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Coal Research and Development: to Support National Energy Policy
TABLE 4.3 Coal Production by Rank for 2005
Production (thousand short tons)
No. of Mines
Production per Mine (thousand short tons)
Total Energy Content, (quadrillion Btu)
NOTE: Because of their lower energy contents, lignite and subbituminous coals represent a smaller percentage of coal production in the United States on an energy basis (~40 %) than on a tonnage basis (~50 %).
SOURCE: EIA (2006b).
Chapter 2) rely heavily on increased production from this region for consumption east of the Mississippi River. Because it takes about 50 percent more subbituminous coal (on a tonnage basis) to replace a ton of bituminous coal in electricity generation,1 this has significant implications for transportation infrastructure and power plant design and capacity.
When used for electricity generation, coal from the PRB generally produces more CO2 per kilowatt-hour than the bituminous coal mined in the east. Combustion of subbituminous coal from the PRB produces about 226 pounds of CO2 for every million Btu (British thermal units) of heat generated (on a net calorific basis), compared with about 211 pounds for the bituminous coal mined in the East (Winschel, 1990). Another possible constraint on the use of coal from the southern PRB might be future air quality regulation of coarse particulates, although Environmental Protection Agency’s (EPA’s) proposal to exempt mining and agricultural operations in its update of particulate standards (EPA, 2006c) may remove or defer this potential constraint.
An increasingly important by-product of U.S. coal production is coal mine methane recovered during or prior to mining, in addition to coal bed methane produced independently of mining. Captured methane may be used as a fuel source at the mine or, where feasible, distributed in natural gas pipelines. In recent years, coal bed methane production has increased and now comprises about 8 percent of the U.S. natural gas supply. An ancillary benefit of recovering coal mine methane is reduced atmospheric methane emissions, because methane is a potent greenhouse gas.
In addition to the difference in heating value (i.e., Btu/lb), electricity generating units fueled with subbituminous and lignite coals tend to operate at lower efficiency (higher heat rate) than units fueled with bituminous coal. This can lead to differences in generating capacity when using different coals.