Case study of industrial symbiosis for improved residual material utilisation in the steel industry

Steel production is a material and energy intensive industry which, in addition to steel products, generates residual materials such as metallurgical slag, dust and sludge. These residual materials are recycled and used to a great extent as well in-house as for external purposes. Even so, some materials are currently landfilled due to difficulties in finding use or recycling possibilities. This applies, for example, to zinc-containing sludge and dust from ore-based steel production and certain iron-rich, lime and carbon-containing materials from scrap-based steel production. A case study has been performed with the aim to develop a methodology for evaluating industrial symbiosis possibilities in regard to increased material efficiency in steel production systems. The methodology is based on system analysis of steel production routes in combination with economical assessment of hypothetical business concepts by using residual materials from one industry as secondary raw materials in another. The paper presents case study results and indicates how this methodology could be applied to maximise the residual materials utilisation. By the methodology discussed and with a circular-economic perspective, it is shown that high economic potential for one material could be used to increase the utilisation of other materials with lower economic potential.