The media, politicians and environmentalists throw around terms like "carbon footprint," "CO2 emissions," and "carbon tax" as if we all know what they mean. Fact of the matter is, very few people who use those words even know what they mean.
Carbon is the fourth most common element on earth (behind hydrogen, helium, and oxygen). We are, as you may remember from high school biology, carbon-based life forms. The amount of carbon on earth is pretty much constant. So what's all the fuss about?
Carbon occurs in lots of different forms. When it is acting as the second most abundant part of our human bodies (behind oxygen), we need it. When it is in diamonds, we covet it. When it is in coal or oil, we burn it. When it is the carbon in carbon dioxide (CO2) or the carbon in methane (CH4) that is where the discussion of carbon footprints comes in.
Carbon changes between its various manifestations through a biogeochemical cycle. This means that the chemical element called carbon moves through both the living (bio-) and non-living (geo) parts of earth's ecosystem. There are some "sinks" along the way that hold carbon for a period of time before it returns to the cycle, at which point the sink becomes a "source." A growing tree for example is a sink while it is taking carbon dioxide out of the atmosphere and converting the carbon into tree matter. Once the tree dies or is cut down it becomes a source of carbon. If it naturally decays, some of the decay becomes methane gas for instance. If the tree is burned, some of it becomes carbon dioxide. This is all part of the carbon cycle.
Another sink is fossil fuel. When carbon-based life forms decompose and eventually (over millions of years) turn into oil wells, all of that carbon is stored up in the oil. When the oil is burned, the carbon bonds with oxygen and creates gaseous carbon dioxide. This is where the cycle gets out of balance. It took millions of years to slowly collect the concentrated carbon in the fossil fuels. Burning them releases the carbon much faster than it was created. So, until we can figure out how to push the carbon back into a sink as fast as we source the carbon through burning, the cycle will continue to be out of whack.
This line of thought provides a nice sanity check on our greener living decisions. For instance, this shows us that planting trees should not be viewed as a one-to-one offset for burning fossil fuels because when trees die they ultimately produce just as much carbon as they removed. So what does make sense? Reducing our energy use! Perhaps technology will eventually bring us a carbon sink that allows us to remove or sequester the greenhouse gases as fast as we source them, but until then let's focus on doing what we can to slow down the unbalancing.
Does this make sense? Was it valuable to you? Did I miss anything? Please let me know in the comments. I'll dive into the actual math behind the "pounds of CO2" that make up our carbon footprint in a later post.
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