Carbon Cycle

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Carbon Cycle
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Since carbon is the major ingredient in fossil fuels, it is relevant to discuss
 +
the carbon balance in the atmosphere. Carbon exists primarily in the form
 +
of carbon dioxide, which is present in the air, dissolved in ocean water,
 +
or trapped in rocks and in plants through photosynthetic processes (See
 +
Chapter 7). Animals (including humans) consume plants as a source of
 +
nutrients and are part of the carbon cycle as well.
 +
Depending on the ultimate fate of dead animals and plants, carbon may
 +
return to the atmosphere as carbon dioxide or turn into fossil fuel. If the
 +
environment dries up, dead plants and animals will become exposed
 +
to air and react with it to produce carbon dioxide, thus completing the
 +
carbon cycle (Figure 7-2). However, if the environment is fl ooded with
 +
mud, stagnant water, silt, or sand, oxygen is cut off and the proteins
 +
and carbohydrates decompose from bacteria into a wax-like, organic,
 +
insoluble material called kerogen.2 Th e time it takes for kerogen to
 +
transform into fossil fuel ranges from tens to hundreds of millions of years,
 +
and depends on its depth in the ground, temperature, and pressure.
 +
Whether a fossil ultimately ends up as coal, oil, or gas depends on the
 +
original constituents of the kerogen and the conditions under which it
 +
is kept. If the origin of kerogen is from giant plants and stronger parts of
 +
plants such as lignin (material that strengthens the trunks and branches
 +
of trees), then carbon forms into very complicated structures and rings.
 +
Th ese rings eventually connect together into a graphitic structure called
 +
coal. If the kerogen is formed from algae or plankton, they break into
 +
shorter chains that depending on their lengths, become a mixture of
 +
liquids (crude oil) and gases (natural gas). Th e deeper in the earth and
 +
more aged the kerogen, the greater the probability that the chains will
 +
break into lighter materials and a higher fraction of the kerogen will be in
 +
the form of natural gas. Th e carbon cycle is completed when fossil fuels
 +
are extracted and burned to form carbon dioxide and water.
==References==
==References==

Revision as of 00:02, 29 June 2010

Carbon Cycle Since carbon is the major ingredient in fossil fuels, it is relevant to discuss the carbon balance in the atmosphere. Carbon exists primarily in the form of carbon dioxide, which is present in the air, dissolved in ocean water, or trapped in rocks and in plants through photosynthetic processes (See Chapter 7). Animals (including humans) consume plants as a source of nutrients and are part of the carbon cycle as well. Depending on the ultimate fate of dead animals and plants, carbon may return to the atmosphere as carbon dioxide or turn into fossil fuel. If the environment dries up, dead plants and animals will become exposed to air and react with it to produce carbon dioxide, thus completing the carbon cycle (Figure 7-2). However, if the environment is fl ooded with mud, stagnant water, silt, or sand, oxygen is cut off and the proteins and carbohydrates decompose from bacteria into a wax-like, organic, insoluble material called kerogen.2 Th e time it takes for kerogen to transform into fossil fuel ranges from tens to hundreds of millions of years, and depends on its depth in the ground, temperature, and pressure. Whether a fossil ultimately ends up as coal, oil, or gas depends on the original constituents of the kerogen and the conditions under which it is kept. If the origin of kerogen is from giant plants and stronger parts of plants such as lignin (material that strengthens the trunks and branches of trees), then carbon forms into very complicated structures and rings. Th ese rings eventually connect together into a graphitic structure called coal. If the kerogen is formed from algae or plankton, they break into shorter chains that depending on their lengths, become a mixture of liquids (crude oil) and gases (natural gas). Th e deeper in the earth and more aged the kerogen, the greater the probability that the chains will break into lighter materials and a higher fraction of the kerogen will be in the form of natural gas. Th e carbon cycle is completed when fossil fuels are extracted and burned to form carbon dioxide and water.

References

Further Reading

External Links