Because the US has the world’s largest coal reserves, it has sometimes been called "the Saudi Arabia of coal." It is the world’s second-largest coal producer, after China, but surpasses both the number three and four producer nations (India and Australia) by nearly a factor of three.
Wood was this nation’s primary fuel until the mid-1880s, when deforestation necessitated greater reliance on abundant coal resources. Coal then remained America’s main energy source until the 1930s, when it was overtaken by oil. Today coal fuels about 50 percent of US electricity production and provides about a quarter of the country’s total energy.
The US currently produces over a billion tons of coal per year, with quantities increasing annually. This is well over double the amount produced in 1960. However, due to a decline in the average amount of energy contained in each ton of coal produced (i.e., declining resource quality), the total amount of energy flowing into the US economy from coal is now falling, having peaked in 1998. This decline in energy content per unit of weight (also known as "heating value") amounts to more than 30 percent since 1955. It can partly be explained by the depletion of anthracite reserves and the nation’s increasing reliance on sub-bituminous coal and even lignite, a trend that began in the 1970s. But resource quality is declining even within each coal class.
Full article
