The EU project PHOSTER is co-funded within the ERA-MIN 3 framework. It aims to deliver a sustainable, replicable, and scalable circular economy solution (TRL 4) for the recovery of secondary minerals and metals from sewage sludge ashes and mining industry by-products to substitute primary critical raw materials (P, Mg) in the fertilizers' manufacturing. In more detail, the University of Ljubljana will re-design the sewage sludge thermal treatment by setting the recovery of secondary materials as the first-priority design parameter (1), while Politecnico di Milano will attempt to optimise the wet chemical extraction of P from ashes (2). Meanwhile, Magnesitas Navarras will work on the selection of the best mining by-products (3) to promote the co-precipitation of P and Mg, which will be carried out by Politecnico di Milano (4). Timac Agro Italia will receive the recovered materials and will mix them with other raw materials in a fertiliser formula complying with relevant regulations on fertilisers and able to satisfy the market demand (5). Then, Social Life Cycle Assessment (SLCA) and Cost-Effectiveness Analysis (CEA) will make it possible to evaluate environmental and social impacts of the fertilisers obtained from the recovered products. All steps will be linked in a feedback loop (6) to fine-tune the process and maximise the beneficial impacts on both crops and the environment. The PHOSTER project proudly became a member of the European Sustainable Phosphorus Platform in the view of networking with the most relevant stakeholders in Europe and of broadly disseminating the project concept and results.