Brief portrait of CO2

• Colour- and odourless gas, heavier than air; natural content in the atmosphere: 0.03 – 0.04 per cent; forms carbonic acid when dissolved in water (about 880 millilitres of CO2 can be dissolved in a litre of H2O); does not support combustion, flames are extinguished at volume concentrations of 8 – 10 per cent carbon dioxide in the air. (Important note: we are in danger of falling unconscious at concentrations of 6 per cent in the air we breathe, even higher concentrations are fatal!)

• At 20 degrees, CO2 can be liquefied at a pressure of 55.4 bar. In the case of a rapid drop in pressure, so much evaporation coldness is produced that the temperature cools down to below -80 degrees and solid carbonic acid snow develops – which is the way that CO2 fire extinguishers work. If the temperature increases to more than -78.464° (sublimation point), dry ice turns directly into gas again – without an intermediate liquid phase.

• CO2 gas is very stable when heated; it only splits up into carbon monoxide and oxygen gradually at temperatures of more than 2,000 degrees.

• CO2 is responsible for about 20 per cent of the natural (geogenic) greenhouse effect and about 60 per cent of the greenhouse effect caused by human beings (anthropogenic). It takes an average of 120 years to degrade in the atmosphere.

• Anthropogenic CO2 production most recently amounted to more than 33 gigatonnes per year. The immense volume of 550 gigatonnes is produced every year geogenically; this is, however, compensated for by natural consumption of approximately the same amount, particularly by plants (photosynthesis) and calcifying organisms.