In the greater Paris area, several million humans generate enormous amounts of waste and wastewater. In order to make the best possible use of this waste, the Cométha research partnership was set up. One of the consortia entrusted with the research is a Franco-German consortium with the participation of Fraunhofer IGB. Here a new modular solution is being tested for digesting the organic components to biogas, subsequent gasification of the digestion residues to synthesis gas and biological conversion of the CO2 to methane, as well as recovery of the inorganic nutrient salts phosphate and ammonium. In the three-stage project the developments at laboratory scale will be followed by piloting on site. Finally, a large-scale plant is to be planned and built based on one of the tested concepts.