Phosphogypsum recycling: first insights reveal both opportunities and challenges
The initial results of the European FIC-FIGHTERS project show that phosphogypsum recycling has considerable technical potential, but also presents significant challenges related to radioactivity, regulation, and waste management. Research conducted at six European phosphogypsum disposal sites further demonstrates that there is no universal solution: the composition and radioactivity levels of phosphogypsum vary considerably from one site to another.
Recap
FIC FIGHTERS brings together 26 partners from 11 countries to investigate how phosphogypsum, a by-product of the fertilizer industry, can be recycled safely and sustainably. The project combines sample analysis, process development, environmental impact assessments, economic valorisation studies, and stakeholder research. Ultimately, the partners aim to scale up the technology to a demonstration process capable of treating 80 tonnes of phosphogypsum over 160 operational days. As the project's sole radiological partner, SCK CEN plays a central role in the characterization of disposal sites, radiological sample analysis, and evaluation of impacts on humans and the environment. In addition, SCK CEN’s social scientists are examining the societal and governance aspects of phosphogypsum recycling.
Major differences between sites
As part of the project, six phosphogypsum disposal sites across Europe were investigated. SCK CEN characterized the sites and analysed samples for their chemical, mineralogical, and radiological properties. The results revealed substantial differences between locations, depending on the origin of the phosphate rock and historical production processes.
The most promising results were obtained from Kutina (Croatia), Veles (North Macedonia), and Turnu Măgurele (Romania), where radioactivity levels remained well below 1 Bq/g*. These sites therefore offer potential for future commercial applications. Cartagena (Spain) exhibited the highest radioactivity levels, while some samples from Barreiro (Portugal) were close to relevant regulatory thresholds. The Serbian site falls between these extremes and appears highly dependent on the processing technology selected. Significant differences were also observed in the non-radiological characterization of the materials among the various disposal sites.
These findings clearly demonstrate that there is no one-size-fits-all solution for phosphogypsum recycling. Each site requires a dedicated evaluation of both technical possibilities and radiological conditions.
*The 1 Bq/g figure mentioned above is not a strict safety limit, but a screening level for Naturally Occurring Radioactive Material (NORM) established under the EU Basic Safety Standards Directive (2013/59/Euratom). It is based on the radionuclide radium-226 (Ra-226), whose decay products often contribute significantly to radiation exposure in phosphogypsum handling and reuse scenarios. Materials exceeding this level are not necessarily unsafe. Rather, the threshold serves as a trigger for a more detailed radiological assessment and, in many cases, additional regulatory or licensing requirements before reuse can be authorised.
Radiological aspects at the core
One of the key lessons from the project is that radiological considerations play a crucial role in the recycling process. Given its recognized expertise in low-level radioactivity measurements and radiochemistry, SCK CEN’s experts carried out the radiological characterization of the material from all six sites. To address the broader radiological challenges, SCK CEN conducted comprehensive impact assessments to evaluate effects on both people and the environment.
Nathalie Impens, project leader at SCK CEN, emphasizes: “These impact assessments are essential for understanding potential exposure pathways and risks from the outset. Only then can we develop recycling processes that are not only technically effective, but also safe for people and the environment.”
The studies covered the entire process chain: from phosphogypsum treatment and potential worker exposure to the radiological properties of end products and residual streams. Results indicate that radioactive components may redistribute during processing and become concentrated in certain product streams. Some processing steps can increase the radioactivity per gram of material in the final product to roughly twice that of the original material. At the same time, other product streams are generated with much lower radioactivity levels or are virtually free of radioactive components.
Reuse requires a clear regulatory framework
This creates opportunities for reuse, but also raises new questions regarding waste management, safety, and regulation. Currently, technological developments are advancing faster than regulatory frameworks. Nowhere in the world are regulations for the recycling of NORM waste streams fully developed. For materials containing elevated concentrations of naturally occurring radioactive substances, separate demonstrations of safe use are often required, which may involve additional studies and licensing procedures. Furthermore, national regulations differ significantly, meaning that an application accepted in one country may not automatically be permitted elsewhere.
Market acceptance is another important factor. As long as conventional alternatives remain available, users are likely to choose the option offering the highest degree of certainty. Successfully introducing recycled phosphogypsum-derived materials therefore requires not only clear regulations, but also a compelling economic value proposition.
“As a result of its radiological impact assessments and scientific expertise, SCK CEN is helping to build the knowledge base needed to support future policy and licensing decisions,” Nathalie adds.
New opportunity: rare earth elements
Alongside these challenges, phosphogypsum also presents interesting opportunities. Analyses have shown that certain phosphogypsum streams contain significant concentrations of rare earth elements (REEs). These are critical raw materials for renewable energy technologies, electronics, and advanced industrial applications. Because Europe remains heavily dependent on imports of these materials, interest is growing in recovering them from secondary sources such as industrial residues. Phosphogypsum could therefore evolve from a waste management challenge into a strategic source of raw materials within a circular economy.
Within FIC-FIGHTERS, SCK CEN investigated the presence of rare earth elements in various samples using neutron activation analysis. The samples were irradiated in the BR1 research reactor and, following a controlled decay period, researchers analysed the emitted signals to determine precisely which elements were present and in what concentrations. The results show that some phosphogypsum streams contain substantial quantities of valuable elements. Samples from the Cartagena disposal site, in particular, proved to be highly interesting from a resource recovery perspective.
From laboratory installation to industrial scale-up
A major milestone within FIC-FIGHTERS is the development of a demonstration plant in Spain. The facility has now been constructed and is operational, capable of processing batches of approximately seven litres. Ultimately, the partners aim to scale up the technology to a pilot-scale demonstration process with a treatment capacity of up to 1 tonne of phosphogypsum per day. Its performance will then be validated during an extended operational campaign.
SCK CEN’s radiological impact assessments form a crucial part of the licensing pathway for the process that will later be tested on a larger scale in the pilot plant. These studies provide the data required to obtain permits and develop safe operational procedures for future industrial-scale applications.
The human dimension: local context matters
In addition to technical analyses, FIC-FIGHTERS also examines the societal dimension of phosphogypsum recycling. Stakeholder interviews reveal that perceptions of phosphogypsum differ significantly across regions. In Romania, for example, residents tend to focus less on the phosphogypsum itself and more on broader issues such as economic development and site redevelopment.
For local communities, recycling offers prospects for new economic activity. At the same time, people are calling for greater transparency and involvement in decision-making processes. As Catrinel Turcanu, social scientist at SCK CEN, summarizes: “Successful solutions must not only be technically sound, but also aligned with local contexts and expectations.”
These insights demonstrate that technological innovation and societal engagement must go hand in hand.
Towards further results
Research within FIC-FIGHTERS is ongoing and is expected to provide additional insights in the coming years. SCK CEN is continuing neutron activation analyses on samples from other locations and is currently using low-level radioactivity measurements to investigate the properties of end products produced by the demonstration plant. In 2027, SCK CEN will also analyse new samples to assess whether residual streams from phosphogypsum treatment can be used as fertilizers for plants.
Together, these studies will provide greater clarity regarding the technical feasibility, economic value, and radiological safety of large-scale applications.
Through FIC-FIGHTERS, the project partners are taking further steps toward a future in which phosphogypsum is no longer viewed solely as waste, but can also become a valuable source of critical raw materials within a safe and sustainable circular economy.