The HEPHAESTUS project is built around one key, overarching objective: To develop a set of scalable and tuneable unit operations, to be built as integrated processing plant, featuring the capacity to treat multiple process wastes deriving from primary mineral and metallurgical (primary and secondary) streams. The unit operations are: - Clean-Tech electric furnace, to transform the EAF and AOD dust into metal alloy to be immediately remelted, process supported with streams of fines by-products from the mineral primary extractions (construction, aggregates and dimensional stone) - EZINEX process, to extract the zinc present in the dust of the furnace - Fibre drawing, for mineral wool manufacturing out of the process slag in molten state - Catalytic conversion of CO2 gas into methanol or formic acid - Ammonia-ammonium carbonate (AAC) and methanesulfonic acid (MSA) based hydrometallurgical processes, to produce a recyclable Fe-rich residue and to recover metals (e.g.e.g., ZnS) from EAF dust The project is targeting primarily small-scale applications (order of magnitude 10 k tons waste dust per year), to cope with the typically fragmented European process size. Such scale is matching the waste volumes and differentiation and granting positive environmental AND economic sustainability through the valorisation of different streams of by-products at low operational and capital expenditure, ensuring vast replicability and short ROI Project will be demonstrated in two pilot applications, in Greece and Italy, with the purpose of creating awareness on the business potential and to generate the conditions for a long-term exploitation, leading to meaningful reduction of wastes for the extractive and steel industries.