Abstract
Despite growing interest in low-emission material supply chains, magnesium production continues to rely heavily on the Pidgeon process, a high-temperature and energy-intensive technology. Dolomite remains the cornerstone feedstock supporting this dominant production route. Hydrometallurgical extraction from dolomite offers a potential lower-emission alternative; however, its environmental advantages remain uncertain due to limited integration of experimentally informed process modeling and life-cycle assessment. In particular, the absence of full “grinding-to-ingot” simulations constrains consistent comparisons with established pyrometallurgical routes.
This study presents a process-based modeling and life-cycle assessment of competing magnesium production pathways, combining experimentally informed unit operations with full-scale process simulation. A hydrometallurgical flowsheet was developed based on optimized leaching and purification steps, identified through laboratory studies of dolomite leaching and impurity removal. Thermogravimetric analysis supported feedstock selection by clarifying the role of calcination on downstream process performance. These experimental insights were embedded into a comprehensive HSC Chemistry simulation that models the complete circuit from comminution and leaching to purification, spray drying, electrowinning, and ingot casting.
In parallel, the conventional Pidgeon process was modeled using thermodynamic modules and literature-validated operating conditions to ensure a consistent functional unit and system boundary. Life-cycle inventory (LCI) data generated directly from both simulations were implemented in openLCA using the Ecoinvent 3.11 Cut-off system model. Environmental impacts were evaluated using the ReCiPe 2016 midpoint method within a Canadian context. For the hydrometallurgical route, two allocation scenarios were examined: one excluding by-product credits and one incorporating potential credits associated with co-produced materials, enabling assessment of their influence on comparative outcomes.
The results indicate that the hydrometallurgical pathway offers clear advantages in several impact categories, including global warming potential and fine particulate matter formation, relative to the Pidgeon process. However, higher contributions to acidification and water consumption were observed, highlighting trade-offs associated with reagent use and aqueous processing. Sensitivity to allocation assumptions further emphasizes the importance of transparent modeling choices in sustainability evaluations. Taken together, this work demonstrates that process-integrated modeling combined with life-cycle assessment is essential for robust comparison of magnesium production routes. The findings show that hydrometallurgical magnesium production can achieve improved environmental performance, but only when evaluated through comprehensive system-level analysis that explicitly accounts for burden shifting and modeling assumptions.