A Guide to Geothermal Energy and the Environment in 2007

Geothermal Energy / Related Environmental Issues

Alyssa Kagel, et al., reported in 2007 that geothermal energy, defined as heat from the Earth, is a statute-recognized renewable resource. The first U.S. geothermal power plant, opened at The Geysers in California in 1960, continues to operate successfully. The United States, as the world's largest producer of geothermal electricity, generates an average of 15 billion kilowatt hours of power per year, comparable to burning close to 25 million barrels of oil or 6 million short tons of coal per year. Geothermal has a higher capacity factor (a measure of the amount of real time during which a facility is used) than many other power sources. Unlike wind and solar resources, which are more dependent upon weather fluctuations and climate changes, geothermal resources are available 24 hours a day, 7 days a week. While the carrier medium for geothermal electricity (water) must be properly managed, the source of geothermal energy, the Earthís heat, will be available indefinitely.

A geothermal resource assessment shows that nine western states together have the potential to provide over 20 percent of national electricity needs. Although geothermal
power plants, concentrated in the West, provide the third largest domestic source of renewable electricity after hydropower and biomass, they currently produce less than one percent of total U.S. electricity.

The visible plumes seen rising from some geothermal power plants are actually water vapor emissions (steam), not smoke. Because geothermal power plants do not burn fuel like fossil fuel plants, they release virtually no air emissions. A case study of a coal plant updated with scrubbers and other emissions control technologies emits 24 times more carbon dioxide, 10,837 times more sulfur dioxide, and 3,865 times more nitrous oxides per megawatt hour than a geothermal steam plant. Averages of four significant pollutants, as emitted from geothermal and coal facilities, are discussed in this report, as well as a brief discussion of other emissions that have sometimes been
associated with geothermal development.

Original URL: http://www.geo-energy.org/reports/Environmental%20Guide.pdf