Wyoming Coal vs. Eastern U.S. Coal
Coal Fields of the U.S.
Western coals were formed between 100 and 45 million years Ago in two completely different types of swamps. The earlier coal swamps (100 to 65 ma) were marginal to the Cretaceous Epeiric Sea much like the eastern swamps were some 200 million years earlier. These are the coals of Utah, Colorado, and western Wyoming.
The younger western coals (65 to 45 ma) originated in intermontane valley swamps in eastern Wyoming and SE Montana far removed from any marine influence. These are the primary producing coal beds of the west. The majority of the coal in Montana and N. Dakota, although forming at the same time, never underwent the coalification process and remained as lignite.
The differing geologic histories have resulted in coals with differing characteristics.
This is a generalized comparison:
| Western coal | Eastern coal |
| Subbituminous | Bituminous |
| Lower in BTU | Higher in BTU |
| Lower in ash | Higher in ash |
| Lower in sulfur | Higher in sulfur |
| Thicker seams | Thinner seams |
| Surface mining | Underground mining (some surface) |
Due to the differing swamp environments, geologic age and local geology, , the western coals have significant differences when compared to the Eastern coals. here is a typical Wyoming Powder River Basin Coal (Wyodak) with a typical Illinois coal (Illinois #6).
| Content | Western coal | Eastern coal |
| Ash | 8.77% | 15.48% |
| Sulfur | 0.63% | 4.82% |
| Carbon | 68.43% | 65.20% |
| Hydrogen | 4.88% | 4.23% |
| Oxygen | 1.02% | 1.16% |
| Nitrogen | 16.27% | 10.11% |
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