Squaring the circle of the circular economy. The need to properly account for scarcity to guide mineral resource management

Over the last decades, extractivism and its derived socio-ecological impacts have increased exponentially, suggesting that prices of minerals are poor indicators of their absolute scarcity. Aware that we need to move towards a more circular economy (CE), we propose a methodology which builds on the use of an exergy-based indicator of absolute scarcity to create the much-needed taxonomy of mineral substances to make CE-oriented policies more effective. This indicator will not only allow overcoming the limitations usually attributed to physical indicators as scarcity's proxy measures. Transcending the usual mass-based approach to absolute scarcity, it warns that depletion is more about the loss of mineral quality than quantity, which is fundamental in a physical world governed by the Law of Entropy where ore grades decline over time. Even more, beyond enabling the calibration of economic tools to ensure we move towards circularity, this indicator can also set the basis for designing depletion charges targeted at raising social awareness and putting upward pressure on prices well before reserves are exhausted. Our methodology will also allow providing new insights into mineral price formation. By warning that we must learn from the biosphere, we argue that society can reach sustainability if it increases the use of renewable resources while moving towards that of abundant, recyclable, and physically easy-to-obtain mineral substances. In so doing, not only we show the importance of interdisciplinary work. We also point to the relevance of integrating weak and strong sustainability approaches in economics, thus avoiding the existing divorce between monetary and physical analyses.