"This giant bubble on the island of Sardinia holds 2,000 tonnes of carbon dioxide. But the gas wasn’t captured from factory emissions, nor was it pulled from the air. It came from a gas supplier… “The facility compresses and expands CO2 daily in its closed system, turning a turbine that generates 200 megawatt-hours of electricity, or 20 MW over 10 hours.”
I was thinking about much larger scale bubbles in “unwanted” geological depressions such as old open pit mines or rock quarries. The depression in the ground might offer more protection allowing it to scale up higher in volume.