<p>The transition toward low-carbon steelmaking increases the need for efficient recycling of iron-bearing residues such as mill scale and pellet fines. In this study, lignin, a by-product of the pulp and paper industry, is evaluated as a renewable binder and supplementary carbon source in metallurgical briquettes. Briquettes were produced using different binder formulations, including various lignin types and inorganic binders, and assessed for mechanical strength. Reduction behavior was studied using thermogravimetric analysis and validated through high-temperature experiments in a Tammann furnace. The results show that lignin improves green strength, while the addition of 1 wt% hydrated lime enhances overall mechanical stability. Initial formulations achieved limited oxygen removal from the iron-oxide fraction; after deducting moisture loss and the loss-on-ignition of the lignin and biocarbon from the total thermogravimetric analysis (TGA) mass loss following the principle of ISO 4695:2015 and ISO 11258:2015, the corrected reduction degrees were <i>R</i> = 60% (mill scale, R10) and <i>R</i> = 65% (pellet fines, R2). These corrected values, together with the oxygen and carbon balances reported in the study, indicate that the carbon supplied by lignin alone was sub-stoichiometric for the iron-oxide content of the briquettes. Optimized briquettes with additional biocarbon significantly improved reduction, producing a high-purity metallic phase (&gt; 98% Fe). However, iron recovery varied owing to FeO retention in slag, highlighting the importance of carbon balance and process conditions. Overall, lignin can function as a sustainable binder and partial carbon source, while additional carbon is required to achieve efficient reduction. This approach offers a promising route for recycling steelmaking residues within ironmaking processes, although further optimization is needed for improved metallization efficiency.</p> Graphical Abstract <p></p>