An apparatus is provided according to embodiments of the present invention which includes a reaction chamber having a wall defining an interior of the reaction chamber and an exterior of the reaction chamber; exoelectrogenic bacteria disposed in the interior of the reaction chamber; an aqueous medium having a pH in the range of 3-9, inclusive, the aqueous medium including an organic substrate oxidizable by exoelectrogenic bacteria and the medium disposed in the interior of the reaction chamber. An inventive apparatus further includes an anode at least partially contained within the interior of the reaction chamber; and a brush or mesh cathode including stainless steel, nickel or titanium, the cathode at least partially contained within the interior of the reaction chamber.