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Size: 3142
Comment:
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Size: 3149
Comment:
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CO2
1ppm global CO2 is how many tonnes of carbon?
The mass of the atmosphere is 5.15e18 kg. We will assume mole fraction is proportional to volume fraction
Gas |
Mole Fraction |
At wt |
Mass*e12 kg |
N₂ Nitrogen |
0.7808 |
28 |
4054226 |
O₂ Oxygen |
0.2095 |
32 |
1087808 |
Ar Argon |
0.0093 |
40 |
48289 |
CO₂ Carbon Dioxide |
0.0004 |
48 |
2077 |
Dry air atomic wt |
1.0000 |
28.9576 |
5129400 |
|
|||
|
0.9960 |
28.9576 |
5129400 |
H₂O Water |
0.0040 |
18 |
20600 |
Wet air atomic wt |
1.0000 |
28.9138 |
5150000 |
400ppm CO₂ is 2077e12 kg, of which 12/44 is carbon, or 566.45e12 kg. Hence 1ppm CO₂ is 1.42e12 kg of carbon atoms.
Wild Speculation Follows
Toray T1100G carbon fiber has a density of 1.79 ( 1790 kg/m³), a tensile modulus of 324 GPa, and a tensile strength of 7 GPa.
If 100ppm of excess CO₂ was magically converted into oxygen and 1.42e14 kg of Toray T1100 carbon fiber, that would 80 cubic kilometers of carbon fiber.
For comparison, high strength steel has a tensile strength of 600 MPa and a density of 8000 kg/m³. So, T1100G is 11.6 times stronger and 0.224 denser, hence a kilogram of T1100 might replace 50 times its weight of high strength steel. Annual global steel production is around 2 billion tonnes per year (2e12 kg), so 1.4e14 kg could supply 3500 years of structural needs at current global demand.
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How much energy would it take to extract 1.42e14 kg of carbon from 5.2e14 kg of CO₂? CO₂ enthapy of formation is 393.5 kJ/mol, and a mole of CO₂ is 0.044 kg, so at 100% efficiency that would be 8.94 MJ/kg, or 4.65e21 Joules to split 100ppm of CO₂ at 100% efficiency. If the process was 3% energy efficient, starting with sunlight, that is 1.55e23 Joules.
The Earth is 70% ocean, and the average surface insolation is around 500 W/m². The earth's disk averages 6371 km radius, about 1.27e14 square meters total, perhaps 8e13 of that being ocean, capturing perhaps 4e16 watts of sunlight. If 1% of that ocean surface (which is mostly lifeless now) was covered with 3% energy-efficient "carbon fiber plankton", that would be 4e14 joules/second, 1.26e14 joules per year - converting all the atmospheric CO₂ excess into structural fiber in 12 years.
A long string of speculations with a multiplied probability approaching zero, but still ...
As the old joke goes, "If I had all the money I have spent on drink ... I would spend it ... on drink!". Chances are, if we could design magic plankton that could make carbon fiber from excess CO₂, we would probably design plankton to make motor fuel instead, and give everyone on the planet V8 muscle cars. And make even more steel. Humans are perverse.