Simultaneous achievement of high volumetric productivities (HP = 231.3 mmol H-2/L/h) and high hydrogen yields (HY = 3.55 mol H-2/mol glucose) was obtained by increasing the temperature to 70 degrees C and by reducing the total bioreactor system volume (V) to 5.74 L and increasing the degassed effluent recycle rate (F-er) to 3.2 L/min, giving a V/F-er value of 1.8 mm. The bioprocess involved the recycling of degassed effluent at a high flow rate through a quasi-stationary fluidized granular bed. In this process the rate of physical removal of H-2 trapped in the bulk liquid phase surrounding the fluidized granules reduced the thermodynamic constraints preventing the simultaneous achievement of high HPs and high HYs in the anaerobic fluidized granular bed bioreactor. Energy balance analysis showed that with heat recycling the bioreactor system could achieve a net positive volumetric energy output of 11.76 W/L at an energy efficiency of 49.3%. Copyright (C) 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.