[S-CG46] New Insights of Fluid-Rock Interactions: From Surface to Deep Subduction Zone

[SCG46-06] A method to enhance CO₂ geological storage and mineralization using biodegradable chelating agents

*Jiajie Wang¹, Ryota Sekiai¹, Atsushi Okamoto¹, Noriaki Watanabe¹ (1.Graduate School of Environmental Studies, Tohoku University, Japan)

Keywords:CO2 geological storage, chelating agent, mineral dissolution, pore property, permeability

To address climate change, greenhouse gas emissions must decline 43% by 2030, which will require scaling up to approximately 10 Gt CO₂ to be removed and stored annually by 2050. Among various options for CO₂ storage, the enhanced CO₂ mineralization in mafic and ultramafic rocks which are enriched with calcium (Ca), magnesium (Mg), and iron (Fe), such as basalt, has garnered significant global attention. These rocks have the potential of sequestering up to 60,000,000 Gt CO₂ through carbonation. However, the efficiency, capacity, and safety for CO₂ mineralization in rock reservoirs still need to be improved. First, basalt reservoirs targeted for CO₂ storage are usually not sufficiently reactive due to their low temperature (20-50 °C). Moreover, they generally suffer from inadequate pore space and connectivity, as well as insufficient permeability.
This study proposed an advanced CO₂ geological storage and mineralization enhancement method through the innovative utilization of biodegradable chelating agents such as N,N-Dicarboxymethyl glutamic acid (GLDA). This method consists of (1) injection an acid solution containing chelating agents to improve pore space and connectivity, rock permeability through enhanced and selective mineral dissolution; (2) injection of alkaline GLDA seawater solution with captured CO₂, which further expands the storage space while allowing CO₂ storage take place in a stable hydraulic environment; (3) CO₂ mineralized by reacting with the metal divalent leached from basalt or contained in the initial seawater with the decomposition of the chelating agents in a couple of months. This study elucidates the feasibility, effectiveness, and suitable operational conditions for implementing this enhanced CO₂ storage method through comprehensive laboratory experiments.