Energy Return On Investment

Energy Return On Investment (EROI) is an important concept theoretically, but I haven't run across a lot of solid data that show the EROIs for various fossil fuels or how they have changed over time. I created the graph below based on data quoted in this post on the web site of The Oil Drum. If and when I come upon other data, I'll post them for review and comparison.

EROI expresses the amount of energy that is received for a unit of energy invested - the amount of "bang for the buck," so to speak. Obviously, the higher this ratio, the better. One of the unique characteristics of oil as a fuel is that this ratio has historically been quite high. It has apparently been declining, reflective of the fact that the energy costs of extracting the oil have been increasing. (This makes intuitive sense, since one would expect that the easy-to-get oil would be pumped before the harder-to-get oil and that over time, the harder-to-get stuff would make up a greater proportion of the remaining reserves.)

Clearly, if the ratio were to drop below 1, it would make no sense to get the oil, no matter how much of it remained.