Water Infrastructure Ressources (Institute)


Project duration: 01.03.2021 - 31.03.2024

Project processing and coordination by:rewa



The project is funded by the Ministry of the Environment, Climate and Energy Management Baden-Württemberg within the framework of the EFRE funding program "Bioeconomy - Biorefineries for the recovery of raw materials from waste and wastewater - Bio-Ab-Cycling".

Project partners:

Fraunhofer Institute for Interfacial Engineering and Biotechnology (IGB)
University of Stuttgart
University of Kassel
University of Kaiserslautern
SolarSpring GmbH
Deukum GmbH
Nanoscience for life GmbH
Environmental technology-BW GmbH
City of Erbach
Sewage treatment plant Steinhäule

Project description

The RoKKa project (raw material source sewage sludge and climate protection at sewage treatment plants) is investigating possibilities for treating the filtrate from sewage sludge digestion at the sewage treatment plant of the city of Erbach. The scientists are testing processes to obtain phosphorus and nitrogen compounds for fertilizers. In addition, microalgae are used to produce plant fortifiers and soil improvers for agriculture. Even the CO2 produced during the production of biogas is captured and reprocessed into a raw material for the chemical industry.

The Fraunhofer IGB's ePhos process is dedicated to phosphorus recovery. With the help of a sacrificial anode made of magnesium, the phosphorus is electrochemically precipitated as struvite. Then two pilot plants GmbH separate the ammonium nitrogen from the sludge water. The nutrients that remain in the water after the processes are fed to microalgae. In addition to light, the algae also require CO2 for photosynthesis. For this purpose, the CO2 produced during biogas digestion is separated with the help of an amino acid solution and recovered via an electrodialysis device. The excess CO2 that the microalgae do not need is converted into formate by an electrosynthesis unit.

The Rewa department will provide scientific support and advice to the project with its wide-ranging expertise. In doing so, Rewa will bring together the scientific findings of all project partners gained in the course of the project at least every six months in order to be able to discuss and solve interfaces and interface problems with all participants. This guarantees the scientific reflection and questioning of the project partners active in the work packages.

Project goal

The project aims to demonstrate that it is possible to convert a wastewater treatment plant into a biorefinery. In addition to the goal of wastewater treatment, raw materials are extracted from the wastewater. By avoiding nutrient recirculation, climate-relevant emissions are reduced, thus contributing to climate neutrality. The aim is to implement the project results on a large scale at wastewater treatment plants. Large-scale implementation supports the state's Sustainable Bioeconomy Strategy. Recycling phosphorus and nitrogen reduces the use of fossil raw materials. Raw material recovery also leads to a reduction in greenhouse gas emissions by avoiding freight impacts. The planned linking of innovative processes can contribute to a more intensive circular economy and more climate protection. In addition to the resource efficiency strategy, the project also supports Baden-Württemberg's sustainability and innovation strategy and climate protection goals. 

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