[J. Strebel]

I would like to create a crowdsourcing approach to scrubbing CO2 from the atmosphere. To this end, I am looking for a chemical reaction with the following properties:

• scalable from an indiviual use to a large facility
• uses CO2 as one of its inputs; the other inputs should be readily available.
• produces a liquid or a solid which possess some economic value; the whole process does not need to have a busines case or a clear return on investment. Ideally, the reaction product and the CO2 form some sort of cycle, thus being sustainable.
• reaction can be exothermal
• no exotic catalysts needed

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I would love to hear your input on this hypothetical chemical reaction!

[chenbeier]

Any alkaline material like sodium,- potassium-, calcium- hydroxide can be used. It form the carbonate.
The question is  how these are made. Some uses the carbonate as source, so it's milk maid calculation.

[Enthalpy]

This objective is extremely difficult because of cost. Our atmosphere is huge at technological scale.

The hard point IS the method to do it. So my feeling about "I want to crowdsource, but how to absorb the CO₂?" is less than enthusiastic. I'd be far more pleased with "Here's how I want to absorb the CO₂ economically, you can check the provided figures including cost" - and then, funding details wouldn't be a problem.

Presently, the most advanced projects don't extract CO₂ from the atmosphere, despite we'll have to do it. They only catch the CO₂ at a few sites that produce it, locally and in big amount. Power plants, cement plants. Already this is badly difficult to pay, and the efforts collapsed after 2008 when the price of CO₂ emission rights dropped.

Besides compressing gaseous CO₂ in some natural reservoirs like abandoned gas and oil wells, a tried approach uses silicates. These don't release CO₂ to produce, as opposed to CaO for instance. Added CO₂ transforms them to silica and solid carbonates. The silicates aren't processed, nor even moved: CO₂ is injected in the ground at the silicates.

These two attempts cost magnitudes less than scrubbing the CO₂ from the atmosphere with a processed chemical, and nevertheless they find no use because of cost. So I suggest to put some cost figures early on any attempt, even if the detailed compounds aren't still known. Do you plan to move air actively for instance? Even power plants don't do it at the cooling tower.

Grow bamboo to bury it, deep enough that most carbon stays there? If you catch the methane it has a value and is emission-free. Or collect algae without growing them? Collect wood waste when a forest is harvested? At a paper factory? Vegetable waste on crop fields? At the bottom of a barrage lake?