Microbial fuel (MFCs) and electrolysis cells (MECs) can be used to recover energy directly as electricity or hydrogen from organic matter. Organic removal efficiencies and values of the different energy products were compared for MFCs and MECs fed winery or domestic wastewater. TCOD removal (%) and energy recoveries (kWh/kg-COD) were higher for MFCs than MECs with both wastewaters. At a cost of $4.51/kg-H(2) for winery wastewater and $3.01/kg-H(2) for domestic wastewater, the hydrogen produced using MECs cost less than the estimated merchant value of hydrogen ($6/kg-H(2)). 16S rRNA clone libraries indicated the predominance of Geobacter species in anodic microbial communities in MECs for both wastewaters, suggesting low current densities were the result of substrate limitations. The results of this study show that energy recovery and organic removal from wastewater are more effective with MFCs than MECs, but that hydrogen production from wastewater fed MECs can be cost effective. (C) 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.