About the Upstart Farmers Roundtables
Upstart Farmers Roundtables are an informal, biweekly event. Using Google Hangouts video calling, a small group of Upstart Farmers comes together to share their experiences and learn from each other. Each week is guided by a discussion topic, with growers welcome to ask their own questions.
Roundtables are exclusively for Upstart Farmers, and recordings are only released to the Upstart Farmers Community.
Roundtable: CO2
Carbon dioxide, or CO2, is an easy (but important!) supplement for growers in controlled environments. There’s tons of information we could cover on CO2, but due to our small audience at this Roundtable, we kept the conversation light!
Intro to CO2
As you know from past science classes, plant respiration requires CO2, which they then convert into oxygen (O2). By opening the stomates in their leaves, CO2 diffuses in, and O2 is released. When there isn’t much CO2 in the air, and the concentration outside of the leaf is not significantly different from the concentration inside, plants must leave their stomates open for a longer amount of time for the CO2 to move into the plant tissues.
When stomates are open, the plant is losing water. In a growing environment, there are even more problems when photosynthesis grinds to a halt due to a lack of CO2. At the same time, slowing or stopping photosynthesis also means that lighting the plant becomes negative, as the plant loses or consumes energy if it is lighted when there isn’t enough CO2.
If there’s not enough CO2, the best case scenario is that plant growth stops. Worst case scenario, plant health is affected.
In confined, indoor environments or Freight Farms, CO2 is consumed rapidly and may drop below outdoor, ambient levels.
Equipment for CO2 Supplementing
While there are several ways to supplement CO2, Nate focuses on two primary options:
- A tank of CO2, coupled with a regulator, is the first option. However, this method is incredibly expensive and would be prohibitive for most growers. The additional value of the plant growth when supplementing CO2 would not exceed the cost of the tank.
- Burning natural gas is the most common, low cost option. This does release water vapor into the environment, which may adversely affect humidity in an enclosed environment.
The Cost of CO2
CO2 is really cheap – if you have access to natural gas. In almost all enclosed growing environments, supplementing CO2 is economical, and the additional growth will exceed the cost.
Buying bottled CO2 is prohibitively expensive, as is burning propane for CO2.
Ideal Levels
While every crop responds to CO2 enrichment in a slightly different way, most growers supplement up to 800 – 900 ppm of CO2. The highest growers will supplement if 1200 ppm.
These levels aren’t even close to OSHA’s CO2 safety standards for humans.
Eliminating Bottlenecks – and Illustrating Others
The object of supplementing CO2 is to eliminate bottlenecks in the production process. CO2 was traditionally (and still is) the holdup in indoor growing operations.
When you start adding CO2, you may notice other problems appear in your system as a different bottleneck becomes apparent. If you’re just starting to supplement and start to see issues, feel free to get in touch with us!