Plastic-Derived Syngas for Metallurgical Applications: Why It Is Not Industrially Viable Yet

Plastic waste has been widely proposed as an alternative carbon source for syngas (CO–H₂) production to support decarbonization strategies in metallurgical operations. In principle, plastic-derived syngas could partially replace fossil-based reductants or fuels in processes such as direct reduction, smelting, roasting, and secondary metallurgy. Despite extensive laboratory- and pilot-scale research, no large-scale metallurgical implementation has been demonstrated to date. This critical review examines the fundamental, operational, and economic barriers that currently prevent plastic-derived syngas from achieving industrial viability in metallurgical applications. Particular attention is given to feedstock heterogeneity, halogen- and heteroatom-derived contaminants (Cl, F, S, N), tar formation, unstable syngas composition, low effective carbon utilization, and incompatibility with metallurgical process requirements. Furthermore, the review highlights critical challenges related to gas cleaning, refractory corrosion, secondary emissions (including HCl, HF, dioxins, and furans), and higher CAPEX and OPEX costs compared with conventional fossil-based syngas routes. By systematically contrasting academic claims with industrial constraints, this review clarifies why plastic-derived syngas remains technologically immature for metallurgy and identifies the research gaps that must be addressed before industrial adoption can be realistically considered.