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Vol. 232 No. 5 |
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HENRY TERRELL, CONTRIBUTING NEWS EDITOR
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The hydrocarbon blip
The Anasazi people of the prehistoric American West built a civilization between about 800 and 1200 AD, centered around what is now the Four Corners area of New Mexico, Arizona, Colorado and Utah. The Anasazi, or more properly the Early Pueblo (“Anasazi” is a Navajo word meaning, approximately, “the enemies of our ancestors”) experienced a Golden Age of sorts, characterized by rapidly rising populations, sophisticated construction, pottery and art. They were also adept at road building, and their widely spaced communities were linked by a system of highways.
By the 13th century the Anasazi civilization was collapsing, almost as rapidly as it had formed. The villages became denuded of population and isolated from each other, and then abandoned. The last few generations built their homes along cliff walls, in more defensible positions, suggesting that hostile raids were becoming common. At Mesa Verde, Colorado, the last cliff house to be built can be precisely dated from tree-ring analysis of its ceiling beams. The year was 1300. Exactly. The year Dante turned 35 and Amsterdam was officially declared a city. Within a few years, the Anasazi were all gone, leaving behind tools, pots, mummies and a remarkably intact cliff city.
The early 20th century writer Willa Cather, in her novel The Professor’s House, romanticized their fate:
“They were probably wiped out, utterly exterminated, by some roving Indian tribe without culture or domestic virtues, some horde fell upon them for their hides and clothing and weapons, or from the mere love of slaughter. I feel sure that these brutal invaders never learned of the existence of this mesa, honeycombed with habitations. If they had come here, they would have destroyed. They killed and went their way . . . But what of the last survivors? It is possible that when autumn wore on, and no one returned from the farms, the aged banded together, went in search of their people, and perished in the plain.”
I don’t know the current scholarship on this subject, but I do remember that an anthropology teacher I had in college was dismissive of the sudden tragic demise theory. “It’s not so much of a mystery,” he said. “They ran out of firewood. There’s only so much wood up there, and it grows slowly. No fuel and nothing to replace it with. So they left.” I guess you’d call that Peak Firewood theory.
Whether you belong to AAPG or Earth First!, everyone agrees that human beings will run out of fossil fuels, sooner or later. (Well, there are “limitless abiogenic oil” proponents, a tiny but hopeful minority, but they don’t figure in regular energy conversations. See this column, December 2010.) The number and uncertainty of factors in the running-out equation are so great that answers are wide apart indeed. But you have to start somewhere.
How much oil is left? A number that gets tossed about is 1.2 trillion bbl. New discoveries are made regularly, but these have not kept up with declining production from mature fields, where most of the oil comes from. As prices rise, secondary, tertiary and quadrary production methods become economic. The rate of decline is also a matter of opinion, but a commonly used figure is 6–7% per year. With demand rising relentlessly as the developing countries enter the developed column, usage will rise and production will decline faster. There will come a day, say 50 years from now (optimistic scenario) when oil as fuel will cease to be an affordable option. Oil for chemicals and materials will last a lot longer, consumed in smaller quantities. So far, for the world’s plastics, there are few good substitutes (ceramics have been suggested as the Next Big Thing). But gasoline will be a specialized, niche fuel, bought in 5-gallon jerry cans by rich people who collect “classic” cars.
How much natural gas? Proven gas reserves are truly enormous, with the most recent estimates hovering in the 6,200–6,500-Tcf range. Even more than oil, gas is subject to changes brought by exploration and technology. One of the biggest obstacles in the way of economic gas production is the transportation problem. Pipeline grids have an advantage in that when they’re built they tend to stay built, and the more extensive their reach, the more out-of-the-way places can be exploited at a profit. But, again, the really easy gas is largely depleted, and the more problematic and difficult deposits will have to wait for better prices. (I don’t think they’ll have to wait that long.)
Anyway, by making a lot of vague assumptions, it is not unreasonable to suggest that natural gas will be practical to produce for 60–70 more years before being relegated to hobbyists.
You can’t leave out coal. The hydrocarbon era started with coal and will end with coal. Despite pressure from environmental interests, despite the maneuverings of parliaments and kings, coal use will only increase, and it’s already staggering. China alone consumes over 2.3 billion metric tons per year, and that figure goes up steadily. Even a heroic effort to develop alternative and renewable fuels will not slow down demand for the black rock. As oil peaks and falls, as natural gas approaches its sunset, coal will be the last fossil fuel. The world may indeed find a way to diminish and avoid its use—it may have to, long before the stocks are exhausted—but current scenarios give the world more than 250 years of remaining coal.
The blip. So 300 years from now the age of hydrocarbons will be over. Human civilization survives and finds some sort of equilibrium. Draw a graph beginning at the beginning. Just to have a place to start, put it at 10,000 BC, when the walls of Jericho were built. Then place the other end 8,000 years from now. In a chart that spans a page, the hydrocarbon age is a sharp little spike right in the middle.
As far as the human species goes, we either find more firewood, learn how to live without it, or we head south. 
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