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Coal Science
Leslie Ruppert

Rumors of the demise of coal are much exaggerated: Coal will remain a viable energy source worldwide. And according to an Energy Information Agency report this year, consumption is expected to increase, as developing countries rely on their coal resources to generate electricity.

Increased usage of coal is driving coal research towards more standardization and precise resource assessments. Currently, the West Virginia Geologic and Economic Survey is remapping and recorrelating all of the coal in the state and utilizing geographic information systems (GIS) technology to create digital, up-to-date coal resource assessments. In addition, the U.S. Geological Survey (USGS) is revising their coal resource assessment methodology to assess the amount and quality of coal that will actually be produced.

In 2004, geoscientists have shown that coal may have the potential to provide continuous time-calibrated terrestrial climate data. D.J. Large and colleagues, as published in the April 2003 Geology, and Roy C. Davies, as presented at the 2004 meeting of the American Association of Petroleum Geologists, have used vitrinite and inertinite, two environmentally sensitive coal macerals, to show evidence of orbital periodicities in coal beds in Australia and the United States.

The rapid development of coalbed methane as a significant component of natural gas production has spurred new research in coal and coal gases globally. Even though the United States is the top producer, significant new resources may yet be realized in underexplored Western coal basins and the Gulf Coast Plain. USGS coal assessments in the latter have identified Paleocene-Eocene Wilcox coals that underlie large areas of the Gulf Coast and have recognized coalbed methane potential, especially in southern Texas where Wilcox coals reach a rank of subbituminous B or greater at depths of approximately 1,500 meters.

One promising line of research is the potential for enhanced coal bed methane production through injection of nitrogen, carbon dioxide or methanogen growth media into coals to stimulate methane production. New experiments conducted at USGS demonstrate that methane production can be enhanced in some subbituminous coals by injecting inexpensive methanogen growth media into coal beds. The use of nutrient stimulation by injection could provide an environmentally sound and inexpensive method to reinject the vast amount of water produced during the life of a coalbed methane field and increase yields. Injection of carbon dioxide into coal beds for enhanced methane recovery has a secondary benefit: Carbon dioxide is more strongly adsorbed on coals than methane and may remain trapped (sequestered) for long periods of time. Lower rank coals have a stronger adsorption capacity than higher rank coals, lending themselves to greater opportunities for enhanced coalbed methane recovery as well as being large reservoirs for carbon dioxide.

Carbon dioxide sequestration requires new information about the chemical and physical interactions of carbon dioxide with coals at subsurface pressure and temperature conditions and offers new opportunities for coal geoscientists. Work must be designed to identify the physical interactions of deeply buried coals (greater than 1 kilometer) where carbon dioxide is supercritical. In 2002, Bernhard M. Krooss and co-workers examined carbon dioxide adsorption isotherms at supercritical conditions and showed that traditional methods of measuring gas adsorption need to be modified to obtain useful data (International Journal of Coal Geology, vol. 51, p. 69). And Jonathan J. Kolak and Robert C. Burruss both at USGS are examining the potential for carbon dioxide injected into coal beds to mobilize high molecular weight components of coals, including components that are potentially toxic if released to the surface environment.

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Ruppert is a coal geologist and inorganic petrologist with the U.S. Geological Survey's Eastern Energy Resources Team. E-mail:


Davis, R.C., Howell, J.A., Flint, S., Diessel, C., and Boyd, R., 2004, Identifying high resolution records of base-level and climate change using coal seam micro-stratigraphy, AAPG 2004 abstract.

Davis, R.C., Howell, J.A., Flint, S., Diessel, C., and Boyd, R., 2004, An integrated study of the sedimentology, stratigraphy, and coal petrography of the Sunnyside Member of the Blackhawk Formation, Book Cliffs, Eastern Utah, AAPG 2004 abstract.

Energy Information Agency, 2004, International coal consumption information.

Kolak, J. J., and Burruss, R. C., 2003, The effect of coal rank on the physicochemical interactions between coal and CO2 — Implications for CO2 storage in coal beds, in Proceedings, Second Annual Conference on Carbon Sequestration, DOE, CD-ROM, also, USGS Open File Report 03-543.

Krooss, B.M., van Bergen, F., Gensterblum, Y., Siemons, N., Pagnier, H.J.N., and David, P., 2002, High-pressure methane and carbon dioxide adsorption on dry and moisture-equilibrated Pennsylvanian coals, International Journal of Coal Geology, v. 51, p. 69-92.

Large, D.J., Jones, T.F., Somerfield, C., Gorringe, M.C., Spiro, B., Macquaker, J.H.S., and Atkin, B.P., 2003, High-resolution terrestrial record of orbital climate forcing in coal, Geology, v. 31, p. 303-306.

West Virginia Geologic and Economic Survey, 2004, Coal bed mapping project (CBMP).

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