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Lignite

This soft brown coal is geologically youngest of all coals

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Lignite coal vein in Kentucky.

Lignite coal vein in Kentucky.

Photo (c) Open-File Report 2006-1078 pubs.usgs.gov

Sometimes called “brown coal,” lignite is the lowest quality and most crumbly coal. This softer and geologically “younger” coal sits relatively close to the earth’s surface.

According to the Lignite Energy Council, 13.5 percent of lignite coal is gasified into synthetic natural gas and 7.5 percent goes into production of ammonia-based fertilizers. The balance is used to generate electricity. Because of its high weight relative to its heat content, lignite is typically used in pulverized coal or cyclone-fired electric production power plants close to the mine.

Through a process called coal gasification, lignite can be broken down chemically to create synthetic natural gas that delivers more power and is easier to operate in commercial scale electric generations.

Heating value: Lignite has a heating value of approximately 4,000 to 8,300 Btu per pound.

ASTM D388 - 05 Standard Classification of Coals by Rank

Characteristics: Lignite contains the lowest level of fixed carbon (25 to 35 percent) and highest level of moisture (typically 20 to 40 percent by weight, but can go as high as 60 to 70 percent) of all the coals. Ash varies up to 50 percent by weight. Lignite has low levels of sulfur (less than 1 percent) and ash (approximately 4 percent), but high levels of volatile matter (32 percent and higher by weight) and produces high levels of air pollution emissions.

Availability: Moderate. Approximately 7 percent of coal mined in the U.S. is lignite.

Location: Found primarily in North Dakota (McLean, Mercer, and Oliver counties) Texas, Mississippi (Kemper county), and to a lesser degree, Montana.

Global Production: According to the World Coal Association, the top ten countries that produce brown coal are (ranked from most to least): Germany, Indonesia, Russia, Turkey, Australia, U.S.A., Greece, Poland, Czech Republic, and Servia. In 2010, Indonesia leaped into second place with the highest growth in coal production of any country.

Despite their small size, Germany and Indonesia both produced more than 160 million tonnes of lignite (brown coal) in 2010. Each produced more than 200 percent, or more than double, the lignite output of any other country in the world.

Additional Notes: Because of its high moisture content, lignite may be dried to reduce moisture content and increase calorific fuel value. The drying process requires energy, but can be used to reduce volatile matter and sulfur as well.

Ranking: Lignite ranks 4th, or last, in heat and carbon content compared with other types of coal, according to ASTM D388 - 05 Standard Classification of Coals by Rank.

Learn about other types of coal

#1 Ranked Coal - Anthracite

#2 Ranked Coal - Bituminous

#3 Ranked Coal - Sub-bituminous

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