Well, now we “just” need an efficient solar furnace for smelting rust into iron.
Theres two giant solar power towers in Nevada near Vegas that easily reach 1000’C more than enough for direct reduction of iron oxide to iron. This process is similar to the chemical looping combustion system that was proposed to allow the direct production of hydrogen and high pressure CO2 from any carbon source with minimal losses in the process and high purity hydrogen and CO2. Both are valuable industry chemicals, hydrogen particularly is used in massive quantities by the petrochemical industry to make high octane gasoline and low sulfur diesels. Nearly all of the nitrogen based fertilizers that feed the whole planet are hydrogen based via ammonia synthesis and Urea also made from gaseous hydrogen. CO2 is used as a solvent for hundreds of chemical processes from vegetable oil extractions, caffeine purification, even processing nuclear wastes via supercritical solvent extraction. CO2 is also used in massive amounts to drive oil from older wells via tertiary recovery methods. I worked with Denbry on a CO2 Project in graduate school it takes two to three barrels of CO2 injected to get one bbl of oil back it’s actually a net carbon sink more carbon is sequestered underground than the amounts released by burning the oil produced how’s that for green tech :)