The porous particulate carriers of activated carbon, bagasse and brick were used for Clostridium acetobutylicum immobilization for coproduction of hydrogen and butanol. The dense microbial population was growing on the carrier surface with the biofilms formed during fermentation. The homogeneous array of the microbial cells on the surface looks some interesting behaviors. The cells have the ability to shuttle between holes in bagasse. Higher efficiency of cell immobilization could be achieved accordingly. The cell concentration during immobilized fermentation was about one order magnitude higher than that during free cell fermentation. Enhanced fermentation for hydrogen and butanol has been achieved during the immobilized fermentation. The highest yield of hydrogen was 1.81 mol/mol when brick was used as immobilization carrier, while the highest butanol yield of 0.22 g/g was achieved during fermentation with bagasse as immobilization carrier. Hydrogen productivity and butanol productivity were up to 403.2 ml/L/h and 0.44 g/L/h, respectively. Hydrogen and butanol production behaved differently in organic and inorganic carrier materials. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.