In recent years, increasing attention has been given to the potential supply risks of critical battery materials, such as cobalt, for electric mobility transitions. While battery technology and recycling advancement are two widely acknowledged strategies for addressing such supply risks, the extent to which they will relieve global and regional cobalt demand–supply imbalance remains poorly understood. Here, we address this gap by simulating historical (1998-2019) and future (2020-2050) global cobalt cycles covering both traditional and emerging end uses with regional resolution (China, the U.S., Japan, the EU, and the rest of the world). We show that cobalt-free batteries and recycling progress can indeed significantly alleviate long-term cobalt supply risks. However, the cobalt supply shortage appears inevitable in the short- to medium-term (during 2028-2033), even under the most technologically optimistic scenario. Our results reveal varying cobalt supply security levels by region and indicate the urgency of boosting primary cobalt supply to ensure global e-mobility ambitions.

Wind energy is key to addressing the global climate challenge, but its development is subject to potential constraints of finite primary materials. Prior studies on material demand forecasting of wind power development are often limited to a few materials and with low technological resolution, thus hindering a comprehensive understanding of the impact of microengineering parameters on the resource implications of wind energy. In this study, we developed a component-by-component and stock-driven prospective material flow analysis model and used bottom-up data on engineering parameters and wind power capacities to characterize the materials demand and secondary supply potentials of wind energy development in Denmark, a pioneering and leading country in wind power. We also explicitly addressed the uncertainties in the prospective modeling by the means of statistical estimation and sensitivity analysis methods. Our results reveal increasing challenges of materials provision and end-oflife (EoL) management in Denmark's ambitious transition toward 100% renewable energy in the next decades. Harnessing potential secondary resource supply from EoL and extending lifetime could curtail the primary material demand, but they could not fully alleviate the material supply risk. Such a model framework that considers bottom-up engineering parameters with increased precision could be applied to other emerging technologies and help reveal synergies and trade-offs of relevant resource, energy, and climate strategies in the future renewable energy and climate transition.

The rapid urbanization in China since the 1970s has led to an exponential growth of metal stocks (MS) in use in cities. A retrospect on the quantity, quality, and patterns of these MS is a prerequisite for projecting future metal demand, identifying urban mining potentials of metals, and informing sustainable urbanization strategies. Here, we deployed a bottom-up stock accounting method to estimate stocks of iron, copper, and aluminum embodied in 51 categories of products and infrastructure across ten Chinese megacities from 1980 to 2016. We found that the MS in Chinese megacities had reached a level of 2.6-6.3 t/cap (on average 3.7 t/cap for iron, 58 kg/cap for copper, and 151 kg/cap for aluminum) in 2016, which still remained behind the level of western cities or potential saturation level on the country level (e.g., approximately 13 t/cap for iron). Economic development was identified as the most powerful driver for MS growth based on an IPAT decomposition analysis, indicating further increase in MS as China's

The concept of value co-creation brings about changes in tourists’ roles from value receivers to producers. Most existing studies take value co-creation behavior as a single dimension, ignoring the role switching of tourists. Starting from the precise constitution of value co-creation behavior, this paper, utilizing the method of structural equation modeling (SEM), discusses the mechanism of the effects of tourist participation behavior and citizenship behavior on destination loyalty through each sub-dimension of perceived value. The results showed the following: (1) The participation behavior (in-role) and citizenship behavior (extra-role) of tourists affect different value dimensions. (2) The value co-created by tourists presents a hierarchical state from the primary to the higher level. Among the types of value, novelty and social value belong to the primary level while quality, economic, knowledge, and emotional value belong to the higher level. (3) Destination loyalty is driven not only by tourist behavior (in-role) but also by citizenship behavior (extra-role). Based on the perspective of role switching, this paper establishes the theoretical framework of role switching in the era of value co-creation and proposes some strategic suggestions for marketing transformation.