Peak coal

The term Peak coal is used to refer to the point in time at which coal production and consumption reaches its maximum, after which, it is assumed, production and consumption will decline steadily. The term was originally used in connection with M. King Hubbert's Hubbert peak theory, in which the finite nature of the resource determines a constraint on production. However, since the expansion of renewable energy particularly in electricity generation, the term is now commonly used with reference to a peak in coal demand, which may already have occurred.

According to M. King Hubbert's Hubbert peak theory, Peak coal is the point in time at which the maximum global coal production rate is reached, after which, according to the theory, the rate of production will enter a terminal decline. Coal is a fossil fuel formed from plant matter over the course of millions of years. It is a finite resource and thus considered to be a non-renewable energy source.

There are two different possible peaks: one measured by mass (i.e. metric tons) and another by energy output (i.e. petajoules). The world average heat content per mass of mined coal rose from 8,020 BTU/lb. in 1989 to 9,060 BTU/lb. in 1999. Since 1999, the world average heat content of mined coal has been fairly steady, and was 9,030 BTU/lb. in 2011.

The estimates for global peak coal extraction vary wildly. Many coal associations suggest the peak could occur in 200 years or more, while scholarly estimates predict the peak to occur as soon as the immediate future. Research in 2009 by the University of Newcastle in Australia concluded that global coal extraction could peak sometime between the present and 2048. A 2007 study by the German Energy Watch Group predicted that global peak coal extraction may occur sometime around 2025 at 30 percent above the 2005 rate.

The contemporary concept of peak coal follows from Hubbert peak theory, which is most commonly associated with Peak oil. Hubbert concluded that each oil region and nation has a Bell-shaped depletion curve. However, this question was originally raised by William Stanley Jevons in his book The Coal Question in 1865.

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