This report is the fourth in a series published by the Energy Information Administration (EIA) to provide data on coal resources and reserves (see "Important Terminology" box) allocated by estimated ranges of heat and sulfur content. EIA's estimated recoverable reserves are derived from the demonstrated reserve base (DRB) of coal in the United States (see DRB discussion in next section) by applying adjustments for the percentages of the DRB expected to be accessible, and then for the percentages of the accessible DRB expected to be recoverable by surface and underground mining. The usual understanding of the term "reserves" as referring to quantities that can be recovered at a sustainable profit cannot technically be extended to EIA's estimated recoverable reserves because economic and engineering data to project mining and development costs and coal resource market values are not available. EIA's recoverable reserves at active mines, about which EIA is authorized to collect simple tonnage and recovery rate estimates in its annual Coal Production Report survey, rely on mine operator estimates, and cannot be classified as to geologic assurance (see "Measured Resources" in "Important Terminology" box).

Originally developed for use in EIA coal supply models, the data in the first report⁽¹⁾ (1989) were published to broaden communication with the public on the available data and analyses of coal resources and their characteristics and to refine estimates of the resources that may be recoverable and suitable for future needs. The second report,⁽²⁾ published in 1993, included new State data in major portions of Ohio and Wyoming, resulting in significant revisions. It also contained EIA revisions in the Pennsylvania anthracite coal fields and Btu/sulfur range allocations for the DRB in parts of 10 other, non-producing States. For the first time, coal quality and recoverability estimates were available for all States with DRB data. The third report,⁽³⁾ released in 1996, revised data in New Mexico, Illinois, and Eastern Kentucky and documented the increasing cooperation among EIA, the U.S. Geological Survey, and State geological agencies in order to share data and coordinate efforts in their coal resource and reserve programs. This report (the fourth) incorporates additional new resource data in Illinois and applies depletion adjustment through January 1, 1997. The DRB is the only publicly available, nationwide data file of the quantities of minable coal conforming to a unified set of criteria. The DRB provides the basic input for numerous coal and energy analysis and forecasting models--both government and private. These include the National Energy Modeling System (NEMS), EIA's integrated energy forecasting system. The NEMS forecasts are the basis for EIA's Annual Energy Outlook⁽⁴⁾ and are used to answer congressional and executive department requests and ad hoc analyses. The DRB is also used in commercial models, such as ICF, Incorporated's Coal and Electric Utility Model.

The in-place coal resources in the United States, including the DRB and the identified and undiscovered resources, occur primarily as tabular deposits, or "coalbeds," within the rocks in certain coal-bearing areas (Figure 1).

Figure 1. Coal-Bearing Areas of the United States

Sources: United States Geological Survey, Coalfields of the United States, 1960-1961; Texas Bureau of Economic Geology, Lignite Resources in Texas, 1980; Louisiana Geological Survey, Near Surface Lignite in Louisiana, 1981; Colorado Geological Survey, Coal Resources and Development Map, 1981; and Mississippi Bureau of Geology, 1983.

The DRB predates the estimated recoverable reserves database and was originally devised to impart a uniform set of definitions and criteria and replace the compila- tions of variously defined coal reserve and resource data in Federal and State studies available in the 1950's and 1960's. Engineers and geologists at the U.S. Bureau of Mines (BOM) inaugurated the DRB in 1974.⁽⁵⁾ They selected geologic reliability criteria ("measured" and "indicated") that included only resources based on multiple field measurements or resource extensions corroborated by measurements, within defined study areas. Further, for the 1974 DRB, the BOM used information from field personnel and coal mining specialists and it applied engineering judgment to derive what has turned out to be a one-time national assessment at the county/coalbed level.⁽⁶⁾ Working with the thickness categories common to contemporary coal assessments, they selected as minability criteria those broad ranges of coalbed thickness and overburden thickness that encompassed most commercial mining. For a discussion of the significance of the data and criteria on updates of the DRB and related databases, see Appendix A of the 1996 U.S. Coal Reserves report.

The EIA assumed responsibility for the DRB and for coal reserves data in 1977, when DOE was established. Between 1983 and 1993, EIA published annual updates to the DRB in its annual Coal Production reports.⁽⁷⁾ Because of differences between DRB data and the production data as reported by coalbeds the EIA up- dates could be maintained only at the State level, by coal rank and type of mining. Some State updates by EIA incorporated new resource data by coalbed, but it was not feasible to maintain the national DRB at the coalbed level. DRB updates during the 1980s also broadened criteria in locations where evidence showed that coal was being mined from beds thinner or deeper than the standards (Appendix A, 1996 U.S. Coal Reserves report).

In 1990, EIA initiated the Coal Reserves Data Base (CRDB) program, to help meet the growing need for new sources of data for U.S. coal reserves estimates. Years of unpublished mapping data and coal quality data from various sources were being warehoused at State geological surveys in a wide range of formats. In order to promote the processing, analysis, and promulgation of such data, EIA encourages active participation of State surveys in the CRDB program.

The resulting CRDB coal resource estimates include the DRB, along with accessibility adjustments, estimated recoverable reserves (recoverable coal), and allocations by Btu, sulfur, and ash content using coal quality data that are coordinated with mapped resources.

EIA's objective is to develop reliable data on coal reserves, but the coal reserves data EIA is authorized to collect from the coal industry are too limited for mid- or long-term analyses. To supply a broader national database of coal reserves, EIA analyzes coal resource data--primarily the DRB, but also the other measured, indicated, and inferred resource categories from which the DRB might be derived. EIA develops the estimated recoverable reserves from the DRB and from data on coal accessibility and recoverability. The USGS and State geological surveys estimate identified resources (which include measured and indicated resources from which the DRB may be derived, as well as resources currently too thin or too deep to include in the DRB) and inferred resources, also not included in the DRB. Finally, the undiscovered resources estimated by the USGS, along with identified resources, constitute the comprehensive "total resources" classification (Figure 2).

Figure 2. Delineation of U.S. Coal Resources and Reserves

Notes: Resources and reserves data are in billion short tons. Darker shading in the diagram corresponds to greater relative data reliability. The estimated recoverable reserves depicted near the top of the diagram assume that the 19 billion short tons of recoverable reserves at active mines reported by mine operators to the Energy Information Administration (EIA) are part of the same body of resource data. This diagram portrays the theoretical relationships of data magnitude and reliability among coal resource data. All numbers are subject to revision with changes in knowledge of coal resource data.     Sources: The DRB estimate was compiled by the EIA as of January 1, 1997. Estimated recoverable reserves were compiled in EIA's Coal Reserves Data Base (CRDB) program. Recoverable reserves at active mines were reported in EIA's Coal Industry Annual, 1996. Identified resources and total resources are estimates as of January 1, 1974, compiled and published by the U.S. Geological Survey in Coal Resources of the United States, January 1, 1974.

Although all the data represented in Figure 2 are interrelated conceptually, in practice they cannot be maintained uniformly. The recoverable reserves at active mines are updated annually but they represent only a fraction of the reserves controlled by major mining companies. EIA treats recoverable reserves at active mines as though they constitute a portion of its estimated recoverable reserves. In reality, some of the data at mines may incorporate reserves located beyond the coverage of the DRB and EIA's estimated recoverable reserves. The mine data EIA receives are not detailed enough to allow comparative analysis.

Further, the data for reserves at active mines are clearly more timely than the broader resource studies from which estimated recoverable reserves are derived. Similarly, the DRB data are derived from more recent sources in many areas than were available when the USGS compiled identified resources and total resources as of 1974. Thus, in Figure 2, the data for active mines are generally more current than the DRB and its associated recoverable reserve estimates, which are in turn more up to date than much of the total resource data. Under current planning, there is little likelihood that total resources of coal will be updated by the USGS in the near future.

Inferred coal resources are not listed in this report because they are less reliable than the DRB and because the coverage of inferred data is not consistent from one State to another. Recent CRDB studies include updated DRB and inferred resources and they extend allocations and analyses to the inferred if supported by the geologic evidence. Even though inferred data are not published by EIA, they are retained on file to supply information about mining potential in important areas.

Since EIA's previous report, in 1996, data have been incorporated from Part 2 of the Illinois CRDB study, completed in March 1997 (described in the next section). A cooperative agreement is under way with the Colorado Geological Survey to revise coal resource estimates and update the CRDB in the two leading coalfields in Colorado. Results from the Uintah coal-fields were completed in July 1998⁽⁸⁾ and updates for the Yampa field are due by May 1999. A coal reserves update study in Utah, in cooperation with the Utah Geological Survey, started up in December 1997. New resource and reserve estimates for the major producing areas in the Book Cliffs and Wasatch Plateau coalfields are scheduled for completion by August 1999.

EIA has obtained valuable new accessibility and recoverability data for recent coal reserve estimates from the USGS Coal Availability Studies (CAS) and from the BOM Coal Recoverability Studies (CRS) conducted before the Bureau of Mines was shut down. The USGS, recognizing the value of the CRS to complement its availability studies with economic mining feasibility data, included a small CRS program in its current operations. As discussed later, EIA has also adopted some of the CAS criteria for "restricted resources" in its own accessibility adjustments. This allows the DRB criteria to remain constant while using accessibility factors to update local coal minability restrictions.

The USGS is also proceeding with its National Coal Resource Assessment (NCRA)--a project running from 1995 to 1999 to update basic U.S. coal resources data. The NCRA is incorporating new data in a systematic study of designated major coal deposits: specifically of those coalbeds expected to produce the majority of U.S. coal for the next 25 to 30 years. It does not attempt to compile the data necessary for a new estimate of total U.S. coal resources, which would currently be beyond the scope of any fundable Federal project. When completed, the NCRA data may serve an important role in updating or replacing EIA's DRB.

Endnotes

1. Energy Information Administration, Estimation of U.S. Coal Reserves by Coal Type: Heat and Sulfur Content, DOE/EIA-0529 (Washington, DC, October 1989).

2. Energy Information Administration, U.S. Coal Reserves: An Update by Heat and Sulfur Content, DOE/EIA-0529(92) (Washington, DC, February 1993).

3. Energy Information Administration, U.S. Coal Reserves: A Review and Update, DOE/EIA-0529(95) (Washington, DC, August 1996).

4. Energy Information Administration, Annual Energy Outlook, DOE/EIA-0383 (various years) (Washington, DC).

5. U.S. Department of the Interior, Bureau of Mines, Mineral Industry Surveys, "Demonstrated Coal Reserve Base of the United States on January1, 1974" (Washington, DC, June 1974).

6. U.S. Bureau of Mines, The Reserve Base of U.S. Coals by Sulfur Content: Part 1, The Eastern States, Information Circular 8680 (Washington, DC) and U.S. Bureau of Mines, The Reserve Base of U.S. Coals by Sulfur Content: Part 2, The Western States, Information Circular 8693 (Washington, DC, 1975). The first DRB determined by the BOM was improperly labeled as the 1974 DRB; actually, it was estimated for 1971, and subsequent DRB updates by the EIA reflect depletion adjustments from 1971.

7. Energy Information Administration, Coal Production, DOE/EIA-0118 (Washington, DC, various years).

8. The new Colorado data are being reviewed and processed. They are not included in the present update.