Anaerobic digestion is a multi-step biotechnological process, in which H-2 is not detected as it is consumed immediately e.g. by hydrogenotrophic methanogens to produce CH4 and CO2. Recently a two-stage AD concept consisting of hydrogenic process followed by methanogenic process was suggested. However, only few models of this process are known. In this study a mathematical model of a continuous process of AD with production of hydrogen and methane in a cascade of two bioreactors, including some intermediate products in the first bioreactor was developed and investigated. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.