The green leaves of any plant take carbon from the air through the process of photosynthesis, which is stored in the plant. At the end of life cycle of the plant, the carbon dioxide is released back into the air by decomposition of the plant by bacteria. Thus, carbon taken from the air is returned to the air.
→ If the dry plant is burnt, the carbon dioxide goes in the air in the form of smoke and maintains the balance of carbon in the air.
This is a system of nature, the matter that is obtained from the nature, will go back to it.