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CO2 is used as fertilizer in aquariums where it's brought into the water with diffusors from compressed form in cylinders. Direct Air Capture machines for CO2 have been presented for experimental geo-engineering purposes.

I was wondering whether it's possible to use the technology on a much smaller scale which allows one to supply the fertilizer as a constant CO2 stream (a few g per hours) or somehow compress the CO2 into a cylinder to produce it at home. This should avoid the the need for at least transport and energy for compression and allows to near endless supply for free.

Could I emit CO2 certificates? Just kidding...

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    $\begingroup$ plant a tree... $\endgroup$ – Pete W Jan 16 at 20:30
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It is possible and this is currently being done at the OpenAir Collective. There are two direct air carbon capture (DACC) machines under active development, Violet and Cyan. Both are small-scale, open-sourced, non-commercial systems that could be used to take CO2 out of the air and to supply it as fertilizer to plants. These units do not offer CO2 compression into a cylinder however.

Violet is OpenAir's version of a prototype system by Prof. Tao Wang; his prototype captures about 1 kg CO2 per day and releases it into a greenhouse to improve plant growth. Here is a photo of his system. It operates in cycles so some storage will be required to supply CO2 as a constant stream.

Photograph of the moisture-swing prototype

Violet is still being developed at present but the prototype system above is currently in service.

Cyan is an even smaller system buildable for under $100 that presently captures a few grams per day and locks the CO2 into calcium carbonate. The CO2 can be released through combination with vinegar or other acids. Cyan is a very portable unit that can be used at home.

Photograph of the outside of the Cyan unit

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  • $\begingroup$ Please add any details to this post instead of linking to them. Without the specific details that answer the question, this post is somewhere between a "link-only" answer and "spam or self promotion". $\endgroup$ – hazzey Feb 4 at 13:48
  • $\begingroup$ Thank you @hazzey, I'd appreciate guidance on additional details that would help answer this question. The question was whether it was possible and I demonstrated that it was possible and attempted to provide evidence that this technology is in use. I have removed the links, hopefully that will help. $\endgroup$ – Dahl Winters Feb 4 at 17:21

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