Lignite, often referred to as brown coal, is the lowest rank of coal and used almost exclusively as fuel for steam-electric power generation. It is brownish-black and has a high inherent moisture content, sometimes as high as 66 percent, and very high ash content compared to bituminous coal. It is also a heterogeneous mixture of compounds for which no single structural formula will suffice.
The heat content of lignite ranges from 9 to 17 million Btu per short ton (10 to 20 MJ/kg) on a moist, mineral-matter-free basis. The heat content of lignite consumed in the United States averages 13 million Btu/ton (15 MJ/kg), on the as-received basis (i.e., containing both inherent moisture and mineral matter). When reacted with quaternary amine, amine treated lignite (ATL) forms. ATL is used in oil well drilling fluids to reduce fluid loss. Lignite mined in millions of metric tons:
| 1970 | 1980 | 1990 | 2000 | 2001 | ||
|---|---|---|---|---|---|---|
| 1. | Germany | 369,300 | 388,000 | 356,500 | 167,700 | 175,400 |
| 2. | Russia | 127,000 | 141,000 | 137,300 | 86,400 | 83,200 |
| 3. | USA | 5,400 | 42,300 | 82,600 | 83,500 | 80,500 |
| 4. | Australia | 24,200 | 32,900 | 46,000 | 65,000 | 67,800 |
| 5. | Greece | 8,100 | 23,200 | 51,700 | 63,300 | 67,000 |
| 6. | Poland | 32,800 | 36,900 | 67,600 | 61,300 | 59,500 |
| 7. | Turkey | 4,400 | 15,000 | 43,800 | 63,000 | 57,200 |
| 8. | Czech Republic | 67,000 | 87,000 | 71,000 | 50,100 | 50,700 |
| 9. | China | 13,000 | 22,000 | 38,000 | 40,000 | 47,000 |
| 10. | SFR Yugoslavia | 26,000 | 43,000 | 60,000 | - | - |
| 10. | FR Yugoslavia | - | - | - | 35,500 | 35,500 |
| 11. | Romania | 14,100 | 27,100 | 33,500 | 17,900 | 29,800 |
| 12. | North Korea | 5,700 | 10,000 | 10,000 | 26,000 | 26,500 |
| ... | ... | ... | ... | ... | ... | ... |
| ... | Austria | 3,700 | 1,700 | 2,500 | 1,300 | 1,200 |
| ... | Total | 804,000 | 1.028,000 | 1.214,000 | 877,400 | 894,800 |
Braunkohle | Λιγνίτης | Lignite | Lignite | Węgiel brunatny | Бурый уголь