We’ve heard a lot about “peak oil” in the last few years, but coal industry officials and their supporters are always quick to tell us we have hundreds of years of coal left in the ground.

But now, some researchers are starting to strongly question this assumption.

I first wrote about this issue in June 2007, when the National Research Council published a report which warned that federal policymakers did not have accurate estimates of the amount, location and quality of mineable coal:

It is clear that there is enough coal at current rates of production to meet anticipated needs through 2030, and probably enough for 100 years.  However, it is not possible to confirm the often-quoted assertion that there is a sufficient supply for the next 250 years.

More recently, Joe Romm’s Climate Progress blog made me aware of a U.S. Geological Survey study which  warned that all was not well in Powder River Basin of Wyoming, the nation’s most productive coalfield:

The total original coal resource in the Gillette coalfield for all eleven coal beds assessed, and no restrictions applied, was calculated to be 201 billion short tons. Available coal resources, which are part of the original coal resource that is accessible for potential mine development after subtracting all restrictions, are about 164 billion short tons (81 percent of the original coal resource).

Recoverable coal, which is the portion of available coal remaining after subtracting mining and processing losses, was determined for a stripping ratio of 10:1 or less. After mining and processing losses were subtracted, a total of 77 billion short tons of coal were calculated (48 percent of the original coal resource).

Coal reserves are the portion of the recoverable coal that can be mined, processed, and marketed at a profit at the time of the economic evaluation. With a discounted cash flow at 8 percent rate of return, the coal reserves estimate for the Gillette coalfield is10.1 billion short tons of coal (6 percent of the original resource total) for the 6 coal beds evaluated.

Then today, the group Clean Energy Action has issued a report further questioning the oft-cited optimistic estimates of the nation’s existing coal reserves.

“Americans often assert that there is a ‘200-year supply’ of coal in the United States, but the truth is almost no one has ever investigated the claim,” says the report’s author, Leslie Glustrom, a member of the Colorado-based group. Among the findings:

It appears that rather than having a “200-year-supply of coal”, the United States has a much shorter planning horizon for moving beyond coal-fired power plants. Depending on the resolution of geologic, economic, legal and transportation constraints facing future coal mine expansion, the planning horizon for moving beyond coal could be as short as 20-30 years.

Read more discussion of this at Climate Progress, and  thanks to Tom Rodd and his Appalachian Coalfields Climate Change Forum, for bringing the new study to my attention.