Direct MgOMagnesium Oxide (MgO) reduction in an aluminum smelterAluminum smelter could reduce capex and time to market by 60–80% vs. a greenfield plant, while producing more magnesiumMagnesium than aluminumAluminum at the same current. A reactive liquid tin cathode both keeps the Mg product at the cell bottom and reduces Mg activity to reduce its bath solubility, resulting in >90% current efficiency. Efficient distillationDistillation using the G-METS process recovers pure Mg, and tin returns to the electrolysis cellElectrolysis cell. The present work focuses on chemical, operational, and economic comparisons with aluminumAluminum potlines. Similarities with Hall-Héroult cells include operating temperature, carbon anodeCarbon anode compatibility, raw material feeding, and exhaustExhaust handling. MgOMagnesium Oxide (MgO) is more effective than Al₂O₃ at scrubbing SO₂, fluoridesFluoride/Particulate emissions, and even PFCs from exhaustExhaust gases. MgF₂–CaF₂ is less volatile than cryolite, and compatible with zirconia as a solid oxide membrane inert anodeInert anode or refractoryRefractory. Thermal insulation and high cathode density can potentially enable very small anodeAnode-cathode distance, improving energy efficiencyEnergy efficiency.