this 16 minutes provides a clue
One trait that humans share with all organisms is that we use the easiest to obtain and highest-quality resources first. When we use the earth’s resources, we start with the deepest soils, the largest trees, and the richest fishing waters. That is, we naturally exploit the highest quality resources first.
At this point, I want to recall that oil is a finite natural resource, and because of this we find that individual oil fields and collections of oil fields exhibit a classic extraction profile that resembles a bell curve.
We can broaden this to create a generalized resource extraction profile, where we start with the closest, richest, most accessible, and highest grade resources first, before moving on to successively harder, poorer, thinner, or more distant resources. What this means is that over time, the energy required to obtain those resources goes up, as do the costs. About this, there can be no doubt.
Here’s an example. When we first came to this country, we were finding some pretty spectacular things just lying around, like this copper nugget. Soon those were all gone, and then we were onto smaller nuggets, and then onto copper ores that had the highest concentrations. Now?
Now we have things like the Bingham canyon mine in Utah. It is two and a half miles across and three-fourths of a mile deep, and it started out as a mountain. It sports a final ore concentration of 0.2%. Do you think we’d have gone to this effort if there were still massive copper nuggets lying around in stream beds? No way.
Let’s take a closer look. See that truck way down there? It’s fueled by petroleum; diesel, specifically. If we couldn’t spare the fuel to run that truck, what do you suppose we’d carry the ore out with? Donkeys? These trucks carry 255 tons/ per load. Suppose a donkey could carry 150 lbs. This means this truck carries the same in a single load as 3,400 donkeys. That’s quite a lot of donkeys.
My point here is that a hole in the ground a couple miles across and three fourths of a mile deep is a pretty spectacular display of the use of energy. When energy begins to get scarce, it seems unlikely to me that we’ll be digging too many more holes like it, which means copper will become scarce.
Now here’s where the concept gets interesting. The amount of energy and money that is required to extract any mineral or metal is a function of the ore grade. We would measure that as the percent of the ore that consists of the desired substance. So a 10% copper ore, for example, would consist of 10% copper and 90%, uh, other stuff. Like rock or something. If we plot out how much other stuff we have to extract and then dispose of in pursuit of our desired substance, we get a chart that looks like this. Look familiar to you yet? It should; it’s an exponential chart.
It tells us that if we had an ore body with only 0.2% copper in it, we’d need to mine 500 pounds of ore in order to extract one pound of copper. I used this particular value because that happens to be the concentration of the Bingham Canyon mine. This helps to explain why this hole is so big. It tells us that without these giant trucks, we probably wouldn’t be mining such low ore grades. It means that we are already on the far right edge of this bell curve, in terms of energy and cost.
Do we do this because we like the challenge of low ore grades? No, we do it because we’ve already high-graded all the other known ore bodies, and this is what we are down to. We do it because it is the best option left. We do it because, in only 200 years, we’ve already burned through all the better grades.
Let’s look at another example, coal. Coal production, as measured by tons mined, has been steadily growing at 2% per year since the 1940’s. This sort of stable, continuous, exponential growth is exactly what our economy and society demand. President Bush recently said we have 250 years of coal left, implying that this red arrow can continue in this direction for another 250 years. In other words, there is no urgency here; just a whole lot of coal waiting for us to come and get it.
But there’s a wrinkle in this story. Coal comes in several different grades. The most desirable is shiny, hard, black, anthracite coal. It yields the most heat when burned, has low moisture content, and is highly valued in the steel-making industry. Then comes bituminous, offering slightly less energy per pound of weight. Then subbituminous. And then finally something called lignite, which is really low energy/high moisture stuff that is pretty much only useful for burning. The next grade below lignite is, uh, rocks, which burn only slightly less vigorously than lignite.
Let’s look at the US history with mining anthracite. Notice a trend here? The reason we are not mining more of the stuff is because it’s pretty much all gone. Our entire bequeathment of anthracite, formed over hundreds of millions of years, was largely used over a span of about 100 years.
So we moved on to the next best stuff, bituminous coal, and here we might note that a peak in production was hit in 1990. Was this because we lost interest in this better grade of coal? No, it simply means we started to run out of it. Naturally, we then moved on to the next grade, subbituminous coal, which we see here making up the difference. And even lignite is getting into the game, although I wouldn’t expect to see that line really begin to move up until subbituminous coal production peaks out.
Now here’s the REALLY interesting part. Remember I said that the heat content, or available free energy, of coal got progressively worse with each grade? If we plot the total energy content of the coal mined, instead of the tonnage, we get a very different picture. Where the tonnage has been moving up in a nice neat 2% climb, we note that the total energy has leveled off and has climbed by exactly zero percent over the last 9 years. Ah! So we’re using energy and spending money to mine more and more coal, but we are receiving less and less back from those efforts? Let’s bring back this image again. Where do you think we are on this curve? Are the best years still in front of us? Do you feel secure with the “250 years of coal” that the President has said we have left?