Geological, geochemical and social-scientific assessment of basaltic aquifers as potential storage sites for CO_2

摘要

Basaltic aquifers have the potential to provide secure option for CO_2 sequestration. Because basaltic rocks are widely distributed around the world, their capacity for storage of anthropogenic CO_2 emissions is enormous. In addition, geochemical trapping of CO_2 injected into basaltic aquifers occurs quickly, because basaltic rocks contain many cations that react with CO_2 to form stable carbonate minerals. Two types of large-scale basaltic aquifers may be suitable for sequestering huge amounts of anthropogenic CO_2: continental flood basalt aquifers and deep-sea basalt aquifers. Here, we assess the potential of these two CO_2 sequestration options from geological, geochemical and social-scientific perspectives. From a geological and geochemical viewpoint, both continental flood basalt and deep-sea basalt aquifers have excellent CO_2 storage potential. In deep-sea basalt aquifers, however, storage of injected CO_2 may be more secure than in continental flood basalt aquifers, because leakage of CO_2 to the atmosphere is minimized by geological, geochemical and physical barriers associated with the deep-sea environment. In addition, from a social-scientific point of view, several current CO_2 injection projects in continental flood basalts have encountered problems due to groundwater depletion, and large-scale implementation of CO_2 storage in continental flood basalt aquifers might cause contamination of freshwater resources needed for domestic and agricultural use. In striking contrast to continental flood basalts, deep-sea basalts can be used for CO_2 storage without encountering critical problems, because deep-sea basalt aquifers have no economic value. We conclude, therefore, that deep-sea basalt aquifers are a better option for CO_2 storage than continental flood basalt aquifers.