Carbon dioxide is a chemical compound composed of two oxygen atoms bonded covalently to a single carbon atom. At standard temperature and pressure, carbon dioxide exists in gaseous state. CO2 is commonly found in gaseous and solid form. The solid form of carbon dioxide is known as Dry Ice. Currently the global average concentration of CO2 is approximately 383 ppm by volume. Although this level may differs both by time and location. Carbon dioxide is a significant greenhouse gas because it communicates visible light but assimilates strongly in the infrared rays.

Carbon dioxide is produced by all microorganisms, animals, plants and fungi during respiration and is used by plants during photosynthesis to make sugars which may either be consumed again in respiration or used as the raw material for plant growth. Thus, carbon dioxide is a major component of the carbon cycle. Carbon dioxide is generated as a by-product of the burning of fossil fuels or vegetable matter, among other chemical procedures. Inorganic carbon dioxide is the output of volcanoes and other geothermal processes like hot springs etc.

Production of CO₂
Carbon dioxide can be obtained out of the following six processes :-

• From thermal decomposition of limestone, CaCO3, in the manufacture of lime,ie, CaO.
  
  
• As a byproduct of sodium phosphate manufacturing process.
  
  
• CO₂ emerges as a byproduct in ammonia and hydrogen plants, where methane is converted to CO2.
  
  
• From combustion of wood, fossil and petro fuels like deisel, kerosene, natural gas etc.
  
  
• As a byproduct of fermentation of sugar in the brewing of whiskey, beer and other alcoholic beverages.
  
  
• Directly from natural carbon dioxide springs, where it is produced by the action of acidified water on limestone.

Uses of CO₂
Carbon dioxide has a vast field of applications. Following are few uses of CO2 :-

• Carbon dioxide extinguishes flames, and some fire extinguishers, especially those designed for electrical fires, contain liquid carbon dioxide under pressure
  
  
• Carbon dioxide is used to produce carbonated soft drinks and soda water.
  
  
• Carbon dioxide is the most commonly used compressed gas for pneumatic systems in portable pressure tools and combat robots.
  
  
• Liquid carbon dioxide is a good solvent for many organic compounds.
  
  
• Carbon dioxide are important refrigerants, especially in the food industry, where they are employed during the transportation and storage of ice cream and other frozen foods. Solid carbon dioxide is called "dry ice" and is used for small shipments where refrigeration equipment is not practical.
  
  
• Carbon dioxide also plays an important role in Photosynthesis.
  
  
• Plants require carbon dioxide to conduct photosynthesis, and greenhouses may enrich their atmospheres with additional CO2 to boost plant growth.
  
  
• Carbon dioxide can also be combined with limonene oxide from orange peels or other epoxides to create polymers and plastics.