Your Plants Breathe
As humans, we breathe in the air around us, and most of what we actually use is the oxygen content. It makes up about 20.9% of naturally occurring air, depending on elevation and pollution levels. We use oxygen by taking it into our lungs, where it enters our bloodstream. We exhale the parts of the air that we don’t use, along with excess carbon dioxide that comes back to the lungs through the bloodstream.
Plants essentially do the opposite. They use carbon dioxide and exhale oxygen.
So, How Do I Use This Information?
Without building or buying a separate device to add to your tent, the only way you have to increase the carbon dioxide or CO2 level is to sit in the tent and breathe. Seeing as that is completely ridiculous, let’s build a carbon dioxide generator.
There are a few different ways to create carbon dioxide, some being more complex than others:
- The method they generally use in mosquito attracting devices, where they slowly burn propane to use oxygen and results in water and carbon dioxide (not exactly practical in a tent where we are concerned with heat and possible carbon monoxide toxicity).
- Separately grow fungus mycelium (the part that grows in a substrate, usually white) inside the tent. It can be complicated to build your own, and takes a perfectly sterile substrate to not grow mould, which is potentially harmful to your plants.
- A refillable CO2 tank with a regulator. Can be expensive to set up, but definitely a worthy upgrade in the future.
- Yeast. The method we will be building today, as it is the least complicated and the least likely to cause problems in your growing environment.
How Does Yeast Make CO2?
Yeast grows and multiplies when it is given water and food, like most living things. Its food consists of sugars and starches. Anyone who has made beer or wine knows that yeast will feed on whatever you have in your primary bucket.
As the yeast grows and feeds on the sugars and starches, it creates two very important waste products: alcohol and carbon dioxide. It is the original method for carbonating beer (before we started using a CO2 tank for draft beer).
Yeast also creates heat while fermenting, but not enough to worry about in your grow space.
Let’s Make CO2!
As mentioned above, a popular way that yeast is used is in the home-brewing hobby. So, let’s skip a few steps of building our own device, and borrow from that.
Here is the short list of things we will need to build our yeast fermenter:
- Home Brewing Primary Bucket with Air Lock
- Plastic Tubing
- White Gorilla Tape
- Utility Knife
- 6″ White Twist Ties (these are useful for lots of things in the grow tent)
- 10 Lb Sugar
- Yeast (you can use normal bread yeast if you have it)
- Brewing Sanitizer
- 24″ Stirring Spoon
- This first step is pretty simple. We are going to use the utility knife to cut a small hole in the top of the airlock that came with your fermenting bucket. Make the hole in the center, about 1/2″ across.
- Center the tubing over the hole you just created, and securely tape it in place. Trim any tape that hangs down, like the picture. It doesn’t have to look perfect, but it has to stay attached.
- Follow the directions on the sanitizer and sanitize the bucket, lid and the untaped parts of the airlock.
- Pour about 20 litres or 5 gallons of filtered warm water into the sanitized bucket.
- Stir in sugar until it stops dissolving.
- If you haven’t already, move the bucket to the corner below your upper circulation fan in your grow tent.
- Measure the distance between the rim of the bucket and the fan, and cut the tube that you taped to the airlock cover to that length.
- Sprinkle one packet of yeast on the top of the sugar water in the bucket.
- Put the sanitized lid on the bucket, and install the airlock (add some water like in the first picture). The airlock should be as close to the corner of the tent as possible.
- Clip the cover that is taped to the measured and cut tubing onto the airlock.
- Use the twist ties to run the tube up behind the fan. It should end near or above the top of the fan. (Carbon dioxide is heavier than the rest of the air in the tent, so you want the fan to push around as much as possible before it sinks to the bottom)
- Empty, sanitize and refill the bucket with yeasted sugar water every 2 weeks.