Chemical symbol: CO2
Available supply: Most carbon dioxide is in the form of CO2, hydrogen carbonate or carbonation dissolved in the water of the oceans and rivers. Only about two per cent of the Earth’s supply is found in the atmosphere, the share of CO2 of which is about 0.04 per cent by volume
Sublimation point: - 79 °C
transitions directly to gaseous state at standard pressure
Triple point: - 57 °C
Chemical properties: Colourless and odourless, incombustible, inert, but dissolves readily in water. With basic metal oxides or metal hydroxides, it forms carbonates and hydrogen carbonates.
Production method: Primarily as a by-product of biochemical or chemical processes. One such process is steam reforming, a basic process for the production of hydrogen, ammonium and other basic chemicals. It is also generated in ethylene oxide production and in other industrial processes such as alcohol fermentation in relatively pure, easily recoverable form. Natural CO2 sources exist mainly in areas of volcanic origin.
Plants cannot grow without CO2, which makes it an indispensable prerequisite for higher life.
Along with water, plants contain mainly carbon compounds. They draw the carbon they need for their roots, stems, leaves and fruit from the share of CO2 found in the air. Plants, in turn, form the nutritional basis for the entire animal world, including humans.
And over the course of hundreds of millions of years, that biomass also transformed into the huge reserves of carbon, oil and natural gas, which man is now burning back into CO2 with increasing speed. That’s why the share of carbon dioxide in the air is increasing and its thermal insulation effect is contributing to global warming.
Some of those CO2 waste gases are collected again and reused in another process. The best-known among them is the enrichment of soft drinks, which owe their sparkle to the gas.
In the form of dry ice, it is used for cooling and freezing. And it is playing an ever increasingly important and extremely eco-friendly role in the treatment of drinking water and in wastewater neutralisation. Unlike the aggressive mineral acids which are otherwise used, it leaves no problematic residues behind
When used in greenhouses, the carbon dioxide is converted back into biomass, because the plants draw carbon from it for their growth and release the oxygen. Paper recycling with CO2 makes an important contribution to environmental protection.