Circular Economy最新文献

Electronic waste (e-waste) refers to obsolete electronic and electrical equipment and its materials. Due to the complex structure and composition of e-waste, improper disposal may generate substances harmful to humans and the environment and result in the loss of recyclable substances. To tackle the challenges in the end-of-life management of e-waste, there is a need for a systematic review of what the literature has investigated and found. Therefore, this paper aims to explore the extensive scientific literature related to e-waste management using a visualized approach. Overall, 8149 research articles were selected and exported from the Web of Science and then analyzed based on mapping knowledge domains. CiteSpace and Gephi, as effective tools, were utilized to identify hidden patterns and correlations from large and complex research outcomes from 1998 to 2019. This research discussed the evolution of global e-waste management, the knowledge-based network, research topics, frontiers and the cooperation relationships. Finally, this state-of-the-art review generated a few research directions that can be further investigated in this research field.

The benefits of consumer electronic products have transformed every societal sector worldwide. However, the adverse impacts of electronic waste (e-waste) disproportionately affect low-income communities and marginalized ecosystems in nations with economies in transition. The embodied carbon footprint of new electronic products, especially information and communications technology (ICT) devices, is an important source of greenhouse gas (GHG) emissions, accounting for 67% ± 15% of total lifetime emissions, instigated by mineral mining, manufacturing, and supply chain transportation. We estimate that between 2014 and 2020, embodied GHG emissions from selected e-waste generated from ICT devices increased by 53%, with 580 million metric tons (MMT) of CO₂e emitted in 2020. Without specific interventions, emissions from this source will increase to ∼852 MMT of CO₂e annually by 2030. Increasing the useful lifespan expectancy of electronic devices by 50%–100% can mitigate up to half of the total GHG emissions. Such outcomes will require coordination of eco-design and source reduction, repair, refurbishment, and reuse. These strategies can be a key to efforts towards climate neutrality for the electronics industry, which is currently among the top eight sectors accounting for more than 50% of the global carbon footprint.

Visual recognition technologies based on deep learning have been gradually playing an important role in various resource recovery fields. However, in the field of metal resource recycling, there is still a lack of intelligent and accurate recognition of metallic products, which seriously hinders the operation of the metal resource recycling industry chain. In this article, a convolutional neural network with dual attention mechanism and multi-branch residual blocks is proposed to realize the recognition of metallic products with a high accuracy. First, a channel-spatial dual attention mechanism is introduced to enhance the model sensitivity on key features. The model can focus on key features even when extracting features of metallic products with too much confusing information. Second, a deep convolutional network with multi-branch residual blocks as the backbone while embedding a dual-attention mechanism module is designed to satisfy deeper and more effective feature extraction for metallic products with complex characteristic features. To evaluate the proposed model, a waste electrical and electronic equipment (WEEE) dataset containing 9266 images in 18 categories and a waste household metal appliance (WHMA) dataset containing 11,757 images in 23 categories are built. The experimental results show that the accuracy reaches 94.31% and 95.88% in WEEE and WHMA, respectively, achieving high accuracy and high quality recycling.

Lithium (Li) is primarily found in mineral resources, brines, and seawater. Extraction of Li from mineral ore deposits is expensive and energy-intensive. Li-ion batteries (LIBs) are certainly one of the important alternatives to lessen the dependence on fossil fuel resources. The global demand for LIBs for portable electrical and electronic equipment (EEE) and EVs have increased significantly, and the amount of spent LIBs (S-LIBs) is rising logarithmically. S-LIBs contain both hazardous heavy metals and toxic organic chemicals that create a serious threat to human health and the ecosystem. The current position requires the recycling of S-LIBs indispensable for the protection of the environment and the recycling of scarce raw materials from economic aspects. In this manuscript, recent developments and state-of-the-art technologies for LIB recycling were focused on and reviewed comprehensively. Pretreatment methods (such as discharging, dismantling, cathode active material (CAM) removal, binder elimination methods, classification, and separation) for S-LIBs are introduced, and all available and novel technologies that are used in different physical and chemical recovery processes are summarized and compared. The pretreatment process in LIB recycling can both improve the recovery rate of the valuable components and significantly lessen the subsequent energy consumption. Notably, pretreatment, metal extraction, and product preparation stages play vital roles in all LIB recovery processes, based on pyrometallurgy, hydrometallurgy, biometallurgy, direct recycling, and mechanical treatment and water leaching. The main goal of this review is to address the novel S-LIB materials’ current recycling research status and innovations for integrated, eco-friendly, economic, low carbon, and clean energy technologies. In the end, different industrial recycling processes are compared, existing challenges are identified and suggestions and perspectives for future LIBs recycling applications are highlighted.

Urban construction, especially the ongoing large-scale expansion and utilization of underground space, has resulted in massive excavated soil and rock (ESR) from buildings and subways. Therefore, this study aims to explore the technical ways of ESR sintering utilization from the perspective of technology, environment, and policy through qualitative and quantitative methods. The study analyzes the soil properties and distribution of different depths, and the annual production of clay-rich ESR accounts for about 30 million m³ in Shenzhen. More importantly, the comparison between various pollutant concentrations of ESR in Shenzhen and local soil background values showed that the ESR in Shenzhen had no environmental risks. This study can not only provide a scientific basis for ESR as the raw material of sintering but also provide a theoretical basis for the promotion of the pilot of “Zero waste city”.

Circular economy is recognized as a powerful integrative framework envisioned to solve societal problems linked to environmental pollution and resource depletion. Its adoption is rapidly reforming manufacturing, production, consumption, and recycling across various segments of the economy. However, circular economy may not always be effective or even desirable owing to the spatiotemporal dimensions of environmental risk of materials, and variability of global policies. Circular flows involving toxic materials may impose a high risk on the environment and public health such that overemphasis on anthropogenic circularity is not desirable. Moreover, waste flows at a global scale might result in an uneven distribution of risks and costs associated with a circular economy. Among other benefits, circular economy needs to generate environmental advantages, energy savings, and reductions of greenhouse gas emissions. Recent attempts to implement the carbon neutrality strategy globally will likely push the circular economy further into more economic sectors, but challenges remain in implementing and enforcing international policies across national boundaries. The United Nations Basel Convention on the Transboundary Movement of Hazardous Waste and their disposal is used here as an example to illustrate the challenges and to propose a way forward for anthropogenic circularity.

The construction industry is often seen as one of the most dynamic sectors, referring to large resource consumption and waste generation, and has grown rapidly in the last few decades. Under the background of “Zero Waste City,” it will be essential to understand the metabolic stock-flow process and the driving forces of urban building resources. By combining the top-down and bottom-up methods, this study establishes a dynamic material flow analysis (MFA) model to clarify the stock and flow characteristics, driving forces, and future trends of urban building resources in Macao China. The result shows that the total material stock increased from 14.13 million metric tons (Mt) in 1999 to 32.75 Mt in 2018, with an average annual growth rate of 4.29%. In 2018, metal resources accounted for 10.73% of the total building stock (steel and aluminum resources accounted for 10.30% and 0.43%, respectively), and non-metal resources accounted for 89.27%. The construction demolition waste (CD&W) increased from 0.02 Mt in 1999 to 0.69 Mt in 2018. Among metal materials, steel and aluminum accounted for 7.11% and 0.4%, respectively. The demolition quantity of metal resources increased from 1.6 kilotons (kt) in 1999 to 51.8 kt in 2018 (an average annual increase of 1.59%) and peaked at 95.2 kt in 2007. The IPAT (I-environment impact; P-population factor; A-social affluence factor; T-technology factor) method results show that the economy and population are always the driving force for urban building resources stock in Macao China. The scenario analysis shows that, by 2035, the maximum stock of urban building materials in Macao will reach 65.19 Mt, about twice in 2018. The results are expected to provide a theoretical basis for establishing scientific resource management and recycling systems for urban buildings.