NOVELTY - Producing hydrogen from organic material (12), comprises: providing organic material and hydrogen-producing microorganisms into a completely mixed bioreactor (14) for breaking down; recovering at least a portion of the hydrogen and the carbon dioxide and recovering at least a portion of a first liquid effluent (18); providing the effluent into a gravity settler for separating a concentrated biomass; recovering the concentrated biomass and providing into the bioreactor; and applying an input voltage to at least one of the completely mixed bioreactor and the gravity settler.    USE - The method is useful for producing hydrogen (claimed) and methane from organic material e.g. industrial organic waste and biomass.    ADVANTAGE - The method provides hydrogen with high yields in short retention time.    DETAILED DESCRIPTION - Producing hydrogen from organic material (12), comprises: providing organic material and hydrogen-producing microorganisms into a completely mixed bioreactor (14) for breaking down the organic material into products including hydrogen, carbon dioxide, fatty acids, and alcohols; recovering at least a portion of the hydrogen and the carbon dioxide from the completely mixed bioreactor; recovering at least a portion of a first liquid effluent (18) from the completely mixed bioreactor, where the first liquid effluent includes at least a portion of the hydrogen-producing microorganisms, the fatty acids, and the alcohols; providing at least a portion of the first liquid effluent into a gravity settler (16) for separating at least a portion of the first liquid effluent into a concentrated biomass including at least a portion of the hydrogen-producing microorganisms and a second liquid effluent including at least a portion of the fatty acids and the alcohols; recovering at least a portion of the concentrated biomass from the gravity settler and providing the concentrated biomass into the completely mixed bioreactor; and applying an input voltage to at least one of the completely mixed bioreactor and the gravity settler for facilitating an electrohydrogenesis process. An INDEPENDENT CLAIM is included for an electrobiohydrogenator system (10) for producing hydrogen from organic material, comprising: a completely mixed bioreactor for microorganism-mediated breakdown of the organic material into the products, where the bioreactor comprises an inlet for receiving the organic material, a first outlet for recovering at least a portion of the hydrogen and of the carbon dioxide from the completely mixed bioreactor, and a second outlet for recovering at least a portion of the first liquid effluent from the completely mixed bioreactor; a gravity settler hydraulically connected to the second outlet for receiving at least a portion of the first liquid effluent, where the gravity settler comprises a settling container for separating at least a portion of the first liquid effluent into a concentrated biomass including at least a portion of the hydrogen-producing microorganisms and a second liquid effluent including at least a portion of the fatty acids and of the alcohols, and a third outlet hydraulically connected to the settling container and located at a lower portion of the settling container for recovering at least a portion of the concentrated biomass from the gravity settler and providing the concentrated biomass into the completely mixed bioreactor; and at least one pair of electrodes for applying an input voltage to at least one of the completely mixed bioreactor and the gravity settler for facilitating an electrohydrogenesis process.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic view of an electrobiohydrogenator reactor.    Electrobiohydrogenator system (10)    Organic material (12)    Bioreactor (14)    Gravity settler (16)    First liquid effluent. (18)