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How is CO2 Produced?

Carbon dioxide (CO2) is emitted in a number of ways. It is emitted naturally through the carbon cycle and through human activities like the burning of fossil fuels.

In Nature

The primary natural processes that release CO2 into the atmosphere (sources) and that remove CO2 from the atmosphere (sinks) are:

  • Animal and plant respiration, by which oxygen and nutrients are converted into CO2 and energy (source), and plant photosynthesis by which CO2 is removed from the atmosphere and stored as carbon in plant biomass (sinks);
  • Ocean-atmosphere exchange, in which the oceans absorb and release CO2 at the sea surface; and
  • Volcanic eruptions, which release carbon from rocks deep in the Earth's crust (this source is very small).
  • Large amounts of carbon dioxide are also emitted from volcanoes and other geothermal processes such as hot springs and geysers.
  • Carbon dioxide sources include all animals, plants, fungi and microorganisms. For example, in addition to producing large amount of methane, cows also produce about 11 kilograms of CO2 each day from breathing.

Human Activities

A variety of human activities lead to the emission (sources) of carbon dioxide (CO2):

  • When any carbon-based fuel is burned, it produces carbon dioxide (CO2), water (H2O) and other product of combustion depending on the fuel.
  • When you drive your car, the engine burns gasoline or diesel fuel and creates a certain amount of CO2, depending on its fuel consumption, fuel type, and the driving distance.
  • When you heat your home with oil, natural gas or propane, you also generate CO2.
  • When you cool your home, use your appliances or watch your new flat screen TV, the generation of the electrical power may also have emitted a certain amount of CO2.
  • When you buy food and goods, the production of the food and goods also emitted some quantities of CO2 in the process.
  • When you take a trip on an airplane, the jet fuel used to transport you to and from your destination produces CO2.
  • Humans produce about one kilogram of CO2 each day just by breathing.