Exploring New Pathways – FlashPhos Workshop on Integration into the Cement Industry

The central focus of the workshop was on FlashPhos slag, a by-product of the thermochemical recycling of sewage sludge, and its potential use as a raw material in cement production. Additionally, the integration of fuel gases produced during the FlashPhos process into cement kilns was critically discussed in terms of both opportunities and challenges.

Following a welcome by Marcus Paul (Dyckerhoff), Christian Schmidberger (University of Stuttgart) gave an overview of the FlashPhos process, highlighting its potential alignment with cement plant infrastructure. The process doesn’t only recover white phosphorus but also produces mineral-rich slag and high-temperature gas streams, opening the door for industrial symbiosis.

In his presentation, Marcus Paul emphasised the transformation underway in the cement and concrete sectors: from reducing CO₂ emissions to rethinking raw material inputs and entire process chains. He presented early-stage results on the activity index of cements blended with FlashPhos slag, which showed promising performance characteristics.

Stefan Papkalla (VDZ), representing the German cement industry, provided a deep dive into the thermodynamic and operational implications of integrating FlashPhos fuel gases. He explained that the amount of gas produced when recovering 5,000 tonnes of phosphorus annually corresponds to around 60% of a typical cement plant’s raw gas volume. The resulting excess heat – especially at lower gas temperatures – must be reused efficiently, for example in sewage sludge drying, to avoid additional CO₂ emissions. However, if the fuel gases are renewable, CO₂ emissions could be reduced by up to 64% per megajoule.

Sabrina Frühauf (A TEC) highlighted the company’s role in bridging FlashPhos with cement pyroprocessing, emphasizing A TEC’s expertise in integrating alternative gas flows and materials into clinker production. She presented a holistic approach to CO₂ reduction and shared sustainable engineering examples, including carbon capture, utilization, and storage (CCUS) strategies.

The open discussion after the presentations brought lively exchange. Topics ranged from using FlashPhos off-gas for calcining clay, to introducing organic waste into the hot gas stream for hydrogen production. Participants also debated how best to position FlashPhos within the broader waste management and circular economy framework – not just as a phosphorus recovery solution, but as a multi-benefit technology.

Economic factors were also on the table: current market prices for white phosphorus, cost considerations for sewage sludge treatment, and energy input requirements. The central takeaway was that integration must be designed with process synergies in mind – from energy reuse to material compatibility. Scientific models and industrial realities must be aligned for successful large-scale implementation.

The workshop concluded with a guided plant tour at Dyckerhoff, where participants gained direct insight into the cement production process and potential integration points for the FlashPhos concept.

The event was jointly organized by Dyckerhoff, Steinbeis Europa Zentrum, VDZ Technology gGmbH, A TEC Production and Services GmbH and Italmatch Chemicals.