Organic-inorganic carbon cycling: Implications for CO2 mineralization of brucite-bearing mine tailings

• Brucite [Mg(OH)2] carbonation in mine tailings is accelerated by increasing CO2 supply • Column experiments investigated the use of organics as an alternative CO2 source • CO2 sequestration rates were ∼8 × faster using compost compared to controls • Stable carbon isotopes demonstrated the sequestration of organically derived C • Incorporating these processes into mine remediation can lead to reducing net CO2 emissions in mining Enhanced weathering and mineralization of ultramafic tailings permanently stores carbon dioxide (CO 2 ) within stable carbonate minerals. Brucite [Mg(OH) 2 ], a minor phase (up to ∼13 wt.%) of ultramafic tailings, offers substantial potential for CO 2 sequestration, yet its carbonation is limited by CO 2 supply. Here, we propose coupling organic and inorganic carbon cycling to accelerate brucite carbonation by amending ultramafic tailings with waste organics, a strategy often employed for remediation. This study aimed to understand the influence of tailings grain size and organics content on brucite carbonation and tailings cementation. Column experiments (∼20 cm height, 10 weeks) involved layering waste organics and brucite-bearing tailings (2 wt.%) of different grain sizes (