“The United States is the Saudi Arabia of coal.” This claim has become routine for presidential candidates, including Rudy Giuliani, Rick Perry, Hillary Clinton, and Barack Obama. There is some truth to this statement. The United States has estimated coal reserves of 260 billion tons which, at current usage rates, would last about 200 years. If that were the complete story then this would be a very short blog, but there are some other things you need to know.
Coal, like petroleum, was formed from ancient plants which were buried and converted over the millennia to today’s fossil fuels.   Petroleum comes from algae and bacteria, starting materials which could be converted to liquid crude oil. Coal comes from more fibrous land plants like ferns and bushes. Time, pressure, and heat converted these more complex plants into coal. 
The composition of coal varies from place to place based on which plants lived in that area hundreds of millions of years ago.   These variations result in differing amounts of impurities, like sulfur or mercury, and also variations in the energy content of the coal. These variations are essential to understanding the energy and environmental challenges that we face in the 21st century, but apparently are something to gloss over if you are running for president.
The various types of coal in the US are divided into four categories; anthracite, bituminous, sub-bituminous, and lignite. By far, the largest use of coal is for electricity generation. (See my earlier blog “Electricity Production 101” for more details.) Anthracite is the good stuff, low in impurities, high in energy content. Unfortunately, the peak for production of anthracite coal in the US occurred in 1914. Below is a graph of the production of coal, including both the total and the breakdown by category, in the United States from 1949 forward using data from the U.S. Energy Information Agency.

You can see from the purple line that anthracite is no longer a large portion of coal mined in the US. For many decades, nearly all of the coal mined in the US was bituminous, the dark blue line on the graph. Starting in the 1960s, when energy demand could no longer be met with bituminous coal, we began to extract sub-bituminous coal (whose name gives you some idea of its quality) and lignite coal. The reason coal miners extracted the bituminous coal first was due to its high energy content. The table below shows the energy content of the four grades of coal.
If you look at the blue line in the graph above you will see that peak production of bituminous coal occurred in about 1990. The shift to lesser grades of coal results in an easily calculated reduction in the average energy content of US coal with time, as shown in the graph below.

As time moves forward this trend is only going to continue, requiring us to mine more and more coal simply to maintain the amount of electricity we use today, let alone the increased electricity demand projected for the future. 
This trend towards lower-quality fossil fuels sources is universal. Just as the coal industry is becoming reliant on sub-bituminous coal, the oil industry is pursuing low quality oil sands and shale oil and the natural gas industry is chasing deeper, more difficult to reach sources through a technique called fracking. (For more on shale oil see my blog “A Science Question for Michele Bachmann” and for more on fracking see my blog “To Frack or Not to Frack”.)
There are few, if any issues, which will have more impact on the future economic and environmental health of the nation than the ongoing limitations which we are already experiencing in energy sources. Despite the importance of these issues to our national well being, even in our presidential elections we can’t seem to maintain the maturity and focus to examine these important and troubling trends and their implications. It seems that the topic is just to troubling for us to confront.   So perhaps instead of being the Saudi Arabia of coal we are the Saudi Arabia of denial.
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