Supplemental CO₂ can help optimize growth
By Dr. Who
Humans breathe in oxygen (O₂) and breathe out carbon dioxide (CO₂). Plants do the reverse. They “breathe in” CO₂ and “breathe out” oxygen (O₂). This is why plant life is an essential part of the worlds’ ecosystem. Without plants, CO₂ levels would rise to intolerable levels. Plants use CO₂ for growth. It is the essential building block for photosynthesis (along with light and water). Plants cannot grow without CO₂. The current levels in the atmosphere are about 350 parts per million (PPM). It is theorized that millions of years ago, levels of CO₂ were about 1,500 PPM. Throughout the years, plants have evolved in many ways—and in many ways have stayed the same. Knowing this can be advantageous for us all.
It seems that plants have not lost the ability to use up to 1,500 PPM of CO₂. Plant growth can be accelerated by increasing the CO₂ levels in your growing area. Conversely, CO₂ levels below 250 PPM have a detrimental effect on your plants. If you have six plants growing in your closet, and there is no ventilation, your plants can use the CO₂ in a few hours. They then stop growing. You must, at a minimum, provide fresh air for your plants every hour or so. An even better way is to provide supplemental CO₂ for your plants by using either a CO₂ generator or bottled CO₂. Any of these solutions will keep your plants growing at optimal rates. It has been proven that you can increase your growth rates by up to 20 percent and size by up to 30 percent by providing supplemental CO₂ at levels over 1,200 PPM. You should never go over 1,500 PPM, as this soon becomes toxic for the plants, and they tend to grow very stringy.
CO₂ generators are simply specialized burners that burn either propane or natural gas to produce CO₂. A byproduct of this process is water, in the form of humidity. When using a generator, it is a good idea to keep an eye on your humidity levels. CO₂ generators are optimized to produce as little heat as possible, while producing as much CO₂ as possible. They are normally rated in cubic feet per hour (CFH). A standard 10-foot-by-10-foot-by-8-foot room containing 350 PPM takes about 1 CFH to raise the levels to 1,500 PPM. The level will drop throughout the day, requiring smaller burns to keep the levels constant. A CO₂ PPM controller works great for keeping your levels constant with a CO₂ generator.
Bottled CO₂ can be obtained at most hydroponic or welding stores. You need a regulator/flow meter to get the CO₂ out of the bottle in a measured manner. You set the flow rate in CFH and set the regulator on a timer to bring your CO₂ levels to the desired level. A few calculations will be needed to set your CO₂ levels correctly. You can also use a CO₂ PPM controller to maintain your levels.
Plants do not use CO₂ at night. It is not necessary to supplement CO₂ during your dark cycles (mushrooms are an exception). Properly used, supplemental CO₂ will only help your crops if you have all of your other factors in line, such as using a good nutrient mixed at an appropriate strength, changing your nutrients to prevent nutrient deficiencies, having enough (and not too much light) and keeping your temperature and humidity are also plant limiting factors. Once you have dialed in all these, supplemental CO₂ can help you gain the most return on your plant growth.
DR. WHO is a Southern California expert in plant cultivation. Reach him at firstname.lastname@example.org.