Gulf Coast lignite occurs mainly in Eocene strata with the majority of the resources in the lower Eocene Wilcox Group. Strippable resources in the Gulf Coast area are about 20 to 25 billion short tons (18 to 22.5 billion Mg) of which one-half are in Texas. Grade (5,000 to 7,000 Btu/lb or 11,630 to 16,282 kJ/kg, 20 to 50% moisture, 10 to 40% ash, and 0.5 to 2% sulfur) decreases from west to east and with progressively younger stratigraphic units. Seams are typically 2 to 10 ft (0.6 to 3 m) thick; differences in continuity and grade can be correlated with depositional system.

Large acreages are under lease--2.5 million acres (1,000,000 ha.) in Texas alone. At the near-surface, development drilling is most common whereas exploration drilling is now under way for deep-basin lignite. Deposit size depends on end use, for example, a 150 million ton (135 million mg) reserve for power plants and 15 million tons (13.5 million mg) for industrial boilers. Mining is by dragline or scrapers at less than 120 ft (36 m) and stripping ratios of less than 10:1; minimum seam thickness is 2 ft (0.6 m). Reclamation cost is approximately $1,000/acre ($400/ha.). Bucket-wheel excavators are inevitable as multiseam thin-bed deposits are mined at increasing depths.

All current production is in Texas and was about 21 million tons (19 million Mg) in 1978. Almost all the production is pulverized fired in mine-mouth plants where lignite-produced energy costs 50¢ per million

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Btu. In Texas, air-quality standards (AAQS and PSD) could restrict the siting of future power plants. Future use in atmospheric fluidized bed combustion and medium-Btu gasification is probable. Underground gasification should be commercialized by 1990.

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