Circular Economy最新文献

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.

Aluminium is one widely used metal that plays an important role in China's industrial and economic development. The life cycles of aluminium products involve high energy inputs, intensive material consumption and heavy environmental emissions. China has released its ambitious climate change targets, namely reaching carbon peak in 2030 and achieving carbon neutrality in 2060. It is therefore urgent to take appropriate actions to reduce the overall greenhouse gas emissions from aluminium production and increase resource efficiency along the entire aluminium life cycle. Under such circumstances, this study aims to explore China's aluminium recycling potential through dynamic material flow analysis for the period of 2000–2019, covering its whole life cycle and including relevant international trade activities. An entropy analysis method is also applied to identify optimal pathways to improve aluminum resource efficiency and circularity. Results indicate that China has experienced fast growth of aluminum production and consumption during the last two decades, with its output of primary aluminium increasing from 4.18 Mt in 2000 to 35.11 Mt in 2019 and its aluminium consumption increasing from 2.99 Mt in 2000 to 32.5 Mt in 2019. Such rapid growth has resulted in significant environmental impacts. For instance, environmental loss of aluminium at the production stage accounted for 46% of the total loss throughout its entire life cycle in 2000, while such a rate increased to 69% in 2019. As such, entropy analysis results reflect that at the stage of waste management, the relative entropy of aluminium is rising, which indicates that any pollutants discharged into the environment will cause significant damage. Scenarios analysis results further help to identify the optimal pathway of aluminium metabolism system. Finally, several policy recommendations are proposed to improve the overall aluminium resource efficiency.

Circular economy seems a vital enabler for sustainable use of natural resources which is also important for achieving the 2030 agenda for sustainable development goals. Therefore, a special session addressing issues of “sustainable solutions and remarkable practices in circular economy focusing materials downstream” was held at the 16th International Conference on Waste Management and Technology, where researchers and attendees worldwide were convened to share their experiences and visions. Presentations focusing on many key points such as new strategies, innovative technologies, management methods, and practical cases were discussed during the session. Accordingly, this article compiled all these distinctive presentations and gave insights into the pathway of circular economy towards the sustainable development goals. We summarized that the transition to circular economy can keep the value of resources and products at a high level and minimize waste production; the focus of governmental policies and plans with the involvement of public-private-partnership on 3Rs (reduce, reuse, and recycle) helps to improve the use of natural resources and take a step ahead to approach or achieve the sustainability.

In this study, the yield of conversion process of plastic and biomass wastes has been investigated using the pyrolysis process. To study the pyrolysis process and its yield, a quadratic model has been adopted and the coefficients of the model have been identified from the theoretical and experimental work. The pyrolysis of biomass and plastics has been analyzed through the kinetic model. The model has predicted bio-oil, bio-gas, and bio-char yields. Through kinetic model analysis, thermodynamic parameters have been identified. The Arrhenius coefficient of reaction rate constant has been calculated from the activation energy and absolute reaction temperature. The enthalpy, Gibbs free energy, and entropy of reaction have also been calculated. The activation energy has been observed to vary from 144.9 to 158.5 kJ/mol. The Arrhenius coefficient of reaction rate constant has been identified as 0.000779 per minute. The enthalpy and Gibbs free energy have been observed to have values of 154.35 and 103.65 kJ/mol, respectively. The bio-oil yield has been observed to vary from 60% to 80% of the total yield. For bio-char production, the weight percentage of bio-char has been found as 2 to 3 percent of the total yield. Bio-gas has been found as 10%–25% of the total yield. Therefore, the addition of plastic for pyrolysis can make a positive contribution to the quality of syngas and bio-oil in terms of high heating value, efficiency, and energy output.