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Disposing of wastewater treatment plant waste while simultaneously recovering white phosphorus: The new thermochemical FlashPhos process demonstrates how this works. It is currently the only technology in Europe capable of producing this essential raw material for industrial use in an environmentally friendly, efficient, and cost-effective way. A Europe-wide consortium, coordinated by the University of Stuttgart, has developed and studied the technology.
Title: Sustainable raw material supply: New FlashPhos process converts sewage sludge into phosphorus for industrial use
Teaser: Disposing of wastewater treatment plant waste while simultaneously recovering white phosphorus: The new thermochemical FlashPhos process demonstrates how this works. It is currently the only technology in Europe capable of producing this essential raw material for industrial use in an environmentally friendly, efficient, and cost-effective way. A Europe-wide consortium, coordinated by the University of Stuttgart, has developed and studied the technology.
Text:
An essential raw material
White phosphorus (P₄) is an indispensable raw material for the chemical, pharmaceutical, food, and electronics industries. “Our goal is to secure a sustainable supply of economically important raw materials that are difficult to access and increasingly scarce,” says Prof. Markus Reinmöller, Director of the Institute for Energy Process Engineering and Dynamics in Energy Systems (IED) at the University of Stuttgart. “This can only be achieved if we produce these critical raw materials within a circular economy, as demonstrated by the FlashPhos process.” While conventional methods recover phosphorus from sewage sludge for use in fertilizers, FlashPhos produces P₄ as a starting material for a wide range of industrial applications, including car batteries, flame retardants, catalysts, and chip manufacturing. Currently, only four countries produce white phosphorus, making Europe heavily dependent on imports.
Closing resource loops through sewage sludge treatment
Economically viable phosphate deposits are unevenly distributed around the world. Apart from a few small deposits in Finland, there are currently no exploitable deposits in Europe, and even well-known deposits in Norway are difficult to exploit. Since the last P4-producing furnace was shut down in 2012, the European Union (EU) has relied entirely on imports. Given its economic importance, import dependence, and limited availability, the EU classifies white phosphorus as a critical raw material. At the same time, phosphorus-rich sewage sludge from wastewater treatment poses increasing environmental and disposal challenges. Therefore, phosphorus recovery from sewage sludge will become mandatory in Germany from 2029 onwards.
In the future, FlashPhos plants are expected to enable environmentally friendly sewage sludge disposal while recovering valuable materials. In addition to white phosphorus, the process yields other useful products that can replace CO₂-intensive raw materials. “This reduces import dependance and strengthens the circular economy,” explains Christian Schmidberger, researcher at IED and FlashPhos coordinator.
An innovative three-stage process
The FlashPhos process involves three stages designed to separate and recover phosphorus from sewage sludge. First, wet sewage sludge is processed in a newly developed “dryer grinder” producing a fine, nearly water-free powder. In the second stage, this powder is converted within milliseconds in the “flash reactor” into a combustible gas and phosphate-containing slag. This process takes place at temperatures of 1,600°C. The required process energy comes from the organic (carbon-containing) components of the sewage sludge itself. In the final stage of the process the phosphate-containing slag is treated at high temperatures in a so-called “refiner”.This step produces elemental white phosphorus as the main product. Additional outputs include a climate-friendly cement substitute, an iron alloy and a heavy metal concentrate suitable for further processing in the metals industry. The gases and waste heat produced during these steps can be reused in other industrial processes, reducing the need for fossil fuels.
Scaling up for industrial production
The “dryer grinder,” developed by project partner Buss-SMS-Canzler GmbH (SMS), was tested and optimized at the Institute for Sanitary Engineering, Water Quality, and Solid Waste Management (ISWA) at the University of Stuttgart. The flash reactor and refiner demonstrators were jointly developed by multiple project partners and assembled at the facilities of Aufbereitung, Recycling und Prüftechnik GmbH (ARP) in Leoben, Austria. The pilot plant processes up to 250 kilograms of sewage sludge powder per hour.
The next step is to build the first full-scale production facility. The industry partners involved in FlashPhos aim to start industrial production of white phosphorus by 2028. One remaining challenge is the availability of sewage sludge. Only a few densely populated regions have sufficient quantities of sewage sludge. “Metropolitan areas such as the Ruhr region, Barcelona, Madrid, or Milano would be particularly suitable,” says Schmidberger. By 2050, FlashPhos plants could cover up to half of Europe’s P₄ demand. Looking ahead, the research team is already exploring further applications: “Our long-term vision at IED is to recover additional critical raw materials from waste streams.”
About the FlashPhos collaborative project
The FlashPhos project (May 2021 to April 2026) is funded by the European Union with approximately €12 million under the Horizon 2020 research and innovation programme, under grant agreement No 958267. Coordinated by the University of Stuttgart, the consortium brings together 17 partners from industry and academia across Austria, Germany, Belgium, Italy, and Spain.
The project will conclude with a final conference on April 21, 2026, at the Communications Center Donawitz and will include a guided tour of the test facilities.
Christian Schmidberger, University of Stuttgart, Institute for Energy Process Engineering and Dynamics in Energy Systems, Tel: +49 711 685-67762, email: christian.schmidberger@ied.uni-stuttgart.de
Prof. Markus Reinmöller, University of Stuttgart, Institute for Energy Process Engineering and Dynamics in Energy Systems, Tel: +49 711 685-63488, email: markus.reinmoeller@ied.uni-stuttgart.de
https://www.uni-stuttgart.de/en/university/news/all/Sustainable-raw-material-sup... Website der Universität Stuttgart
The “Dryer-Grinder”: The newly developed Dryer-Grinder turns wet sewage sludge into a fine, nearly w ...
Copyright: University of Stuttgart / Ayumi Schober
Measurements at the flash reactor: It converts the pulverized sewage sludge into a combustible gas a ...
Source: Christian Schmidberger
Copyright: University of Stuttgart/ Christian Schmidberger
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