21. CO2

Higher CO2 levels can give up to 30-100% higher yields. Several methods are available for elevating CO2 levels, like: making use of a CO2 tank or the burning of natural gas. The disadvantage of a CO2 tank is obvious, you have to carry it around and it is costly. The burning of natural gas on the other hand gives extra wet circumstances and a higher temperature.

When a heater is already available it can be used to produce CO2 while its warmth can for example be used to warm the building or water. For this you need a T-Pipe, CO2 controller, hose and an electrical shutter. With the T-Pipe and hose, CO2, that is normally been thrown out, can be guided to the plantation. The air pumps that are already in use to take the moisture and heat out of the plantation will automatically suck the CO2 in the room. Connect the electrical shutter, to a CO2 controller. In this way, the hose will be closed when the maximum level of CO2 has been reached. Make sure CO2 only gets in when the lights are on. Set the CO2 controller on 1200 ppm. With a value over 1500 the leaves of the plants will turn yellow and eventually it will die. 

Even though CO2 enrichment can mean 30-100% yield increases, the hassle, expense, space, danger, and time involved can make it not a good option. Furthermore, lots of growers could easy improve their harvests in another way. When a plantation is not good functioning, injecting CO2 will only make it worse.