Sep 14, 2018

Growing with CO2: Improve Your Yield

When growing in an artificial environment, the goal is to mimic nature and all of its benefits. When aiming to increase your product yield with a natural option, using CO2 in your grow is sure to produce results.

How Does Growing with CO2 Work?

Biology 101

The biological use of CO2 in plants can be explained in Biology 101. Plants use CO2 in the production of their own nutrients that enable them to grow during a process known as photosynthesis. Plants receive water (H2O) and carbon dioxide (CO2) that when activated by the sun or artificial light releases oxygen (O2) and carbohydrates (C6H12O6) that they use as food. The concept of increasing CO2 levels in your grow acts as a catalyst for growth using its biological processes.

Plant cells only make use of CO2 during light exposure. When increasing the CO2 levels, it is necessary to also increase water, nutrients, and light proximity to plants. The presence of CO2 enables the plant to grow at a faster rate than it would in an unaltered environment. The stomata (the porous openings of the plant) take in the CO2 that is available and release water vapor when open. When increasing CO2 levels, the stomata do not open as widely due to high availability thus producing less water vapor. This creates a stronger and more resistant plant structure.

Integrating CO2

In an unaltered environment, a plant will be exposed to an atmosphere containing 390-400 parts per million (ppm) of carbon dioxide. A plant will not grow or thrive in environments with less than 300 ppm in its atmosphere. When modifying the growing environment to increase the yield of your plants, a grower will increase their CO2 up to 2,000 ppm. Although, the recommended CO2 level is 1,200-1,500 ppm. You can relate elevating CO2 levels to natural steroids- the plants can only sustain so much growth over a shortened amount of time before the plant experiences tissue damage and no longer produces a desirable product. Higher CO2 levels create a more compact cellular structure in the plant that yields a denser, not bigger, product.

CO2 Systems

There are numerous ways to integrate additional CO2 into your grow space. The two most common ways are CO2 tanks and CO2 burners.

CO2 Pressurized Tank

Titan Controls Atlas 8 Digital CO2 Controller with Fuzzy Logic

CO2 integration by installing a CO2 tank into your grow room is the preferred method in larger grow systems. A CO2 tank can be easily equipped with a standard CO2 controller that will turn releases off and on based on desired levels. You can also equip yourself with a fuzzy logic controller, such as the Atlas 8 by Titan Controls, that will turn on your exhaust fan and shut off the CO2 tank when temps rise above optimum levels. The fuzzy logic is also equipped with a light sensor that will turn off the tank when the plants enter the dormant stage. Most controllers do, and should, come equipped with an emergency shut-off valve.

CO2 Burner

A CO2 burner or generator is used by burning natural gas, butane, or propane to introduce CO2 to the atmosphere. The danger associated with fire and the risk of elevated monoxide levels make burners a less appealing option, although the risk is minimal and manageable.

When using a CO2 burner it is important to pay close attention to the color of the flame. Anything besides a white flame (red, orange, and yellow are most often seen) is a sign of incomplete combustion and the high probability of introducing another element to your environment, most notably carbon monoxide. For your safety, it is highly suggested to keep a monoxide detector within the grow space where a burner is being utilized.

In a comparison of the two systems, a CO2 burner emits heat that must be accommodated with elevated use of air conditioning units, whereas a CO2 tank does not. For every one pound of fuel that is burned, 22,000 BTU of heat is generated- as well as 1.5 pounds of water vapor. Due to the elevated process of transpiration, both burners and tanks raise humidity levels that must be accounted for with dehumidifying systems.

CO2 Burner/Generator Recommendations

To avoid potential fire risks you may consider implementing a burner with a built-in “tip over” switch, such as the Titan Ares 2 CO2 Generator. Although the Autopilot CO2 LP generator is listed as the safest generator on the market, it is best used for more condensed growing areas such as spaces 14’ x 14’ and smaller. An option for a larger growing space is the Autopilot CO2 NG generator which provides 22 cubic feet per hour of CO2.

Other CO2 Generating Options

For smaller growing systems, there are many other options to explore. A few can be made at home and will add smaller amounts of CO2 to your grow but will still allow you to reap the benefits. An inexpensive at-home option is to fill a large container or jug with sugar, water, and yeast mixture. The yeast will need to be replenished daily but will emit small amounts of CO2 into the air when left in an open container.

Another inexpensive option is mushroom colonies that have been placed into a bag with a one-way filter, such as the Exhale CO2 bag. The downfall of these systems is not having any way to regulate them. However, this does not propose an issue due to the minimal amounts of CO2 being emitted.

CO2 Level Range

What is Normal?

A plant in an unaltered environment, in a 400 ppm atmosphere, will typically take 12-16 weeks from seed to harvest. When adding CO2 to your grow, it speeds up the metabolic processes that the plant naturally conducts and allows it to reach harvest in a shorter amount of time. Elevating CO2 levels will depend on your own grow system and the amount of stress that you are willing to put on your plants, which in turn can affect your end product.

What is Ideal?

Most commonly, growers will begin by increasing their CO2 levels to 1,200 ppm. At this level, there is a lower risk for error. You will see your plant's production rate increase substantially and produce a high-quality dense product. At 1,500 ppm, you will see the best results in your grow, and is regarded as the ideal level. Raising the CO2 levels incrementally to 1,600 ppm will see a slightly higher yield but the quality of your product diminishes at this point. When reaching levels above 1,800 ppm, the plant begins to produce a lower yield as it becomes highly stressed due to the environment. At higher CO2 levels, it is also a great environment for spores and fungus to thrive and becomes another battle to combat in your grow.


The ideal growing space would not have an exhaust, intake, or ventilation. The concept is that as fresh air enters or leaves the grow area it requires adjustments to the CO2 levels. Even the most tightly sealed environments are still assumed to have a 100% air exchange in an estimated two-hour time frame.

With the use of an air conditioning unit and a dehumidifier, micro-adjustments can be made to temperature and humidity that fluctuates during times of light exposure and dormant phases. To add further ventilation to a closed grow area, you can pull in outside air through the ducting of your lighting system to cool the lights and provide airflow.

It is recommended to incorporate oscillating fans, such as the Hurricane Supreme 16 with three adjustable speed settings, into your grow. They assist in circulating air within the growing space and can help to avoid stagnant CO2-rich air (a depletion layer effect) from skewing your meter readings and throwing your system off. CO2-rich air is heavier than oxygenated air and will reside closer to the plants and ground, causing the plant's respiratory system to work harder than is necessary. The use of oscillating fans also mimics a natural environment and strengthens the plants against wind resistance.

Nutrient Levels

With an increase in CO2 levels, you will require an increase in light intensity (proximity), water and nutrients. Adding CO2 to your grow is increasing the rate of all metabolic processes, which also means an increased rate of deficiencies. About the law of limiting factors, the plant will only thrive when the four factors (light, nutrients, CO2, and water) create the ideal growing environment. The plants will use more nutrients when processing higher amounts of CO2 requiring the grower to feed the plants more often than at the 300 ppm CO2 range.

Controllers and Regulators

What Does My System Need?

Whether working with a closed or open system, it is important to monitor levels to ensure that you have created the ideal environment for your plants to thrive. It is quintessential to have a measurement tool to gauge your CO2 ppm levels and it is recommended to install a regulator to disperse the CO2 as needed and in a controlled fashion. To allow the garden to be less time-consuming for the grower, some automatic regulators and controllers that measure the CO2 ppm and release the gas as needed.

Product Variations and Recommendations

A controller measures the CO2 ppm of the growing space and communicates with the regulator that will turn a CO2 generator or tank on or off as needed. The Titan Atlas 3 controller can be used for both CO2 tanks and CO2 generators. When using a CO2 tank, coupling the Atlas 3 with the Titan CO2 regulator is a perfect pairing. The Grozone SCO2 can be used with systems that are operating with a CO2 generator and comes equipped with a low and high CO2 setting.

The More You Know the Better You Grow!

So what are our takeaways here?

  • Use CO2 during the lights-on period in your grow so that your plants can utilize the CO2 that is being added.
  • Decide which CO2 system is right for you, burner, tank, or natural.
  • Ventilate properly to ensure you are not removing CO2 at the same rate you are adding it.
  • Keep your CO2 in the optimal range of 1,200- 1,500 ppm.
  • Increase light proximity, water, and nutrient inputs to account for accelerated growth.