A slight variation to the systems described on the previous page involves the pumping of water into geologic hotspots in the Earth to be heated, rather than relying on the presence of pre-existing hot water and steam. After that the cycle is the same; the liquid is brought back to the surface to turn the turbines and generators. Several companies are now trying a new variation. Instead of water, they are using carbon dioxide, which is more efficient at transferring heat than water. CO2 is pumped into the hotspots, heated, and brought back up to run the system. This may be a preferable option in areas where water is already scarce. CO2 is found in naturally occurring pockets, but is also a byproduct of many of our industries. Rather than release it into the atmosphere it can be sent underground, and incorporated into a power plant. The oil industry aleady injects it underground, to re-pressurize their wells, so that they can recover more oil. An added bonus is the reaction of certain rocks when in contact with carbon dioxide. They trap it. Some of the CO2 can be removed from the atmosphere, and stored in rocks. Coal absorbs CO2, but it releases methane in exchange. Dissolved CO2 in seawater creates calcite, CaCO3, and limestone, both are fairly permanent storage sites for carbon dioxide. They are stable at normal surface conditions (although they can be dissolved by hydrochloric acid, and slowly by water). Olivine, dunite and serpentinite are also good places to store excess CO2. They undergo a chemical change, and become magnesite, MgCO3, and magnetite, Fe3O4. The weathering of copper ores, which also uses CO2, creates malachite, azurite, calcite, and goethite, especially when the copper deposits are near limestone. We use calcite; it has cool optical properties. We build with  limestone. Magnesite and magnetite have industrial uses. Malachite and azurite can be gem quality. It is probably not economically feasible to mine these minerals and rocks, but it is a possibility.

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Brief Summary We can remove excess carbon dioxide from our atmosphere by siphoning it from the gaseous exhaust of industry. We can send it underground, and use it to power generators, and create electricity. If the geology permits, if the mineral and rock content are correct, the CO2 is incorporated into the rock itself, and permanently removed from our environment. While at the same time creating a resource that we can use. We can then use more industry exhaust to continue the energy production cycle, and continue to remove more carbon dioxide from our atmosphere.

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