An Environmental Overview of Geothermal Resources Development

A large part of the case for the increased development of geothermal resources is that this energy source is environmentally superior to fossil fuel and nuclear produced electricity, and arguably even hydroelectric power.1 Geothermal energy can be produced with less landscape disturbance and residual discharge than is required for fossil fuel, nuclear and hydroelectric power.2 For example, at The Geysers in northern California about twelve square miles are necessary for the 150 wells required to support a 1000 M-2 plant. In 1972 the Atomic Energy Commission estimated that the nuclear industry held more than nineteen million acres of land for uranium mining and exploration. When the land use requirements of The Geysers' field are extrapolated to all geothermal sites that may be in production by 1986, the favorable comparison between geothermal and nuclear energy is evident, and similar comparisons can be made between geothermal and coal.3 Similar comparisons can be made for residual discharges. A 1000 M-w plant at The Geysers without pre-treatment discharges about one fourth the sulfur dioxide of a coal-fired plant.4

There are two major variables in the level of any potential adverse environmental impact from geothermal development. These are the character of the heat resource and the stage of development. The two most important hydrothermal geothermal reservoirs are li