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How to Use CO2 in Cannabis Grows

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How to use CO2 in cannabis grows is one of the many questions that we’re frequently asked. CO2 is essential for cannabis plants and every other plant, as to them CO2 is like oxygen and they need it to survive. Cannabis plants can deal with CO2 levels of up to 600% the amount that there naturally is in the air around us. Basically, it makes their cells multiply much faster, so if you use extra CO2 during the flowering period you’ll get buds that are much thicker than usual which, if done correctly, makes for a much bigger yield.

If you don’t use CO2 in the right way you could end up with yellowing plants, or long stretched out plants with hardly any buds. You’re going to need to know what you’re doing to implement CO2 correctly. There are many systems that can be used to get more CO2 into your crop; beginner systems that are used as a little extra boost and don’t require much care, and then professional systems that measure the PPM of CO2 that there is in the atmosphere. Professional systems are obviously much more effective and efficient than beginner ones, but they also require more work and attention.

You can use any way of dispensing CO2, connected to a CO2 controller that will shut off the flow of CO2 once it reaches a certain level, and open it again once it gets too low. If all you have is a normal CO2 meter, you can still control the CO2 levels by opening and closing a solenoid valve using a timer. (Solenoid valves are valves that are opened and closed with an electromagnetic charge). Whichever kind of system you use, you must know the exact PPM (parts per million) of CO2 in your grow room.

CO2 needs to be introduced into your room through a silicone tube, with one outlet per plant near the bottom of the trunk. You can also use a 2m tube to go around the grow area with holes facing the center, towards the plants.

Once everything’s installed and ready to go, you’ll need to know exactly how to use CO2. Well, it’s used in the flowering period from the 21 st day onwards, once the buds start to take shape and are slowly popping up at the tips of all of the branches. You’ll need to change your air filtration so that the extractor only works for around 15 minutes an hour because if it’s left on it will get rid of all of the CO2 and all of the effort will have been for nothing. You can use another timer to program the CO2 controller so that it doesn’t turn on when the extractor is on. CO2 should only be administered when the lights are on, as the extraction should be on constantly when the lights are off.

CO2 increases your plants cell walls and multiplies them rapidly, but make sure that you fertilize them also as they’ll end up light and pretty down looking if they get a lot of CO2 but not any nutrition. They’ll also need a slightly higher heat than usual, around 28-32ºC so that the water in the leaves can evaporate slightly faster and the plants can absorb the nutrients straight away. Basically, we want the plants to absorb the nutrients but get rid of the water fast. You’ll need a dehumidifier to lower the ambient humidity to normal levels, because once the temp is raised and your plants begin evaporating water, humidity levels will raise a lot.

Here’s a guide on what you should do and the strength of the CO2 in your grow room from the 21 st day of flowering onwards. EC levels apply if you’re growing in hydro or aeroponics. If you want to measure them in soil you’ll need to measure the water that comes out from the bottom of the flowerpot once you’ve watered; if more is needed you can add it in the next watering, and if it’s too high then the next watering should just be water on its own.

  • Day 21 of flowering: Begin with 800 PPM, and keep it at that when the extractor isn’t on. When watering, you’ll need to raise the EC every time to raise the CO2 levels. For this first week you’ll need about 1.7 EC using normal irrigation water.
  • Day 24 of flowering: Raise the CO2 to 850 PPM, and the EC to 1.8.
  • Day 27 of flowering: CO2 to 900 PPM and EC to 1.9
  • Day 29 of flowering: From this day onwards you’ll need to increase both CO2 and EC every two days. 950 PPM and 2.0 EC.
  • Day 31 of flowering: 1000 PPM and 2.1 EC.
  • Day 33 of flowering: 1050 PPM and 2.2 EC
  • Day 35 of flowering: 1100 PPM and 2.3 EC
  • Day 37 of flowering: 1150 PPM and 2.4 EC
  • Day 39 of flowering: 1200 PPM and 2.5 EC. From this day onwards, increase levels every day.
  • Day 40 of flowering: 1250 PPM and 2.6 EC
  • Day 41 of flowering: 1300 PPM and 2.7 EC
  • Day 42 of flowering: 1350 PPM and 2.8 EC
  • Day 43 of flowering: 1400 PPM and 2.9 EC
  • Day 44 of flowering: 1450 PPM and 3.0 EC (this is the max EC level)
  • Day 45 of flowering: 1500 PPM and 3.0 EC
  • Day 46 of flowering: 1550 PPM and 3.0 EC
  • Day 47 of flowering: 1600 PPM and 3.0 EC
  • Day 48 of flowering: 1650 PPM and 3.0 EC
  • Day 49 of flowering: 1700 PPM and 3.0 EC
  • Day 50 of flowering: 1750 PPM and 3.0 EC
  • Day 51 of flowering: 1800 PPM and 3.0 EC – This is the max CO2 level you can have in your grow room. Continue the rest of the flowering period without raising anything, and make sure to do that root wash 10 days before harvesting.

If you notice your plants get weak or yellowish at any moment, or worse, then stop using CO2 immediately and try and find out what’s going wrong. Either too much CO2 is accumulating or we’re giving them too little and it’s too warm. Make sure you follow the parameters exactly or using it can actually do more harm than good. If done properly, your harvest will be ready a few days earlier and you’ll get a higher yield.

If you have any questions feel free to leave a comment.

Author: Javier Chinesta
Translation: Ciara Murphy

How to Use CO2 in Cannabis Grows; here's a step by step guide on how to correctly use CO2 to get the most out of your plants.

CO2 for the cannabis plants

Increasing the levels of carbon dioxide offers the potential to increase speed of growth, which could even reach double normal standards. A plant is able to use the CO2 in the process of photosynthesis to help with creating sugars needed for building plant tissue. An elevated level of CO2 is desirable for helping the plants manufacture these sugars, and this has the consequence of significantly increasing the growth rate.

CO2 is likely to be a difficult process to manufacture conveniently, cheaply, and safely, and often found to be quite high cost if planning on using a CO2 tank system. You will likely find that CO2 is most beneficial in the flowering stage as this is the point that the plant life is the most dense and likely to experience difficulty in circulating air to all of the foliage. If planning on restricting the growth to the vegetative stage inside the home (with plants later transferred outside), then the use of CO2 is as likely to be a significant issue unless planning on using a sealed bedroom, closet, or greenhouse.

A medium size operation inside the home might include using the CO2 canisters that come from the welding supplies stores. Initial outlay might be quite expensive, but over the long-term you will find that this can be a highly effective option for the medium-size crops.

CO2 is it likely to be reduced quite cost effectively by burning natural gas. But it is vital that the carbon monoxide and heat is adequately vented externally. CO2 is available by leasing or buy in the cylinders from a suitable supplier.

If using a compact size closet set-up, a suitable canister could last in the region of two months, although this is dependent on how it is released, dispersion methods, enrichment levels, room leaks, light cycles, and the ventilation in the room. But you might find that this process can often be quite excessive for the small arrangements.

It is often claimed that a good quality flow of CO2 is certain to help the plants when the lamps are in operation. It can be dispersed over the plants throughout the periods that the exhaust fans are switched off.

You might find that it is possible to take steps to conserve the CO2, although you might find that it can be quite costly. If you have the lamps off it isn’t necessary to use the flow of CO2, so throughout the stage of flowering, the consumption of CO2 is likely to be half of what you might regularly use. An automatic timer set-up might benefit to ensure that you are able to control the CO2 in the most efficient way possible.

Bottled gas is likely to be a more eco-friendly options since the process of manufacturing it is likely to impact environment. Bottled CO2 is often captured during the process of manufacturing certain materials, which is then used in the process of recycling. Vinegar, baking soda, CO2 generators, and fermenting are likely to create a fresh supply of CO2 and impact on the greenhouse effect.

Generating CO2 from generators and fermentation is certain to be a possibility. A basic CO2 generator might relate to a propane heater. A set-up like this might offer an ideal arrangement provided the gases are prevented to the growth site, and a fan is in place to help with circulating the hot CO2. Exhaust venting and fire are likely to be concerns. A room that is designed to vent half the time to eliminate the heat from the heater and lamp it is likely to get similar CO2 levels of the room that is un-vented for a good number of hours. A CO2 generator is likely to be the only option if you are looking at the large-scale operations.

Vinegar or fermentation and the use of baking soda is likely to benefit if you aren’t relying on several vent cycles, but if a significant amount of heat is present that makes regular or constant venting a necessity, this practice isn’t likely to be usable. Pouring the vinegar over the top of the baking soda is all that is needed; then the room door can be closed. This isn’t likely to be the most desirable option as it would be very difficult to automate, and will require day-to-day attention. But, you will find that it is a possibility to produce the desired the O2 using fermentation. Leave the wine to become vinegar, and have that poured over the top of the baking soda. It is likely to be the most affordable option for the small scale closet set-ups.

In the fermentation process, you will likely be aware that the yeast constantly attacks itself, which means a lot of space is required. Ideally, you will require a large sized bin to keep topping up with water to make certain that the level of alcohol is unlikely to rise too high and cause damage to the yeast. You will likely use a lot of sugar in this process. A 10 lb bag is likely to last in the region of two to three weeks. In order to help with establishing what is being released from the jar you might want to place a tube from the jar into a container of water. If you start to notice the water bubbling this is a clear indication that the CO2 is being produced.

Alternative options are also available. You might want to look at combining vinegar with sodium bicarbonate, 1 tablespoon:

30cc is likely to create a froth-like appearance at the start to release the CO2. Once you notice the frothing you can close the door immediately on the closet. A very cost efficient option to produce the CO2 is to use 2 L of water with 2 oz of sugar in a sterilised bottle, which needs combining with a couple cc of human urine. A substitute for the urine if preferred can include a yeast nutrient sourced from a home brewing kit.

An ideal container is likely to include a plastic 1 gallon milk or water jug, with a small hole in lid. It might also benefit to include a clear tube into the jar to help with keeping out microbes and offering ease in checking the fermentation process is working.

If looking at a completely different option for maintaining the plant growth you might want to look at spraying seltzer water on at least two occasions per day. The quality of using this option can vary significantly between who you ask that the many people see this process as highly beneficial in the process of enhancing the crops. A set-up of this type is likely to be a viable in only the small closet crops, since it is likely to be quite cost prohibitive if you look large-scale operations. Make certain to use seltzer and not club soda as the sodium level will be much less, which could impact the plants stomata. If using the seltzer spray it will be necessary to clean the plants with plain water after two or three goes. This is likely to be a significant amount of work and this is a process that can’t be automated. A product like seltzer is easily source at the local food shops. Club soda can be used if you aren’t able to easily locate the seltzer, but is likely to contain almost double sodium content. Using a watered-down version Miracle Grow is also able to help with the plant growth. A quality aspect of spraying seltzer water is that it is able to help in raising the level of humidity. Be certain that you are able to vent the humidity throughout the dark cycles. If this step isn’t taken you could be left with increased internode length and a potential fungus outbreak.

NOTE: Avoid spraying any liquids too close to the lamps or naked bulbs. Aim a spray in a downward direction, or simply switch off the lamp prior to using the solution.

With the right CO2 enrichment you have the potential to achieve increased yields of 30 to 100%, you might find to the time involved, danger, space, expense, and hassle might make the process of near constant or full venting and attractive proposition to enrichment. Provided that the plant life and the option of taking fresh CO2 from the atmosphere with 200+ ppm then the crop are certain to have sufficient nutrients for the photosynthesis stage. A typical closet is likely to require fresh CO2 on a 2 or 3 hour bases. It is often claimed that high CO2 levels can impact on the potency of the plants, so it might be beneficial to switch off CO2 about two weeks prior to harvesting.

Increasing the levels of carbon dioxide offers the potential to increase speed of growth, which could even reach double normal standards. ]]>