What Is CO2?
Carbon dioxide is a naturally occurring substance composed of one atom of carbon (C) and two atoms of oxygen (O2). Its chemical formula is CO2.
CO2 is gas under normal conditions
CO2 occurs naturally in small amounts (about 0.04%) in the Earth's atmosphere.1
As a major greenhouse gas, CO2 helps create and maintain the natural greenhouse effect
that keeps our planet hospitable to life.
CO2 is essential to plant life. Plants take in CO2, exhale the oxygen, and use the carbon to live and grow. When the plant dies
or burns, the carbon recombines with oxygen in the atmosphere, and CO2 is formed again. This process is a key part of the global
CO2 is a by-product of our body’s metabolism. Our lungs absorb oxygen from the air we breathe and exhale CO2 as a waste product of
CO2 is produced naturally by processes deep in the earth. This CO2 might be trapped in
underground geologic CO2 deposits similar to the underground deposits of oil and natural gas. Or it might be released at the surface by volcanoes
or through natural ground seeps.
Naturally carbonated waters have historically been highly sought after for their supposed curative properties because these waters
are high in mineral content.
Some bottled water is from naturally carbonated springs. Some examples are Apollinaris, Badoit, Gerolsteiner, Wattwiller, Ferrarelle,
Borsec, and Perrier.
CO2 is added to soft drinks to make them bubbly.
Dry ice (frozen CO2) is used to keep things cold.
CO2 is also used in fire extinguishers (CO2 displaces the oxygen the fire needs to burn).
Every day, millions of tons of CO2 are injected into underground geologic zones to help produce oil in a well-known industry practice
called "CO2 flooding" or enhanced oil recovery.
CO2 formed by human action is called anthropogenic CO2. Plowing the land, making cement, and burning fossil fuels for energy all create
anthropogenic CO2, which adds carbon to the global carbon cycle. Between 1751 and 2013, approximately 1440 billion metric tons of CO2 has been emitted to
the atmosphere from these sources.2 This is raising concerns about climate change.
The U.S. Environmental Protection Agency has ruled CO2 a pollutant in order to be able to regulate anthropogenic CO2 emissions from human
activities under the Clean Air Act of 1970.
Energy, CO2, and Our
nssdc.gsfc.nasa.gov/planetary/factsheet/earthfact.html (accessed August 2006).
Boden, T.A., Marland, G., and Andres, R.J., 2016, Global, regional, and national fossil-fuel CO2 emissions: Carbon Dioxide Information Analysis Center,
Oak Ridge National Laboratory, U.S. Department of Energy, Oak Ridge, Tennessee, U.S.A. doi 10.3334/CDIAC/00001_V2016,
http://cdiac.ornl.gov/trends/emis/tre_glob_2013.html (accessed June 16, 2016).