Removing CO₂ from the atmosphere
- Thread starter svetz
- Start date
Boondock Saint
Solar Enthusiast
- Joined
- Apr 8, 2021
- Messages
- 661
12 Monkeys.
svetz
Works in theory! Practice? That's something else
Seawater has 150 times the concentration of CO₂ than the air [ref], seems like most of the focus should be there or at the source (smoke stacks).
A lot of the existing ideas around removing CO₂ from saltwater are around changing the solubility by altering the alkalinity, heating seawater up, or electrolysis.
As H₂O has a molecular weight (MW) of 18 and CO₂ a MW of 44, I wonder if you could continuously centrifuge seawater forcing the CO₂ into a gas permeable membrane?
Update: Looks like it's possible, but not energy efficient (wonder how it compares with heating seawater?).
A more practical way might be with a CalciumOxide slurry (CaO) to make CaCO₃, which has a MW of 100, isn't soluble, and also binds the CO₂ in an environmentally friendly way. But CaO usually comes from burning seashells (CaCO3(s) → CaO(s) + CO₂(g)) which makes CO₂, so as a binder that sounds like a bust. Hmm, sea creatures making seashells must get the CO₂ from the seawater, perhaps more barnacles?
A lot of the existing ideas around removing CO₂ from saltwater are around changing the solubility by altering the alkalinity, heating seawater up, or electrolysis.
As H₂O has a molecular weight (MW) of 18 and CO₂ a MW of 44, I wonder if you could continuously centrifuge seawater forcing the CO₂ into a gas permeable membrane?
Update: Looks like it's possible, but not energy efficient (wonder how it compares with heating seawater?).
A more practical way might be with a CalciumOxide slurry (CaO) to make CaCO₃, which has a MW of 100, isn't soluble, and also binds the CO₂ in an environmentally friendly way. But CaO usually comes from burning seashells (CaCO3(s) → CaO(s) + CO₂(g)) which makes CO₂, so as a binder that sounds like a bust. Hmm, sea creatures making seashells must get the CO₂ from the seawater, perhaps more barnacles?
Last edited:
sequestration: Kelp, or mangroves, or "An “air capturing” plant is taking in air through giant fans, filtering out the carbon dioxide, absorbing the gas in liquid, and converting it into pellets in a bid to combat climate change." or by using concrete. Pine trees capture carbon the quickest.
"Kiss The Ground" with Woody Harrelson is a fantastic documentary on carbon sequestration for those that are interested.
Our "factory farms" destroy the earth's ability to reabsorb CO2, as well as the way livestock are raised. People tend to focus on methane from cow farts, which is a joke compared to the environmental damage that the farms themselves cause.
I'm not an expert, but the general idea is that farms destroy the soil and hinder it's ability to trap carbon. Cattle need food, food is grown, and growing cattle food is what is destructive. For every pound of meat, it requires something like 10x more weight in feed to make.
The way we (mostly) farm is by using fertilizers, not by proper crop rotation and off seasons like was done before chemical fertilizers were available. Farming now depletes the soil of all nutrients, and stops it from sequestering carbon.
Our damage to the oceans also screws with algae and aquatic plants, which are the most prolific life on the planet, and it happens to sequester quite a bit of carbon as well.
Woody does a MUCH better job of explaining it, but that's the general idea.
Our "factory farms" destroy the earth's ability to reabsorb CO2, as well as the way livestock are raised. People tend to focus on methane from cow farts, which is a joke compared to the environmental damage that the farms themselves cause.
I'm not an expert, but the general idea is that farms destroy the soil and hinder it's ability to trap carbon. Cattle need food, food is grown, and growing cattle food is what is destructive. For every pound of meat, it requires something like 10x more weight in feed to make.
The way we (mostly) farm is by using fertilizers, not by proper crop rotation and off seasons like was done before chemical fertilizers were available. Farming now depletes the soil of all nutrients, and stops it from sequestering carbon.
Our damage to the oceans also screws with algae and aquatic plants, which are the most prolific life on the planet, and it happens to sequester quite a bit of carbon as well.
Woody does a MUCH better job of explaining it, but that's the general idea.
pollenface
Solar Addict
Plant lots of trees and stop clearing forests.
svetz
Works in theory! Practice? That's something else
Could a 300W solar panel remove 5 liters of CO2 from the atmosphere per day?
3.5% of seawater is "salts", of which Calcium ions are 1.2% and Magnesium 3.6% (both of which can sequester CO₂). Aqueous CO₂ is around 100 mg per liter of seawater (ref).
As there are 1000 liters per cubic meter, from the above
Those back-of-the-envelope calculations ignore the thermodynamic effects and assume separation is achievable at 5200 rpm @ 500W/m³, which is completely unknown to me and probably bogus. There are also other possibilities, for example, some solar heating of the water before separation should improve the yield (most gases are less soluble as temperature increases). Similarly, both calcium and magnesium are less soluble and more likely to bind to CO₂ at lower temperatures. So it might be more/less efficient either way.
One study says 274 kg of CO₂ is created per kW of panel produced/delivered. 137 Kg of Coal would produce about 274 kg of CO₂ and 0.5MWh of power. Over its life, a kW solar panel would produce 40 to 60 MWh. So solar is better than coal in terms of energy to CO₂.
But in terms of CO₂ removal via a centrifuge, the numbers aren't so friendly. If any of the math above is correct (very unlikely), such a panel would have to run for 75 years just to break even. So, this technique to remove CO2 from the atmosphere seems like a bust.
3.5% of seawater is "salts", of which Calcium ions are 1.2% and Magnesium 3.6% (both of which can sequester CO₂). Aqueous CO₂ is around 100 mg per liter of seawater (ref).
From this ref, looks like 500 W/m³ would be state-of-the-art.
As there are 1000 liters per cubic meter, from the above
100 mg / l x 1000 l/m³ / 1000 mg/g = 100 grams / m³
2 m³ / kW, that would be 200 grams CO₂/kW.
That assumes 100% efficiency, which isn't likely. But, also dissolved into seawater is carbonate (that causes the acidification damaging to reefs), as the aqueous CO₂ is removed, the carbonate should shift into aqueous form. So, it might be possible to be over 100%.Those back-of-the-envelope calculations ignore the thermodynamic effects and assume separation is achievable at 5200 rpm @ 500W/m³, which is completely unknown to me and probably bogus. There are also other possibilities, for example, some solar heating of the water before separation should improve the yield (most gases are less soluble as temperature increases). Similarly, both calcium and magnesium are less soluble and more likely to bind to CO₂ at lower temperatures. So it might be more/less efficient either way.
One study says 274 kg of CO₂ is created per kW of panel produced/delivered. 137 Kg of Coal would produce about 274 kg of CO₂ and 0.5MWh of power. Over its life, a kW solar panel would produce 40 to 60 MWh. So solar is better than coal in terms of energy to CO₂.
But in terms of CO₂ removal via a centrifuge, the numbers aren't so friendly. If any of the math above is correct (very unlikely), such a panel would have to run for 75 years just to break even. So, this technique to remove CO2 from the atmosphere seems like a bust.
Q-Dog
¯\_(ツ)_/¯
More trees, less paving.
"They paved paradise to put up a parking lot" and "Hey farmer, farmer, put away that DDT now" – and sentimental sound. The line "They took all the trees, and put 'em in a tree museum / And charged the people a dollar and a half just to see 'em"
Similar threads
