Carbon-fixing backfill materials for in-situ conversion Mining: Design, performance and CO₂ mitigation potential

Abstract

Despite its abundance and technological maturity, coal imposes severe environmental and geological impacts during traditional extraction and use, including land subsidence, waste generation, and large CO₂ emissions that challenge sustainable development. Carbon-fixing backfill technology, integrating mineral carbonation with cemented gangue backfill, offers a promising pathway to emission reduction, carbon fixation, ecological restoration, and hazard mitigation. However, the mechanical performance and geological compatibility of carbon-fixing backfill, along with the carbon fixation capacity of the cementitious system have been overlooked, limiting practical implementation and development. Given its resource endowment, China relies on coal as its primary energy source and has set dual-carbon targets to ensure both energy security and emission reduction. As one of the world’s largest CO₂ emitters, the country faces substantial pressure to curb carbon emissions. We propose an in-situ conversion mining and carbon-fixing backfill approach, enabled by an intelligent unmanned mining machine, to achieve simultaneous CO₂ sequestration and large-scale disposal of coal-derived solid waste. Tailored formulations for varying gangue contents deliver tunable compressive strength (1.2–24.1 MPa), adequate fluidity, and net-negative carbon emissions of up to 145 kg CO₂/t. Life-cycle assessment and national scenario modeling show a sequestration potential of 133–315 Mt CO₂/yr and utilization of 191 Mt waste/yr. By targeting the core mining regions, this framework delivers a viable solution for low-carbon resource conversion, directly addressing the dual challenges of carbon mitigation and waste disposal.

Keywords

In-situ conversion mining / Carbon-fixing backfill materials / Performance optimization / Life-cycle assessment / National CO₂ mitigation potential

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