Carbon dioxide, (CO2), a colourless gas having a faint sharp odour and a sour taste. It is one of the most important greenhouse gases linked to global warming, but it is a minor component of Earth’s atmosphere (about 3 volumes in 10,000), formed in combustion of carbon-containing materials, in fermentation, and in respiration of animals and employed by plants in the photosynthesis of carbohydrates. The presence of the gas in the atmosphere keeps some of the radiant energy received by Earth from being returned to space, thus producing the so-called greenhouse effect. Industrially, it is recovered for numerous diverse applications from flue gases, as a by-product of the preparation of hydrogen for synthesis of ammonia, from limekilns, and from other sources.
