Saturday, 27 June 2009

Need for renewables more urgent than previously thought

Peak Oil is the name of the time when the amount of oil that we've already used up is approximately equal to the amount of oil recoverable left in the ground. Many serious commentators believe that point was reached in 2008. After Peak Oil, fossil fuel will steadily become not only less available but also (because of market economics) increasingly expensive. The conventional shape of the Hubbert graph is the symmetrical volcano shape (coloured blue) in the image below.

The story I reproduce below takes into the calculations the fact that the amount of energy it takes to find and extract the remaining reserves is rapidly increasing. In 1930 we got out around 100 barrels of oil for every barrel of oil equivalent of energy that we used to get it out of the ground - a ratio of 100:1. By 1970 that was down to 30:1 and by 2000 it was only 11:1. All the low hanging fruit of easy shallow reserves, that gushed like they did in fifties movies, have probably been discovered. Reserves yet to be exploited take far more energy and difficulty to get the goods to the surface. Because of this, it's mathematically predictable that at some point the amount of energy needed to bring one barrel of oil to the surface will be one barrel of oil equivalent, at which point there will be absolutely no point in doing it any more because there will be little or no gain in doing so.

If one plugs this idea into a Hubbert’s peak graph, one gets a real sense of where we are in exploiting the main fossil fuel reserves of Earth and the resultant graph shape shows that the drop off in production will be much faster, and will arrive much earlier, than the conventional graph suggests. The grey coloured "net Hubbert curve" suggests that productive oil extraction will have fallen by more than 90% by as soon as 2035 -the conventional Hubbert curve did not have oil production falling this far until after 2110! Yikes! Of course the assumptions made by the author may be wrong but the results of his calculations make it seem likely that we have actually used up 73% of the productively recoverable fuel already.

The post: taken from JL's post on the World Changing blog

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.


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