By Jeffrey Winters
If there’s one constant in discussions of future power production, it’s that no matter what, we’ll be burning coal. Compared to current consumption, the coal resource is usually spoken about in multi-generational terms—a 100-year supply, a 250-year supply, a 500-year supply. At the very least, there’s supposed to be enough coal that we don’t have to think about it.
The abundance of coal is taken so much for granted that the very idea of “peak coal”—an upper limit to production similar to what has been predicted for oil—is the stuff of doomsayers. And yet in August, Tadeusz Patzek, the head of the petroleum and geosystems engineering department at the University of Texas in Austin, made that very forecast. More astonishing, Patzek predicted that world coal production would begin to decline not in two or three decades, but next year or shortly thereafter.
Like all projections of this sort, Patzek’s is only as good as his methodology. Patzek uses a technique, Hubbert linearization, that has found favor among some petroleum geologists of late. In very simple terms, the Hubbert linearization begins with the assumption that for a depleting resource such as petroleum, the amount of the resource that may be ultimately recovered is related to the current production rate, the cumulative production, and the change in the production rate. As a newly drilled field is exploited, the production increases, and it is hard to get a fix on just what the ultimately recoverable resource will be. But once production nears and then passes the half-way point, the plot of the current production as a fraction of cumulative production versus the cumulative production will produce a fairly clear downward trend.
It also turns out that once production nears half of the recoverable resource, production reaches a peak; graphically, it looks like a bell curve.
The linearization technique works for entire fields, and was used by Marion King Hubbert to predict the decline in U.S. oil production that began in the 1970s. Some geologists applying Hubbert linearization on global petroleum production data have claimed that crude oil production will peak in the next five years, if it hasn’t already.
Patzek and his co-author, Gregory Croft of the University of California, Berkeley, examine the production rates for major coal producing regions and then utilize Hubbert linearization to project future production rates. Some countries, such as Australia and Mongolia, look to be able to produce coal at high rates for decades to come. But global production is so dominated by China and the United States that once those nations peak, it’s a quick and steady decline for coal production overall. Indeed, Patzek and Croft conclude that by 2050 worldwide coal production will be half of what it is now.
It’s easy to generate a linearization of world oil production figures, but the pattern doesn’t show up in widely available world coal production data. The regional nature of the coal industry may present problems for worldwide analysis. Patzek and Croft emphasized that they were deriving Hubbert curves for each coal-producing region and then aggregating them into a global estimate.
Even so, it’s possible that Hubbert linearization doesn’t work as well on coal production as it does on petroleum. Oil producers tend to pump all they can, as fast as they can. Coal fields, on the other hand, have been left idle in the United States and the United Kingdom because the minerals they contained were either sulfur-laden or simply uneconomical. Were coal production to decline, those mines would likely be reopened and new technologies would be exploited.
Given the critical role coal plays today, it seems hard to believe that we won’t rip apart every mountainside rather than accept its disappearance.