Constructing Artificial Cover Layers for Supercritical Carbon Dioxide Sequestration: A Novel Approach to Old Goaf Remediation and Carbon Emission Reduction

Over the past centuries, global coal mining activities have resulted in the formation of 242.36 billion cubic meters of underground goaf areas, resulting in the waste of billions of square meters of land resources. Furthermore, this phenomenon has introduced significant safety hazards and environmental risks. In addressing the challenge of the inability to directly sequester supercritical carbon dioxide in coal mine goaf areas due to extensive fracturing of the surrounding rock mass caused by underground mining, an innovative approach is proposed. This involves the construction of artificial cover layers within the overlying rock strata of abandoned coal mine goaf areas, offering a novel strategy for the sequestration of supercritical CO2 in such geological contexts. Considering the development characteristics of fractures in the overlying strata of coal mine goaf areas, a functional relationship model is established to delineate the sealing capacity of artificial cover layers in relation to the burial depth, length, width, and thickness of the cover layers. A design methodology for constructing artificial cover layers tailored for sequestering supercritical CO2 in abandoned coal mine goaf areas is proposed, providing technical support for its widespread application. Building upon this foundation, an assessment model for the sequestration capacity of abandoned coal mine goaf areas for supercritical CO2 is developed. The calculations indicate a global sequestration potential of approximately 72.71–218.12 billion tons of supercritical CO2, with anticipated economic benefits ranging from 657.36 to 1991.47 billion USD. The research outcomes present a promising avenue to assist carbon-neutral initiatives in coal-dependent urban areas globally.