Dry Ice

Marijuana Horticulture

by Jorge Cervantes

Dry ice gets very expensive with prolonged use. Two pounds of dry ice will raise the CO2 level in a 10 x 10 foot grow room to abut 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 CO2. Dry ice is carbon dioxide that has been chilled and compressed. As it melts, it changes from slid to gas. Gaseous CO2 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 and inexpensive. Because Co2 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 f CO2 being released. A pound of dry ice is equal to a pound of liquid CO2. Determining the thawing period for a particular size of dry ice will all allow you to estimate how much CO2 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 CO2. The size and number of holes allow you to control the rate at which the block melts and releases CO2.

Dry ice is economical and risk free; it releases no toxic gases, heat, or water. Although dry ice is easier to handle than compressed CO2 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 damage or burn the skin after prolonged contact.