Studies at the Brookhaven National Laboratory (BNL) have led to the development of a technically and economically feasible, as well as environmentally acceptable, biochemical process for detoxification of geothermal residues. For this process, selected microorganisms that live in extreme environments have served as models for the new biotechnology. Assuming a 2,500-kg / h sludge production rate, the new technology is capable of a better than 80% removal rate of toxic metals, usually in less than a 25-hour period. The process itself depends on a number of flexible parameters, allowing this technology to be tailored to specific needs of different geothermal producing regimes, such as those found in the Salton Sea and the Geysers area of California. Thus geothermal residual sludges and brines can be processed to remove only a few metals, such as arsenic and mercury, or many metals, ranging from valuable metals such as chromium, gold, and silver to radionuclides, such as radium. In some cases, combined metal removal and metal recovery processes may be cost efficient and therefore advantageous. The emerging biotechnology for the treatment of geothermal energy production wastes is versatile and offers a number of application options, which are discussed in the paper.