Microbially catalyzed production of gaseous fuels in bioelectrochemical systems

This research focuses on the production of hydrogen and methane by using microorganisms as the electrocatalytic agents for the reduction of H+ or CO2 respectively, at the cathode of bioelectrochemical systems. As for H2 generation, our previous results (Villano et al., 2011) showed the ability of hydrogenophilic dechlorinating bacteria to catalyze the reaction with graphite electrodes serving as electron donors. Based on these findings, we are currently exploring the potential for application of other hydrogenase-possessing microorganisms, such as sulphate-reducing bacteria (e.g., Desulfovibrio sp.). To accomplish this objective, a combination of electrochemical techniques (i.e., cyclic voltammetry, impedance spectroscopy, etc...) and potentiostatic H2-production experiments have been performed. With regard to CH4 production, a fully biological bioelectrochemical reactor coupling acetate oxidation to CO2 reduction has been developed. The reactor consists of two compartments filled with graphite granules serving as both electrodic material and support for microbial biofilm formation. The performance of the reactor, in terms of methane generation, organic substrates removal, and coulombic and energy efficiency, has been evaluated under different operating conditions (such as: potentiostatic control of the biocathode or bioanode potential; type and amount of microorganisms in each compartment, temperature, etc…). Main attention has been paid at identifying the rate-limiting steps in order to optimize the process performance.