University of St Andrews study finds metal‑mining carbon footprint could be ten‑fold higher

Researchers at the University of St Andrews have published the first comprehensive peer‑reviewed assessment of carbon dioxide emissions released during the neutralisation of acid mine drainage (AMD). The analysis of 82 historic and active mines in Spain’s Iberian Pyrite Belt shows that CO₂ emitted when acidic water is treated can exceed traditional mining‑related emissions by more than ten times.

The study estimates that producing a tonne of copper could generate between 7 and 165 t of CO₂, with a median value roughly ten times higher than current industry estimates. Because AMD continues to release CO₂ long after mines close, the hidden emissions may persist for centuries. The researchers highlight the need for more accurate accounting of these emissions as global demand for metals such as copper, lithium, nickel and cobalt spikes to support electric vehicles, renewable‑energy infrastructure and batteries.

Potential mitigation strategies are being explored, including the use of mineral olivine to neutralise acidic runoff without releasing additional carbon. Accurate inclusion of AMD‑related emissions will be critical for meeting net‑zero targets and for policy makers assessing the climate impact of the expanding metal‑mining sector.