Study on coal gangue weathering into soil and carbon emission reduction based on gas bio-oxidation

Both coal gangue and gas are the main by-products in the process of coal mining. The direct discharge of low concentration of gas easily causes carbon emission and resource waste, the large accumulation of coal gangue destroys the ecological environment, which seriously restricts the sustainable development of the coal industry. To solve the problems of carbon emission from gas and ecological destruction of coal gangue, a new strategy is proposed based on that the organic acids produced from the biological oxidation of coal gangue accelerate the weathering of coal gangue into soil. The composition of metabolic products from methane bio-oxidation was analyzed, and the impact of these products on coal gangue bio-weathering was investigated. Then, the soil performance of weathering products was evaluated, and the mechanism of gas bio-oxidation and coal gangue weathering into soil was explained in detail. The carbon reduction amount was also calculated. In order to open up a new way for the ecological matrix utilization of coal gangue and the reduction of gas carbon emissions. The results showed that methane-oxidizing bacteria effectively adhered to the surface of coal gangue to degrade gas, and their metabolites were consisted of organic acids and extracellular polymers. The generated organic acids enhanced the structural pulverization and mineral decomposition reconstruction of coal gangue, while extracellular polymers improved the reagglomeration of weathered particles. The mass fractions of organic carbon, alkali-hydrolysable nitrogen, and available potassium in weathering products were increased by 111%, 185%, and 105%, and the plant germination rate and biomass of weathering product were increased by 43% and 236%. Methane in the gas was converted to organic carbon, which realized carbon sequestration in the form of biological carbon and carbonate minerals. The carbon emission reduction of the reactor is 16.47 kg/m3 per day, and the carbon sequestration amount of coal gangue is 4.49 g/kg per day.