Modeling of Gasification of Sewage Sludge for Phosphorus Recovery and Hydrogen Generation

Due to the amendment of sewage sludge ordinance in Germany, phosphorus must be recovered from sewage sludge in the future. Previously developed phosphorus recycling processes are not economically viable due to high material and energetic expenditures. Gasification of dried sewage sludge enables the energetic utilization of sewage sludge and provides the energy for phosphorus recovery. The present paper focuses on thermodynamic modeling of the gasification system to demonstrate the potential for holistic utilization of dried sewage sludge as phosphorus fertilizer. The results shows that an energy self‐sufficient, optimized process can be realized for recovery of phosphorus by gasification and subsequent thermo‐chemical treatment of dried sewage sludge. The energy recovery of dried sewage sludge with subsequent material recovery using the product gas and LF slags, enables energy‐efficient phosphorus recovery from sewage sludge ash. Thermodynamic modeling can be used to verify energy self‐sufficiency with simultaneous hydrogen separation for this holistic recycling concept.