# CO2 removal from mushroom growing tent

I'm trying to grow oyster mushrooms that like high temperatures. They look great in an indoor terrarium, and can eventually yield several tasty meals :)

However oyster mushrooms are hard to grow indoors, because they need low $\ce{CO2}$ levels (<1000 ppm according to Paul Stamets), AND high humidity (>95%).

Warm climate oysters tend to grow fast, and can generate quite a lot of $\ce{CO2}$ fast.

If I vent the air in tent about 10 times a day, humidity will suffer (and I can't do that all the time).

If I close the tent, mushrooms will be stunted and club-like, and yields will be next to nothing.

I'm thinking about putting a tray with $\ce{NaOH}$ crytals on it, probably with a fan to slightly move the humid air around a bit.

An other method would be to use an aquarium pump to bubble air through NaOH solution.

My questions are:

• Does this look like something feasible? Can some $\ce{NaOH}$ remove enough $\ce{CO2}$ from the air to keep it under 1000ppm?
• Which of the above methods seem to be the better one given the aquarium pump can bubble about 100-200 litres of air in every hour and the tent is about 500 L ?
• Removing CO2 from gasses is a process called sweetening in industry. I'm really not sure how feasible this would be to implement on a tiny scale like this but maybe something worth researching! en.wikipedia.org/wiki/Amine_gas_treating – CTKlein Oct 31 '14 at 14:54
• I would not use $\ce{NaOH}$ as it is potentially dangerous and unnecessary costly. Soda $\ce{Na2CO3}$ solutions can accept quite an amount of $\ce{CO2}$. In case of large use, regenerable adsorber could be beneficial, preferably diethanolamine as having highte boiling point. – permeakra Oct 31 '14 at 14:56
• Could you grow a plant along with the mushrooms to use the CO2? Something like a spider plant grows fast and doesn't take much light. Vegetables would be a better solution, but they're going to require stronger lighting. Another idea is to just pump fresh air into the tent, through a container of water to maintain humidity, and continuously displace the excess CO2. – Jason Patterson Oct 31 '14 at 16:58
• The plant would require additional lighting, and the heat from the light course would also have to be removed. That is too complex and frankly I have even more doubt in the efficiency as the NaOH solution. Since the mushroom blocks don't generate much $CO_2$, the costs of the NaOH is not a problem. I would need to quesstimate how fast a NaOH solution with given surface area can absorb $CO_2$ from the air at atmospheric pressure given the concentration and temperature. – netom Oct 31 '14 at 17:57
• ...maybe algae could remove $\ce{CO2}$, but that's a different story. At least they would be easier to arrange in the terrarium than plants with leaves. :) – netom Oct 31 '14 at 20:42

Please stay away from sodium hydroxide, it's way too nasty to use in non-lab setup. You can handle it safely in dry conditions, but in contact with water, it becomes sticky and causes bad burns.

As a substitute, I suggest $\ce{Ca(OH)_2}$, readily available as slaked lime. You can structure it into relatively high-surface sculptures and it solidifies into common plaster upon binding enough $\ce{CO_2}$. It is often used for this purpose due to its low price, low toxicity and ease of handling.

In your situation, I would just put some vertically fixed mesh soaked in very viscous suspension of calcium hydroxide. In the high humidity conditions you'd have no problems with normal drying, so once it solidifies it has done its job and you can just hit the mesh against the ground to crumble the plaster away and put on new layer. It is advisable to use gloves and goggles, but it is not as necessary as it would be in the case of sodium hydroxide (look at all the masons around).

• Thank you for the advices. I already tried $\ce{Ca(OH)2}$ with limited success. The vertical mesh idea is very good, i'll try it thank you! – netom Dec 4 '14 at 9:34
• Actually, the vertical mesh setup doubles as a humidifier! I tried to use a large piece of textile soaked in thick calcium hydroxide slurry. If it was kept humid, no other means of humidification were needed. No ventillation was used beside accidental, and the oysters looked much better. Since the system is pretty much closed, only a little humidity escapes. (The reaction itself produces a small amount of water too, although probably it does not matter much.) Thank you for the suggestion! – netom Sep 9 '15 at 14:36

If your chamber was small enough, you could try having racks of germinating seeds. As they sprout they would be absorbing a minuscule amount of co2. They wouldn’t need light. If you’ve ever made sprouts in your kitchen cupboard this can be easily achieved. I am going to try this. Sunflower would be ideal as they germinate easily, cheap and easy to come by.

Stratification Best of all, use no chemicals. If you have an air circulating fan in your chamber, use it intermittently. When not running, ambient air enters small hole(s) at the top of your chamber, and carbon dioxide will escape out small hole(s) at the bottom of your chamber. CO2 at standard temp/press is invisible, but it definitely will sink beneath the unmoving oxygen and nitrogen of ambient air.

• You should probably expand on this to address the OP's query. As it stands, it's borderline NAA. – Todd Minehardt Oct 11 '16 at 2:57