Carbon dioxide

Carbon dioxide (chemical formula CO2) is a colorless and odorless gas that is vital to life on Earth. This chemical compound is made up of a carbon atom covalently double bonded to two oxygen atoms. 

A space filling model of a carbon dioxide molecule. image: wikipedia

Carbon dioxide exists in Earth's atmosphere as a trace gas at a concentration of about 0.04 percent (410 ppm) by volume.

Top: AIRS (atmospheric  infrared sounder) satellite  2011 annual mean carbon dioxide concentration in the free troposphere. The graph on the bottom shows parts per million (ppm) of CO2 in the atmosphere. image: wikipedia 

Atmospheric carbon dioxide  levels continue to rise on average. image: NOAA

Natural sources include volcanoes, hot springs and geysers, and it is freed from carbonate rocks by dissolution in water and acids. Because carbon dioxide is soluble in water, it occurs naturally in groundwater, rivers and lakes, in ice caps and glaciers and also in seawater. It is present in deposits of petroleum and natural gas.

A ball and stick model of carbonic acid that forms when carbon dioxide dissolves in water. image: wikipedia

A critical component of life on Earth

Carbon dioxide in the atmosphere is the primary source of carbon in life on Earth and its concentration in Earth's pre-industrial atmosphere since late in the Precambrian was regulated by photosynthetic (photosynthesis requires CO2 to produce O2 and carbohydrates) organisms and geological phenomena. 

Carbon dioxide is a significant greenhouse effect gas in the Earth's atmosphere.

Since the Industrial Revolution, anthropogenic (human created) emissions - including the burning of carbon-based fossil fuels and land use changes (primarily deforestation) - have rapidly increased its concentration in the atmosphere, leading to global warming. Carbon dioxide also causes ocean acidification because it dissolves in water to form carbonic acid. This can cause weakening of shells of marine animals.

Part of the carbon cycle

As part of the carbon cycle, plants, algae, and cyanobacteria use light energy to photosynthesize carbohydrate from carbon dioxide and water, with oxygen produced as a waste product.


the fast carbon cycle shows the movement of carbon between land, atmosphere, and oceans in billions of tons per year. image: wikipedia

It is part of life metabolism

Carbon dioxide (CO2) is produced by all aerobic organisms when they metabolize carbohydrates and lipids to produce energy by respiration. 

It is returned to water via the gills of fish and to the air via the lungs of air-breathing land animals, including humans. 

The citric acid cycle takes in O2 + Sugars releasing energy and CO2. image: wikipedia

CO2 is produced from  decay and food

Carbon dioxide is produced during the processes of decay of organic materials and the fermentation of sugars in bread, beer and winemaking.

 CO2 is released from combustion

It is produced from the combustion (burning) of wood , organic materials and fossil fuels such as coal, peat, petroleum and natural gas.

CO2 is used in Industry 

It is a versatile industrial material, used, for example, as an inert gas in welding and fire extinguishers, as a pressurizing gas in air guns and oil recovery, as a chemical feedstock and in liquid form as a solvent in decaffeination of coffee and supercritical drying. 

Bubbly water anyone?

It is added to drinking water and carbonated beverages including beer and sparkling wine to add effervescence. 

Freeze it

The frozen solid form of CO2, known as "dry ice" is used as a refrigerant and as an abrasive in dry-ice blasting.

Source: Adapted from: Carbon dioxide. (2017, February 7). In Wikipedia, The Free Encyclopedia. Retrieved 06:40, February 9, 2017, from