If you are green to gardening you might not know that carbon dioxide, the gas we all exhale, is critical to plant growth and development. Photosynthesis, the process through which plants use light to create food, requires carbon dioxide. CO2 concentration in ambient air ranges from 300-500 parts per million (ppm), with a global atmospheric average of about 400 ppm. If you are growing in a greenhouse or indoors, the CO2 levels will be reduced as the plants use it up during photosynthesis. Increasing the CO2 levels in these environments is essential for good results. Additionally, there are benefits to raising the CO2 level higher than the global average, up to 1500 ppm. With CO2 maintained at this level, yields can be increased by as much as 30%!
Commercial greenhouses are aware of this and commonly use CO2 generators to maximize production. One thing to keep in mind while designing a CO2 system is that yields will only increase if CO2 is your ‘limiting factor’ (for more on ‘limiting factors’ and ‘Leibig’s Barrel’, see our previous post here). This means that if all your other variables are not optimal (light, fertilizer, temp/humidity, pH, etc.) you will not achieve the benefits of increased CO2 levels.
Now that we know the benefit of adding CO2 to your indoor growing environment, one thing to note is that CO2 enrichment will not be as effective if your grow area is not sealed since it will be exhausted before the plants can use it. Ideally, air should not be exchanged in an out of your grow room. If you have an air-cooled reflector, the air drawn through the fan to cool the bulb must enter and exit the grow area without coming in contact with the air in the grow room. Sealing your grow space allows plants to more completely use the CO2 that you enrich the environment with.
Another thing to note is that during the night cycle plants actually give off CO2. This causes a gradual increase during the night, until the lights come on and the plants resume absorbing CO2; you can save CO2 by waiting an hour or so into your daylight cycle to cut your CO2 device on.
Lastly, CO2 is notably heavier than air, so it is essential that your CO2 be dispensed from above your plant canopy. Oscillating fans in the grow space, particularly around the CO2 dispensed, will help distribute the CO2 around the area.
Now, let’s look at the various ways you can increase CO2 levels:
Homegrown CO2’s Exhale bags are a great option if you would like to see what CO2 can do for your garden on a budget and without a lot of equipment (i.e. timers, regulators and monitors). Exhale bags are filled with mycelium (non-fruiting mushrooms) that give off steady amounts of CO2 as a byproduct of their metabolism. These bags end up costing less and can save you a ton of hassle compared to the infamous fermentation and dry ice methods. For $32.99 you can buy an Exhale bag (available in-store only) that covers a 4×4 area for 6 months. After hanging your Exhale bag above the canopy you can use a CO2 test kit to see how much it raises CO2 levels.
If you are ready to move up to a longer term, more efficient CO2 delivery system, then the next system involves using a pin timer (Apollo 8), a CO2 regulator and either a CO2 tank (available for purchase or refill) or a CO2 generator. Tanks are typically the better option for smaller spaces for ease of use whereas generators tend to be the better option for larger spaces since they run off of propane and can generate large volumes of CO2 at low cost. Now, with either source, set the pin timer to turn the regulator on for 15 minutes every 90 minutes or so. A CO2 calculator like this one, available from Greentrees Hydroponics, will help you determine how much CO2 you need to release to achieve optimal concentrations for plant growth. You can also use a CO2 test kit to dial in your system so that 1500ppm level is maintained. As your plants grow and the garden changes, retesting your CO2 levels monthly can help you tweak your system to maintain optimum levels. Note, if you are using a Titan CO2 Regulator, a ¼” dispensing tube is included. Hang this line above your canopy in a circle with small holes every couple of inches (to allow the CO2 to ‘rain’).
Finally, for gardeners that want to achieve constant optimal growth conditions without ever wasting extra CO2, a CO2 monitor is a great device. These monitors, such as the Titan Atlas-3, completely automate your CO2 system by constantly measuring the CO2 in the area. If the ppm level falls lower than what you set on the monitor, it will automatically open the regulator and dispense CO2. These monitors also come equipped with a photocell to ensure that you never dispense CO2 during the night cycle.
By: Chase Werner
Useful Resources:
CO2 Calculator – This is a great tool to use to make an intelligent first calibration of what your requirements will be for your room size instead of guessing and checking.
Jessica_P says
Thanks for sharing the information. I love planting but I don’t have that bone for scientific understanding and explanations. The article explains the aspects of carbon dioxide in plantation in some easy ways. Thanks for clearing my myths 🙂
Brandon Colman says
Glad you found the article helpful. Happy horticulture!
D Costa says
Great site with great info.
Will go check out your instore setup today.
Alan says
Aloha,
Great information. I have the CO2 bag delivery system & learned a lot from your article. 2 – 3 weeks from harvest on Wonder Woman & was not wanting to damage this plant with CO2, if that’s possible. Will start this project on some new sprouts after harvest…
Mahalo for the good information…
Dave Hunt says
How else can you get Co2 in a grow tent? I was told that you can use yeast, sugar, and water. Is this true, and how much of every thing do I need for a 1.2×1.2x2m tent?
Brandon Colman says
Hi Dave! Indeed, the main byproducts of anaerobic yeast fermentation are ethanol and CO2. You could produce CO2 this way, but because the yeast population is always changing – growing or shrinking – as is the level of available sugar it would be difficult to produce a predictable amount of CO2 using this method. Rather than trying to ‘dial it in’, I’d recommend giving it a try using a solution of 3 lb of corn sugar in a gallon of water and making a simple science experiment out of it first looking for whether you can see a noticeable difference in the growth rate or production of your plants. Everything you need (a fermentation bucket with an air lock, corn sugar, yeast, yeast nutrients, etc) can be found in the brew section of our webstore.
John says
I have a 4 x 4 x 9 grow closet. I have rigged a 4 inch in-line fan with ducting. I am ducting outside air into the growth area.Will that provide adequate CO2 for approximately eight plants?
ashley says
Supplying fresh air from the outside would supply sufficient CO2 for your tent, at the rate of 300-500ppm. You could however supplement with a co2 bag to add another 600ppm, as plants grown at an accelerated rate and required to fruit and flower would benefit from co2 enrichment.
pj says
Using an ambient wind for co2 enrichment. How long each day would we need to leave the exhaust fans off to increase co2 levels with a composting bucket?
ashley says
Hi PJ, That would be really hard to answer without knowing a few facts about the space and the composter. The easiest way would be to obtain the co2 syringe test. They can be purchased from us and the kits come with two test (about $20, I think). Additional test can be purchased for around $5. That’s the only to get a true sense of co2 concentration on a budget. Co2 sniffers are available, but that seems expensive for determining what a composting bucket will off-gas. Hope that helps!
Wannes Voorend says
Hi all,
the CO2 is captured by the plant and constantly fed by a CO2 generator. But the plant also produces O2. So, imagine a perfectly sealed room, O2 will continue to rise?
Gurjot singh says
Hello Sir
I’m interested in Commercial greenhouse growing hydroponic tomatoes with CO2 enriched air We want to develop business in INDIA So pl brief about all technicalities
Dave Anderson says
I have a small garden in my back yard but for some reason no matter what I do, the plants just aren’t growing as much as I want them to. I am going to take your advice and get a CO2 system that will increase the CO2 in the air while the sun is up like you mentioned so that they can absorb as much as possible. Hopefully, that will help with the growing problem that my plants are having.
Nathanael says
Are you familiar with new studies showing that higher levels of CO2 cause plants to increase yield, but sacrifice nutrition? The attached article argues that plants grown in environments with higher CO2 create produce that is higher in sugar and starch.
http://www.politico.com/agenda/story/2017/09/13/food-nutrients-carbon-dioxide-000511
Swim says
Do these bags cause anyone else problems with humididty?
ashley says
They do raise the humidity a little since they are wet with a living organism. Usually if you are bringing cooler air into the environment and exiting some air, there shouldn’t be a large humidity problem unless you are using 3 or more of those bags in a 4×4 area or less.
Zaheer Ahmed says
currently, I have 01 acor tunnel farm and growing cucumber but in the air only 50ppm co2 available if we inject Co2 and increase the level at 1500 ppm by liquid Co2 then who much increase the production and required qty of CO2 in Kgs
Simon says
why is it advisable to allow in less carbon dioxide in green house at high temperatures
ashley says
Hi Simon,
It is actually encouraged to raise co2 while the greenhouse temperatures are warmer. The co2 levels will naturally be reduced due to the plants actively taking up more in these growing conditions, thus needing to enrich more. Hope this clears up any confusion. Cheers! Mike W.
Raj says
Hi, I am new to hydroponics and planned to develop a new design. Now I all totally lost in understanding the CO2 and O2 levels. So if I am going to generate CO2 for a indoor facility climate controlled with AC and heaters, using CO2 controllers, the plants would use the CO2 and also generate equal amounts of O2. So in an controlled environment how could we manage to remove the O2 and utilize maximum CO2. Please advice.
Kris
ashley says
Hi Kris,
Generally, if you are enriching a space with co2, you don’t have to worry about purging the o2. If your room is really, really sealed, you may choose to exhaust the space once or twice per day, but you are certainly wasting some of your co2 doing that.
real American says
So why are the alarmists trying to LOWER C02 levels in our environment??
ashley says
Because all scientific evidence shows us that, while a bit of increased CO2 in your small growing environment can be good for your crops, increased CO2 in the atmosphere as a whole is already leading to catastrophic results. We’re big accepters of scientific data here at Fifth Season; so we support efforts to reduce CO2 (and other greenhouse gases) in our atmosphere!
WuXing Kyaw says
Thank you very much for kind informations. I do have some questions if I may,
1. Which lighting system is good for medical marijuana plant?
2. Why most of peoples used “air-cooled reflector” instead of LED light and why?
3. How many light do I need Or brightness? Go by each plant or go by squire feet?
3. How to control room temperature? By using Air condition and heater in greenhouse?. (Because CO2 need to be completely seal the green house).
4. Completely seal green house with CO2 air is safe for people while working inside the greenhouse?
Respectfully,
WuXing Kyaw
ashley says
We’ll try to answer your questions in order, where we can.
1. Can’t really recommend anything for you there, because it is illegal to grow marijuana where we are located.
2. You can use either an air-cooled reflector with traditional Metal Halide or HPS lights, OR you can use the newer LED technology, which puts out far less heat. People decide which system they want to use based on familiarity, initial vs. long-term costs to buy and run the lights, and personal preference.
3. Generally you want to look at the square footage of the area your plants will take up, and base your lighting decisions on that area, rather than number of plants.
4. Yes, air conditioning and/or heat is commonly used to keep air temperatures in a favorable range for growing.
5. Yes, your CO2 generator should not produce so much CO2 that it would be unsafe for people. Plants don’t need that much supplementary CO2, so it would be a waste to overproduce it.
Hope this helps you!
Jeff says
Do you want to continue to add co2 during flush ?
ashley says
Hi Jeff, typically by the time you’re doing your end of cycle flush, adding CO2 isn’t really going to get you much. It won’t hurt, but it’s not really going to increase output.
Nono says
How about CO2 levels beyond 1500ppm. Will they harm plant growth?
In my bedroom I measured 2000-2500ppm after a 8-10h sleep with closed door/window… :O
Pat says
So I have a small grow room,absolutely air tight, so I don’t run my exaust fans at all to remove air, but what about the smell that u need to run threw the carbon filters, I do run a O zone machine also, what does that do to the C02 in the room if anything. Thank you . Pat
Kim Marconi says
Growing plants on 44 sqm in a 82 sqm room with great ventilation and good lightning … how many Co2 bags will be needed to reach the magic 1500 ppm?
Is it actually so, that the Co2 i not distributed evenly in the air, so it is essential to place the Co2 bags up and close to the plants?
Thank you for a lot of good information in general. I am looking forward to your answer on these questions.
Kim
ashley says
Hi Kim,
Here’s a handy dandy CO2 calculator to help you figure out your needs: https://www.hydroponics.net/learn/co2_calculator.php
and to answer your other question, yes, if possible, you should have your CO2 source above your plants and as close to them as possible.
Susan says
On a larger scale…Do you think it would make sense to link food growing facilities (that use CO2) with coal power plants (that generate CO2)? Might this be a solution to the so-called climate change problem? Why shut the generators down (as seems to be the trend) if CO2 is such a good resource?
Just asking.
ashley says
Hi Susan, Anything we can do to capture and sequester CO2 in large amounts would help with the climate change catastrophe that is already starting. You are seeing some of this re-capturing of greenhouse gasses with methane from landfills (and then using the methane to generate power). WRT coal-fired power plants, I don’t know that technology exists to capture CO2 and transport it to indoor growing spaces.
DRapp83 says
What about in terms of temperature regulation? Increasing CO² also raises the optimal growing temperature required so wouldn’t it require a heat source as well? Or does increasing the CO² also increase the temperature?
ashley says
In general, if you’re growing under lights, you’re going to be generating heat, so being below optimal temperature shouldn’t be much of an issue with supplementary CO2. That being said, you do want to keep tabs on your temps to make sure you are staying in a good range.
Robert G says
I use a glass of sugar water and yeast.
shenila says
Hello,
The article is very informative and interesting.
I would like to understand how the carbon offsets can be measured in controlled settings in different plants and whether there is any data that exists.
S.C. says
Will adding CO2 saturated charcoal to the plants eath bed help or hinder the growth of the plant?
ashley says
If you are talking about adding biochar to your soil, it is a soil amendment that helps with growth of fungi and bacteria that aid root growth and nutrient uptake in your plants.
But CO2 enhancement, in terms of adding CO2 to your growing environment, works on the plant’s leaves as they absorb the gas from the atmosphere.
So those are 2 different things.
Hope that helps!
Chris Bester says
Our plant research is now in its 2nd generation. The results are amazing. We have successfully increased root mass by more than 400% on average. This increase in root mass caused various effects on the plant. Greater yield, much bigger leaves, faster canopy growth for example. We do not use any Chimicals, any Energy source, No genetics, no extra fertilizers, no hot houses. Our system is called Terra- Nebula+O2. The system does not exist or occur in nature. We have created a city under ground, a perfect habitat for the Rhizosphere, M. Fungi, Deep Earth Root System. Now that it is done it seems so logical, easy and cost the same as existing equipment, like the seedling trays. But with a difference. The I formation is a lot. This will stop Global Warming and Reverse its effect
zoella says
Yay! Thanks for ur help. myths are cleared!
Sirajul says
You said a lot, but did not tell minimum concentration of CO2 is good for plant in the Atmos…
billy says
I bought 2 grow cabinets, hydroponics kit, all the nutrients, LED, distilled water, co2 tank, rock wool, aIr bubblers, timers, fans I have meters for everything, feed rate, co2 meter, ph, humidity, temp. They are about 2 inches tall and look burnt and terrible. other cabinet same thing but just potting soil and paper cups. they are 14 inches high and look awesome. I read, research, follow instructions exactly. the only thing is temp inside is 82F. I can’t get it down any lower other than that everything is exact. I am doing something wrong on the hydro cabinet obviously but what I can’t figure out what is going on. Any thoughts?
ashley says
Our first thought is that you may be running your nutrient solution too strong. We would advise cutting your nutrient in half and see if your plants start to improve in health. Young plants don’t generally need a ton of fertilizing.
Jerry says
I set a candle in a coffee can at the up wind (breeze) base of each of my blueberry plants each morning. The results are fantastic. The plant size doubled in four months. The berries are 50 percent larger than last year. This was the fourth year after planting. Now harvesting. Plant growth is far beyond anything in previous years. Impressive !
BABITA SAKDEO says
sir, which type of plant for example algae,fungi , lichens or flowering plant etc grow to increase co2 level in polthouses?
ashley says
Lichens, algae and flowering plants absorb CO2 and give off O2 while fungi release Co2. So fungi are your best bet.
BABITA SAKDEO says
which type of plant for example algae,fungi , lichens or flowering plant etc grow to increase co2 level in polyhouses?
ashley says-Lichens, algae and flowering plants absorb CO2 and give off O2 while fungi release Co2. So fungi are your best bet.
thank you sir , but which types of fungi , please mention the name of fungi .