274 3 1 5 9 1+1 37℃ 3. Results and discussions Thermogravimetric analysis (TGA) was performed in order to quantify carbonate minerals precipitated during the experiment. The result clearly shows that Case-3, i.e., the twostage injection method, can produce the largest amount of carbonate minerals, compared to the other two cases. It was deduced that the reason why Case-2 produces a less amount of carbonate minerals compared to Case-3 is the buffering effect of the microbial solution that hinders the dissolution of divalent cations from the rock. This suggests that the timing of microbial solution injection be delayed by a couple of weeks, in order for a sufficient amount of cations to be released from the rock in the carbonic water. 4. Conclusion The present study investigated the potential of carbonate precipitation with the chemical reaction between ultramafic rocks and carbonic water under the conditions of deep underground mines. The result shows that by using the microbial enzyme, i.e., carbonic anhydrase, it is possible to enhance the chemical reaction and precipitate carbonate minerals under low temperature conditions. Furthermore, it was suggested that the buffering effect of the microbial solution needs to be taken into account in order to maximize the effect of the microbial enzyme and realize efficient carbonate precipitation. ACKNOWLEDGEMENTS This work was supported by JST FOREST (JPMJFR225S). REFERENCES Cao, X., Li, Q., Xu, L., & Tan, Y. (2024). Experiments of CO2-basalt-fluid interactions and micromechanical alterations: implications for carbon mineralization. Energy & Fuels, 38(7), 6205-6214.
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