Enhanced CO2 underground sequestration via concurrent gas hydrate formation and carbon mineralization

Abstract

Rapid increase in atmospheric CO2 concentrations and intensified climate change highlight the importance of carbon capture and storage (CCS), with CO2 underground sequestration emerging as a promising approach. This study experimentally investigated gas hydrate-based CO2 underground sequestration, emphasizing simultaneous CO2 hydrate formation and carbon mineralization, with particular emphasis on their interplay and combined effects on CO2 storage dynamics. Total gas uptake and initial absorption rates increased with CaO concentrations, which was attributed to co-generation of CO2 hydrate formation and carbon mineralization. In-situ Raman spectroscopy revealed that carbon mineralization predominantly occurs in the early stage, with calcium carbonate (CaCO3) forming and transforming into a calcite structure alongside the formation of CO2 hydrates. PXRD analysis combined with Rietveld refinement showed that distribution pattern of captured CO2 shifted from 'gas hydrate-dominant storage' to 'carbon mineralization-dominant storage' with increasing CaO concentrations. At higher CaO concentrations, the amount of CO2 captured in gas hydrates decreased (from 0.145 mol CO2/mol water in pure water to 0.110 mol CO2/mol water in CaO (20 wt%) solution) due to growth hindrance by calcite particles, while the amount of CO2 stored in calcite increased (from 0.015 mol CO2/mol water in CaO (5 wt%) solution to 0.074 mol CO2/mol water in CaO (20 wt%) solution), resulting in enhanced total CO2 storage capacity. These findings provide valuable insights into gas hydrate-based CO2 underground sequestration, highlighting complex interactions between gas hydrate formation and carbon mineralization, contributing to the optimization of carbon storage strategies for large-scale implementation.