Abstract: An active solid state fermentation bioreactor for producing gases, liquid(s) or solids from gaseous or gaseous and liquid starting materials and a fermentation process using the reactor are disclosed, The bioreactor includes three major phases; a solid phase including the porous solid support, a liquid phase comprising liquid, and a gaseous phase. The solid phase includes a porous solid support, in which at least 20% of the pore volumes have a size resulting in a liquid suction of about 0.01 to about 0.1 bars if these pores are filled with liquid, the porous solid support is inoculated with desired micro-organisms, the volume of the gaseous phase is 20% to 60% of the volume of the bioreactor, and the liquid phase is at least 20% of the reactor volume, The unsaturated capillary conductivity of filling/packing solid material of the bioreactor is at least 0.1 cm/ h.

Abstract: The present invention relates to a solid state fermentation process for producing hydrogen, and to a bioreactor and solid support for use in the fermentation process.