How to classify anthropogenic mineral resources reserve?

As global mining expands to meet growing material demand, the world faces an urgent question: where will the next generation of resources come from? A new study led by Dr. Guochang Xu and Prof. Xianlai Zeng from Tsinghua University, in collaboration with Prof. Kenichi Nakajima and Dr. Keisuke Nansai from National Institute for Environmental Studies, Japan, offers a transformative answer—cities themselves may be the mines of the future.

Published in Science Bulletin, the research introduces the first structural, evidence-based, and quantifiable framework for classifying urban mineral resources and reserves. Unlike traditional geological minerals, anthropogenic mineral resources are basically recyclable materials—such as metals in end-of-life vehicles, electronic devices, and appliances—embedded within human settlements. These anthropogenic resources represent an enormous, yet largely untapped, stock of materials critical to decarbonization and sustainable development.

The authors propose a five-category classification system, ranging from urban mineral resources (UM-R) to reserves (UM-E), along with a three-step model that integrates urban metabolism flows, recycling value thresholds, and recovery efficiencies. This method enables policymakers and industries to quantify both the availability and accessibility of secondary resources within the urban environment, and aligns directly with the United Nations Framework Classification for Resources (UNFC).

Using China’s electric and electronic equipment and automobile sectors as a case study, the team found that urban mineral formation reached 27 million tons in 2023. Among 42 metals analyzed, eight were found to be economically mineable, while 26 were not yet feasible under current conditions. By improving separation and recovery rates of Fe, Al, Cu, and precious metals, dependence on natural mining can drop by 9–15%. Optimizing recycling thresholds for light metals and rare earth elements can substitute 7–42% of virgin mining demand, potentially boosting the circularity of electric and electronic equipment and automobiles from one-third to one-half.

This framework bridges natural and anthropogenic resource management. It provides both a scientific basis for policymaking in the circular economy and a practical tool for resource security planning.

The study underscores that urban minerals are not a replacement for geological resources, but their spatial and temporal extension, together forming a dual supply system that can enhance material security. As more countries pursue “zero-waste city” programs and invest in high-value recycling technologies, the researchers argue that urban mining will become an indispensable pillar of sustainable resource governance.

The work also contributes directly to global circular economy goals and offers a methodological foundation for future applications of the UNFC to anthropogenic resources.