A cost-effective microbial fuel cell (MFC) system was developed in order to recover silver metal from silver ion containing wastewaters. After 8 h reaction, silver metal recovery efficiencies as high as 99.91 +/- 0.00%-98.26 +/- 0.01% were achieved. The initial concentrations were from 50 ppm to 200 ppm with a load resistor of 1000 Omega. In the batch-fed cathode and continuous-fed anode system with an initial silver concentration of 200 ppm, discharge curves display the production of both silver metal and electric energy at a rate of 69.9 kg silver per KWh energy output. The maximum power of about 4.25 W/m(2), maximum voltage of 0.749 V, maximum current density of 5.67 A/m(2), and a fill factor of 0.626 were achieved at 1000 ppm initial silver ion concentration. (C) 2011 Elsevier Ltd. All rights reserved.