Hydrate-based CO2 sequestration technology: Feasibilities, mechanisms, influencing factors, and applications

CO2 is the primary contributor to greenhouse gas that causes rapid global warming. CO2 capture, utilization, and storage (CCUS) is a crucial technology for CO2 reduction, typically, CO2 hydrates form at pressures and tem-peratures greater than 3 MPa and lower than 10 degrees C. These non-harsh environmental conditions determine the value of hydrate-based CO2 sequestration technology, which can be used as a potential effective sequestration measure. In addition, hydrates have the advantages of rapid formation kinetics, high stability, and a low probability of gas leakage; therefore, they can be used to sequester CO2 in the near future. In this review, we summarize the development status and existing problems of various hydrate-based CO2 sequestration methods and analyze the mechanisms, influencing factors, and appropriate sequestration locations. The paper focuses on the CO2 replacement reaction of CH4 hydrates technology. The feasibility of this method is discussed in terms of thermodynamics and kinetics, the mechanism and influencing factors of the replacement process are analyzed, and various methods to improve the replacement efficiency are illustrated, including the temperature and pressure conditions, the injection phase state of CO2, the use of additives, and the assistance of other gases (N2 and H2). Next, the method of direct injection of CO2 into marine sediments to form hydrates for sequestration is discussed. We also generalize appropriate sequestration locations and summarize experimental and simulation studies on CO2 sequestration in marine sediments, including the technical feasibility, sequestration mechanism, and influencing factors. In addition, the hydrate cap is also discussed. Finally, we briefly introduce a hydrate -based CO2 sequestration method for reusing depleted deposits. This review paper can provide insights for future research and may help accelerate the field application of the hydrate method for CO2 sequestration technology.