Steel Decarbonization—from Optimization to Transformation

The Paris Agreement necessitates global net-zero emissions by 2055–2070, including steel industry emissions that currently amount to about 7% of global energy system emissions. In this article we review the literature on steel decarbonization. Steel industry emission mitigation measures include reduced demand through materials efficiency, increased high-quality recycling, and decarbonization of iron ore–based primary production. Low and decreasing costs for renewable electricity makes green hydrogen direct reduction an increasingly promising and preferred alternative for primary production of iron, and there is growing policy support for demonstration and deployment of low-carbon steelmaking, particularly involving hydrogen. Decarbonizing the global steel industry involves a system transformation that must evolve in tandem with reduced overcapacity, a phase-out of conventional steelmaking, and meeting increased demand in developing countries. A switch to renewable energy as a key input in steelmaking may give rise to new competitive advantages and industrial relocation, potentially exacerbating geopolitical tensions in the transition. While steel decarbonization research previously focused on how to optimize the fossil-based steel system, recent studies are oriented toward transformation and development of alternatives.