Toward decarbonization in steelmaking: A review on direct reduced iron using biomass-based syngas

Abstract

The steel industry, responsible for 7–9 % of global CO₂ emissions, faces increasing pressure to decarbonize its process. This review explores the potential of biomass-based syngas as a sustainable alternative to fossil fuels in direct reduced iron (DRI) production, drawing on previous research, and presents a thermodynamic analysis. Biomass gasification generates syngas rich in hydrogen (H₂) and carbon monoxide (CO), which are the main reducing agents for the iron oxide to produce iron. Thermodynamic analysis reveals that CO is more effective for reduction at lower temperatures, while H₂ becomes favorable at temperatures above 1088 K. However, challenges such as biomass availability, variability in syngas composition produced, and impurities in the solid and gas phases (e.g., H₂S, N₂, and phosphorus) hinder widespread adoption. Current commercial DRI plants, like MIDREX and HYL/Energiron, primarily use natural gas, but biomass-derived syngas offers a promising pathway for decarbonization. This review provides important insights into biomass utilization for iron production via the direct reduction route and several challenges that need to be addressed to improve the adoption of the technology. It was found that biomass-derived syngas is a highly promising source in the DRI process, especially in terms of energy security, metallization, and carbon content. However, it faces several challenges toward realization, including inconsistent syngas composition/quality, syngas impurities, scaling up, capital investment, and operational cost. Further research and innovation are crucial to improve the performance, stabilize syngas quality, and make biomass utilization in DRI production a competitive option.