One method for reducing the amount of carbon dioxide — a major contributor to global warming, according to scientists — is to inject the gas deep underground for long-term storage.
Three types of subsurface formations can be used — all of which exist in the Illinois Basin (encompassing most of Illinois, southwestern Indiana and western Kentucky):
— Coal formations so deep as to be considered uneconomical for mining. CO2 injection into coal is being tested for methane recovery.
— Depleted or mature oil and natural gas reservoirs. Injecting CO2 into oil reservoirs has been used for oil recovery for over 30 years.
— And saline aquifers that contain non-potable water. Saline aquifers have been used for natural gas storage in the Illinois Basin for decades.
Sources: Sallie E. Greenberg and Robert J. Finley for the Midwest Geological Sequestration Consortium. Produced by the Illinois State Geological Survey, William Shilts, chief.