# 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

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.
• 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