Jim Castro, PhD, Reclamation Specialist/Geochemist, Environmental Management Bureau, Montana Dept. of Environmental Quality, Helena, Montana
Bio–Electrochemical Systems (BES) constitute a technology that is getting close to practical industrial application. BES come in two varieties: microbial fuel cells (MFCs) and microbial electrolysis cells (MECs). Both varieties are based on microbially mediated chemical reactions, and in both cases the microbial reaction is coupled to an electrochemical cell.
In microbial fuel cells, the energy produced by the microbes (usually bacteria) is used to generate electric power. The amount of power can be fairly significant and could, for example, supply a source of auxiliary power to a wastewater treatment plant. A small treatment plant can produce one to two kilowatts. In microbial electrolysis cells, a voltage is supplied to assist in driving a microbial reaction that would not otherwise happen. Efforts in MEC development have so far concentrated on methane and hydrogen production from waste.
In the mining industry, BES could be used for treatment of wastes (nitrate/nitrite, organic waste, cyanide, sulfate, selenium, uranium (VI), etc.) and possibly for recovery of gold and base metals from process solutions, or pit lakes. Auxiliary power in remote areas where power failures are frequent is another possible benefit.
In a post–mining environment, mine wastes may offer a source of electric power through MFCs.
If bacteria are known in mediate a reaction, there is probably an application there for BES. The technology is five to ten years away from widespread industrial use, but it is coming.
Jim Castro received a B.S. in Chemistry from the University of San Francisco in 1968 and, after serving in the U.S. Air Force, received an M.S. in Physical Chemistry from the University of California at Davis. He worked as an industrial chemist from 1976 to 1994 before returning to school. He received a Ph.D. in Geology from the University of Montana in 1998. He taught at the University of Montana and the University of Great Falls and worked for three years for the Montana Bureau of Mines and Geology. He now works in the Hard Rock Mining Section of the Montana DEQ’s Environmental Management Bureau. His research interests include pit lake geochemistry, the environmental geochemistry of arsenic, and mine reclamation.