Can CO <subscript>2</subscript> sequestration in basalt efficiently reduce greenhouse gas emission?

The research on the Columbia River Basalt is a unique combination of projects that minimise CO 2 emissions to the atmosphere. Both are underground waste disposal projects: CO 2 waste versus nuclear waste. The recent Wallula CO 2 project and the previous nuclear-waste project in the Columbia River Basalt (CRB), USA, provide the database for a high-capacity CO 2 sequestration model. Due to geomechanical constraints, the injection rate of CO 2 sequestration must be limited in order not to jeopardise the integrity of the reservoir and cap rock. The interbed in the continental flood basalt tested in the Wallula project only allows injection at a rate in the range of 9-19 kg CO 2 /s, depending on permeability (4 × 10 -14 -10 -13  m 2 ) and porosity (0.1-0.15). At the end of a 50-year injection period, the fraction of CO 2 converted to carbonate minerals is 37.1-67.1%. Underground space for waste disposal is a rare asset. The Columbia River Basalt occupies an area of 200,000 km 2 . Fifty years of CO 2 sequestration from a single well would require about the same fraction of the area as that of a nuclear waste repository (0.025%). The repository design is for a capacity of 70,000 MTHM (metric tons heavy metal). If all the waste is spent nuclear fuel, it originates from 1.2 × 10 4 -8.4 × 10 4  TWh electric power production, depending on reactor type. The CO 2 injection well operating at maximum capacity (19 kg CO 2 /s) represents 50 TWh generated in a gas power station minus the energy consumed for CO 2 separation, i.e. less than 0.4% of the nuclear option.