| Abstract |
Industrial uses of geothermal energy in the United States have included both industrial applications and agricultural drying. A zinc extraction plant was partially completed in the Imperial Valley of California using electricity from geothermal power plants for the recovery of the metal from geothermal brines. The plant was to eventually extract 30,000 tonnes (33,000 tons) of zinc annually from the waste water from ten power plants; however, it has since shut down and been dismantled due to technical problems. Two large gold and silver ore heap leaching projects are located in Nevada with an installed capacity of 15 MWt and use 250 TJ (69 GWh) annually. They are able to increase the extraction of ore by 17% and extend their operating season into the colder months, compared to conventional means. At present, these extraction operations was suspended due to the low price of gold and silvern at the time, and in part due to the cost of Federal royalties for energy from wells on public lands. Geothermal milk pasteurization was in operation in Oregon for over 50 years, processing 225,000 kg (500,000 lbs) of milk each month with 87°C (189°F) fluid. Wastewater sludge digestion is assisted with geothermal heat in the city of San Bernardino, California using 58°C (136°F) fluid transferring 6.4 GJ/hr (6.1 million Btu/hr) through spiral plate heat exchangers to the sludge in four tanks. The agricultural drying operations consist of two large onion and garlic dehydration plants, also located in Nevada. They can process up to 280 tonnes (310 tons) of raw product per day producing almost 60 tonnes (65 tons) of dried product at 5% moisture. Other smaller uses, include a mushroom growing operation in Oregon, mineral water processing in California, an industrial park in Hawaii, and laundries in Oregon, Nevada, California and Montana. |