Carbon sequestration is a method used to remove unwanted carbon dioxide, which is a greenhouse gas, from our atmosphere. Carbon dioxide and other greenhouse gases contribute to the greenhouse effect that results in the warming of the earth. To sequester carbon is to remove it from our atmosphere by effectively storing it for the long term. This can be done by encouraging the natural processes that remove carbon dioxide from our atmosphere. Just as we breathe in oxygen and exhale carbon dioxide, all plants take carbon dioxide in and emit oxygen. In this way, plants are an effective form of carbon sequestration.
Forests are often referred to as "carbon sinks" because they store carbon dioxide so effectively. When they are cut down, this carbon is eventually released back into our atmosphere as the wood is burned or decays. The use of forests as effective sequestration methods acts as an argument against deforestation. Some scientists believe it may one day be possible to sequester carbon by capturing it and piping it deep into the rock layers of our earth for storage. This is still a controversial and largely unstudied idea, but could be mentioned to your students.
To illustrate to your students how carbon dioxide builds up in our atmosphere, do a simple science experiment. You will need a balloon, four Alka-seltzer tablets, scissors, Plasticine or a type of putty, an empty peanut butter jar and plastic water bottle, plastic aquarium tubing, and quick lime. First poke two holes that will fit the plastic aquarium tubing into the lid of the peanut butter jar. Pour a teaspoon of quick lime into the peanut butter jar and add warm tap water. Thread the tubing through the two holes and secure them with putty so no air will escape. One should be long enough to almost reach to the bottom of the jar. Poke a hole in the lid of the water bottle and thread the long tubing through it so that one end of the long tubing resides in each container. Take the second shorter piece of tubing and affix a balloon to the end of it with a piece of putty. The balloon will capture the carbon and act as our example of carbon sequestration.
Once you have built your carbon sequestration experiment you can add the four alka seltzer tablets to the water bottle. Quickly screw the water bottle's lid back on and watch the balloon grow. The balloon is capturing all the carbon dioxide emitted by the reaction between the alka seltzer tablets and the quick lime solution. The balloon is acting like a forest does. Once the balloon is quite full (and before it begins to deflate as the experiment ends) hold it tight and pop it. Tell your students that you popping the balloon represents burning or decaying wood. Ask your students what happened to the carbon dioxide and explain to them that it has been released back into our atmosphere, just as it would if the balloon really were a burning or decaying tree.