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In principle, hydrogen is produced underground when iron (II) silicate reacts with water: 2 FeSiO3 + H2O >> H2 + Fe2O3 + SiO2 As I understand it, this is a "l
by scythe 4y ago
In principle, hydrogen is produced underground when iron (II) silicate reacts with water:
2 FeSiO3 + H2O >> H2 + Fe2O3 + SiO2
As I understand it, this is a "low-pressure" reaction. The FeSiO3 regeneration happens when iron (III) oxide sinks deep into the crust and reacts with silicates, releasing oxygen. I'm not clear on the specifics, but the ultimate energy source is (necessarily) plate tectonics, driven by the decay of uranium, potassium-40 and thorium in the deep Earth. The gross power driving tectonic forces (total underground radioactivity) is estimated with decent confidence at around 30 terawatts; this exceeds humanity's total energy consumption by a small factor (around 2–3), and probably only a fraction of this energy is converted to hydrogen.
So using Brian Cohen's definition [1], I'm not sure geohydrogen is truly "renewable" at world scale, but it's renewed at some scale.
1: http://large.stanford.edu/publications/coal/references/docs/pad11983cohen.pdf http://large.stanford.edu/publications/coal/references/docs/...
- amluto 4y agoI think it’s renewable in a somewhat weaker sense: there is a lot of iron (II) (and perhaps other minerals that can also reduce water) in the crust, and there is a lot of water, and water percolates and finds these minerals at a rate that may produce hydrogen continuously at a sufficient rate for humanity. More strongly, even if plate tectonics were needed, it doesn’t necessarily take anywhere near 1 TW of power to move enough material to produce 1 TW worth of useful stuff. The energy in question here is chemical, not kinetic.