A new paper on the Recovery of Minerals and Metals from Geothermal Fluids has some great news for those of us hoping we can green up our drives in 2010 with lithium-powered electric vehicles. There is a real symbiotic relationship between geothermal power and the battery electric car.
Geothermal fluids contain significant concentrations of potentially valuable mineral resources. This paper focuses on extracting silica, lithium and zinc, the resources that have the greatest potential to be economically extracted. Mineral content was often considered more a nuisance than an asset, because they can cause corrosive scaling both in the plant and in reinjection wells, which creates operational limitations in Geothermal power plants.
We will need these minerals, especially lithium, for powering the batteries for the many electric vehicles that are due on the market in the next few years. The lithium automotive market could reach $1.6 Billion by 2015 .
Many constituents of geothermal fluids are valuable if they can be separated and purified. The geothermal waters have had intimate and lengthy contact with the layers of the earth’s crust that they flow through, resulting in dissolution of minerals and metals from the rocks, and solution into the hot water. These aqueous solutions can be processed to recover minerals and metals, such as silica, zinc and lithium.
Mineral recovery improves the economics of geothermal energy production by helping to minimize the nuisance of corrosive scaling, and there is now increasing interest in improving the economics of geothermal energy by co-producing and marketing some of the dissolved constituents: in particular the easiest to extract economically, which turn out to be silica, zinc and lithium.
In the early history of geothermal resource development, boric acid, sulfur, and ammonium salts were recovered commercially until they lost economic competitiveness to other mining processes.
Although the enrichment of target elements in geothermal fluids is not as high as the enrichment in fluids commonly treated with hydrometallurgical methods, the costs associated with resource extraction from geothermal fluids are potentially low for several reasons:
Plant costs are split between power and mineral production. Geothermal power plants already pump and process the fluids. Mineral extraction would consist of an additional treatment step added to existing plant facilities and would be economically feasible for several reasons.
1. There are no costs associated with mining and physical processing of the ore, and no negative environmental impacts;
2. There are no costs associated with dissolution of ore minerals into an aqueous phase because they are already in solution;
3. Geothermal systems process large volumes of water, commonly tens of millions of gallons per day, so that the mass of mineral resource is large in spite of relatively low concentrations.
This is good news. Lithium for all our electric vehicles could be readily mined along with clean geothermal energy to supply the sockets in our garages the juice to power our plug in vehicles.
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