Tuesday, December 22, 2009


THE CARBON CYCLE is the cycle by which carbon is exchanged among the atmosphere of the Earth.

One of the process by which carbon is exchanged among the atmosphere of the Earth is through the combustion of organic material (i.e,
wood, eggs, carrots, human flesh etc. ) which oxidizes the carbon it contains, producing carbon dioxide. Burning fossil fuels such as coal, petroleum products, and natural gas releases carbon that has been stored in the geosphere for millions of years. Burning agrofuels also releases carbon dioxide which has been stored for only a few years or less.
Word equation: Fuel + Oxygen -> Heat + Water + Carbon dioxide

Another process
is through respiration, which is performed by plants and animals. This is an exothermic reaction and it involves the breaking down of glucose,
C6H12O6 (or other organic molecules) into carbon dioxide and water.

Carbon Respiration
Carbon respiration
is a phrase used in combination with carbon storage to calculate the amount of carbon (as carbon accumulation), and formation of minerals such as coal.

The calculation of the annual net difference between carbon respiration and carbon storage constitutes the annual global atmospheric carbon accumulation rate. Using this method, the annual carbon flux ratio has been calculated to be approaching zero. This means that the carbon respiration rate and carbon storage rate are in balance when generating a global estimate of this figure.

Annual net carbon flux has been grossly calculated to be close to zero, implying the respiration and storage rates are roughly in balance worldwide. This finding is contradicted by measuring the concentrations of carbon dioxide in the atmosphere, an important indication that the balance is tipped toward emission. Using this data atmospheric concentrations appear to have increased rapidly over the past 100 years and are currently higher than ever in human history. This suggests that more carbon is being released than can be absorbed on earth.

Cellular respiration
Respiration is a process where cells releases the energy contained in sugars for use in and changes carbohydrate “fuel” back into carbon dioxide, which is in turn released to back to the atmosphere.

Word equation:
Glucose + Oxygen -> Carbon Dioxide + Water + Energy

Chemical equation:
6H12O6 + 6O2 -> 6CO2 + 6 H2O + energy

Lastly, carbon in the atmosphere is exhanged by photosynthesis.

During photosynthesis, green plants/trees use solar energy to convert atmospheric carbon dioxide into carbohydrates (sugars), releasing oxygen in the process. Plants and animals use these carbohydrates (and other products derived from them) through respiration.

The amount of carbon taken up by photosynthesis and released back to the atmosphere by respiration each year is about 1,000 times greater than the amount of carbon that moves through the geological cycle on an annual basis.

Word equation: Carbon Dioxide + Water ------> Glucose + Oxygen
Sunlight energy
Chemical equation: 6CO2 + 6H2O ------> C6H12O6 + 6O2

How photosynthesis and cellular respiration are linked in the carbon cycle.

Plants convert the carbon in atmospheric carbon dioxide into carbon-containing organic compounds, such as sugars, fats, and proteins. Plants take in carbon dioxide through microscopic openings in their leaves, called stomata. They combine atmospheric carbon with water and manufacture organic compounds, using energy trapped from sunlight in a process called photosynthesis. The by-product of photosynthesis is oxygen, which plants release into the atmosphere through the stomata.

Animals that eat these plants, or that eat other animals which have consumed the plants, incorporate the carbon in the sugars, fats, and proteins derived from the ingested biomass into their bodies. Inside their cells, energy is extracted from the food in a process called cellular respiration. Cellular respiration requires oxygen (which is the by-product of photosynthesis) and it produces carbon dioxide, which is used in photosynthesis. In this way, photosynthesis and cellular respiration are linked in the carbon cycle.

How the carbon cycle regulates the amount of carbon dioxide in the atmostphere?

1. Respiration performed by plants and animals. Carbon dioxide and water are given out when glucose (or other organic molecules) are being broken down, causing heat to be given out.

2. The decaying of animal and plant matter. The fungi and bacteria break down the carbon compounds in dead animals and plants, converting the carbon to carbon dioxide if oxygen is present, or methane if not.

Combustion of organic material which oxidizes the carbon it contains, Burning fossil fuels such as coal, petroleum products, and natural gas releases carbon into the atmosphere. Burning agrofuels also releases carbon dioxide which has been stored for only a few years or less.

Production of cement. Carbon dioxide is released when limestone (calcium carbonate) is heated to produce lime (calcium oxide), a component of cement.

At the surface of the oceans where the water becomes warmer, dissolved carbon dioxide is released back into the atmosphere.

Volcanic eruptions and metamorphism release gases such as water vapour carbon dioxide and sulfur dioxide into the atmosphere. The amount of carbon dioxide released is roughly equal to the amount removed by silicate weathering [citation needed]; so the two processes, which are the chemical reverse of each other, sum to roughly zero, and do not affect the level of atmospheric carbon dioxide on time scales of less than about 100,000 years.

asically, how does greenhouse gases cause global warming is that it selectively allows the heat waves to pass through and those that don’t would remain in our atmosphere. This would then cause the temperature to rise and in turn cause global warming. Both Carbon dioxide ( CO₂ ) and Methane (
CH₄ ) are greenhouse gases and would thus cause global warming.

Sources of Methane (CH₄ ) and Carbon dioxide ( CO₂ )

Carbon dioxide

Carbon Dioxide (CO₂) is a colourless, odorless non-flammable gas and is the most prominent Greenhouse gas in Earth's atmosphere. Several sources of this greenhouse gases are :

1. Animals and plants

Both animals and plants take in oxygen and give out carbon dioxide during respiration and thus is one of the main source of carbon dioxide on earth.

2. Deforestation

Trees take in carbon dioxide during photosynthesis and give out oxygen, this is part of recycling of carbon dioxide. With more trees being chopped or burned down, there would be lesser trees to take part in the exchange of gases and there would be more carbon dioxide in our atmosphere. To add on, the burning of trees would also increase the emission of carbon dioxide to our atmosphere and as such explains why deforestation is a source of carbon dioxide.

3. Vehicles and machines

Cars and machines burn petroleum to produce energy for them to operate. Burning of Petroleum produces Carbon dioxide. And as the technology would gets more advance, the use of cars and machineries are more convenient and common as such , this is one of the main source of carbon dioxide .

Other sources of carbon dioxide includes; Volcanic eruptions, Ocean-atmosphere exchange, burning of fossil fuel and more.


Methane is a colourless, odourless, flammable gas. It is formed when plants decay and where there is very little air. Sources of Methane are as follows.

1. Fossil fuel mining/distribution

Methane is released whenever fossil fuels are extracted from our earth. During transportation and refinement of the fossil fuels, more methane is emitted to our atmosphere and thus fossil fuel mining/distribution is a source of methane. In fact, it is one of the main sources as fossil fuels are in demand.

2. Livestock

Farm animals emit methane during digestion or from their manure. Firstly, for animals like cows, sheep and goats, methane is produced as a by-product during digestion due to the occurrence of enteric fermentation in the stomach of these animals

The second way they can create methane emission is from their manure. In farms , large amount of manure are produced by these animals and to manage all these manure, they are treated by waste treatment system and then stored in holding tanks. In the enclosed tanks, the manure decomposes anaerobically and large amount of methane is produced.

Other sources of methane emission includes, wildfire, termites, wetland, landfills, mobile combustion, rice cultivation and more.

Video on carbon cycle!