There are a number of environmental impacts that are associated with geothermal power production . Some of these, such as impacts during site preparation, well drilling, and construction are limited to initial development of the power plant. Others, such as potential emissions to the air and water and generation of solid wastes, will continue throughout the life of the plant. During operation, hydrogen sulfide (H2S), ammonia (NH3), and trace quantities of Hg are the compounds of greatest concern. Most geothermal plants re-inject the geothermal fluid back into the ground, but potential remains for leaks or spills into nearby water bodies. There is significant potential for water contamination from drilling fluids used during the drilling process.
Other impacts, such as ground subsidence from the long-term extraction of the geothermal fluid, contamination of water by toxic compounds, and disposal of solid wastes removed from the geothermal fluid, may also occur.
Emissions of air pollutants can occur from geothermal plants because of the presence of these compounds in the geothermal fluid. Emission rates depend upon both the concentration of these compounds in the fluid and the design of the plant (dry steam, flash steam, or binary designs). Bloomfield and Moore reported emissions of H2S, NH3, and CH4 from several U.S. geothermal power plants of different designs in a report on emissions of CO2 from geothermal power . They reported average emissions of 0.82 kg (0.18 lb) of H2S per MWh. These emissions can usually be reduced through application of control technologies, particularly for H2S abatement.
Numerous documents are available that provide guidance for geothermal developers and identify appropriate measures to minimize adverse environmental impacts.
Among the organizations that provide guidance are the International Finance Corporation (associated with the World Bank) and the United Nations Environment Program [65, 67].
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