A new study published in Environmental Science and Technology reveals that metal mining's carbon footprint could be up to 10 times larger than conventional estimates. Researchers from the University of St Andrews found that acid mine drainage, a common byproduct of mining sulfide ores, releases significant amounts of CO2 when acidic water reacts with rocks or seawater. This emission source has been largely overlooked in standard carbon accounting for the mining industry. The study focused on the Iberian Pyrite Belt in Spain, a major copper mining region. Results show that acid mine drainage since the 19th century has produced as much CO2 as all other mining emissions combined, effectively doubling the historical footprint. Additionally, sulfide minerals can continue reacting for hundreds to thousands of years, meaning emissions persist long after mines close. The researchers estimate 7 to 165 tons of CO2 per ton of copper produced, depending on ore composition. Identifying and mitigating these emissions is critical for achieving net-zero goals. The team is testing olivine as a potential solution to neutralize acidic runoff without releasing CO2. This research highlights the need for tailored decarbonization strategies in the mining sector, which is essential for supplying metals for renewables, EVs, and grid infrastructure.
