Marijuana Horticulture: The Indoor/Outdoor Medical Grower's Bible

can capture CO 2 from this decomposition, it is most often impractical for indoor growers. Piping indoors the CO 2 and fumes from a compost pile is complicated, expensive, and more work than it is worth.

The Excellofizz puck is a low-cost product that releases CO 2 when it is bathed in water.
Fermentation
    Small-scale growers use fermentation to produce CO 2 . Combine water, sugar, and yeast to produce CO 2 . The yeast eats the sugar and releases CO 2 and alcohol as by-products. Growers who brew beer at home can use a small-scale system to increase the CO 2 levels in a room. Non-brewers can mix one cup of sugar, a packet of brewer’s yeast, and three quarts of warm water in a gallon jug to make CO 2 . You will have to experiment a little with the water temperature to get it right. Yeast dies in hot water and does not activate in cold water. Once the yeast is activated, CO 2 is released into the air in bursts. Punch a small hole in the cap of the jug, and place it in a warm spot (80 to 95°F [26 to 34°C]) in your grow room. Many gardeners buy a fermentation lock (available for under $10 at beer-brewing stores). Such locks prevent contaminants from entering the jug, and they bubble CO 2 through water so the rate of production can be observed. The hitch is that you must change the concoction up to three times a day. Pour out half the solution, and add 1.5 quarts (1.4 L) of water and another cup (24 cl) of sugar. As long as the yeast continues to grow and bubble, the mixture can last indefinitely. When the yeast starts to die, add another packet. This basic formula can be adapted tomake smaller or larger-scale fermenters. Several jugs scattered around the garden room have a significant impact on CO 2 levels.

Put dry ice in a plastic container with holes to slow evaporation of CO 2 gas.
    Fermentation is an inexpensive alternative to produce CO 2 . It releases no heat, toxic gases, or water and uses no electricity. But because it stinks, it is unlikely that a gardener could tolerate a large-scale fermentation process. In addition, it is difficult to measure CO 2 production from this system, making it difficult to maintain uniform levels throughout the day.
Dry Ice
    Dry ice gets very expensive with prolonged use. Two pounds of dry ice will raise the CO 2 level in a 10 × 10-foot (3 m 2 ) grow room to about 2000 ppm for a 24-hour period. One chagrined grower remarked, “I can’t believe that stuff melts so fast.”
    Growers have long used large, insulated tanks filled with dry ice to add CO 2 . Dry ice is carbon dioxide that has been chilled and compressed. As it melts, it changes from solid to gas. Gaseous CO 2 can be mixed into the air with fans that circulate it among the plants. Dry ice works well on a smaller scale without a tank and converter. It is readily available (check out the Yellow Pages) and inexpensive. Because CO 2 has no liquid stage, the transformation from solid to gas as the ice melts is clean and tidy. It’s also easy to approximate the amount of CO 2 being released. A pound of dry ice is equal to a pound of liquid CO 2 . Determining the thawing period for a particular size of dry ice will allow you to estimate how much CO 2 is released during a particular time period. To prolong the thawing process, put dry ice in insulating containers such as foam ice coolers, and cut holes in the top and sides to release the CO 2 . The size and number of holes allow you to control the rate at which the block melts and releases CO 2 .
    Dry ice is economical and risk free; it releases no toxic gases, heat, or water. Although dry ice is easier to handle than compressed CO 2 tanks, it is difficult to store. The melting can be slowed through insulation, but it cannot be stopped. Because it is extremely cold, dry ice can also cause tissue damage or burn the skin after prolonged contact.
Baking Soda and Vinegar
    Consider using vinegar and baking soda to produce CO 2 in a small grow room. This method eliminates excess heat and water vapor production and requires only household items. Create a system that drips vinegar (acetic acid) into a bed of baking soda. The main disadvantage of this system is the erratic level of CO 2 produced. It takes a considerable amount of time for the CO 2 to build up to a level where it helps plants. However, once it reaches an optimum level, it can continue to rise until it reaches levels detrimental to plants. If you have time to experiment, it is possible to set up a drip system operated