Linking material flow analysis and resource policy via future scenarios of in-use stock: an example for copper

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.

Mining the Built Environment: Telling the Story of Urban Mining

Materials are continuously accumulating in the human-built environment since massive amounts of materials are required for building, developing, and maintaining cities. At the end of their life cycles, these materials are considered valuable sources of secondary materials. The increasing construction and demolition waste released from aging stock each year make up the heaviest, most voluminous waste outflow, presenting challenges and opportunities. These material stocks should be utilized and exploited since the reuse and recycling of construction materials would positively impact the natural environment and resource efficiency, leading to sustainable cities within a grander scheme of a circular economy. The exploitation of material stock is known as urban mining. In order to make these materials accessible for future mining, material quantities need to be estimated and extrapolated to regional levels. This demanding task requires a vast knowledge of the existing building stock, which can only be obtained through labor-intensive, time-consuming methodologies or new technologies, such as building information modeling (BIM), geographic information systems (GISs), artificial intelligence (AI), and machine learning. This review paper gives a general overview of the literature body and tracks the evolution of this research field.

Uncovering material flow analysis of waste cathode ray tubes television in China

Cathode ray tube televisions (TVs) contributes significantly to the rapidly increasing waste stream of cathode ray tubes in the e-waste. This study mainly focused on the material flow of waste cathode ray tube TVs in China. Currently, waste cathode ray tubes constitute a major part of the total generation of e-waste in China. The study aimed to emphasise the flow of materials in the generated waste cathode ray tube TVs by using stock-based material flow analysis model. The modelling was conducted to investigate the disposable number of obsolete devices, in-use stock, and end-of-life of cathode ray tube TVs. SubSTance flow ANalysis (STAN) software was used to perform the material flow analysis modelling and graphical model of the waste cathode ray tube TVs. The results show that in a period of 10 years, overall about 3241.37 kt of cathode ray tube TVs were net produced in China, containing 183.6 kt of glass, 1718.2 kt of plastic, 243 kt of steel/iron, 153.5 kt of lead, 76.6 kt of copper, 7.8 kt of aluminium, and 1.6 kt of antimony. The results revealed that almost 125 kt of end-of-life cathode ray tube TVs containing about 68 kt of glass, 40 kt of plastic, 9 kt of steel/iron, 6 kt of lead, 3 kt of copper, 0.3 kt of aluminium, and 0.07 kt of antimony were dumped in the period of 10 years. Therefore, the management of waste cathode ray tube TVs required better infrastructure for recycling and better regulation to achieve better results in the high recovery of valuable resources.

An Assessment of the Environmental Sustainability and Circularity of Future Scenarios of the Copper Life Cycle in the U.S

Assessments of availability and sustainability of metals necessary for economic development into the future are important for planning by producers, consumers, and governments. This work assessed the U.S. copper life cycle and examined six future scenarios by which to assess the circular economy and sustainability of copper to 2030. Regression analysis methodology was used to identify relationships among seven drivers and eight materials flows. These relationships were used to develop six forecasts of future scenarios for U.S. production, consumption, old scrap collection, new scrap recovery, landfilling, and scrap exports of copper. Flow forecasts were used to quantify circularity and environmental footprint metrics to assess sustainability. Results of the scenario analyses provide insights into the types of behaviors and trends that could be incentivized to allow for increased circularity of copper. One such finding was that slow population growth and high urbanization resulted in the most circular scenario. Major limitations to circularity are import reliance and scrap exports. Analysis of the scenarios leads to the conclusions that population dynamics are critical to the circularity of copper, as well as that both environmental footprint metrics and circularity indicators must be considered when assessing environmental sustainability.

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.

Calculation of Characterization Factors of Mineral Resources Considering Future Primary Resource Use Changes: A Comparison between Iron and Copper

The future availability of mineral resources has attracted much attention; therefore, a quantitative evaluation of the potential impacts of resource use on future availability is important. Although the surplus cost model is often recommended among the existing endpoint characterization models of mineral resources, it has a shortcoming as it does not consider the changes in future primary resource use. This paper introduces a new characterization model considering future primary resource use changes, due to future changes in total demand and secondary resource use. Using material flow analysis, this study estimated time-series primary resource use for iron and copper for five shared socioeconomic pathways (SSPs) and a constant total demand scenario. New characterization factors, i.e., demand change-based surplus costs (DCSC), are calculated for each resource. In all of the SSPs, the calculated DCSCs are larger than the conventional surplus costs (SC) for both iron and copper. The DCSC, relative to the SC of copper, is larger than that of iron for all of the SSPs, which suggests that the potential impacts of copper use, relative to iron, will be underestimated, unless future primary resource use changes are considered. In calculating DCSC for other resources, it is important to choose an appropriate approach for forecasting future total demands.

Characterizing copper flows in international trade of China, 1975-2015

Since the economic reform, China has actively participated in the global market with rapid industrialization and gradually dominated the utilization and consumption of some critical materials, one of which is copper. China has reigned the global anthropogenic cycle of copper since 2004. We explore copper flows along with the international trade of China during 1975-2015, through life cycle lens, from ore to final products. Our main finding is that China has become more active in the copper-related trade, indicated by its great increase in trade volume and the number of trade partners. The physical volume of copper flows through trade increased over 119 times between 1975 and 2015, mainly because of more imported raw materials of copper and exported copper products. Generally, China is a net importer of copper, with increasing import dependence through the study period, whereas the degree of dependence slightly decreased from 2010 to 2015. The indicator of Export Support Rate took a decreasing percentage, which has fallen about 35% since 2010. It suggests China's changing position in the global resource and manufacturing market. In terms of trade price of different copper products, the price of imported copper concentrate was noticeably higher than that of exported one, revealing the poor copper resource endowment of China; while the different trend of copper semis in recent years signifies that China is in urgent need to improve its capability of producing high value-added semis. From international trade perspective, the copper resource of China presented stable supply as well as demand. The One Belt One Road strategy proposed by the state will further expand both the resource and market of copper.

Assessment of the Secondary Copper Reserves of Nations

The sustainable use of metals demands consideration not only of primary metals in the natural environment but also of secondary metals in society as alternative resources. This study applied our proposed classification framework of secondary resources to copper (1) to investigate the applicability of the framework and (2) to assess the secondary copper reserves and resources of selected countries. To estimate secondary copper reserves, we introduced the variable "secondary reserve ratio": the fraction of in-use copper stocks that is technically and economically recoverable. Our estimates showed that the United States and China have secondary copper reserves of 44 and 33 Mt, respectively, and showed that global secondary copper reserves are about 30% of global primary reserves. The application of the classification framework showed that considerable amounts of secondary copper resources are in landfills, which are potential targets of future extraction of secondary copper through landfill mining. Overall, the classification framework provides a better understanding of the current size of available secondary resources and waste deposits. It also highlights the need for integrated management of primary and secondary resources.

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.

Accounting for the Material Stock of Nations

National material stock (MS) accounts have been a neglected field of analysis in industrial ecology, possibly because of the difficulty in establishing such accounts. In this research, we propose a novel method to model national MS based on historical material flow data. This enables us to avoid the laborious data work involved with bottom-up accounts for stocks and to arrive at plausible levels of stock accumulation for nations. We apply the method for the United States and Japan to establish a proof of concept for two very different cases of industrial development. Looking at a period of 75 years (1930-2005), we find that per capita MS has been much higher in the United States for the entire period, but that Japan has experienced much higher growth rates throughout, in line with Japan's late industrial development. By 2005, however, both Japan and the United States arrive at a very similar level of national MS of 310 to 375 tonnes per capita, respectively. This research provides new insight into the relationship between MS and flows in national economies and enables us to extend the debate about material efficiency from a narrow perspective of throughput to a broader perspective of stocks.

Modeling metal stocks and flows: a review of dynamic material flow analysis methods

Dynamic material flow analysis (MFA) is a frequently used method to assess past, present, and future stocks and flows of metals in the anthroposphere. Over the past fifteen years, dynamic MFA has contributed to increased knowledge about the quantities, qualities, and locations of metal-containing goods. This article presents a literature review of the methodologies applied in 60 dynamic MFAs of metals. The review is based on a standardized model description format, the ODD (overview, design concepts, details) protocol. We focus on giving a comprehensive overview of modeling approaches and structure them according to essential aspects, such as their treatment of material dissipation, spatial dimension of flows, or data uncertainty. The reviewed literature features similar basic modeling principles but very diverse extrapolation methods. Basic principles include the calculation of outflows of the in-use stock based on inflow or stock data and a lifetime distribution function. For extrapolating stocks and flows, authors apply constant, linear, exponential, and logistic models or approaches based on socioeconomic variables, such as regression models or the intensity-of-use hypothesis. The consideration and treatment of further aspects, such as dissipation, spatial distribution, and data uncertainty, vary significantly and highly depends on the objectives of each study.

Dynamic analysis of global copper flows. Global stocks, postconsumer material flows, recycling indicators, and uncertainty evaluation

We present a dynamic model of global copper stocks and flows which allows a detailed analysis of recycling efficiencies, copper stocks in use, and dissipated and landfilled copper. The model is based on historical mining and refined copper production data (1910-2010) enhanced by a unique data set of recent global semifinished goods production and copper end-use sectors provided by the copper industry. To enable the consistency of the simulated copper life cycle in terms of a closed mass balance, particularly the matching of recycled metal flows to reported historical annual production data, a method was developed to estimate the yearly global collection rates of end-of-life (postconsumer) scrap. Based on this method, we provide estimates of 8 different recycling indicators over time. The main indicator for the efficiency of global copper recycling from end-of-life (EoL) scrap--the EoL recycling rate--was estimated to be 45% on average, ± 5% (one standard deviation) due to uncertainty and variability over time in the period 2000-2010. As uncertainties of specific input data--mainly concerning assumptions on end-use lifetimes and their distribution--are high, a sensitivity analysis with regard to the effect of uncertainties in the input data on the calculated recycling indicators was performed. The sensitivity analysis included a stochastic (Monte Carlo) uncertainty evaluation with 10(5) simulation runs.

Centennial evolution of aluminum in-use stocks on our aluminized planet

A dynamic material flow model was developed to simulate the evolution of global aluminum stocks in geological reserve and anthropogenic reservoir from 1900 to 2010 on a country level. The contemporary global aluminum stock in use (0.6 Gt or 90 kg/capita) has reached about 10% of that in known bauxite reserves and represents an embodied energy amount that is equivalent to three-quarters of the present global annual electricity consumption. The largest proportions of in-use stock are located in the U.S. (28%), China (15%), Japan (7%), and Germany (6%) and in sectors of building and construction (40%) and transportation (27%). Industrialized countries have shown similar patterns of aluminum in-use stock growth: once the per-capita stocks have reached a threshold level of 50 kg, they kept a near linear annual growth of 5-10 kg/capita; no clear signs of saturation can yet be observed. The present aluminum in-use stocks vary widely across countries: approximately 100-600 kg/capita in industrialized countries and below 100 kg/capita in developing countries. The growing global aluminum in-use stock has significant implications on future aluminum demand and provides important recycling opportunities that will be critical for greenhouse gas emissions mitigation in the aluminum industry in the coming decades.

Anthropogenic cycles of the elements: a critical review

A cycle is the quantitative characterization of the flows of a specific material into, within, and from a given system. An anthropogenic elemental cycle can be static (for a point in time) or dynamic (over a time interval). The about 350 publications collected for this review contain a total of 1074 individual cycle determinations, 989 static and 85 dynamic, for 59 elements; more than 90% of the publications have appeared since 2000. The cycles are of varying quality and completeness, with about 80% at country- or territory-level, addressing 45 elements, and 5% at global-level, addressing 30 elements. Despite their limitations, cycles have often been successful in revealing otherwise unknown information. Most of the elements for which no cycles exist are radioactively unstable or are used rarely and in small amounts. For a variety of reasons, the anthropogenic cycles of only perhaps a dozen elements are well characterized. For all the others, with cycles limited or nonexistent, our knowledge of types of uses, lifetimes in those uses, international trade, losses to the environment, and rates of recycling is quite limited, thereby making attempts to evaluate resource sustainability particularly problematic.

Outlook of the world steel cycle based on the stock and flow dynamics

We present a comprehensive analysis of steel use in the future compiled using dynamic material flow analysis (MFA). A dynamic MFA for 42 countries depicted the global in-use stock and flow up to the end of 2005. On the basis of the transition of steel stock for 2005, the growth of future steel stock was then estimated considering the economic growth for every country. Future steel demand was estimated using dynamic analysis under the new concept of "stocks drive flows". The significant results follow. World steel stock reached 12.7 billion t in 2005, and has doubled in the last 25 years. The world stock in 2005 mainly consisted of construction (60%) and vehicles (10%). Stock in these end uses will reach 55 billion t in 2050, driven by a 10-fold increase in Asia. Steel demand will reach 1.8 billion t in 2025, then slightly decrease, and rise again by replacement of buildings. The forecast of demand clearly represents the industrial shift; at first the increase is dominated by construction, and then, after 2025, demand for construction decreases and demand for vehicles increases instead. This study thus provides the dynamic mechanism of steel stock and flow toward the future, which contributes to the design of sustainable steel use.