This study presents an innovative strategy for decarbonizing underground construction based on circular waste management by reducing coal mine methane emissions through goaf backfill. High methane emissions are often underestimated due to their low concentrations in ventilation air and leaks from abandoned mines. However, they significantly contribute to the global greenhouse effect. The study combines modeling and evaluation of the underground construction decarbonization effects and coal mining with the development and testing of goaf backfill monoliths based on tailings (Gai Mining and Processing Plant). By analyzing the methane emissions dynamics during coal and gas co-mining, we investigate and quantify gas losses arising from the low efficiency of the mine's gas drainage system, which could be converted into energy. It was found that activation of geomaterials increases the strength properties of backfill composites from 2.54 to 4.56 MPa. The use of activated tailings results in a denser and more homogeneous matrix with a more uniform pore space distribution. Furthermore, their use to ensure the stability of underground drainage boreholes will prevent the emission of 257,195 m³ of coal mine methane. This study confirms the viability of circular waste management in mining, demonstrating significant potential for additional benefits from the transition to sustainable underground construction.