As reported over at Worldchanging;
"The More Oil We Use, The More Oil it Takes to Get Oil...
David Murphy at The Oil Drum gave an interesting analysis of the Net Hubbert Curve this week. He bases his predictions on a report from Cutler Cleveland of Boston University about the sharp decline in EROI (energy return on investment) -- in other words, it now requires much more energy to extract energy that we can use. Specifically, the report says, EROI has declined (in the U.S.) from 100:1 in the 1930s to 11:1 as of 2000.
How did we go from spending 1 barrel of oil per 100 to spending the same amount for a mere 11? Well, Murphy explains, as we use more and more of the world's oil reserves, the remaining oil is much more difficult to extract. This we knew. But Murphy takes this equation to the Hubbert Curve to produce an new curve, showing that post-peak oil, we don't actually have half the world's reserves left in net energy. We actually have much less.
Figure 3 shows the results of this analysis. Unlike the original Hubbert curve that shows equal quantities of gross energy resources on the left and right side, the Net Hubbert Curve is skewed so that most resources are on the left. For example, according to the original Hubbert curve, 50% of the energy resource is remaining when production levels reach the peak, but this is quite different for the Net Hubbert curve. Due to declining EROI, by the time peak production is reached, 73% of the net energy available is already used.
The implications of these results are vast, but in general, declining EROI is going to make it very difficult to meet the net energy needs of future society. Although this study may not be very precise, it does imply that if we have reached Peak Oil (and I think we have), that society has already spent quite a bit more than half of the net (or discretionary) oil energy that will ever be available."