Urban mining demonstration bases in China: A new approach to the reclamation of resources

Insights into the evolution of cobalt use and implications through dynamic analysis of cobalt flows and stocks and the recycling potential of cobalt from urban mines in China during 2000-2021

Several countries regard cobalt as a critical material due to its extensive use in clean energy technology and high-tech industries. To comprehensively examine how China's cobalt industry developed and evolved from 2000 to 2021, our study quantified cobalt flows, stocks and the recycling potential of cobalt from China's urban cobalt mines using dynamic material flow analysis. In 2021, China's in-use cobalt stocks for cobalt-containing end products reached 131 kt, of which battery products and superalloys accounted for 83.8% and 8.1%, respectively. The theoretical cumulative recycling potential of cobalt from China's urban cobalt mines reached 204-356 kt between 2000 and 2021 under different scenarios. However, the actual cumulative exploitation of cobalt from urban cobalt mines was 46-80 kt, of which consumer electronics, cemented carbides, and superalloys were the main recycled products. The cumulative exports and imports of cobalt in all commodities reached 558 and 1117 kt, respectively. China exported a large quantity of cobalt chemicals, chemical derivatives and cobalt-containing end products produced from imported cobalt raw materials. China imported 84.7% of the cobalt raw materials consumed domestically, and 32.6% of the domestically produced cobalt-containing end products were exported. Over the entire life cycle of cobalt, cobalt losses totaled 288 kt, with 51.0% of losses coming from refining, and a 73.8% cobalt utilization efficiency was achieved. China recovered 76.7 kt of cobalt, and the recycling rate of cobalt from end-of-life cobalt-containing end products reached 20.0%. The findings can serve as a scientific basis for China's cobalt industry to develop efficiently and economically.

Issues and solutions of electronic waste urban mining for circular economy transition: An Indian context

The rapid consumption of advanced e-products has intensified problems for the linear economy; constantly diminishing natural resources employed in production processes have created a need of recycle and reuse. Although the transition to a circular economy proposes to end the loop of e-products, it needs the application of processes such as urban mining to recover resources as secondary raw material. The present study intends to examine the issues and challenges of electronic waste urban mining (EWUM) in India that need to be assessed for the development of a sustainable economy. To accomplish this, the current study employs integrated Multi-Criteria-Decision making methods (MCDM). Step-Wise Weight Assessment Ratio Analysis (SWARA) is used to prioritize issues and their possible solutions with Weighted Assessment Sum Product Assessment (WASPAS) methods introduced to explore these challenges and provide solutions for managing EWUM. There is an immediate need to acknowledge the issues confronted by stakeholders in urban mining processes for successful transition to a circular economy. A better understanding of the issues will help policy makers and decision makers to implement best practices to enhance the urban mining process in India. This study has shown that socio-economic (SE) issues are the most critical issues in EWUM in India. The possible solutions that would have most impact are to enhance awareness campaigns for people to educate themselves regarding e-waste, train staff to handle safe disposal of e-waste and produce eco-friendly electronic products.

The valorisation of residual waste bales by urban mining

In the last decade, the approach to waste management has undergone severe changes. The urgent need to face the sustainable demand for energy and materials while limiting the burdens associated to traditional waste handling practices have figured out the concept of waste as a resource. New strategies boosting the extensive recovery and diverting waste from disposal activities have been promoted and framed in the wider context of the urban mining, promoting the full exploitation of waste as resource for either new materials or energy production. Such approach has been recently proposed to handle over 5 million tons of pretreated municipal solid waste produced and stored in the form of bales in Campania Region, in southern Italy, between 2000 and 2009. However, since the feasibility of this approach is related to the waste composition as well as to the selection process, an experimental study was performed at an industrial mechanical treatment plant to assess the potential for valorisation of this waste. Results showed that the overall sustainability of the urban mining strategies for the management of Campania waste bales is tightly linked to the flexibility of the selection process scheme to be adopted, which should make the waste recovery fit the market demand of either material or energy.

Comprehensive characterization on Ga (In)-bearing dust generated from semiconductor industry for effective recovery of critical metals

Gallium (indium)-bearing dust generated from semiconductor industry is an important secondary resource for critical metal recycling. However, the diverse and distinct physicochemical natures of such waste material have made its recycling less effective, e.g. low extraction rate and complex treatment procedures. This research is devoted to gaining in-depth knowledge of the physical and chemical properties of such waste, including the chemical composition, physical phases, particle size distribution and chemical-thermal properties with a series of technologies. As a consequence, the occurrence and distribution of GaN and metallic indium phases are found to be crucial to efficient metal recycling. The thermal-chemical behavior shows that continuous oxidation occurred in the air atmosphere, indicating that heat-treatment followed by acid leaching is feasible to improve their recycling efficiencies. This process is able to leach 80.35% of gallium and 95.78% of indium with one-step operation. Furthermore, different treatment strategies for the waste material are preliminarily evaluated and discussed for the aim of metal recovery. The results show that gallium can be selectively recycled with recycling rate of 89.59% using alkaline leaching. With this research, the understanding on the recyclability of different metals and possibilities of selective recovery can be improved. It provides guidelines during the stage of decision-making for critical metal recycling in order to achieve efficient resource circulation.