Forecasting the Potential for Clean Mineral Recycling in the Electrification Transition of Public Buses in Extra-Large Cities: A Case Study of Beijing.

In the context of the low-carbon development of the transport industry, with the trend of low-carbon development of new energy vehicles and rapid growth in the number of demonstrations and promotions, urban public transport has also formally entered the transition period of electrification, and the rapid development of electrification of public transport is becoming an important part of the realization of low-carbon transport systems. To provide a detailed description of the clean minerals stock and its structure in the public transportation system of a megacity, this paper uses Beijing's urban public transport as a case study. By integrating material flow analysis methods and diverse heterogeneous data sets, this study investigates the stock of eight clean mineralslithium (Li), cobalt (Co), nickel (Ni), manganese (Mn), aluminum (Al), platinum (Pt), palladium (Pd), and rhodium (Rh)in the city's bus system. Additionally, the accumulation patterns and recycling potential of these clean minerals under scenarios of the accelerated electrification of urban buses and the development of lithium battery cathode technologies are discussed. The study finds that the total stock of the eight clean minerals in Beijing's urban buses exceeds 10,000 tons from 2011 to 2022, with a nearly 7-fold increase in the annual stock of the metals, of which nickel and manganese account for approximately 30% of the total stock of the metals. Under the scenario of accelerated electrification of urban buses, the total metal stock reaches 28,000 tons in 2023-2050, and the lithium metal increases by 65% compared with that in the baseline scenario. Under the scenario of development of lithium battery cathode technology, the total metal stock decreases by nearly 20% compared with that in the baseline scenario, which shows that the development of lithium battery cathode technology plays an important role in saving clean mineral resources. Under the dual acceleration scenario of urban public transport and lithium batteries, the metal stock decreases to 22,000 tons, with lithium stock accounting for 3/4 of the total stock, showing that the development of electrification and lithium battery technology may lead to significant challenges in terms of the lithium supply. This study estimates the stock of clean mineral materials for urban public transport in Beijing, and the case study of Beijing is useful not only for comparison with similar cities in industrialized countries but also as a reference for the sustainability transition of other types of cities.