What is the best DIY CO2 generator for grow tents?

Elevated CO₂ will increase yields by up to 30%

New research by Dr Bruce Bugbee at Utah State University has shown conclusively that enriching CO₂ in your grow room to 1,000 ppm can increase medicinal herb growth by up to 30%. 

Should I add CO2 to my grow tent?

It can be the best way to increase your yield in the same sized space. However not all home growers can afford the cost of CO₂ cannisters, regulators or the alternative gas burners.

There are cheaper and easier to use DIY and home grower CO₂ systems but do they work?

We have tested the most common solutions you can DIY or buy from your local grow shop. We put them in a closed 4ft x 2ft (120cm x 60cm) grow tent and sealed the vents. We used a CO₂ sensor to monitor the increase in CO₂ over 1/2 hour.

DIY yeast and sugar bottle

Although very cheap and easy to setup it does not generate enough CO₂  for a small grow tent.

Mushroom bag by Exhale

This has mycelium and substrate in it to last 6 months and is relatively cheap and required no maintenance. However it is not effective, even in a small space

Mother Nature CO₂ 

Another mycelium based product with an air pump to stimulate CO2 production. The air pump runs for 5 minutes every hour with lights on. It can generate short spikes of CO2 when the pump comes on but is unable to sustain that level for very long.

Airbomz CO₂ 

This is an automatic dispenser with settings for duration and frequency of dispensing. There is only 60g of CO₂  and we elevated the grow tent to 800ppm but for only 48 hours. It performs of but at $85 it is way too expensive to be worth while.

The best way to elevate CO₂ in your grow tent?

 Unfortunately it requires some investment in equipment. There are two options:

• Cold CO₂  enrichment with CO₂  cylinder and valves
• Hot CO₂  enrichment with a gas burner

Cold CO₂  enrichment requires investment of about $500 -$1,000 for a CO₂  cylinder, regulator valve, controller and sensor. It is more expensive to run than a gas burner but does not produce heat or water vapour when running. It is therefore easier to control the closed environment required to achieve elevated CO₂ in the grow room.

Hot CO₂  devices burn a pilot flame of gas in a safe container. The system outputs CO₂ , water vapour and heat. The CO₂  burner costs about $300 to $700 depending on output but you also require a CO₂  sensor and controller which cost about $200 to $300. the investment in a hot CO₂  burner is more upfront but it is cheaper to run as propane gas is much cheaper than CO₂  cylinders.

The additional downside to a hot burner is it generates heat and water vapour which must be removed from the grow room with air conditioning.