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Potential of urban cobalt mines in China: An estimation of dynamic material flow from 2007 to 2016

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Highlights

  • Eight scenarios were considered to estimate the potential of urban cobalt mines.

  • China's cobalt in-use stock reached 115,100 tons.

  • The potential of China's urban cobalt mines was 78,800–186,500 tons.

  • The actual exploitable volume of China's urban cobalt mines was only 30,700–60,700 tons.

Abstract

The development of clean energy and high-tech materials is prospering. Cobalt, an indispensable material in this process, has drawn attention worldwide. China has a high demand for cobalt; the uncertainty of raw material supply and increasing domestic demand for cobalt may trigger a severe cobalt crisis in China. Thus, increasing urban mining may be essential for securing cobalt. This study analysed the changes in China's in-use stock of cobalt over 10 years using dynamic material flow analysis. We modelled the material flow cycle of China's cobalt in 2007–2016. Scenario analysis was conducted to estimate the potential of urban cobalt mines in China in 2007–2016, considering the final cobalt-bearing product lifespan distributions; the recycling rate of cobalt waste; and ideal (A1, A2), intermediate (B1, B2, C1, C2) and poor (D1, D2) scenarios. In 2007–2016, China's in-use stock of cobalt reached 115,100 tons (68.45% from batteries and 15.24% from superalloys). In the eight scenarios, the potential of China's urban cobalt mines was 78,800–186,500 tons. China's urban cobalt mines have great potential, but the actual exploitable volume is low, mainly due to the low overall recycling efficiency of domestic cobalt waste, e.g., the recycling rate of waste lithium-ion batteries is less than 10%. A frame of influencing factors for cobalt recycling was proposed, and the actual exploitable volume of China's urban cobalt mines in 2007–2016 was evaluated to be 30,700–60,700 tons. Policymakers should introduce effective policies to encourage cobalt recycling and increase awareness of recycling in the long run.

Introduction

Cobalt is a widely used material in modern industry and military affairs due to its high melting point, high strength grade, and good magnetic properties (Tkaczyk et al., 2018; Petavratzi et al., 2019). Cobalt has become indispensable for developing clean energy and other high-technology products. It has been listed as a strategic mineral resource in Japan, the EU, China and the US (MEIT,2009; European Commission, 2010; The State Council,2016; U.S. Department of the Interior,2018). Cobalt is widely used in batteries, cemented carbides, superalloys, catalysts, magnetic materials, and ceramic pigments (CI,2019; Shen et al., 2017; Pollock,2016; Budiman et al., 2012). In recent years, the global consumption of cobalt has accelerated; 50% of this consumption is used for consumer electronics (CEs) and electric vehicles (EVs) (Shedd,2017). Cobalt plays an important role in lithium-ion batteries(LIBs) and is associated with the stability of the molecular structure and the safety of batteries (Manthiram et al., 2015). Cobalt-containing batteries, e.g., lithium cobalt oxide batteries (LCOs) and lithium nickel manganese cobalt oxide batteries (NMCs), are very popular worldwide.

Since 2007, China has been the largest cobalt producing and consuming country in the world (Harper et al., 2012). In 2016, the amount of Chinese-produced refined cobalt was 34 times greater than that produced in 2000 (Shedd et al., 2017). China is the main supplier of refined cobalt and supplies approximately 60% of refined cobalt products and 80% of cobalt chemical products (Robin,2019). In 2016, the global consumption of cobalt was 95,000 tons, of which China's cobalt consumption represented approximately 50% (CNMIA, 2017).

The domestic demand for cobalt in China is increasing, but the cobalt supply is insufficient. To support the domestic supply chain, China imports a large amount of cobalt resources from the Democratic Republic of the Congo (DR Congo). However, because of instability in parts of the DR Congo, China's cobalt supply will experience a shortage. In recent years, batteries with low cobalt content and free cobalt have led to a wave of research on power batteries due to the high price of cobalt. Even major players such as Glencore have planned to reduce their production.1 At present, however, replacing cobalt in LIBs is not easy, especially because the existence of cobalt increases the power of batteries and the mileage of EVs (Li and Lu, 2020). EVs are highly promoted by the Chinese government because they contribute to reducing greenhouse gas (GHG) emissions (Huang and Ge, 2019). In 2010, EV manufacturing was listed as a strategic new industry. Through 2015, China was the largest EV market, and EV sales amounted to nearly 380,000 units (MIIT,2016). The predicted total accumulated sales will reach 12–14 million in 2020 (Li et al., 2019b). The average cobalt consumption of one EV is 15 kg (Chinacar,2017). China will achieve a high-demand and high-consumption status in the next decade; with the advent of the 5 G era, the replacement of CEs will also increase the demand for cobalt.However, in China, the estimated cobalt reserves are only 80,000 tons, accounting for 1.14% of the world's cobalt reserves, and the grade of cobalt ore is poor (USGS, 2020; Wilburn, 2012). Moreover, the domestic cobalt supply is insufficient. Therefore, China will keep importing cobalt from foreign countries such as the DR Congo. In 2016, 97% of the cobalt used in the Chinese refining industry was obtained from foreign countries (excluding overseas direct investment), mostly from the DR Congo (Gulley et al., 2019). The economic and political situations in some of the critical metal resource exporting countries are often fragile; thus, trade relations can become unstable. In particular, the conflicts in the artisanal cobalt mine areas of the DR Congo have been long-standing (Wakenge,2018; Vogel,2018). Therefore, the security of the supply of cobalt in China is at high risk due to the high import concentration ratio and instability of metal resource exporting countries (Zhou et al., 2019).

Urban mining (UM) is an efficient way to reduce natural resource exploitation and to protect the supply of resources (Hu and Poustie, 2018). To reduce risks related to the cobalt supply in China, UM could reduce pressure on natural resources and protect resources. UM makes urban spaces a source of recyclable anthropogenic materials (Li,2015; Brunner,2011). For some metals, such as iron (Muller et al., 2006), copper (Daigo et al., 2009), and aluminium (Ciacci et al., 2013), the cyclic utilization of these products will gradually replace the natural supply. Metal materials are accumulated in products or as waste in urban areas, and the metal materials contained inproducts and waste are called “urban mines” (Zuo et al., 2018). Electronic waste (e-waste) is the most important material found in “urban mines”, and it is one of the most abundant recyclable resources (Van Eygen et al., 2016). Many researchers have proven that high-purity cobalt metal can be recycled from wasteLIBs (Dhiman and Gupta, 2019). Cobalt can also be recycled from alloy waste and magnetic waste (Kim et al., 2018; Lee et al., 2011; Xu et al., 2010). Due to the development of recycling technologies and the increasing use ratio of waste, secondary resource utilization will be an important way to alleviate problems associated with resource supply. In this paper, we define “urban cobalt mines” as the cobalt-containing waste produced each year and the “potential of urban cobalt mines” as the amount of cobalt metal that can be recycled from cobalt-containing waste in a socio-economic system within a certain period of time.

Material flow analysis (MFA) is a useful analytical tool for characterizing the circulation of materials; it describes the long-term or short-term flow of materials through the establishment of models, and it shows how materials are transformed, processed, recycled and stored (Lin et al., 2019; Liu and Müller,2013; Chen and Shi,2012; Vexler et al., 2004). Thismethod can provide valuable suggestions for quantifying the recycling ratio and evaluating recycling efficiency, especially in metal research and waste management (Chen and Graedel, 2012; Golev et al., 2016; Cao et al., 2016a). Both static and dynamic MFA models can be used for MFA. A static MFA model describes the flow of materials in the short term (usually one year) by observing the balance of inputs, stocks, and outputs (Spatari et al., 2002). A dynamic MFA model can quantify past material flows by modelling the lifespan of products to track changes in the material flow, including material production, manufacturing, the generation of waste, and transactions within boundaries (Park et al., 2011). Dynamic MFA can also quantify the potential of the accumulated stores of some materials that determine the potential of the secondary supply. Dynamic MFA is often used to predict the flows and stocks of wastes over a period of time (Tazi et al., 2019; Tran et al., 2018; Ziemann et al., 2018; Gusukuma and Kahhat, 2018; Cao et al., 2017). Through MFA, the recycling potential of multiple metal wastes, such as copper (Gorman and Dzombak, 2020), indium (Ciacci et al., 2019b), platinum (Saidani et al., 2019), gallium (Eheliyagoda et al., 2019), and neodymium (Ciacci et al., 2019a), has been quantitatively researched.

In addition, with the results of case analyses and field-tracking surveys, the recycling potential ofmunicipal solid waste, computer waste and e-waste has been evaluated (Gu et al., 2018; Kohl and Gomes, 2018; Zeng et al., 2017). However, few have studied the recycling potential of cobalt waste. In recent studies on cobalt, the cobalt flow cycle has always been popular. Through the circulation of cobalt, the status of China'scobalt production, manufacturing, consumption, application and waste management in 2005, 2008 and 2012has been shown in detail (Harper et al., 2012;Yan et al., 2015;Wen and Han, 2018). Global cobalt flows have also been further analysed (Nansai et al., 2014; Sun et al., 2019). Most studies used dynamic MFA to simulate and predict the future of cobalt. Zeng and Li (2015) were the first to establish the circulation of China's cobalt from 2005 to 2013, and they also forecasted China's domestic demand for cobalt in 2030. The results showed that the accumulated demand for cobalt would equal local cobalt reserves by 2021. Using the same research method, Chen et al. (2019b) performed a historical analysis of the flow and stock of cobalt in China's anthroposphere from 1994 to 2016, and they estimated the domestic demand potential of cobalt from 2017 to 2035.

Researchers have proposed some suggestions for the future consumption of China's cobalt, and there is an urgent need to strengthen the recycling of secondary cobalt. However, few studies have focused on the recycling of cobalt in China. In addition, previous studies on recycling potential had some limitations. First, the majority of studies analyse product lifespan usingthe average lifespan;few studies focus on the range of the product lifespan distribution. Second, previous studies have paid little attention to the differences in the recycling rate of cobalt waste under various recycling technologies. Furthermore, previous studies have mainly evaluated the primary recycling potential of various wastes. However, in this study, we extend prior studies and consider the lifespan and recycling rate of various cobalt-bearing products. Moreover, we evaluate the actual exploitable volume of China's urban cobalt minesbased on a recycling frame consisting of three factors: government policies, public awareness, and the recycling system. Our study provides three main contributions to the field of mineral resource management research in China: first,based on the material flow model, the potential of urban cobalt mines in China from 2007 to 2016 is estimated. Second, a frame of influencing factors for cobalt recycling is proposed, and based on this frame, the actual exploitable volume of China's urban cobalt mines from 2007 to 2016is evaluated. Third, information on cobalt products is expanded, and magnetic materials, ceramic pigments, and other cobalt-bearing products are identified.

Section snippets

Modelling of material flows

In this study, the system boundaries of the cobalt flow model are as follows. The geographical boundary is mainland China (including 31 provinces), and the temporal boundary is 2007–2016. The life cycle of metal resources typically includes stages of mining, refining, manufacturing, use, waste and recycling (Wen et al., 2015). To quantitatively study the flow and stock of cobalt, we use the studies by Chen et al. (2019b), Sun et al. (2019), and Zeng and Li (2015) as a reference. In this study,

Cobalt flow cycles

Fig. 3 shows the flow cycles of cobalt in China in 2007, 2011 and 2016. In this decade, the production and consumption of cobalt in China grew significantly, and the cobalt-related industrial structure transitioned from front-end production to back-end applications.

Regarding the supply of cobalt raw materials, China's domestic cobalt mining volume has decreased, and a large amount of raw materials must be imported from abroad. In 2007, the domestic production of cobalt mines amounted to 1,886

Strategies

This paper proposes some suggestions for improving the actualexploitable volume of urban cobalt mines in China.

Differences from previous studies

Table 8 provides an overview of different studies on cobalt in China.

A comparison between the studies listed in the table and our study shows that few studies have focused on the recycling potential of cobalt in China. Most studies conduct an MFA of cobalt and future prediction simulations to help in understanding China's cobalt cycle and the future trends of China's cobalt consumption demand. However, due to the growth in the CE and EV industries, the security of China's cobalt supply has

Conclusion

To assess the potential of urban cobalt mines in China, this study established an MFA model of China's cobalt from 2007 to 2016. The results show that from 2007 to 2016, China's cobalt stocks mostly came from battery materials and superalloys. Since 2016, as large-scale final cobalt-bearing products have entered the waste management stage, the in-use stock of domestic cobalt has decreased.

Urban cobalt mines in China are mainly composed of waste batteries, cemented carbides, superalloys,

Credit author statement

Yibo Wang: Methodology, Formal analysis, Investigation, Data Curation, Writing - Original Draft

Jianping Ge: Conceptualization, Methodology, Validation, Writing - Review & Editing, Supervision, Project administration, Funding acquisition

Declaration of Competing Interest

The authors declared that they have no conflicts of interest to this work.

We declare that we do not have any commercial or associative interest that represents a conflict of interest in connection with the work submitted.

Acknowledgments

This study is supported by grant from the National Natural Science Foundation of China (Grant no. 71774149), the Fundamental Research Funds for the Central Universities (Grants nos. 292018006 and 292017023), the Beijing Social Science Foundation (Grant no. 16YJB031), and the Key Laboratory of Carrying Capacity Assessment for Resources and the Environment, Ministry of Natural Resources (Grant no. CCA2019.06).

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