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> it's theoretically possible to burn hydrocarbons and turn the CO2 to coal and leave it like that with a net energy gain - it's just hugely impractical compare

> it's theoretically possible to burn hydrocarbons and turn the CO2 to coal and leave it like that with a net energy gain - it's just hugely impractical compared to not burning them in the first place. It's also theoretically possible to have chemical reactions that bind carbon from the air into solid compounds that aren't themselves combustible without a net energy loss, but then you need a very large volume of reactants and produce a very large volume of industrial waste and it still turns out to be highly uneconomical compared to the cost of replacing fossil fuels for power generation.

cyberax 2y ago
> It's also theoretically possible to have chemical reactions that bind carbon from the air into solid compounds that aren't themselves combustible without a net energy loss That's not true. The reactants must have enough stored potential energy to reduce carbon. You might get that for "free" by using accelerated weathering of rocks (the energy ultimately comes from the radioactive decay in Earth's core).
- AnthonyMouse 2y ago
  "Net energy loss" meaning you have to supply some energy in the form of heat or electricity to make the reaction go, and you don't get it back. There are things that will react with CO2 and form something that isn't combustible. That reaction may even generate heat that you could hypothetically use for something, but in practice probably not enough of it to be worth extracting.
  - cyberax 2y ago
    > There are things that will react with CO2 and form something that isn't combustible. Sure. There are plenty of such things. For example, elemental magnesium will happily bind carbon dioxide into pretty inert magnesium carbonate. But to _get_ that elemental magnesium, you need to expend energy, because elemental magnesium can't be found in nature. There is only one realistic option: rock weathering. Silicate rocks can react with carbon dioxide to produce calcium carbonate and (eventually) silicon dioxide.

cyberax 2y ago

> It's also theoretically possible to have chemical reactions that bind carbon from the air into solid compounds that aren't themselves combustible without a net energy loss That's not true. The reactants must have enough stored potential energy to reduce carbon. You might get that for "free" by using accelerated weathering of rocks (the energy ultimately comes from the radioactive decay in Earth's core).

AnthonyMouse 2y ago
"Net energy loss" meaning you have to supply some energy in the form of heat or electricity to make the reaction go, and you don't get it back. There are things that will react with CO2 and form something that isn't combustible. That reaction may even generate heat that you could hypothetically use for something, but in practice probably not enough of it to be worth extracting.
- cyberax 2y ago
  > There are things that will react with CO2 and form something that isn't combustible. Sure. There are plenty of such things. For example, elemental magnesium will happily bind carbon dioxide into pretty inert magnesium carbonate. But to _get_ that elemental magnesium, you need to expend energy, because elemental magnesium can't be found in nature. There is only one realistic option: rock weathering. Silicate rocks can react with carbon dioxide to produce calcium carbonate and (eventually) silicon dioxide.