Macroscopic Evidence for the Hibernating Behavior of Materials Stock

Comparative evaluation for recycling waste power batteries with different collection modes based on Stackelberg game

The new energy vehicle industry is booming, but the subsequent problem of vehicle power batteries' "scrap tide" is still severe. How to establish and improve the end-of-life power battery recycling system to avoid the "catastrophic" environmental consequences has become an urgent global problem needing a solution. This article constructs three recycling models for manufacturer recycling, retailer recycling, and mixed recycling. By using Stackelberg game and market real data, the influence of carbon trading policy outside the supply chain, power battery endurance capacity and advertising effects within the supply chain on the selection of recycling channels was studied. The results showed: (1) Different recycling channels did not affect the wholesale price, retail price, and market demand for raw material power batteries in the positive supply chain; (2) The total profit function of manufacturers and retailers had a "U-shaped" non-linear relationship with power battery endurance capacity and has a positive linear relationship with the advertising effect. Taking the R&D endurance capacity of 0.4 and the total endurance capacity of 62 kWh as the lowest dividing point, it will decrease first and then increase; (3) The increase in the recycling competition coefficient had a greater impact on the consumption of carbon emission rights in the mixed recycling model than on savings in carbon emission rights, and retailers were the indirect "victims" of rising carbon trading prices; (4) Endurance capacity, advertising effects, and carbon trading prices determined the economics of the recycling model and the carbon emission reduction potential. Manufacturers, retailers, and governments can refer to the value range of each variable to select the most appropriate recycling mode.

An infinite life cycle assessment model to re-evaluate resource efficiency and environmental impacts of circular economy systems

Challenges exist in life cycle assessment (LCA) to evaluate resource efficiency and environmental impacts of circular economy systems. Rules attributing recycling benefits/burdens are inconsistent, causing system boundary ambiguity. Besides, LCAs covering one or several life cycles fail to capture the complete resource path, which leads to unfair assessment results for the primary life cycle. This paper develops an infinite life cycle assessment model, which integrates LCA, substance flow analysis, and a state transition matrix into an infinite-life-cycle framework. On this basis, algorithms are formulated to quantify the resource efficiency and attribute environmental impacts following the principle of whole first, then allocation. Our model is demonstrated by a case study of lead-acid batteries. Results show that the resource efficiency of lead in the infinite life cycle assessment model is at least 118.75% higher than that of primary lead derived from the typical finite life cycle models. Measured by the index of environmental toxicity potential, environmental impacts are transferred from the primary product life cycle to recycled product life cycles, with the range fluctuating from 66.26% to 68.12%. Our model enables scholars to make more reasonable assessments for circular economy systems based on traditional LCA adjustment. From the infinite-life-cycle perspective, sustainable production policies should focus on increasing the recycling rate of waste products rather than limiting the exploitation of natural resources.

Forecast of the U.S. Copper Demand: a Framework Based on Scenario Analysis and Stock Dynamics

In a world of finite metallic minerals, demand forecasting is crucial for managing the stocks and flows of these critical resources. Previous studies have projected copper supply and demand at the global level and the regional level of EU and China. However, no comprehensive study exists for the U.S., which has displayed unique copper consumption and dematerialization trends. In this study, we adapted the stock dynamics approach to forecast the U.S. copper in-use stock (IUS), consumption, and end-of-life (EOL) flows from 2016 to 2070 under various U.S.-specific scenarios. Assuming different socio-technological development trajectories, our model results are consistent with a stabilization range of 215-260 kg/person for the IUS. This is projected along with steady growth in the annual copper consumption and EOL copper generation driven mainly by the growing U.S. population. This stabilization trend of per capita IUS indicates that future copper consumption will largely recuperate IUS losses, allowing 34-39% of future demand to be met potentially by recycling 43% of domestic EOL copper. Despite the recent trends of "dematerialization", adaptive policies still need to be designed for enhancing the EOL recovery, especially in light of a potential transitioning to a "green technology" future with increased electrification dictating higher copper demand.

Potential impact of the end-of-life batteries recycling of electric vehicles on lithium demand in China: 2010-2050

China is expected to realise the complete electrification of traditional internal combustion engine vehicles (ICEVs) by 2050. The rapid development of electric vehicles (EVs) has led to the continuous growth of traction lithium-ion battery (LIB) demand, leading to an increase in demand for specific lithium materials. Therefore, end-of-life (EoL) LIB recycling will largely determine the future lithium availability in China. However, the contribution of recovered lithium to lithium availability is unclear, as the possibility of recovering lithium for reuse in traction LIBs manufacturing is uncertain. To analyse the influence of recovered lithium quality on future lithium availability, we evaluated the potential impact of EoL LIB recycling on lithium demand in China. The results indicated that if new LIB manufacturing cannot use the recovered lithium; the secondary resources would soon exceed the needs of the basic demand (BD) field. In the optimistic scenario, when a LiS battery is used, the oversupply could reach 2.33 Mt by 2050 with a recovery rate of 80%, which is equivalent to 44.05% of China's current lithium reserves of 5.29 Mt. Additionally, when the NCM-G battery is used, the total lithium demand would reach approximately 5.67 Mt in 2031, exceeding China's current lithium reserves. In contrast, if the recovered lithium could be reused in new LIB manufacturing, regardless of the type of LIBs used, the recovered lithium would meet approximately 60% (pessimistic scenario), 53% (neutral scenario), and 49% (optimistic scenario) of the lithium demand for LIBs produced with a recovery rate of 80% by 2050. Consequently, the quality of recovered lithium is very important for its reuse, and it is necessary to develop closed-loop recycling with economic benefits vigorously by improving the quality of recovered lithium. Moreover, much work should be done in recycling infrastructure and industrial policies to promote EoL battery recycling.

Mapping anthropogenic mineral generation in China and its implications for a circular economy

Anthropogenic mineral is absorbing wide concern in the context of circular economy, but its generation mechanism and quantity from product to waste remain unclear. Here we consider three product groups, 30 products, and use the revised Weibull lifespan model to map the generation of anthropogenic mineral and 23 types of the capsulated materials by targeting their evolution from 2010 to 2050. Total weight of anthropogenic mineral on average in China reached 39 Mt in 2010, but it will double in 2022 and quadruple in 2045. Stocks of precious metals and rare earths will increase faster than most base materials. The total economic potential in yearly-generated anthropogenic mineral is anticipated to grow markedly from 100 billion US$ in 2020 to 400 billion US$ in 2050. Furthermore, anthropogenic mineral of around 20 materials will be capable to meet projected consumption of three product groups by 2050.

While a large quantity of underground mineral resources can be converted into manufactured products, a majority is still solid waste disposal. Here the authors found a large increase in total weight of anthropogenic mineral from 2010 to 2050 with faster growth rate for precious metals.

Taking Stock of Built Environment Stock Studies: Progress and Prospects

Built environment stocks (buildings and infrastructures) play multiple roles in our socio-economic metabolism: they serve as the backbone of modern societies and human well-being, drive the material cycles throughout the economy, entail temporal and spatial lock-ins on energy use and emissions, and represent an extensive reservoir of secondary materials. This review aims at providing a comprehensive and critical review of the state of the art, progress, and prospects of built environment stocks research which has boomed in the past decades. We included 249 publications published from 1985 to 2018, conducted a bibliometric analysis, and assessed the studies by key characteristics including typology of stocks (status of stock and end-use category), type of measurement (object and unit), spatial boundary and level of resolution, and temporal scope. We also highlighted the strengths and weaknesses of different estimation approaches. A comparability analysis of existing studies shows a clearly higher level of stocks per capita and per area in developed countries and cities, confirming the role of urbanization and industrialization in built environment stock growth. However, more spatially refined case studies (e.g., on developing cities and nonresidential buildings) and standardization and improvement of methodology (e.g., with geographic information system and architectural knowledge) and data (e.g., on material intensity and lifetime) would be urgently needed to reveal more robust conclusions on the patterns, drivers, and implications of built environment stocks. Such advanced knowledge on built environment stocks could foster societal and policy agendas such as urban sustainability, circular economy, climate change, and United Nations 2030 Sustainable Development Goals.

An Extended Model for Tracking Accumulation Pathways of Materials Using Input–Output Tables: Application to Copper Flows in Japan

Recycling has become increasingly important as a means to mitigate not only waste issues but also problems related to primary resource use, such as a decrease in resource availability. In order to promote and plan future recycling efficiently, detailed information on the material stock in society is important. For a detailed analysis of material stocks, quantitative information on flows of a material, such as its accumulation pathways, final destinations, and its processing forms, are required. This paper develops a model for tracking accumulation pathways of materials using input–output tables (IOTs). The main characteristics of the proposed model are as follows: (1) accumulations in sectors other than the final demand sectors (i.e., endogenous sectors) are explicitly evaluated, (2) accumulations as accompaniments to products, such as containers and packaging, are distinguished from the products, and (3) processing forms of materials are considered. The developed model is applied to analyze copper flows in Japan using the Japanese IOTs for the year 2011. The results show that accumulations of copper in endogenous sectors were not negligibly small (9.24% of the overall flow). Although accumulations of copper as accompaniments were very small, they may be larger for other materials that are largely used as containers or packaging. It was found that the destinations of copper showed different characteristics depending on the processing forms.

Global Lithium Flow 1994-2015: Implications for Improving Resource Efficiency and Security

Lithium has been widely recognized as an essential metal for next-generation clean technologies. With the aim of identifying opportunities for improving lithium resource efficiency and security, this study establishes a long-term trade-linked material flow analysis framework to analyze lithium flow throughout the technological life cycle and across national boundaries during the 1994-2015 period. The results indicate that with broader purposes identified, global lithium production and consumption experienced rapid growth over the past decades. A widely distributed, actively functioning lithium trade network has been established, with the United States, China, the European Union, Chile, and Australia playing essential roles. Global lithium in-use stock, which is mainly embodied in ceramics and glass, reached 29 kilotons in 2015. The lithium stock contained in battery-related applications, together with the huge potential production of stock in future decades, represents a major opportunity for secondary lithium recovery. In the context of intensive international trade, international cooperation on lithium waste management is extremely important. It is also suggested that there is a high risk of lithium shortage for countries with strong dependence on lithium import. The establishment of domestic lithium reserves may be an option for these countries.

Global socioeconomic material stocks rise 23-fold over the 20th century and require half of annual resource use

Human-made material stocks accumulating in buildings, infrastructure, and machinery play a crucial but underappreciated role in shaping the use of material and energy resources. Building, maintaining, and in particular operating in-use stocks of materials require raw materials and energy. Material stocks create long-term path-dependencies because of their longevity. Fostering a transition toward environmentally sustainable patterns of resource use requires a more complete understanding of stock-flow relations. Here we show that about half of all materials extracted globally by humans each year are used to build up or renew in-use stocks of materials. Based on a dynamic stock-flow model, we analyze stocks, inflows, and outflows of all materials and their relation to economic growth, energy use, and CO₂ emissions from 1900 to 2010. Over this period, global material stocks increased 23-fold, reaching 792 Pg (±5%) in 2010. Despite efforts to improve recycling rates, continuous stock growth precludes closing material loops; recycling still only contributes 12% of inflows to stocks. Stocks are likely to continue to grow, driven by large infrastructure and building requirements in emerging economies. A convergence of material stocks at the level of industrial countries would lead to a fourfold increase in global stocks, and CO₂ emissions exceeding climate change goals. Reducing expected future increases of material and energy demand and greenhouse gas emissions will require decoupling of services from the stocks and flows of materials through, for example, more intensive utilization of existing stocks, longer service lifetimes, and more efficient design.

Uncovering the Recycling Potential of "New" WEEE in China

Newly defined categories of WEEE have increased the types of China's regulated WEEE from 5 to 14. Identification of the amounts and valuable-resource components of the "new" WEEE generated is critical to solving the e-waste problem, for both governmental policy decisions and recycling enterprise expansions. This study first estimates and predicts China's new WEEE generation for the period of 2010-2030 using material flow analysis and the lifespan model of the Weibull distribution, then determines the amounts of valuable resources (e.g., base materials, precious metals, and rare-earth minerals) encased annually in WEEE, and their dynamic transfer from in-use stock to waste. Main findings include the following: (i) China will generate 15.5 and 28.4 million tons WEEE in 2020 and 2030, respectively, and has already overtaken the U.S. to become the world's leading producer of e-waste; (ii) among all the types of WEEE, air conditioners, desktop personal computers, refrigerators, and washing machines contribute over 70% of total WEEE by weight. The two categories of EEE-electronic devices and electrical appliances-each contribute about half of total WEEE by weight; (iii) more and more valuable resources have been transferred from in-use products to WEEE, significantly enhancing the recycling potential of WEEE from an economic perspective; and (iv) WEEE recycling potential has been evolving from ∼16 (10-22) billion US$ in 2010, to an anticipated ∼42 (26-58) billion US$ in 2020 and ∼73.4 (44.5-103.4) billion US$ by 2030. All the obtained results can improve the knowledge base for closing the loop of WEEE recycling, and contribute to governmental policy making and the recycling industry's business development.