What are the primary sources of CO2?
It is important to note that there are both natural CO2 sources and manmade (anthropogenic) CO2 sources. The primary natural CO2 sources include ocean release, animal and plant respiration, organic matter decomposition, forest fires, and volcanic eruptions, while the primary anthropogenic CO2 sources include fossil fuel burning, cement production, and farmland plowing.
Natural CO2 Sources
Natural CO2 sources account for the majority of CO2 released into the atmosphere. Oceans sometimes release dissolved CO2 into the atmosphere to maintain equilibrium between the two media. Oceans provide the greatest annual amount of CO2 of any natural or anthropogenic source. During animal and plant respiration, oxygen and nutrients are converted into CO2 and energy. Decomposition of organic matter (i.e., plant or animal matter) is a process in which bacteria breaks down the organic compounds and releases CO2 into the atmosphere. Forest fires are caused naturally when hot and dry weather affects an area for an extended length of time. When conditions become both hot and dry enough, vegetation is easily ignited. As it burns, the carbon within the vegetation combines with the oxygen in the air, forming CO2. Magma in volcanic eruptions experiences a drop in pressure as it spews into the atmosphere. The high concentrations of dissolved gases within the magma, including CO2, begin bubbling out with this pressure relief.
Anthropogenic CO2 Sources
Anthropogenic CO2 sources include fossil fuel burning and the use of limestone to make cement. Fossil fuel burning is the foundation of many everyday activities, including driving a car, taking a warm shower, drying clothes, and heating a home. Another significant anthropogenic CO2 source is farmland plowing, where soil is exposed to air, and bacteria within the soil breaks down the organic matter in the presence of oxygen, releasing CO2 in the process.
Although anthropogenic CO2 sources release less CO2 into the atmosphere than do natural sources, it is important to realize that certain anthropogenic sources, like fossil fuel burning, add carbon into the natural carbon cycle, causing atmospheric CO2 to steadily increase. Some scientists are concerned that this gradual increase in atmospheric CO2 above natural levels could lead to potential climate change.
Misconception: Carbon dioxide comes only from anthropogenic sources, especially from the burning of fossil fuels.
Reality: Carbon dioxide comes from both natural and anthropogenic sources; natural sources are predominant.