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The main engine of natural hydrogen production is now thought to be a set of high-temperature reactions between water and iron-rich minerals such as olivine, wh

by sp332 4y ago

The main engine of natural hydrogen production is now thought to be a set of high-temperature reactions between water and iron-rich minerals such as olivine, which dominate Earth’s mantle. One common reaction is called serpentinization, because it converts olivine into another kind of mineral called serpentinite. In the process, the iron oxidizes, grabbing oxygen atoms from water molecules and releasing hydrogen. So we might run out of olivine at some point, but it's going to be a long time.

phkahler 4y ago
But then we burn all that hydrogen and use up all our oxygen. CO2 may be a greenhouse gas, but plants pull the oxygen back off and return it to the air.
- pfdietz 4y ago
  Indeed. The amount of ferrous iron in the Earth far exceeds the capacity of the atmosphere's oxygen to oxidize. The Earth is mostly reduced, with a very thin layer of oxidation on top.
- gilleain 4y ago
  I think that the 21% of the air that is oxygen is unlikely to be used up any time soon? Maybe i'm wrong...
  - anonymouskimmer 4y ago
    You're right. We would need to burn the equivalent of about 1000 times the total biomass of the earth to convert the majority of the oxygen in the air into carbon dioxide (or water in this process). I'm moderately interested in how much hydrogen we could burn without noticeably adding to sea-level rise. Probably quite a bit.
- DennisP 4y ago
  Plants aren't doing that job all that effectively, or the CO2 levels wouldn't be going up. The entire history of industrial civilization has added 140 parts per million of CO2 to the atmosphere. For CO2, that's too much. But Oxygen is 21% of the atmosphere, or 210,000 parts per million. I think we'll be ok for a while.
  - phkahler 4y ago
    >> Plants aren't doing that job all that effectively, or the CO2 levels wouldn't be going up. Sure, but they DO reduce the level over time and they also grow faster with the higher concentration. The CO increase is less than all the CO2 we've produced with industry. It's not ok to say there is 21 percent oxygen and this proposed process won't put a dent in it. One might have thought that about burning hydrocarbons. The question of how long can we "burn rocks" still stands. Is it 10k years or 10M or something else?
  - MarkusQ 4y ago
    Plants do a great job pulling out CO₂ -- that's why CO₂ levels fall in the northern hemisphere's spring and early summer (see https://gml.noaa.gov/ccgg/trends/ https://gml.noaa.gov/ccgg/trends/ ). Unfortunately, insects and fungi are just as good at eating plant matter and exhaling the CO₂ back again (aided somewhat by fires) so it goes right back in to the air again.
    - entropicgravity 4y ago
      Yes my understanding is that before there were fungi that could deal with the fallen trees they just stacked up on the ground and eventually became coal while the earth turned into snowball earth for a few million years. Sucking up CO2 has been too much of a good thing under some past circumstances.
    - zdragnar 4y ago
      Plants also respirate C02 when they use the sugars they generate from photosynthesis. It's why you can grow plants in a completely sealed terrarium. Some do better than others- they generally don't prefer a perfect balance, but they can survive in it.

by sp332 4y ago

phkahler 4y ago

But then we burn all that hydrogen and use up all our oxygen. CO2 may be a greenhouse gas, but plants pull the oxygen back off and return it to the air.

pfdietz 4y ago
Indeed. The amount of ferrous iron in the Earth far exceeds the capacity of the atmosphere's oxygen to oxidize. The Earth is mostly reduced, with a very thin layer of oxidation on top.
gilleain 4y ago
I think that the 21% of the air that is oxygen is unlikely to be used up any time soon? Maybe i'm wrong...
- anonymouskimmer 4y ago
  You're right. We would need to burn the equivalent of about 1000 times the total biomass of the earth to convert the majority of the oxygen in the air into carbon dioxide (or water in this process). I'm moderately interested in how much hydrogen we could burn without noticeably adding to sea-level rise. Probably quite a bit.
DennisP 4y ago
Plants aren't doing that job all that effectively, or the CO2 levels wouldn't be going up. The entire history of industrial civilization has added 140 parts per million of CO2 to the atmosphere. For CO2, that's too much. But Oxygen is 21% of the atmosphere, or 210,000 parts per million. I think we'll be ok for a while.
- phkahler 4y ago
  >> Plants aren't doing that job all that effectively, or the CO2 levels wouldn't be going up. Sure, but they DO reduce the level over time and they also grow faster with the higher concentration. The CO increase is less than all the CO2 we've produced with industry. It's not ok to say there is 21 percent oxygen and this proposed process won't put a dent in it. One might have thought that about burning hydrocarbons. The question of how long can we "burn rocks" still stands. Is it 10k years or 10M or something else?
- MarkusQ 4y ago
  Plants do a great job pulling out CO₂ -- that's why CO₂ levels fall in the northern hemisphere's spring and early summer (see https://gml.noaa.gov/ccgg/trends/ https://gml.noaa.gov/ccgg/trends/ ). Unfortunately, insects and fungi are just as good at eating plant matter and exhaling the CO₂ back again (aided somewhat by fires) so it goes right back in to the air again.
  - entropicgravity 4y ago
    Yes my understanding is that before there were fungi that could deal with the fallen trees they just stacked up on the ground and eventually became coal while the earth turned into snowball earth for a few million years. Sucking up CO2 has been too much of a good thing under some past circumstances.
  - zdragnar 4y ago
    Plants also respirate C02 when they use the sugars they generate from photosynthesis. It's why you can grow plants in a completely sealed terrarium. Some do better than others- they generally don't prefer a perfect balance, but they can survive in it.