Assessment of Mineral Resources in Geothermal Brines in the US

Abstract

Geothermal power plants produce a large volume of brine for power generation. Since these brines are the product of long-term water-rock interactions at elevated temperatures at depth, they contain dissolved chemical components including critical and strategic mineral commodities at various concentrations. Despite the low concentrations for many of the critical and strategic minerals, significant quantities of select minerals could be recovered due to the large volumes of brine utilized by geothermal power plants. The potential economic benefits of mineral recovery from geothermal brines has long been identified, however, no commercial recovery of these materials is on-going in the US. In this paper, we present a summary for mineral contents in geothermal brines in the US. Since the western parts of the US has substantial geothermal resources with numerous operational power plants, we have made a concerted effort to identify the potential economic minerals in geothermal brines in each of the western US geographic provinces. Our resource assessment indicates that several mineral commodities (e.g., Li, Mn, SiO2, etc.) are present in high enough concentrations and sufficient flow rates to be economically recovered from geothermal brines. An appraisal of mineral extraction technologies indicates availability of a number of mineral-specific to multi-minerals bench-scale extraction technologies. Some of these extraction technologies (e.g., SiO2 and Li) have also been successfully tested with pilot-scale facilities in the US. We also present preliminary results on the potential economic values of multiple minerals for several operational power plants. Our study shows that the extraction of targeted minerals at selected sites can add an additional revenue stream. However, several outstanding technological, financial, and market challenges currently hinder the recovery of minerals from geothermal brines.