A Comprehensive Review of Secondary Carbon Carriers for Ironmaking and Steelmaking Processes: Industrial Utilization of Non-biogenic Materials in Steel Production

The steel industry, one of the most challenging sectors to decarbonize, is responsible for approximately 5% of CO 2 emissions in the European Union and 7% globally. Achieving the goal of climate neutrality by 2050 requires reducing the industry’s reliance on carbon-based fossil resources, primarily natural gas and coal. This comprehensive review discusses the use of non-biogenic materials in the steel industry. Various types of waste play a significant role in a circular economy scenario. The circular economy approach is essential for achieving carbon–neutral steel production. The utilization of non-biogenic secondary carbon carriers, such as polymers from waste plastics and rubber from tires, serves as auxiliary reducing agents and slag foaming materials, supporting the smart carbon usage in a process integration framework. In cokemaking, replacing coal with non-biogenic materials has been identified as a cost-effective and sustainable solution. This approach aims to enhance the energy and resource efficiency of recycling processes for both post-consumer (end-of-life products) and post-industrial (materials produced during manufacturing) plastic-containing materials. Finally, the review examines methane cracking, which produces hydrogen and solid carbon. Methane cracking is a promising alternative to water electrolysis due to its lower energy demand, although it is not yet fully mature for industrial application.