Carbon dioxide (CO2) is  seen as a nutrient for plant growth.  It is an essential component of photosynthesis, a chemical process through which plants use light energy to convert CO2 and water into sugars in green plants.  These sugars are then used for growth within the plant, through respiration.  CO2 increases productivity through improved plant growth and vigour. Some ways in which productivity is increased by CO2 include earlier flowering, higher fruit yields, reduced bud abortion in roses, improved stem strength and flower size.  The concentration of CO2 outside the leaf strongly influences the rate of CO2 uptake by the plant.  Increased CO2 levels will shorten the growing period (5%–10%), improve crop quality and yield, as well as, increase leaf size and leaf thickness.

Carbon dioxide can be obtained by burning carbon-based fuels such as propane, in specialized CO2 generators, located throughout the green house, or directly from tanks of pure CO2.  When propane is burned, not only CO2 is produced, but also heat is generated that can supplement the normal heating system.