Lignocellulosic Biochar – a Sustainable Reducing Agent for Iron- and Steelmaking Wastes

Biochar is increasingly recognized as a sustainable alternative to fossil-based reductants such as coke and coal in metallurgical processes. This review examines biochar’s potential for reducing solid iron- and steelmaking wastes, with particular focus on its performance in pyrometallurgical applications such as the Waelz process and Rotary Hearth Furnace. This study consolidates experimental findings, theoretical insights, and practical applications to assess biochar's feasibility as a reducing agent in the industry’s waste management. By addressing key barriers, including variability in biochar quality, reduction performance and mechanical challenges, this review bridges the gap between scientific research and industrial realms. The findings suggest that biochar can serve as an effective reductant. However, large-scale adoption of biochar will require a deeper understanding of its reduction pathways, particularly its role in direct versus indirect reduction mechanisms, as well as the effects of volatiles and ash on reaction behavior, and its mechanical properties to ensure compatibility with industrial-scale applications. Future research and pilot plant trials will be critical to optimizing biochar for metallurgical applications and realizing its potential in decarbonizing the iron and steel sector.Graphical Abstract