Understanding the feasibility of pit lakes for tailings disposal and CO2 sequestration

The pit lakes and tailings are one of major source of acid mine drainage (AMD) and metal contamination in the mining landscapes. The dissolution of metals from pit lakes in the close proximity to aquifers contaminate groundwater in the downstream. The tailings are fine grained particles prone to wind dispersal and contaminate the neighbouring soil and water resources. We purpose the backfilling of carbonated mafic and ultra-mafic tailings into the pit lakes. The tailings are mostly dumped into the dams constructed close to extraction site. The mafic and ultra-mafic tailings enriched in Mg2+ are potential sequester of CO2 and studies suggested carbon mineralisation through tailings is predicated to reach 33Gt by 2100. The carbon mineralisation increases pH and immobilises the metals. It will reduce the environmental contamination caused by the pit lakes and tailings in addition to a potential CO2 sequestration site. A risk assessment studying the pit lake’s hydrological conditions and the potential environmental consequences of tailings backfilling needs to be conducted prior to implementation. The experimental studies are recommended to assess the economic feasibility of the backfilling of tailings into the pit lakes and its role in the CO2 sequestration.