Cogeneration of hydrogen and methane from glucose to improve energy conversion efficiency

In order to reutilize the residual solutions derived from hydrogen production and increase the energy conversion efficiency, a novel process of cogenerating hydrogen and methane from glucose using a two-phase anaerobic fermentation process was proposed and investigated. The effects of substrate concentration, weight ratio of inoculation to substrate, pH value and nutrient medium on hydrogen production were studied. The maximum specific hydrogen yield is 2.75 mol H-2/mol glucose when the initial glucose concentration is 1%, the weight ratio of inoculation to substrate is 2:1 and the pH value is 6. The residual solutions derived from hydrogen production were reused to produce methane by methanogen in another reactor. The maximum specific methane yield is 2.13 mol CH4/mol glucose when the reutilization rates of ethanol, acetic acid, butyric acid, valeric acid, and caproic acid are all above 90%. The cogeneration process can dramatically increase the energy conversion efficiency from 23% (hydrogen only production) to 82%. (C) 2008 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.