Trends in U.S. Recoverable Coal Supply Estimates and Future Production Outlooks (61-84)

摘要

The geological coal resource of the U.S. is abundant and proved coal reserves are listed as the world's largest. However, the reserves are unevenly distributed and located in a small number of states, giving them major influence over future production. A long history of coal mining provides detailed time series of production and reserve estimates, which can be used to identify historical trends. Compilation of data from United States Geological Survey, Energy Information Administration, U.S. Bureau of Mines and others reveal how the recoverable volumes have been decreased since before the 1950s. The exact cause of this reduction is probably a multitude of factors, including depletion, changes in economic conditions, land-use restrictions, environmental protection and social acceptance. In reviewing the historical evolution of coal reserves, one can state that the trend here does not point towards any major increases in available recoverable reserves; rather the opposite is true due to restrictions and increased focus on environmental impacts from coal extraction. The development of new even stricter regulations and environmental laws is also a reasonable assumption and this will further limit the amount of recoverable coal. Future coal production will not be entirely determined by what is geologically available,but rather by the fraction of that amount that is practically recoverable. Consequently, the historical trend towards reduced recoverable amounts is likely to continue into the future, with even stricter regulations imposed by increased environmental concern. Long-term outlooks can be created in many ways, but ultimately the production must be limited by recoverable volumes since coal is a finite resource. Various models, such as the logistic, Hubbert or Gompertz curves, can be used to provide reasonable long-term outlooks for future production. However, such long-term life-cycle projections should not be used as a substitute for meticulous economic studies to forecast perturbations in coal production over the next few years or decades. Based on a logistic model, using the recoverable reserves as an estimate of what is realistically available for production, results in a coal output of around 1400 Mt by 2030 through the rest of the century. The geologic amounts of coal are of much less importance to future production than the practically recoverable volumes. The geological coal supply might be vast, but the important question is how large the share that can be extracted under present restrictions are and how those restrictioris will develop in the future. Production limitations might therefore appear much sooner than previously expected.