Innovative sludge treatment and resource recoveryfor sustainable steel production (ISTRESS 2.0)
iSTRESS 2.0 addresses one of the stainless steel industry’s key challenges: sustainable treatment and resource recovery from pickling sludge. This sludge, classified as hazardous waste, contains valuable raw materials such as nickel, chromium, molybdenum, manganese, and fluorspar, but also poses risks due to the potential formation of toxic hexavalent chromium (Cr(VI)). Today, large volumes are landfilled, resulting in resource losses, high costs, and environmental risks.
The iSTRESS pre-study demonstrated that Cr(VI) formation can be effectively prevented by optimizing reductants (e.g. FeSi, aluminum, biocarbon) and controlling kiln atmospheres with N₂/H₂. These findings enable the transformation of sludge into a safe and valuable Hydrofluss product that can be reused in steelmaking.
The aim of iSTRESS 2.0 is to scale up and validate this innovative process at industrial level. Full-scale trials at Minpro Recycling, using Outokumpu’s sludge, will demonstrate the advanced calcination technology under real industrial conditions. The project also includes life cycle and techno-economic assessments, as well as the development of circular business models, ensuring long-term feasibility and scalability.
The consortium brings together the entire value chain: Outokumpu (steel producer and need owner), Minpro Recycling (technology developer and process owner), Linde Gas (gas handling), Ingelia (biocarbon supplier), Swerim (R&D and project coordination), and RISE (business models and system innovation). This strong collaboration combines expertise in metallurgy, recycling, environmental assessment, and industrial implementation.
The project contributes directly to the UN Sustainable Development Goals by reducing waste and landfill (Goal 12), advancing resource-efficient industrial innovation (Goal 9), and mitigating climate impact (Goal 13). By turning a problematic waste stream into a valuable resource, iSTRESS 2.0 strengthens the competitiveness of the Swedish and European steel industry while supporting the transition to climate-smart and circular manufacturing.