University of StuttgartCircular economy through the recovery of sewage sludge

Elemental white phosphorus (P4) is an indispensable strategic raw material for key industries such as electronics, food and pharmaceuticals. Although Europe has sufficient phosphorus reserves in sewage sludge, the EU is largely dependent on imports from Kazakhstan, Vietnam and China. The FlashPhos project (Horizon 2020) aims to recover high-quality white phosphorus and other valuable raw materials from sewage sludge for the European chemical, metallurgical and cement industries.

To realise this goal, 17 European partners have joined forces under the coordination of the University of Stuttgart. The project consortium, consisting of large industrial companies, SMEs, NGOs and academic institutions, covers a broad spectrum of expertise. FlashPhos receives 12 million euros in funding from the EU for four years.

Steinbeis Europa Zentrum supports administrative project management and coordinates the dissemination and exploitation of the project results as well as communication activities. During the proposal phase, it provided intensive support for the project development and supported the coordinator, University of Stuttgart, with training on the application process.

FlashPhos receives Award “Global Slag Technical Innovation”

The FlashPhos process represents a significant step towards a circular economy in the European industry. The project will not only benefit the environment and society through its circular economy approach but also enable the EU industry to progress through innovation in the fields of chemical engineering, thermal process engineering and cement technology. For its innovative approach, the project was awarded the "Global Slag Technical Innovation" prize in 2023.


Under the coordination of the University of Stuttgart, the 17-member consortium has completed several key milestones since the project’s start in May 2021. The basic components, mass, and energy flows necessary to make the FlashPhos process run have been determined. The core FlashPhos process treats sewage sludge in a specially developed dryer-grinder and subsequently in two different types of high-temperature reactors, the Flash Reactor and the Refiner. In the process, inorganic waste components are melted or evaporated and are then separated in the refiner reactor to produce recycled P4 for the chemical industry as the main product. Other output materials of the process are a climate-friendly alternative cement raw material, an iron alloy and a heavy metal concentrate as valuable outputs for the metal industry. The organic components are gasified at a high temperature and converted into heat and a gaseous fuel. This gas and excess heat can be used in cement plants to substitute fossil fuels.

The proof of concept of the sludge dryer-grinder has been completed and sewage sludge conversion has been experimentally investigated in an electrically heated drop tube furnace. In addition, a Computational Fluid Dynamics (CFD) simulation of the Flash Reactor and Refiner for the FlashPhos pilot plant has been carried out.

The FlashPhos pilot plant is set to be built by 2025 in Leoben, Austria, and will demonstrate the industrial FlashPhos process with up to 250 kg/h sewage sludge throughput. Based on the mass and energy balance supplemented with thermodynamic data, the FlashPhos digital twin has already been built and can now predict how the real-world FlashPhos process will react in the pilot plant.

Further information on FlashPhos:

„FlashPhos is the first and only technology in Europe that produces white phosphorus for the chemical industry from secondary raw materials and at the same time offers a solution for the problematic disposal of sewage sludge. Steinbeis Europa Zentrum helps us to develop an effective communication strategy and to successfully disseminate and exploit the project results. In addition, it provides valuable support in administrative and financial project management.“

Matthias Rapf, Institute of Sanitary Engineering, Water Quality and Waste Management, University of Stuttgart, FlashPhos coordinator

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Dr. Jennifer Bilbao
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Contact us!

Dr. Jennifer Bilbao

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