Carbon footprint of metal production may be 10 times higher than estimated due to acid mine drainage emissions

New research from the University of St Andrews finds that the carbon footprint of metal production, particularly copper mining, could be more than 10 times higher than previously estimated. The study, published in Environmental Science and Technology, is the first to quantify CO2 emissions from acid mine drainage neutralization. Researchers studied 82 historic and active mines in southern Spain, measuring how acidic drainage reacts with minerals and seawater to release CO2. They found that these emissions are comparable to conventional copper production footprints and can continue for centuries after mining stops. This matters for net zero because metal mining is set to increase to supply green technologies like solar panels, wind turbines, and electric grids. If acid mine drainage emissions are not accounted for, the true carbon cost of these technologies could be much higher than current estimates suggest. The study highlights the need for better remediation methods and more accurate carbon accounting across the mining sector.