The classical municipal wastewater treatment in Germany consists of an aerobic carbon and nitrogen elimination and mostly an anaerobic sludge treatment. Organic kitchen wastes from separate waste collection as well as yard wastes are converted mostly in composting plants to soil conditioner. With these conventional types of treatment, the energy potential in waste and wastewater is lost due to aerobic material conversion.

In this article three scenarios for the treatment of municipal wastewater and waste are compared on the subject of energy efficiency and useable potential: Sc1. the classical wastewater treatment and the composting of the organic waste fraction, Sc2. the anaerobic treatment of wastewater combined with deammonification and the digestion of the organic waste fraction, and Sc3. a mutual anaerobic treatment of wastewater and waste as co-digestion with deammonification. The calculation of energy and CO2-balance considers different climatic conditions. In case of using anaerobic treatment, not only the energy balance will be positive, also the CO2-balance is improved by the substitution of fossil fuels with generated biogas.