The main sources of carbon dioxide are: combustion / use of fossil fuels; land use for planting large fields of crops, respiration of humans, plants and animals, decomposition of soil materials, burning of car fuels, production and various technologies used in factories and mass production, ocean gas exchange and the atmosphere (air).

We can divide them into both natural and human sources of carbon dioxide emissions. Natural sources include decomposition, ocean emissions and respiration. Human resources come from activities such as cement production, deforestation, and the burning of fossil fuels such as coal, oil, and natural gas.

Due to human activity, the concentration of carbon dioxide in the atmosphere increases significantly. It has so far reached dangerous levels not seen in the last 3 million years. Human sources of carbon dioxide are much smaller than natural ones, but they have upset the natural balance that existed thousands of years before human influence.

The main threats to increasing the amount of carbon dioxide come from: urbanization (overpopulation of large cities); deforestation; expansion of agriculture and agricultural land at the expense of natural land; construction of long multi-lane highways; the use of coal for heating and production.

The largest human source of carbon dioxide emissions is from the burning of fossil fuels. This produces 87% of the available carbon dioxide. The combustion of these fuels releases energy, which is most often converted into heat, electricity or energy for transportation. Some examples of where these fuels are used are in power plants, cars, airplanes and industrial facilities.

The three most commonly used fossil fuels are coal, natural gas and oil. The main economic areas that use fossil fuels are: electricity / heat, transport and industry.

Deforestation is responsible for most of the carbon dioxide. Deforestation is the permanent removal of living forests and is the most important type of land use change. Forests in many areas have been cut down for timber or burned to farm and pasture. When forested land is cleared, large amounts of greenhouse gases are released and this leads to an increase in carbon dioxide levels.

Trees act as carbon sinks. They remove carbon dioxide from the atmosphere through photosynthesis. Photosynthesis is a process by which green plants and some other organisms use sunlight to create nutrients from carbon dioxide and water. When forests are cleared to create farms or pastures, trees are cut down or burned, or left to rot, this adds carbon dioxide to the atmosphere.

Many industrial processes emit carbon dioxide directly by burning fossil fuels. The production of cement for the construction of buildings produces the largest amount of carbon dioxide among all industrial processes. Steel production is another industrial process that is a major source of carbon dioxide. Fossil fuels are used to create chemicals and petrochemical products, which also leads to an increase in the amount of this gas.

In addition to being created by human activity, carbon dioxide is released into the atmosphere through natural processes. The oceans, soil, plants, animals and volcanoes of the Earth are natural sources of this gas. The largest natural source of carbon dioxide emissions is the ocean. It produces 43% of natural carbon dioxide emissions. The oceans contain dissolved carbon dioxide, which is released into the air on the sea surface. An important natural source of carbon dioxide is also the respiration of plants and animals, which accounts for 29% of natural emissions.

Another important natural source of carbon dioxide is soil respiration and decomposition. Many organisms that live in the earth’s soil use respiration to produce energy. Among them are those that break down dead organic material. Both processes release carbon dioxide as a by-product. Annually, these soil organisms produce about 220 billion tons of carbon dioxide.

Small amounts of carbon dioxide are also created by volcanic eruptions.