Agriculture / Biological applications
Plants require carbon dioxide to conduct photosynthesis. Because of low current atmospheric concentration, carbon dioxide is practically the limiting factor of the Earth life, as compare to two other similarly important components – water and sun light. While plants “in wild” are optimized for this, plant-intense greenhouses may (and of large size – must) enrich their atmospheres with additional CO2 to sustain plant life and growth, because the low present-day atmosphere concentration of CO2 is just above the “suffocation” level for green plants. A photosynthesis-related drop (by a factor less than two) in carbon dioxide concentration in a greenhouse compartment would kill green plants, or, at least, completely stop their growth. At very high concentrations (a factor of 100 or more higher than its atmospheric concentration), carbon dioxide can be toxic to animal life, so raising the concentration to 10,000 ppm (1%) or higher for several hours will eliminate pests such as whiteflies and spider mites in a greenhouse.
It has been proposed that carbon dioxide from power generation be bubbled into ponds to grow algae that could then be converted into biodiesel fuel. Carbon dioxide is already increasingly used in greenhouses as the main carbon source for Spirulina algae. In medicine, up to 5% carbon dioxide (factor 150 as compare to atmospheric concentration) is added to pure oxygen for stimulation of breathing after apnea and to stabilize the O2/CO2 balance in blood.