A lot of misinformation seems to be going around about CO2, especially at the lower end of the price range. And so I present:

El Cheapo Guide to CO2

CO2? What is it? Well, as anyone who has taken high school chemistry knows, CO2 is carbon dioxide, and plants need it in order to grow. As anyone who has been following the news knows, CO2 also appears to contribute to climate change, and is given off by fossil fuels and every life form that doesn't contain chlorophyll.

Of course, the first step you need to take, if you plan to add CO2 to your grow room is to make sure you won't just lose it all by venting. If your room is drafty or in a well-ventilated area, you don't have much to gain by adding CO2. But if there isn't much air exchange between your room and the outside world, read on.

So how do we get it to our plants? Well, we can either buy it or make it. You can buy it in tanks from beer distributors and welding supply shops, but you need all sorts of expensive equipment to regulate it. So this isn't in the scope of El Cheapo Guide. I guess that means we have to make it.

Getting Other Organisms to Make CO2 For You

One way is to put some other organism in your grow room that doesn't need light. One example of such an organism is yourself. Sleeping in the same room as your plants will provide them with plenty. But if your grow lights keep you awake, you may want to enlist the help of some other organism. This includes stuff like bacteria and fungi. For example, fertilizing your plants with molasses not only helps their roots, but the bacteria in the soil will eat the molasses and give off CO2. Like growing mushrooms? Great, put em in your grow room! Like brewing beer or wine? Put those fermenters in your grow room too! Those bubbles coming out the airlock are pure CO2. Want to mask the smell of your plants? Put a huge pile of rotting garbage in your grow room! As it rots, it gives off CO2!

One thing I would not recommend doing is fermenting sugar just for the CO2. It isn't cost effective at all. A molecule of sugar has the atomic formula C6H12O6. Fermenting it yields alcohol and two molecules of CO2. For every kilogram of sugar, you get 250 grams of CO2. Weak.

Making CO2 the Al Gore Way

As we all know, burning fossil fuels produces lots and lots of CO2. How much, you ask? Well, burning a gram of kerosine produces roughly 3.5 grams of CO2. "Wait, I'm too smart to fall for that!", you might be thinking. "You can't turn one gram of one thing into 3.5 grams of something else!" True, except that when you burn hydrocarbons, you combine hydrogen and carbon with oxygen from the air. Oxygen actually weighs kind of a lot, and that's where the extra weight comes from. This works to our advantage when we want to supply our plants with CO2. For instance, a 20 pound tank of propane can generate much more CO2 than a 20 pound tank of CO2 will.

The easiest, cheapest way to supplement your plants' CO2 is probably candles. Go to a store after Christmas and buy all those fat Christmassy candles that are now on sale. Figure out how much one weighs and how long it takes to burn down. Multiply its weight by 3.5. This is how much CO2 the candle will generate in the amount of time it takes to burn down. Just be damn sure that you're careful about it. Put the candle in a metal vented container where it can't possibly catch anything else on fire, and then keep anything flammable away from it just to be sure. If you don't think one candle is enough, you can use two or three. If that's still not enough, one of those Coleman kerosene lanterns might not be a bad investment, if you don't mind refilling it. You can also get something like:

Candle Lamp SL50 50 Hour Liquid "Smokeless" Paraffin Wax Lamp Fuel Cartridge 6/PK Product details

I've seen the oil to refill these things for as cheap as $12 a gallon. Put a ring of them in your grow room and use them to help meditate! Remember, plants only need CO2 when the lights are on, so if you want to save fuel, light them and put them out when your lights go on and off. If that's too much work, don't worry. The CO2 will build up during the dark cycle, then get used during the light one. You might lose some due to leaks, but it's nothing to lose sleep over.

If you need to heat your grow room, consider a propane or natural gas ventless heater. These will vent right into your grow room and contain an oxygen sensor so they cut off fuel if oxygen levels drop too low. Of course, a certain amount of ventilation is necessary in order to use these.

Conclusion

If you're trying to generate CO2, the most cost-effective way is through burning hydrocarbons, ie fossil fuels. Other methods like using seltzer water, dry ice, vinegar and baking soda, or yeast and sugar, are all far more expensive for the amount of CO2 you get. Although hydrocarbons all produce between 3 and 3.5 times their weight in CO2, they do have some issues, namely, you must keep flammable stuff away from them. This isn't a deal breaker, after all, most homes have gas or propane appliances, and many grow lights can get hot enough to start fires. The important thing is to be careful!

Interesting . . .

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A garden of gratitude must first be cultivated in a mans soul before any seed will grow for him.Hydro Q's
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Open unattended flames? Count me in! plus more heat.

CO2 in the root zone? Roots want O2 not CO2. CO2 falls.

Mushrooms typically don't like the killer lights we give our plants.

Indoor CO2 levels are typically knocking on twice that of outdoors.
(At least thats what my CO2 ppm meter tells me)

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The Temporary Relief Assistant Trailer Park Supervisor. Carmelisous Jornl :: ElecUsageCostsCalc (now with carbon footprint) :: FloroTubeCompendium ::

Ive heard of praying your plant with, either carbonated water or fermenting water(ie yeast), im not to sure thou

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We hang the petty thieves and appoint the great ones to public office.{Aesop}

When the power of love overcomes the love of power... the world will know peace. {Hendrix}

oops er spraying lol not praying

__________________
We hang the petty thieves and appoint the great ones to public office.{Aesop}

When the power of love overcomes the love of power... the world will know peace. {Hendrix}

dont spray the fermenting h2o on to the plants.

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a man who wants nothing is invincible

Should spray during lights on and plants don't need/use CO2 with lights off.
(hell my CO2 ppm rises over the dark period)

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The Temporary Relief Assistant Trailer Park Supervisor. Carmelisous Jornl :: ElecUsageCostsCalc (now with carbon footprint) :: FloroTubeCompendium ::

Of course not. Like I said, anything with a flame should be put in a metal vented container far away from anything flammable. A candle will give off heat, but it's not much. About the same as a 40-watt light bulb or a T12 fluorescent tube.

Feeding plants with a small amount of molasses is a widely used strategy. The CO2 will diffuse out of the soil fairly quickly.

Which is why you shouldn't put mushrooms directly under the lights. I don't know about you, but I have a lot of space in my grow room that's dimly lighted, where I keep stuff like fertilizer and unused equipment. Obviously that's not feasible in a really small grow area.

You wouldn't notice any difference from doing this. Some growers might do it because they think it'll help, but there's really not nearly enough CO2 to do anything noticeable.

Can you back this up?

I have a ppm meter/controller and have used molasses, but haven't seen any increases in the ppm over not using molasses.

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The Temporary Relief Assistant Trailer Park Supervisor. Carmelisous Jornl :: ElecUsageCostsCalc (now with carbon footprint) :: FloroTubeCompendium ::

You're actually probably right; thinking back, the amount of molasses used for feeding isn't much, and probably wouldn't contribute much to the CO2 levels. But it does increase the number of soil-dwelling bacteria, which do give off CO2. So even though it's definitely helpful, the CO2 factor might not have much to do with it.

This is a strategy I mostly use with clones, since their CO2 requirements are very small and I cover mine with plastic to keep in moisture. The plastic keeps out CO2, but I think the molasses in the soil generates enough to keep it healthy.