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The Carbon Cycle: Its everywhere you want to be..

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Photosynthesis

Photosynthesis is the process by which plants absorb the sunlight, store it, and convert it into energy to grow and survive. It is represented by the following equation, where the plant takes in Carbon Dioxide and Water, stores and uses the glucose to grow and live, and releases Oxygen back into the environment.

6 CO₂ + 6 H₂O energy C₆H₁₂O₆ + 6 O₂

The energy is supplied by solar energy (sun light). The glucose (C₆H₁₂O₆) is used by the plant as a storage medium for the energy. As the plant grows it will use the glucose to supply the plant with energy.

Decay

When plants die, this process simply works in reverse.

C₆H₁₂O₆ + 6 O₂ decay 6 CO₂ + 6 H₂O

Source: JPM Photosynthesis and decay in the same picture! Splendid!

Walking through almost any forest is the best way to witness the decaying process in action. The ground is generally strewn with dead and decaying leaves, limbs, branches, and sometimes entire trees. If they did not decay, we would be faced with a serious dead-tree population problem in our forests. Then imagine the scope of this problem times millions of years. This helps illustrate, the nature and the value of the carbon cycle.

However, in Pennsylvania about 320 million years ago (and even today) the forests did not decay. Instead, the trees fell into swamps (bogs) and were protected from the decay process. Eventually these trees formed coal, and in the oceans, plankton and algae went through similar processes. There, the stored solar energy eventually formed oil (protection from oxygen at the bottom of the ocean, with sediment burial). Now as we use the fossil fuels (combustion) we release CO₂ back into the atmosphere.

Want to see a swamp?

Click on the speaker icon to listen to this audio file about Bear Meadows. (Text Version)

So What?

The carbon cycles tells us that CO₂ in the atmosphere is in equilibrium with the CO₂ in the oceans and CO₂ in the atmosphere is also in equilibrium with the CO₂ chemically bound within minerals (carbonates like CaCO₃ calcium carbonate, otherwise known as limestone).

Equilibrium () indicates that eventually the chemical reaction will balance such that the forward reaction and the backward reaction both occur a the same rate and so at certain conditions, a certain ratio is achieved (for example 60:40 or 60 percent of a reactant on the left hand side of the reaction and 40 percent in another chemical form on the right hand side of the reaction). The key issue however is that the equilibrium may be reached slowly (thousands of years) or very fast (a fraction of a second). Kinetics decides how fast the reactions will occur (recall discussion on catalytic converters).
Lifetime of greenhouse gases can be very long (slow to reach equilibrium):

Thus, burning fossil fuels will increase the concentration of the greenhouse gases in the atmosphere, and enhance the greenhouse effect, which in turn will increase the global temperature, possibly.