Valuable raw material from sewage sludge (FlashPhos)

Elemental white phosphorus (P4) is essential for key industries such as the food and pharmaceutical sectors and is therefore a strategic raw material of high relevance. Although there are sufficient hidden phosphorus reserves in sewage sludge in Europe, the EU is dependent on imports from Kazakhstan, Vietnam and China. The aim of FlashPhos is to demonstrate a thermochemical process for the sustainable production of high-quality white phosphorus for the chemical industry using sewage sludge on a large scale.

FlashPhos: Recovering valuable raw materials with practically no emissions or waste

The FlashPhos project aims to demonstrate at a large scale a thermochemical process to sustainably produce high-quality white phosphorus (P₄) and other valuable raw materials using sewage sludge as input material. The project follows an economically and ecologically sound and climate-friendly circular economy approach, with all output materials being used in the European industry, some of them substituting critical or CO₂-relevant raw materials.

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 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.

The industrial consortium will then start with industrial-scale white phosphorus production by 2028.

As project partner, the Steinbeis-Europa-Zentrum supports the administrative project management, the communication activities and the dissemination and exploitation of the project results.

Further information: