The RESLAG project proposal is aligned with the challenges outlined in the call WASTE-1-2014: Moving towards a circular economy through industrial symbiosis. In 2010, the European steel industry generated, as waste, about 21.8 Mt of steel slag. The 76 % of the slag was recycled in applications such as aggregates for construction or road materials, but these sectors were unable to absorb the total amount of produced slag. The remaining 24 % was landfilled (2.9 Mt) or self-stored (2.3 Mt). The landfilled slag represents a severe environmental problem. The main aim of RESLAG is to prove that there are industrial sectors able to make an effective use of the 2.9 Mt/y of landfilled slag, if properly supported by the right technologies. In making this prof, the RESLAG project will also prove that there are other very important environmental benefits coming from an “active” use of the slag in industrial processes, as CO2 saving (up to 970 kt/y from CSP applications, at least 71 kg/ton of produced steel from heat recovery applications), and elimination of negative impacts associated with mining (from the recovery of valuable metals and from the production of ceramic materials). To achieve this ambitious goal four large-scale demonstrations to recycle steel slag are considered: Extraction of non-ferrous high added metals; TES for heat recovery applications; TES to increase dispatchability of the CSP plant electricity; Production of innovative refractory ceramic compounds. Overall, the RESLAG project aims at an innovative organizational steel by-products management model able to reach high levels of resource and energy efficiency, which considers a cascade of upgrading processes and a life cycle perspective. All these demonstrations will be lead by the industries involved in the RESLAG consortium. The RESLAG project is supported by the main organizations representing energy-intensive industries, CSP sector, energy platforms, governments, etc.