What causes CO2 to cycle in and out of the atmosphere?
Aerobic respiration and decay
Decomposition is the largest source of atmospheric CO2. When plants and animals die, microorganisms such as bacteria consume them. Their respiration emits CO2 in the atmosphere. Living animals and people also emit CO2 as part of their respiration. We oxidise the food we eat. As part of this process, carbon matter is converted into CO2, which we exhale when we breathe.
Photosynthesis
Trees, plants and some very small organisms are able to make their own food through a process called photosynthesis. In this process, CO2 is absorbed from the air and “stored” in plant and algal matter. Since animals and people can’t make their own food, they get their carbon by eating plants or animals.
Fossil fuel combustion, deforestation and other human activities
Since 1800, earth’s population has grown from fewer than one billion people to more than six billion today. 2 During this period, the use of fossil fuels has steadily increased. Whilst human causes of CO2 emissions are a relatively small percentage of the total carbon exchanged in the natural carbon cycle, most scientists agree that these emissions are causing a significant increase in atmospheric CO2 and other gases, resulting in climate change through a process known as the greenhouse effect.
Ocean diffusion
Earth’s oceans are one of the planet’s greatest carbon stores. Every year, large amounts of CO2 are both released and absorbed by the oceans.
Carbon dioxide in our daily lives
Carbon dioxide itself is not a danger in our everyday lives. In fact, all life on the planet depends on carbon dioxide. Carbon dioxide is also used in many everyday activities. For example, carbon dioxide is used:
- for the bubbles in your beer or soft drink
- to decaffeinate coffee
- in fire extinguishers
- to make ‘dry ice’
- to create the ‘fog’ effect in concerts, theatres and on movie sets
- in welding, sandblasting and construction
- to make flavour additives for food
- as a propellant in aerosol cans
Next time you drink a beer or soft drink, remember that the bubbles came from a natural underground source of carbon dioxide. Geosequestration is the same process, just in reverse.
Why the government regulates CO2 transport
Carbon dioxide (CO2) has been transported safely for many years. It is much less dangerous than carbon monoxide (CO), with which it is sometimes confused. But because CO2 can be unsafe in very high concentrations, the government regulates its transport, as it does for any potentially dangerous material, such as petrol, natural gas and chemicals.