The PHOSTER projects tackles challenges related to supply of critical raw materials in the future and delivers a sustainable, replicable and scalable circular economy solution (TRL 4) for the recovery of secondary minerals and metals from incinerated sewage sludge ashes and mining industry by-products to substitute primary critical raw materials (phosphorus, magnesium) in the manufacturing of fertilisers. The methodology is based on an integrated assessment of the production process for high-value finished product recovery aimed at optimising technical, economic, environmental and social performance of the production process and recovered products from the inception phase onwards.