Biogeochemicle cycles are the pathways by which a chemical substances (carbon, nitrogen, oxygen, phosphorus) moves through biotic (biosphere) and abiotic (lithosphere, atmosphere, and hydrosphere) compartments.
Organic carbon is found in all land-living organisms,, as well as soils in form of the calcium carbonate. Plants and animals(including humans) utilize carbon to produce carbohydrates, fats, and proteins, which are then be used to build their internal structures or to obtain energy. Carbon is released into the air through the processes of respiration in a form of CO2.
The negatively human impact on the carbon cycle is through direct emissions from burning fossil fuels (transfer of carbon from the geosphere into the atmosphere) or through the process of calcination of limestone for clinker production, which releases CO2.