Gogiyev T., Morales Arancibia M.A., Werra M., Watanabe M.D.B., Tangstad M., Cherubini F.
Journal of Cleaner Production, vol. 537, art. no. 147221, 2025
Ferromanganese (FeMn) is critical in modern steelmaking, but its conventional production is highly carbon- and energy-intensive. This study evaluates hydrogen as a low-carbon alternative in the pre-reduction stage of ferromanganese production, using life-cycle assessment to compare conventional production of 1 kg of FeMn with six alternative scenarios based on grey, blue, and green hydrogen. Climate impacts are calculated using global warming potential over 20-year (GWP20) and 100-year (GWP100), assuming 5 % hydrogen leakage. Simulations based on process modelling show that H<sub>2</sub>-based pre-reduction can substitute about 33 % of coke use and reduce electricity demand by 10 %. GWP20 for H<sub>2</sub>-based scenarios ranges from 0.95 ± 0.03 to 1.33 ± 0.03 kg CO<sub>2</sub>-eq/kg FeMn, compared to 1.19 kg CO<sub>2</sub>-eq/kg FeMn for conventional production. With GWP100, H<sub>2</sub>-based alternatives vary between 0.74 ± 0.01 and 1.12 ± 0.01 kg CO<sub>2</sub>-eq/kg FeMn, while the impact of the conventional production is 1.02 kg CO<sub>2</sub>-eq/kg FeMn. All H<sub>2</sub>-based scenarios reduce climate impact of ferromanganese production except grey hydrogen, which shows 10 % higher impact than the conventional case. Green hydrogen from offshore wind with polymer electrolyte membrane electrolysis offers the lowest impacts due to high efficiency and low material demand for infrastructure. The uncertainty analysis indicates that the findings are robust; however, hydrogen leakage rates are the main source of uncertainty in the overall climate impact. Reducing impacts from infrastructure materials can achieve further gains and co-benefits with other environmental impact categories. Overall, hydrogen use for pre-reduction shows strong potential to mitigate emissions in FeMn production and support the transition to sustainable metallurgy.
