The EU project PHOSTER 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 fertilisers manufacturing. The University of Ljubljana will re-design sewage sludge thermal treatment by setting the recovery of secondary materials as the first-priority design parameter. Politecnico di Milano will work to optimise wet chemical extraction of P from ashes. Magnesitas Navarras will investigate the best mining by-products to promote the co-precipitation of P and Mg (Politecnico di Milano). Timac Agro Italia will test the recovered materials, mixed with other raw materials, to develop fertilisers complying with relevant regulations and market demand. Social Life Cycle Assessment (SLCA) and Cost-Effectiveness Analysis (CEA) will evaluate environmental and social impacts of the fertilisers obtained from the recovered products. The different processes will be optimised together to maximise beneficial impacts for 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.