With efforts in the Gulf of Mexico to permanently kill-or more specifically- “bottom kill” the Deepwater Horizon well that caused the world’s largest accidental oil spill in history, I thought it might be interesting to investigate how much of that oil will eventually be broken down-naturally. 

As “nasty” as the oil may look, or may be portrayed in the media, the simple fact of the matter is this: the oil will be, over time, naturally broken down by microbes (microscopic organisms).  This process is referred to as biodegradation.  Over time, any organic material (any material containing carbon atoms) can be broken down by microbes and invertebrates in the environment.  A great set of fact sheets about the oil spill can be found here 

You may find it interesting that annually, more than 20 million gallons of oil spill into the Gulf of Mexico from natural seeps.  By comparison, the Deepwater Horizon spill released over 211 million gallons.  Oil is made up of hydrocarbons-which is just a fancy way of describing an organic compound made up of hydrogen and carbon.  These hydrocarbons can be broken down by microbes and invertebrates, but there are some limiting factors.  For example, it has been discovered that aerobic biodegradation (biodegradation requiring oxygen) is much more efficient than anaerobic (no oxygen required) biodegradation.  A great example of this can be found in this article about the Exxon Valdez Oil Spill from 1989.  That article describes how low concentrations of oxygen are contributing to a very slow breakdown of the remaining oil in the Prince William Sound of Alaska.  Along those very same lines, the oil that made it inland into the sediment along the Gulf will have a much tougher time getting broken down due to the anoxic (not containing oxygen) environment of the sediment.

Another item that can speed up the process are the addition of dispersants to the oil spill.  These dispersants help to break up the oil into smaller droplets, which ultimately increases the surface area upon which the microbes can access.

Much more reading on some of the effects of the spill is available in this article.