Biogeochemical cycles - Carbon cycle in brief

Carbon exists in the nonliving environment as:
• Carbon dioxide (CO2)
• Carbonic acid ( HCO3−)
• Carbonate rocks (limestone and coral = CaCO3)
• Deposits of Fossil fuels
• Dead organic matter

Organic Carbon

• Hydrocarbons:  CH4

• Carbohydrate: CH2O

Inorganic carbon

• Carbon Dioxide: CO2

• Calcium Carbonate: CaCO3 

Carbon is released into the atmosphere in several ways

• Respiration by plants and animals. 

• Decay of animal and plant matter. 

• Combustion of organic material

• Production of cement. 

• The ocean releases CO2 into the atmosphere.

• Volcanic eruptions and metamorphism

Carbon is taken from the atmosphere in several ways

• Photosynthesis. 

• The oceans when the  seawater becomes cooler, more CO2  dissolve and become carbonic acid.

• In the upper ocean areas organisms convert reduced carbon to tissues, or carbonates.

Photosynthesis

• CO2   + H2O  + sunlight   =>  CH2O  + O2

Respiration 

• CH2O  + O2   =>  CO2   + H2O  + energy

Human Impacts on the Carbon Cycle => Combustion or Oxidization of hydrocarbon

86% of global primary energy consumption is fossil fuels.

Fossil Fuels

• Petroleum

• Natural Gas

• Coal

CO2 Concentration

Pre-Industrial value => 280 ppm  (600 billion tons)

Current value => 380 ppm (800 billion tons)

Critical value => 560 ppm (1200 billion tons)