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Coal Resources Available for Development - A Methodology and Pilot Study

By Jane R. Eggleston1, M. Devereux Carter1, and James C. Cobb2
U.S. Geological Survey, Reston, VA 20192, 2Kentucky Geological Survey, Lexington, KY.


In the spring of 1986, a research project (pilot study) was undertaken by the U.S. Geological Survey (USGS), in cooperation with the

Kentucky Geological Survey (KGS), to develop and test a methodology for determining the quantity of coal resources actually available for mining under current conditions. Impetus for the study came from the numerous energy forecasts projecting an increasing domestic dependency on coal in future years and from the lack of specificity in the current literature regarding the availability of coal for development. Conoco, in its 1986 "World Energy Outlook," predicted that about 25 percent of the U. S. energy supply will come from coal by the year 2000 (fig. 1). The Department of Energy's Energy Information Administration (EIA, 1988a) forecast that coal consumption would increase from 26.9 percent today to 37 percent of our domestic energy supply by the year 2000 (fig. 2). Without an adequate reserve base, these forecasts for coal consumption cannot be substantiated (fig. 3).

The reserve base, indicated by the shaded area on figure 3, is defined as that portion of demonstrated coal resources that can be mined economically at the time of determination. Assessing the reserve base is currently an activity of the EIA. Using coal resource data from the State geological surveys and the USGS, the EIA applies minable depth and thickness limits to determine the demonstrated reserve base (DRB), which is currently estimated to be about 475 billion short tons (EIA, 1988b). This is the figure upon which many energy forecasts have been based. Even if coal production increases markedly from its current level of a little over 900 million short tons per year, we should still have several hundred years of coal supply according to this current DRB figure. But how much of this coal really is available?

To determine the actual availability of coal for development, the USGS and KGS developed and tested a methodology that would provide greatly increased specificity to coal resource assessments. In addition to depth and thickness limitations to coal mining, other restrictions that effectively limit mining of coal were applied. In this study, we defined available coal as follows:


Original coal resources are defined as the amount of coal, containing 33 percent or less ash, in the ground prior to production and under less than 6,000 ft of overburden. The coal beds are either 14 in or thicker for anthracite and bituminous coal or 30 in or thicker for subbituminous coal and lignite, in such form and amount that extraction is currently or potentially feasible (Wood and others, 1983). Coal mined and coal lost in mining is the quantity of coal that has been removed or "sterilized"' by surface or underground mining. Remaining coal resources are defined as original resources less coal mined and coal lost in mining. Land-use restricted coal most likely will not be mined because surface features or structures would be disrupted by mining, and the integrity of the natural environment would be threatened, or the rights of the individual or community would be impacted. Technologically restricted coal most likely will not be mined because geologic or mining-related factors would negatively impact the economics or safety of a mine.

Land-use and technological restrictions vary regionally because of types of mining, regulatory variations, land-use differences, and geologic conditions. In addition, available coal can be designated as compliance or noncompliance coal, depending on whether or not it meets the Environmental Protection Agency's (EPA) new-source performance standards for sulfur emissions. According to EPA's requirements (CFR, 1987), compliance coal must release no more than 1.2 lb of sulfur dioxide per 1 million Btu when burned in powerplants.

In the development of the methodology, an optimal size for a study area was determined. This study area had to be small enough to allow for detailed delineation of coal geology, mined areas, and a variety of restrictions in a timely fashion but had to be large enough to be representative of a wider area. If the methodology proved successful, the USGS, in cooperation with Geological Surveys in other coal-bearing States, would propose to apply the methodology to additional study areas.


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