VerKlär²: Innovative utilization concept for self-sufficient and resource-saving wastewater treatment plants

  Picture of a furnace Copyright: © Olaf Rohl

Pilot project in Hassfurt: Self-sufficient wastewater treatment plant saves climate and resources.


Core of the project is an innovative technology for mono-incineration, which for the first time enables the thermal utilization of sewage sludge in small-scale plants directly at the point of origin - decentralized, low-emission and self-sufficient. This is made possible by the use of an innovative fluidization furnace. The city is receiving support for the project from experts in industry and research. In cooperation with Spanner Re2, RWTH Aachen University and the Institute for Energy Technology (IfE) at the Ostbayerische Technische Hochschule Amberg-Weiden, a pilot plant for decentralized incineration and energetic use of sewage sludge is being built at the Hassfurt site.

In the course of climate protection and resource saving, sewage sludge is one of the most relevant biogenic waste materials whose thermal energy must be used efficiently.

The obligations for phosphorus recovery and provisions of the Fertilizer Ordinance, which will come into force in the coming years, considerably restrict the previously established disposal routes for municipal sewage sludge. The agricultural utilization of sewage sludge is being critically evaluated and legally restricted by the increasing public focus on soil, plant and environmental protection. In contrast, the co-incineration of sewage sludge, for example in waste incineration plants and cement plants, does not enable phosphorus recovery. In addition, the co-incineration in coal-fired power plants will be eliminated in the foreseeable future as a result of the coal phase-out. These effects will require a massive expansion of mono-incineration plants for the disposal of sewage sludge in the coming years. So far, sewage sludge mono-incineration is only technically and economically feasible in large plants at central locations.

The consortium in the "VerKlär²" research project has therefore set itself the goal of bringing decentralized mono-incineration to practical maturity in small-scale plants. The project is being funded by the federal government as part of the 7th Energy Research Program of the German Federal Ministry for Economic Affairs and Energy. The project volume is just around € 1.1 million. The aim is to test and demonstrate the environmentally compatible energy recovery of sewage sludge in an innovative fluidization furnace for municipal wastewater treatment plants of size class IV a (10,000 - 50,000 inhabitants).

The wastewater treatment plant in Hassfurt will be expanded by the firing system as part of the project. The heat generated in the incineration process will be used to supply heat to the sewage treatment plant and the surrounding municipal area. On the one hand, the heat is used to dry the sewage sludge; on the other hand, excess heat from the firing system can be fed into the local heating network in the sense of sector coupling. At the same time, the new furnace in Hassfurt replaces an existing combined heat and power unit (CHP), which is operated with natural gas and supplies heat to the sewage sludge drying process. In the future, this will not only eliminate the need for heat from natural gas as a fossil fuel, but will also make the sewage treatment plant self-sufficient in terms of energy supply and waste disposal. The intelligent and flexible combination of sewage sludge incineration with sewer gas power generation leads to an improvement in the energy balance of the wastewater treatment plant and to an increase in energy efficiency.

In the project, RWTH Aachen University is responsible for the practical investigations of sewage sludge incineration. This is being done step by step, from the pilot plant scale to the existing prototype to the commissioning of the first decentralized utilization plant with an innovative fluidized fuel incinerator in Hassfurt. Spanner Re² GmbH, on the other hand, is responsible for the design adaptation for continuous operation and manufactures the pilot plant. The city of Haßfurt is supported by IfE in the planning and conception for the integration of the firing technology into the existing wastewater treatment plant. IfE is also responsible for the scientific, technical and ecological evaluation of the project.

If the project sets a precedent, regional wastewater treatment plants will make a decisive ecological contribution in the future through the use of decentralized incineration technologies - in a climate-friendly and resource-saving manner.