In-situ resource utilization (ISRU) is pivotal for sustainable lunar exploration, enabling the extraction of critical resources like oxygen and metals from lunar regolith to reduce Earth dependency. This review compares three prominent ISRU technologies: Carbothermal Reduction (CTR), Molten Salt Electrolysis (MSE), and Molten Regolith Electrolysis (MRE), focusing on their efficacy in producing aluminum and oxygen from lunar regolith. CTR uses carbon to reduce lunar regolith at theoretically viable temperatures near 850 \(\;{}^{\circ }\hbox {C}\) for certain oxides, though practical operation typically requires temperatures above 1500 \(\;{}^{\circ }\hbox {C}\) . The process currently targets iron and silicon extraction and produces carbon monoxide and/or carbon dioxide as byproducts, but it requires an external carbon source typically in the form of methane or graphite. MSE utilizes a beneficiated feedstock of metal oxides to produce metals and oxygen. The process operates at various temperatures depending on the salt electrolyte used. For \(\hbox {CaCl}_2\) , a commonly researched salt, this operating temperature typically falls between 800 \(\;{}^{\circ }\hbox {C}\) and 1000 \(\;{}^{\circ }\hbox {C}\) . MRE, operating above 1300 \(\;{}^{\circ }\hbox {C}\) , processes unrefined regolith to produce oxygen and a mixed metal alloy, though it faces challenges in material durability and power demands. By analyzing outputs, energy needs, and lunar adaptability, this study highlights synergies between the processes and technological gaps, guiding the development of integrated ISRU systems for lunar infrastructure.
