Non-flammable, colourless and odourless acid gas (also carbon dioxide, CO₂)_. Colloquially, carbon dioxide is often incorrectly referred to as carbonic acid. In solid form, it is used as dry ice (image left) as a coolant and inert gas. The gas is produced during all combustion processes and during the respiration of animal and human organisms. It is also found in volcanic rocks and at great depths in the earth.

Greenhouse effect

Although it only makes up a small proportion of 0.039% of the atmosphere, this tiny amount is essential for all life because it is required by plants during photosynthesis and oxygen is formed in the process. Since industrialisation, the proportion has risen by 44% in connection with climate change and the greenhouse effect. The proportion is greater in the northern hemisphere (due to more land mass). The resulting extreme weather conditions with heat waves also have a negative impact on viticulture (see under decarbonisation).

Proportion of carbon dioxide

Carbon dioxide dissolves in liquids depending on pressure and temperature. During dissolution, carbonic acid is also produced by reaction with water to a very small extent of only 0.2%. However, by far the largest proportion, over 99%, is the carbon dioxide dissolved in the wine (which does not yet produce carbonic acid), which is summarised with the actual carbonic acid as "free carbonic acid". As the vine grows, the sugar in the grapes is formed from carbon dioxide and water. During fermentation, the sugar is then converted into carbon dioxide and alcohol.

At 1.98 g/litre, carbon dioxide is around 1.5 times heavier than air. There is therefore a risk of asphyxiation in the fermentation cellar if the gas is not extracted using exhaust fans. The formation of carbon dioxide is promoted by Hefesatzlagerungthe...