Hey fellow growers, I've been pretty quiet lately just a growing and working. My journals are completed and spring and summer are probably going to me no time to start another journal. At any rate, there seems to be this recurring trend of post after post of how to use co2 so I thought I would purge my knowledge on the subject to help people decide if it right for them....
Advantages of co2: Faster growth, denser growth = more yield. Like big time more. the claims of 40-100% increase in yield are no joke.
Disadvantages: costs money, bottle can be a PIA, burners generate heat and humidity.
How it works: This is the important thing. Co2 is not a magical substance or bloom enhancer. Its a naturally occurring gas, depending on how close you live to a freeway
co2 right now tends to hover around 350-400 PPM. Co2 allows you to take advantage of increases in a plant metabolism when conditions allow for higher metabolism. IF you don't have the conditions for higher metabolism, then your wasting your money. There are not a whole lot of things that a plant needs to grow and bloom. Light, heat, co2, water, and nutrients. Generally when the temperature increases, so does the plants metabolic rate (the speed at which the chemical processes that allow for plant function are happening) They are kind of like cold blooded animals really. When its too cold, they don't do much, when it is too hot, they shut down to conserve energy. well, plants don't really shut down, they do other stuff but this isn't a plant physiology post.
So, as the metabolic rate increases, so does the demand for light, co2, and water. When one of these parameters is not present in high enough amounts to sustain the metabolic rate, it becomes a
limiting factor. That is, inadequate amounts of light, water, or co2 causes an end to the increase in the rate of photosynthesis, and often, stops photosythesis until levels are adequate enough. As the plants metabolic rate increases, the first limiting factor encountered is the presence of adequate levels of CO2 and THAT is why co2 works. In general, a PPM of 1500 or so (i the peak of flowering) is high enough to ensure that photosynthetic rates are maximized.
It is this mechanism that dictates you need to have control of PPM levels. If your co2 level is constantly fluctuating then the level of co2 is going to act like a limiting factor is your running the lights and temp to take advantage of it. If your plants are chugging along and then co2 levels drop, they are going to slow or stop until levels increase. This is not an ideal situation and causes stress on some level to the plant. The other side of the coin is that your runing a tank or burner without a ppm controller and PPM's go through the roof (3-4 thousand) and you kill your plants.
Is co2 right for me? Given our understanding of metabolic rates, you have to ask yourself. Do I have enough light to use co2? and do I have a way to maintain higher temperatures? Lastly, is my room sufficiently sealed to use co2?
Light: your probably going to want in the area of 60 watts per sq. ft. of HID lighting before you think about co2. It more about par and lux at the canopy level but I would use thee above as a general guideline. I have 40 watts a sq.ft. but I have 3 600's on a rail that allows me to have the lights closer and the rail moves in a manner that the plants are always getting some light.
Heat: optimal temps when running co2 are 85-90 degrees. Yes, its warm. Yes, the plants are running full speed; but the is exactly the goal. You need to have a way to get the room in that temperature range and keep it there. An AC unit is the easiest way as its a set it and forget it deal which is nice. The other way is to have temperature controlled exhaust fans.
Sealed room: Obvios-fucking-lee if your room is constantly vented your throwing your co2 away and wasting money. Plants DO NOT NEED "fresh air" they are not international travelers stuck on a public bus in panama with people chain smoking in front of you, chickens screeching behind you, and a steady stream of dust pouring in the windows. They need co2 during the day and oxygen at night. period.
There are many ways to run a sealed room with AC hoods and odor control. My hood inlet is outside the flower room and exhausts outside. Therefore my hoods are a closed system. I used incense to ensure that the hoods were not leaking and pulling co2 out of the room. It is impossible for smell to be exhausted from the hoods..it is a closed system. I have a carbon filter just sitting in the corner scrubbing the air. no exhaust necessary. It actually works better that way.
Make it happen:
Ok, so you have that shit figured out, you know how to not kill a plant, and you have some extra cash around. How much cash? Its going to take about $800.
I'm not going to get into the stupid ass ways that some people "produce" co2. If your putting bowls of yeast in your grow room or using co2 buckets or whatever, that's all cool and the gang but that is not what this post is about. This is about spending the money, understanding the system, and doing it right.
Things you need: tank or burner, fuel supply, PPM controller. There are many a PPM controller on the market and none of them are cheap. You want an IR controller that monitors and reads out the exact PPM. They are going to run you around $400. I got my super pimp daddy CAP XGC-1 for $500 on CL. Two paths diverge in the forrest from here: bottles or burner.
If you have temperature control then GET A BURNER!! Yeah thee bottles are neat and clean and produce no heat but here is the dirty little secret, a bottle lasts about 5-6 days in a small room and they cost is the same as a burner.
For bottles you need: solonoid controlled valve (the CAP one!! b/c it doesn't freeze) $130, and a co2 tank - $160. So your at $290 for a bottle set up. Operating a bottle costs $17 a week plus the gas and time to run your ass to and fro to the welding gas store and having your neighbors hauling co2 tanks in and out and in and out and in and out. Trust me, it gets old really quick.
For a burner I use a cheap tank-less water heater ($150) and I tapped into the natural gas in my house-$65 pipe and fittings and use a $40 harbor freight sump pump to recirculate water from a 50 gallon barrel (free). The tankless set-up costs me around $15 a month in NG. If you have a gas line in your house I would HIGHLY suggest you use it. NG is dirt cheap compared to propane, you never have to fill a tank, and installing a gas line is not rocket science folks, just google it. You can visit my tankless thread for more info here:
https://www.rollitup.org/advanced-marijuana-cultivation/410850-well-fuck-n-tankless-water.html If you want to buy a tankless water heater with a "hydro product" sticker on it, add another $300 to the cost. Me..I like to think of myself as a little smarter than that.
Ok, you have the shit installed.. now what?
Fisrt, smoke a blunt and get ready for some cool shit. Watching your PPM meter rise and fall is pretty damn coo stuff. Plus the plants really do go ape shit. I get 2-3" of growth per day during the stretch on indica/sativa hybrids.
ok, so the default PPM everyone throws around is 1500. Further research on my part uncovered that 1500 is needed during the peak growth phases (flower weeks 3-6) but not all the time. If you have a NG burner its so cheap not to just pump in 1500 then you might as well, can't hurt. If your on bottles then I found the following recommendations as the relate to plant age and metabolism so your not wasting money:
first couple veg weeks: 800-1000
Latter veg: 1000-1100
First couple flower weeks 1200-1300
Mid flower 1500 to 1800
Finish:...see bellow
There is some debate on using co2 in the last two weeks of flower. on one hand, the plants are producing allot of oils and putting on weight so you would think that co2 would be a good thing. However, co2 inhibits the production of ethyelene which promotes fruit maturation. There are several growers that knock down PPM to 400-500 in the final weeks. I know experienced growers who do it both ways. I have been switching strains every grow so really can't tell you definitively.
A couple of other general co2 usage notes:
Co2 is heavier than air and sinks to the floor. This isn't a huge issue but don't place your co2 sensor too high or too low and maintain good air circulation.
Don't mount your co2 sensor too close to your generator. You want the air and co2 to mix and get a good reading for the whole room. If it is too close, your readings will be higher than they actually are. Mine are mounted on the opposite sides of the room with a fan blowing the co2 towards the sensor.
When adjusting dispersal rates, try to balance between the burner being on for a long time (3-5 min) and burning for a short time and "overshooting" the desired PPM. (the ppm meter will sense 1500 and shut the burner off, but the Co2 will still rise as the co2 "gets too the meter".
It is important to have good circulation in the canopy. air movement right next to the leaf surface is very minimal. This is called the boundary layer and has to do with friction of the leave surface. If you don't have fans moving the air, the plant can deplete the amount of co2 present in this thin layer next to the leave so make sure their is air exchange going on. ... just don't overdo it.
Plants will transpire MUCH MORE in high heat and high metabolic environments. Therefore, they will use up much more water and raise the humidity more. compensate by running the dehumidifier more and you hydro folks may want to lower nutrient concentrations a little as the plants will be transporting more water and the nutrient salts that come with them.
Lastly, I can't overstate the need for a proper PPM controller. There are tables and charts to help you guestimate co2 usage but as those with PPM know, the rate of co2 usage is much faster than you would think and is subject to many many variables that just can't be calculated for. while it won't "hurt" to err on the side of not enough co2, I really advise you to just spend the cash and get a proper system. It eliminates waste and actually makes you money in the long run. (allot more).
Hope this has been helpful.
