Environmental Impacts of #Geothermal Energy
Published Mar 5, 2013
Union of Concerned Scientists
"The most widely developed type of geothermal power plant (known as #hydrothermal plants) are located near #geologic “#HotSpots” where hot molten rock is close to the earth’s crust and produces hot water. In other regions enhanced geothermal systems (or hot dry rock geothermal), which involve drilling into Earth’s surface to reach deeper geothermal resources, can allow broader access to geothermal energy."
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"Some geothermal plants also produce small amounts of #mercury emissions, which must be mitigated using mercury filter technology. Scrubbers can reduce air emissions, but they produce a watery #sludge composed of the captured materials, including #sulfur, #vanadium, #silica compounds, chlorides, #arsenic, mercury, #nickel, and other heavy metals. This #ToxicSludge often must be disposed of at hazardous waste sites."
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"Land #subsidence, a phenomenon in which the land surface sinks, is sometimes caused by the removal of water from geothermal reservoirs. Most geothermal facilities address this risk by re-injecting wastewater back into geothermal reservoirs after the water’s heat has been captured.
"Hydrothermal plants are sited on geological “hot spots," which tend to have higher levels of #earthquake risk. There is evidence that hydrothermal plants can lead to an even greater earthquake frequency. Enhanced geothermal systems (hot dry rock) can also increase the risk of small earthquakes. In this process, water is pumped at high pressures to fracture underground hot rock reservoirs similar to technology used in natural gas hydraulic #fracturing. (See How Natural Gas Works for more information.) Earthquake risk associated with enhanced geothermal systems can be minimized by siting plants an appropriate distance away from major fault lines. When a geothermal system is sited near a heavily populated area, constant monitoring and transparent communication with local communities is also necessary."
https://www.ucsusa.org/resources/environmental-impacts-geothermal-energy
