Solar-driven electrochemical lithium extraction for the Salar de Atacama: hydrogen coproduction, CO2 fixation, and circular resource recovery

This work presents a proof-of-concept techno-economic model of a solar-driven electrochemical plant that recovers lithium from Salar de Atacama brine while coproducing hydrogen and fixing carbon dioxide into lithium carbonate, combining two independently reported laboratory devices into a single plant-scale design. A lithium-aluminum-germanium-phosphate (LAGP) membrane cell drives lithium recovery and hydrogen evolution; a carbon-dioxide-driven precipitation stage then fixes carbon as it forms carbonate. Membrane area and photovoltaic capacity are sized jointly against a benchmark evaporation pond, and the plant is evaluated across four representative weeks of measured Atacama solar data under a literature-calibrated fixed-current baseline and a full-foresight optimal-control ceiling. The plant recovers 556–1,063 kg of lithium carbonate and 25–48 kg of hydrogen per week from a 544.9 m2 membrane, at 542–692 USD per m2 per year and 0.710 kg of CO2 fixed per kilogram of carbonate produced. Optimal control raises combined value 13.5–34.8% over the baseline across seasons, averaging 26.7%, and continuous operation replaces a 376-day brine residence time in a conventional pond. Banking the coproduced hydrogen on site for overnight fuel-cell reconversion, instead of exporting it as haul-truck fuel, adds 40–53% more lithium carbonate and repays the fuel cell's own cost in every season. Sustaining one haul truck on exported hydrogen alone would need 12,000–17,600 m2 of membrane, so on-site reconversion is the more effective use of the coproduced hydrogen at this scale.