming. Meanwhile, several other studies have proposed hundreds of indicators for assessing the effectiveness and suitability of recycling technologies, which often complicates the selection process. Consequently, recyclers and other stakeholders often struggle to select effective and suitable recycling technologies for different plastic waste types and under specific conditions. To address these challenges, we propose the recycling technology selection framework (RTSF), a simple tool that enables easy visualization of relevant recycling indicators under five key pillars: economic, technical, environmental, social, and policy. By allowing recyclers and stakeholders to quickly identify, select, and visualize factors of interest from a large pool, the RTSF enables qualitative comparison and enhances the evaluation of the effectiveness and suitability of multiple plastic recycling technologies. Lastly, the RTSF can serve as a preliminary tool and be used in conjunction with other approaches to enhance the effectiveness of plastic recycling technologies.

The co-smelting of electronic waste (e-waste) in copper/lead pyrometallurgical processes is widely recognized as the preferred solution for sustainable development. However, aluminum and halogen elements in e-waste causes new challenges. To address this, the slag chemistry of high Al₂O₃-containing slag was studied, and the distribution behaviors of Au, Ag, Sn, and other elements in the copper alloy/slag/gas system were investigated in the presence of halogen elements (F/Cl/Br) using the equilibration method. The industrial practice of electronic waste smelting was modeled using METSIM, and the material and energy balances of one industrial process were obtained. Under the conditions of electronic waste smelting, the solubility of Al₂O₃ in the FexO–SiO₂–Al₂O₃–CaO slag system decreased with increasing CaO content. When the CaO content was 20 wt%, and the Fe/SiO₂ mass ratio was 0.62–0.95, the solubility of Al₂O₃ in the slag reached 20 wt%. When 1%–10% CaF₂ was added, 93% of Au entered the metal phase. When the same amount of CaCl₂ or CaBr₂ was added, up to 32% Au entered the gas phase. When CaF₂ was added to the system, 22%–49% of Ag entered the gas phase. However, when CaCl₂ or CaBr₂ was added, 3%–34% of Ag entered the gas phase. The proportion of tin in the gas and slag phases increased with increasing temperature or the addition of halides. The METSIM simulation results showed that under optimized conditions, the crude copper contained more than 90 wt% copper, the discharged slag contained approximately 0.5 wt% copper, and the recovery rates of copper, gold, and silver were ≥98%. The heat generated from raw materials and fuel accounted for the largest part of the heat income, representing 65.32% of the total.