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Carbon Dioxode Generators for Growing Marijuana

Carbon-Dioxide Generators for Growing Marijuana

Students learn in school that plants create the oxygen people breathe by converting carbon dioxide (CO2) and light into glucose. In other words, oxygen is the byproduct of the chemical reaction that produces the food plants need to grow, which makes carbon dioxide the raw material required for growth. Not all growers put two and two together to understand what that means when it comes to accelerating growth in their marijuana plants, though.

Just like medical patients suffering from certain diseases can benefit from being put on an oxygen machine, all plants can benefit from breathing in more carbon dioxide. In fact, even healthy plants can benefit from the introduction of extra CO2, but only if growers introduce this valuable gas correctly. This article will provide a comprehensive overview of how CO2 saturation works, what levels of the gas will create the perfect environment for plants, what equipment can be used to saturate the air with CO2, and how growers can keep themselves safe in the process.

CO2 and Photosynthesis

Photosynthesis is the process by which plants use light to convert CO2 into sugar and oxygen. While photosynthesis takes place in the plants’ chloroplasts, found primarily in their leaves, CO2 extraction is localized to its stomata. These two types of organs work together to create food for the plant, but only if carbon dioxide and light are available at the right levels.

In outdoor grows, it is very difficult to regulate CO2 levels. For indoor growers who want to take all possible steps to maximize their yields, regulating CO2 is a great way to increase the amount of energy cannabis plants can create for use producing big, beautiful buds. Balancing CO2 production with light can be a bit tricky, though, and irresponsible use of CO2 can be dangerous, so this technique isn’t for beginners.

Optimum CO2 Levels

The CO2 in the Earth’s atmosphere is around 400 parts per million (ppm). People can only safely breathe air with a CO2 level of 3,000 ppm or less, but plants can benefit from carbon dioxide levels of up to 10,000 ppm if they have sufficient light to process the gas.

Most growers aren’t aiming to provide their plants with 10,000 ppm of CO2 round-the-clock, though, and they shouldn’t be. When carbon dioxide saturation reaches around 5,000 ppm, it is considered lethal to humans. Plus, excess CO2 can, in the absence of light or in high heat grow rooms, damage the plants.

The ideal most growers aim for when it comes to carbon dioxide concentration is a CO2 level of between 1,200 and 2,000 ppm. This will substantially increase the plants’ growth and, eventually, the crop’s yield, but it won’t endanger workers in and around the grow room.

It’s important to tailor CO2 levels to the amount of light plants get, though. Producing enough light for plants to absorb 1,500 ppm of CO2 requires around 7,500 to 10,000 lumens. Since most grow lights measure output in lux, not lumens, growers need to convert the measurement of light output using a lux to lumens calculator.

Those with small spaces can also follow these recommendations:

  • one 600W HPS or LED light for a 3’ x 3’ space
  • two 400W HPS or LED lights for a 3.5’ x 3.5’ space
  • one 1,000W HPS or LED light for a 4’ x 4’ space

CO2 and Heat

Most experts in indoor cannabis cultivation suggest keeping the grow room around 70°F. Plants grown in CO2-saturated air can handle and even thrive at slightly higher temperatures. Some growers who use this method keep their grow rooms as hot as 85 – 90° during the hottest parts of the day.

The best way to add a little extra carbon dioxide to a grow room without investing in fancy equipment is to locate it near a gas heater. These heaters give off safe amounts of CO2 while simultaneously warming the environment on cold nights. The problem with this solution is that it doesn’t allow growers to regulate the exact amount of CO2 in the plants’ atmosphere, so many don’t notice any substantial difference in their yields.

A second problem with this common, but not particularly effective, method is that gas heaters tend to be most useful at night when most growers restrict their plants’ light. Without light, the plants can’t break down the CO2. The amount of CO2 emitted by gas heaters isn’t substantial enough to cause any significant damage, even at night, but it is less likely to do any good.

Professional Equipment

The best way to increase CO2 in a grow room is to purchase specialized equipment designed specifically with this purpose in mind. There are a few DIY methods for generating CO2, which this article will discuss later, but they’re not as effective and they don’t offer growers a way to measure their carbon dioxide output. Professional- grade equipment may be expensive, but for those who are serious about increasing their yield, they’re worth the investment.

CO2 Generators

CO2 generators create CO2 by burning either propane or natural gases. They look a little like patio heaters, and like these less specialized pieces of equipment, they put off heat and increase humidity. They’re best suited for large grow rooms that are equipped with air conditioning and humidity controls.

What’s great about professional-grade CO2 generators is that they can be set to a specific ppm. They can also be set up to power on and off automatically when carbon dioxide levels reach or exceed the target range. Growers should make sure to turn their CO2 generators off at night when the plants will be unable to absorb the extra gas, though. Most CO2 generators can be set to timers.

Compressed CO2

Unlike CO2 generators, compressed CO2 tanks don’t produce heat or alter humidity levels in the grow room. They can be purchased online, from hydroponics stores, or even from home brewing stores, as they are also used to pressurize beer kegs.

Like CO2 generators, compressed CO2 tanks allow growers to introduce carbon dioxide into their grow rooms in controlled quantities. Tanks cost anywhere from around $25 for a 20 oz. tank to around $100 for a 20 lb. tank. They’re perfect for small grows.

There are two ways to use compressed CO2. Some growers slowly bleed the tanks through a hose suspended over their plants, while others flood sealed grow spaces for around 20 seconds at a time every few hours. One advantage of taking the latter approach is that full saturation doesn’t just help to accelerate growth but also kills off any pesky spider mites or other oxygen-breathing pests in the process.

DIY Methods for CO2 Generation

Some small-scale marijuana growers swear by DIY methods like fermentation, burning candles, and combining baking soda and vinegar. These methods don’t allow for controlled application of CO2, and they don’t produce anywhere near the amount of the gas introduced by professional equipment like generators and compressed CO2 tanks.

Yeast Fermentation

Growers who also brew their own beer or other alcoholic beverages sometimes combine their two operations into one space so their plants can take advantage of the carbon dioxide that forms as a byproduct of fermentation. Unlike plants, yeast produces CO2 as part of its digestion process. It takes water, nutrients, and sugar and turns them into a combination of CO2 and alcohol.

Those who don’t care for beer and other fermented drinks can still use fermentation to produce CO2. Just combine yeast and sugar in warm, but not hot, water. The yeast will take care of the rest and since the resultant beverage isn’t intended for consumption, there’s no need to monitor it closely.

Burning Candles

Burning candles also releases a small amount of CO2 into the atmosphere. Just make sure the candles are safely enclosed in glass jars and placed out of the way where they can’t possibly be knocked over. Since candles require oxygen to burn, they’ll go out if the air becomes saturated with CO2.

Vinegar and Baking Soda

Vinegar is acidic and baking soda is basic, which is why mixing them together creates a mild chemical reaction. The products of that reaction are water, sodium acetate, and, most relevantly to growers, carbon dioxide.

To set up a vinegar and baking soda CO2 generator, just suspend a bottle of any kind of vinegar upside down over a bowl of baking soda. Cut a tiny hole in the center of the bottle’s cap so that a minute amount of vinegar can escape to form droplets. Aim for an introduction rate of around one drop of vinegar per minute and replace the set-up when each drop no longer produces a noticeable reaction.

Tips for Using Carbon Monoxide Safely

There’s no need to worry about safety when using the DIY methods just discussed, as none of them produce substantial amounts of CO2. The only thing growers would need to worry about there would be knocking a lit candle on the floor. However, those who choose to install professional-grade equipment should take a few precautions.

Seal the Grow Space

Most established grow rooms are already sealed, so this shouldn’t be a big deal for most growers. After all, carbon dioxide isn’t the only thing that leaks out of grow rooms, which also produce substantial, noticeable odors.

Check the seals around the grow room’s intake and exhaust fans, doors, and other areas prone to air leaks before installing new equipment. It will ensure that the CO2 introduced into the grow room stays put so it can be consumed by the plants instead of leaking out into the surrounding area where it will either dissipate into the air or, if it remains concentrated, cause health problems for humans and their pets.

Monitor Temperature and Humidity

As noted above, plants that live in a CO2-rich environment can handle higher heat than plants grown in an unaltered atmosphere. It’s still wise to regulate heat when using CO2 generators, though, as they produce more of it than some growers expect. Don’t let the temperature in the grow room rise above 90 – 95°F and watch for signs of heat stress because even with all that extra CO2, not all strains of marijuana can handle temperatures that high.

Excess humidity can also be a concern when using CO2 generators. High humidity leaves plants at risk of developing bud rot and other problems with mold and mildew, though. Try to keep the humidity below 60% to prevent these problems. That’s a little higher than normal, so don’t be afraid to further reduce the humidity in grow rooms that have dehumidifiers.

Introduce CO2 from Above

Carbon dioxide is heavier than air, so introducing it below the plants’ canopies won’t do any good. Instead, set up the CO2 generator or compressed CO2 tank to introduce it from above so it rains down on the plants. An even dispersal produces the best results. Some growers even place small fans pointed toward the ceiling on their floors to keep the carbon dioxide circulating where their plants can reach it.

Know When to Stop

CO2 saturation is a great technique for the vegetative stage, when plants should be getting plenty of light. It can also be used during the flowering stage to increase bud production and growth, but only for the first two to three weeks. It’s also essential that growers turn off their CO2 generators at night or whenever the lights are off.

The Bottom Line

Raising the carbon dioxide levels in a grow room to around 1,500 ppm can increase yields by as much as 20%, but only if growers do it right. Those who are looking for real results should invest in a high-quality CO2 generator or purchase compressed CO2 tanks and anyone who wants to use this technique should ensure that their grow rooms are fully sealed. Only use CO2 generators when the lights are turned on and turn them off for the season after the first two to three weeks of flowering.

Starting with seeds from a reputable online cannabis seed distributor like will provide a solid foundation for growing high-quality plants. From there, growers can experiment with different techniques to boost growth, such as introducing supplemental CO2.