Ask Erik: February, 2009
Erik,
My indoor garden is in a well-enclosed environment and does not cycle an exhaust. I want to raise my CO2 levels in the growing area, because it has been reported that this will help to boost growth rates and yields.
In the past, I enriched CO2 levels in the growing area by generating carbon dioxide gas by a natural fermentation process. I noticed it improved my situation a little, but obviously, the CO2 levels couldn’t get too high because of the size of my growing area. The CO2 was being generated through a couple of buckets containing the fermentation to generate the gas.
What kind of carbon dioxide levels do you think I need to hit to really see a significant difference in my growth rates and yields? I already have a CO2 tank regulator, I was just thinking about running this off of a timer. What do you think my best options are?
As you have stated you are running a CEA (Controlled Environment Agriculture) set-up, meaning you are running a sealed or “perfect” room. Because you do not actually remove any of the air from the environment as you are treating the air for purity (carbon scrubber/ozone), temperature (air-conditioner or heat exchanger) and humidity (de-humidifier, heater, air-conditioner) boosting your CO2 levels can be a very efficient way to increase your growth rates and yields.
Typically speaking, if you maintain levels of 1600 to 2000 PPM of CO2 (during the light cycle for most plants) you should see a significant increase in the rates of growth and yield. Most growers will notice a 10 to 30 per cent increase in yield and a 10 to 15 per cent reduction in cropping time.
Before CO2 can be really effective, you should have all of your other growing parameters optimized. This includes, but is not limited to lighting, temperature, a healthy root system and optimal humidity levels. When running CO2, you can maintain a slightly warmer environment (i.e. 85°F) to help accelerate the plant’s metabolism. The increase in plant metabolism can be supported with elevated CO2 levels and can give you the results you are looking for.
Fermentation and other bio-reactions can be used to elevate CO2 levels in smaller growing areas, especially if they are well sealed. While this method is very inexpensive and relatively simple, it does not offer a level of control as to the level of CO2 being maintained in the growing area and when it is dispersed. Additions of high quality worm castings in the growing medium can actually help to raise CO2 levels slightly in CEA grow rooms, particularly where there are large bodies of growing media.
Bottled CO2 can be used on it’s own or in conjunction with a biological process to elevate CO2 levels in a sealed growing environment. The gas can be released via timer and solenoid valve/regulator. With a timer, you control the frequency and duration of the gas released. However, this requires calculations based on the cubic volume of your growing area relative to the amount of gas released. An infrared CO2 monitor can be used instead of a timer, delivering a very high degree of accuracy. Unfortunately, the carbon dioxide tank will require frequent replacement, and the tanks are not especially fun to tote about. The cost of frequent replacement will also be a factor.
All infrared CO2 sniffers are not the same. These are precision instruments, and are often priced as such. Some innovative models allow for the addition of an optional second sensor that will independently control a second CO2 generating/releasing device. This allows for more economical CO2 system set-up for both the vegetative and flowering environment, as one controller is able to control both completely independently from each other.
Arguably, the best way to increase and maintain precise elevated CO2 levels is with an infrared sensor/controller and a gas-fired CO2 generator. The one draw back of gas fired CO2 generators, is the additional heat they generate when increasing CO2 levels. Fortunately, there are some recent innovations that help to address this problem. Water-cooling is a highly effective means of removing heat, whether from a CO2 generator, your HID lighting or the radiator of your super-bike. Water-cooled CO2 generators are now a very efficient and economical option for the grower looking to maximize their growth rates while reducing their inputs. Look for more on this new technology in future articles, including CPS: Continuous Production Systems IV.
Cheers, Erik Biksa
