Carbon Dioxide: Fertilizer For The Air

gore December 31, 2011 10
Carbon Dioxide: Fertilizer For The Air

Plant growth is fueled by the production of glucose through photosynthesis. This process requires three components–water, light and carbon dioxide (CO2).  In other articles, we address lighting and watering. Here, the focus is CO2 –specifically, how to supplement it.

Carbon dioxide enrichment can greatly improve the yield of indoor marijuana crops.  Plants take in carbon dioxide (CO2) and release oxygen through holes in the undersides of their leaves called stomata (plural for stoma). Atmospheric CO2 content is typically somewhere between 300-600 parts per million (ppm). Presence of CO2 at this concentration has proven sufficient for every plant on Earth, from microscopic algae to towering redwood trees.

To maintain high growth rates, you will need to replenish CO2 by adding fresh air or by adding CO2 artificially. Elevating CO2 content to levels higher than what is found outdoors can result in growth rates that are impossible to achieve in nature. This is the reason many indoor growers choose to supplement CO2 artificially.

While you can supplement CO2 in a variety of ways, some methods are more cost effective than others. When choosing a CO2 enrichment method, the single most important factor is the size of your grow room.  Following is an analysis of several of the available options.

Chemical Kits

You can purchase a chemical kit online or at your local grow shop. These kits work by combining non-toxic components to produce a chemical reaction that generates CO2. Chemical kits offer a finite return and are single use only, with each use spending one chemical charge.  One manufacturer claims that their kit, housed in a bucket, can generate enough CO2 to enrich a 10′ x 10′ room by as much as 1600ppm. With a daily cost of $1.50 or more, these kits are probably best suited for smaller rooms.

Baking Soda and Vinegar

Some growers claim to get increased growth rates by mixing these two common household products. This technique is strictly a D.I.Y. enthusiast’s approach, and offers very little CO2 in return.  Gas is produced in an instant release, and has very little lingering effect. This chemical reaction does produce CO2 but is not cost effective. Leave this one for volcano experiments.

Fermentation, Composting and Yeast

The natural process of fermentation and decomposition produces carbon dioxide in measurable quantity. Some enthusiasts have attempted to harness this process for CO2 enrichment. Both of these natural sources of CO2 can be used by indoor growers.  Yeast may be a better source of CO2 than baking soda and vinegar because it generates CO2 for a longer duration and can be reactivated by adding more sugar.  Unless you are a brewer or a baker, do not expect much benefit from this method. Such a system may prove useful for those with very small rooms, closets or grow cabinets.

Bottled Carbon Dioxide

You can purchase filled tanks of CO2 from your local welding supply store. Tank systems make use of a regulator and an electric solenoid that controls the release of CO2. When in the open position the solenoid permits gas to escape the bottle and travel into a thin perforated tube called a halo. The halo is positioned over the plants and serves as a diffuser. The heavier-than-air CO2 then flows down over the plants. Tank systems can be automated with either a CO2 sensor and controller or a repeat cycle timer. Bottled CO2 enrichment offers a heat-free alternative to propane burners, but may be cost prohibitive for larger rooms.

Propane and Natural Gas CO2 Generators

These heater-like units produce carbon dioxide by burning propane or natural gas–both relatively affordable resources. This method raises the issue of heat management in grow rooms, due to abundant heat and humidity–by products of burning hydrocarbons. Even so, such combustion CO2 generators are the most practical and cost-effective method of enriching large rooms or greenhouses.

Exhaust from gas hot water heaters can be routed into grow rooms to achieve CO2 enrichment. This method can generate CO2  at no additional cost, in homes with propane or natural gas water heaters. Enriching in this manner can be dangerous, leading to excessively high CO2 levels and asphyxiation.  Moreover, old malfunctioning hot water heaters can produce lethal carbon monoxide.  For this reason, I  do not recommend the use of appliance exhaust gas as a means of enriching CO2 levels . Should you choose to do so,  be sure to take every precaution not to kill yourself or others.

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  1. earthschild November 4, 2012 at 7:35 pm -

    What about dry ice?

  2. kcarroll December 6, 2012 at 8:36 pm -

    When is the best time to inject CO2?
    I tried this using my first crop; but for only a week (bad regulator connection)

    • Rambo December 6, 2012 at 10:17 pm -

      CO2 will help supercharge your garden through all growth stages. Keep in mind however that it is only effective while the lights are on.

  3. Mike August 14, 2013 at 12:03 pm -

    I have yet to try any Co2 enhancement. I am confused by one point. It I have an oscillating fan blowing on the plants and another fan at the exit venting the room, won’t I just blow the Co2 right out of the room anyway?

    • Rambo August 23, 2013 at 11:34 pm -

      yes, This is a common problem with CO2 in grow rooms. You have to more or less run a sealed room. This means no air exchange with the outside while the CO2 is on.

  4. Tre September 11, 2013 at 11:23 pm -

    Years ago I ran a small propane space heater for heat and accidentally discovered the benefits of CO2. The increased production was significant and the big leaves had a little bud at the base of the mid rib. At that time nobody had ever seen that, and I have yet to see it since.

    • Rambo October 2, 2013 at 9:04 pm -

      I’ve seen it before. also buds growing out of the leaves. now thats some weird shit.

  5. reddybudusa November 1, 2013 at 8:01 pm -

    Im growning a plant n some mini compost with lots of her forms and night crawlers it started growing um so let it grow in about 10 leaves on it so can anyone tell me what should I do um I got a growing man looks like it might be a female can anyone tell me?

    • Rambo November 19, 2013 at 5:18 pm -

      Please post questions like this in the forum

  6. Hippie March 8, 2014 at 1:16 am -

    I started mine in compost made over the past four years by dumping leaves and left over food egg shell sect in a pile. Does that count for the composting co2.? I know my little girl jane loves the soil cause she’s growing like a weed. Lmao!!!