Producing Renewable Liquid Fuels from Atmospheric Carbon Dioxide

[TeethWhitener]

I have a feeling that the energy required to remove CO2 from air is likely to be far less than for obtaining a usable fuel from atmospheric CO2. I know plants are pretty good at doing the whole job but why not approach the removal job as a single problem and use anaerobic digesters and the like for producing fuel?
This thought may have already been expressed, higher in the thread, but it needs re-stating.

Actually, plants are really bad at it. Photosynthetic efficiency in nature tops out at a few percent. In the lab, artificial photosynthesis is closing in on 25%:
https://en.m.wikipedia.org/wiki/Artificial_photosynthesis
But yes, generally you need to break the problem into parts to solve it.

 

[sophiecentaur]

Bad or good? Depends on the criteria. Low efficiency is no bad thing when it avoids catastrophic changes in the environment. The worst you can say about Natural photosynthesis is that it’s inconveniently slow to deal with this man made disaster. Apart from their part in allowing our arrival, I would say they didn’t do too badly. Just imagine what would have happened if the numbers had allowed just a few more percent of atmospheric oxygen.

 

[Bystander]

few more percent of atmospheric oxygen.

..., and...?

 

[sophiecentaur]

Overdosing on O2 is not good for you or living things in general. Tho’ I have to admit that the level of O2 would not be a problem if all the CO2 were converted and then the plants would all die. We have to turn off the super processing machine at an appropriate time.

 

[TeethWhitener]

Yeah I guess I’m not seeing the point either. Atmospheric O2 was 50% higher 300 Mya:
https://en.m.wikipedia.org/wiki/Geological_history_of_oxygen
Also, plants don’t move (at least not very quickly), so they can afford to have low photosynthetic efficiency.

 

[hutchphd]

And a moment of Vonnegut:

 

[Bystander]

Overdosing on O2

See "Fire Safety Oxygen/Fire Codes;"

Atmospheric O2 was 50% higher 300 Mya:

...for perhaps 10 ms (Schuman resonance), first lightning strike; there might be an argument for 50 % higher atmospheric pressure, but what that might be...

 

[sophiecentaur]

And a moment of Vonnegut:
View attachment 297842

I think Vonnegut weathers a lot better than Groucho Marx.

 

[TeethWhitener]

See "Fire Safety Oxygen/Fire Codes;"

...for perhaps 10 ms (Schuman resonance), first lightning strike; there might be an argument for 50 % higher atmospheric pressure, but what that might be...

I guess reading my link was too much to ask, so here’s a picture:

The atmospheric pressure was the same. The fraction of oxygen in the atmosphere was closer to 30% than the current 20%. This is well-established geologically.

 

[sophiecentaur]

The atmospheric pressure was the same. The fraction of oxygen in the atmosphere was closer to 30% than the current 20%. This is well-established geologically.

There is definitely some upper limit to stable atmospheric oxygen proportion, whatever it happens to be.

There has to be a difference between the energy required to lock CO2 away, chemically and producing a fuel with it. I realize it's an attractive idea to combine the two functions in one process but feasibility must be an issue