Anaerobic digestion of biowaste allows a sustainable production of bioenergy and reduces environmental burden. The anaerobic digestion phase was modeled with Anaerobic Digestion Model No.1 (ADM1), which was extended to include three genera of propionate-oxidizing bacteria and two routes of propionate degradation, namely methyl-malonyl CoA and C6-dismutation pathway. Kinetic parameters for anaerobic propionate oxidation were determined with defined tricultures of the three propionate-oxidizing genera together with hydrogenotrophic and acetotrophic methanogens and implemented into ADM1, resulting in the improved model ADM1xpro.