Geothermal Energy and the Environment
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Geothermal energy is a renewable resource: Earth’s heat is continuously radiated from within, and each year rainfall supplies new water to geothermal reservoirs. Production from individual geothermal reservoirs can be sustained for decades and perhaps even centuries.
Compared to other types of power plants, geothermal plants have relatively little effect on the environment. Geothermal power plants have been successfully operated in farm fields, in sensitive desert environments, and in forested recreation areas.
Hydrogen sulfide gas
, which can be toxic at very high concentrations, is sometimes present in geothermal reservoirs. However, this gas is removed from geothermal water with antipollution “scrubbing” equipment.
Geothermal reservoirs contain higher concentrations of minerals and chemicals than do aquifers used for drinking water. Therefore, wells drilled into geothermal reservoirs have several layers of pipes, or casing, cemented into the ground nearly the entire length of a well. The pipes and cement prevent the deep geothermal water from mixing with freshwater aquifers.
Geothermal reservoirs contain some carbon dioxide
which is released when the hot water turns into steam. Some scientists believe that the buildup of carbon dioxide in the atmosphere—partially the result of burning fossil fuels—is contributing to what may be a gradual increase in global temperatures, because carbon dioxide traps heat from the Sun that is reradiated by Earth. The amount of carbon dioxide released from geothermal power plants, however, ranges from zero to 4 percent of the carbon dioxide released by an equivalent power plant fueled by coal or petroleum.
Compared to other types of power plants, geothermal plants have relatively little effect on the environment. Geothermal power plants have been successfully operated in farm fields, in sensitive desert environments, and in forested recreation areas.
Hydrogen sulfide gas
, which can be toxic at very high concentrations, is sometimes present in geothermal reservoirs. However, this gas is removed from geothermal water with antipollution “scrubbing” equipment.Geothermal reservoirs contain higher concentrations of minerals and chemicals than do aquifers used for drinking water. Therefore, wells drilled into geothermal reservoirs have several layers of pipes, or casing, cemented into the ground nearly the entire length of a well. The pipes and cement prevent the deep geothermal water from mixing with freshwater aquifers.
Geothermal reservoirs contain some carbon dioxide
which is released when the hot water turns into steam. Some scientists believe that the buildup of carbon dioxide in the atmosphere—partially the result of burning fossil fuels—is contributing to what may be a gradual increase in global temperatures, because carbon dioxide traps heat from the Sun that is reradiated by Earth. The amount of carbon dioxide released from geothermal power plants, however, ranges from zero to 4 percent of the carbon dioxide released by an equivalent power plant fueled by coal or petroleum. 
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