Various metallurgical processes are still operated by utilizing fossil-based carbon sources for reduction and energy supply generating a carbon footprint which will influence future competitiveness in terms of economy and market. More and more customers look for a kind of green label on the metal product, forcing smelters to bring their CO₂-output down to a certain level.

Hydrogen has been and still is the most popular option to replace fossil carbon in metallurgical processes even though the enthusiasm of previous years has changed into a more realistic view when facing available amounts and prices in near future. Electricity, in some cases could serve as energy source as well as for reduction at least offering the chance to have green electrical power sources and with this a carbon-footprint reduced production. Alternatives like biomass, biogas and charcoal have to be considered as well.

Hydrometallurgy in general is often seen as an option to reduce the carbon footprint due lower energy consumption but suffers often from high efforts for effluent treatment and low product qualities.

The presentation gives an overview about different metallurgical processes and the options to use CO₂-neutral reducing agents. A detailed comparison is done for steel mill dust recycling processes showing opportunities but also challenges for alternative reducing agents.

Despite advancements in new technologies, carbon remains crucial in metallurgy. It works as energy source and, even more importantly, as reducing agent. As many modern pyrometallurgical processes still rely on carbon, it is difficult, respectively impossible in the short term, to remove it completely or to replace it by any other element. As a step towards CO₂ neutrality, the use of pyrolyzed biomass (biocoke) can work as an environmental friendlier solution which is available within a short period of time. In the metallurgical processes hardly any adaptions are necessary, as solid carbon is replaced by another form of solid carbon. However, to ensure this the biocoke must fulfill some requirements, to replace the fossil coke without any drawbacks. This regards for example the grain size, porosity, reactivity and mechanical strength. 

Former trials, presented at SIPS 2023, proved the general applicability in solid-liquid and solid-gas reactors and showed advantages, disadvantages and challenges when using biocoke. Since then, many new results were generated in order to further improve the properties of biocoke. Grainsize reduction, followed by briquetting using different binders, considerably influenced not only the mechanical properties, but also the reactivity and therefore increased the variety of metallurgical processes for which the biocoke could perhaps be used in near future.