Energy strategies of most developed countries include the sustainable development of all types of renewable energy, including energy generation from biomass. Co-digestion of sewage sludge and plant biomass has a number of synergetic effects leading to increasing of the digestion rate and output of biogas. The range of potentially effective co-digestion of sewage sludge with plant raw materials is considered on the example of the full-scale estimation study for Lviv WWTP, Ukraine. Substitution of the 25% of dry organic matter of sewage sludge by the same amount of plant raw matter can increase total output of the methane at the biogas station about on 5.8%.