Lignite, often referred to as brown coal,[1] is a soft, brown, combustible, sedimentary rock formed from naturally compressed peat. It has a carbon content around 25–35%,[1][2] and is considered the lowest rank of coal due to its relatively low heat content. When removed from the ground, it contains a very high amount of moisture which partially explains its low carbon content. Lignite is mined all around the world and is used almost exclusively as a fuel for steam-electric power generation.

A lignite stockpile (above) and a lignite briquette

The combustion of lignite produces less heat for the amount of carbon dioxide and sulfur released than other ranks of coal. As a result lignite is the most harmful coal to human health.[3] Depending on the source, various toxic heavy metals, including naturally occurring radioactive materials may be present in lignite which are left over in the coal fly ash produced from its combustion, further increasing health risks.[4]


Lignite mining, western North Dakota, US (c. 1945)

Lignite is brownish-black in color and has a carbon content of 60–70 percent on a dry ash-free basis. However, its inherent moisture content is sometimes as high as 75 percent[1] and its ash content ranges from 6–19 percent, compared with 6–12 percent for bituminous coal.[5] As a result, its carbon content on the as-received basis (i.e., containing both inherent moisture and mineral matter) is typically just 25-35 percent.[2]

Strip mining lignite at Tagebau Garzweiler in Germany

The energy content of lignite ranges from 10 to 20 MJ/kg (9–17 million BTU per short ton) on a moist, mineral-matter-free basis. The energy content of lignite consumed in the United States averages 15 MJ/kg (13 million BTU/ton), on the as-received basis.[6] The energy content of lignite consumed in Victoria, Australia, averages 8.6 MJ/kg (8.2 million BTU/ton) on a net wet basis.[7]

Lignite has a high content of volatile matter which makes it easier to convert into gas and liquid petroleum products than higher-ranking coals. Unfortunately, its high moisture content and susceptibility to spontaneous combustion can cause problems in transportation and storage. Processes which remove water from brown coal reduce the risk of spontaneous combustion to the same level as black coal, increase the calorific value of brown coal to a black coal equivalent fuel, and significantly reduce the emissions profile of 'densified' brown coal to a level similar to or better than most black coals.[8] However, removing the moisture increases the cost of the final lignite fuel.

Lignite rapidly degrades when exposed to air. This process is called slacking or slackening.[9]


Lignite mine in the background of Lützerath, Germany

Most lignite is used to generate electricity.[2] However, small amounts are used in agriculture, in industry, and even, as jet, in jewelry. Its historical use as fuel for home heating has continuously declined and is now of lower importance than its use to generate electricity.

As fuel

Layer of lignite for mining in Lom ČSA, Czech Republic

Lignite is often found in thick beds located near the surface, making it inexpensive to mine. However, because of its low energy density, tendency to crumble, and typically high moisture content, brown coal is inefficient to transport and is not traded extensively on the world market compared with higher coal grades.[1][7] It is often burned in power stations near the mines, such as in Australia's Latrobe Valley and Luminant's Monticello plant in Texas. Primarily because of latent high moisture content and low energy density of brown coal, carbon dioxide emissions from traditional brown-coal-fired plants are generally much higher per megawatt-hour generated than for comparable black-coal plants, with the world's highest-emitting plant being Australia's Hazelwood Power Station[10] until its closure in March 2017.[11] The operation of traditional brown-coal plants, particularly in combination with strip mining, is politically contentious due to environmental concerns.[12][13]

The German Democratic Republic relied extensively on lignite to become energy self-sufficient, and eventually obtained 70% of its energy requirements from lignite.[14] Lignite was also an important chemical industry feedstock via Bergius process or Fischer-Tropsch synthesis in lieu of petroleum,[15] which had to be imported for hard currency following a change in policy by the Soviet Union in the 1970s, which had previously delivered petroleum at below market rates.[16] East German scientists even converted lignite into coke suitable for metallurgical uses (high temperature lignite coke) and much of the railway network was dependent on lignite either through steam trains or electrified lines mostly fed with lignite derived power.[16] As per the table below, East Germany was the largest producer of lignite for much of its existence as an independent state.

In 2014, about 12 percent of Germany's energy and, specifically, 27 percent of Germany's electricity came from lignite power plants,[17] while in 2014 in Greece, lignite provided about 50 percent of its power needs. Germany has announced plans to phase out lignite by 2038 at the latest.[18][19][20][21] Greece has confirmed that the last coal plant will be shut in 2025 after receiving pressure from the European Union[22] and plans to heavily invest in renewable energy.[23]

Home heating

Lignite was and is used as a replacement for or in combination with firewood for home heating. It is usually pressed into briquettes for that use.[24][25] Due to the smell it gives off when burned, lignite was often seen as a fuel for poor people compared to higher value hard coals. In Germany, briquettes are still readily available to end consumers in home improvement stores and supermarkets.[26][27][28][29]

In agriculture

An environmentally beneficial use of lignite is in agriculture. Lignite may have value as an environmentally benign soil amendment, improving cation exchange and phosphorus availability in soils while reducing availability of heavy metals,[30][31] and may be superior to commercial K humates.[32] Lignite fly ash produced by combustion of lignite in power plants may also be valuable as a soil amendment and fertilizer.[33] However, rigorous studies of the long-term benefits of lignite products in agriculture are lacking.[34]

Lignite may also be used for the cultivation and distribution of biological control microbes that suppress plant pests. The carbon increases the organic matter in the soil while the biological control microbes provide an alternative to chemical pesticides.[35]

Leonardite is a soil conditioner rich in humic acids that is formed by natural oxidation when lignite comes in contact with air.[36] The process can be replicated artificially on a large scale. [37] The less matured xyloid (wood-shaped) lignite also contains high amounts of humic acid.[38]

In drilling mud

Reaction with quaternary amine forms a product called amine-treated lignite (ATL), which is used in drilling mud to reduce fluid loss during drilling.[39]

As an industrial adsorbent

Lignite may have potential uses as an industrial adsorbent. Experiments show that its adsorption of methylene blue falls within the range of activated carbons currently used by industry.[40]

In jewelry

Jet is a form of lignite that has been used as a gemstone.[41] The earliest jet artifacts date to 10,000 BCE[42] and jet was used extensively in necklaces and other ornamentation in Britain from the Neolithic until the end of Roman Britain.[43] Jet experienced a brief revival in Victorian Britain.[44]


Okefenokee Swamp, a modern peat-forming swamp
Partial molecular structure of a lignin-derived organic molecule in lignite

Lignite begins as an accumulation of partially decayed plant material, or peat. Peat accumulates most readily in areas where there is ample moisture, slow subsidence of the land surface, and lack of disturbance by rivers or oceans. Peat swamps are otherwise found in a wide variety of climates and geographical settings. Under these conditions, the area remains saturated with water, which covers dead plant material and protects it from degradation by atmospheric oxygen. Anaerobic bacteria may continue to degrade the peat, but this process is slow, particularly in acid water. Once the peat is buried by other sediments, biological degradation essentially comes to a halt, and further changes are a result of increased temperature and pressure from burial.[45]

Lignite forms from peat that has not experienced deep burial and heating. It forms at temperatures below 100 °C (212 °F),[1] primarily by biochemical degradation. This includes humification, in which microorganisms extract hydrocarbons from the peat and humic acids are formed. The humic acids make the environment more acidic, which slows the rate of further bacterial decay. Humification is still incomplete in lignite, coming to completion only when the coal reaches sub-bituminous rank.[46] The most characteristic chemical change in the organic material during formation of lignite is the sharp reduction in the number of C=O and C-O-R functional groups.[47]

Lignite deposits are typically younger than higher-ranked coals, with the majority of them having formed during the Tertiary period.[1]


Lignite is often found in thick beds located near the surface.[1][7] These are inexpensive to extract using various forms of surface mining, though this can result in serious environmental damage.[48] Regulations in the United States and other countries require that land that is surface mined must be restored to its original productivity once mining is complete.[49]

Strip mining of lignite in the United States begins with drilling to establish the extent of the subsurface beds. Topsoil and subsoil must be properly removed and either used to reclaim previously mined-out areas or stored for future reclamation. Excavator and truck overburden removal prepares the area for dragline overburden removal to expose the lignite beds. These are broken up using specially equipped tractors (coal ripping) and then loaded into bottom dump trucks using front loaders.[50]

Once the lignite is removed, restoration involves grading the mine spoil to as close an approximation as practical of the original ground surface (Approximate Original Contour or AOC). Subsoil and topsoil are restored and the land reseeded with various grasses. In North Dakota, a performance bond is held against the mining company for at least ten years after the end of mining operations to guarantee that the land has been restored to full productivity.[49] A bond (not necessary in this form) for mine reclamation is required in the US by the Surface Mining Control and Reclamation Act of 1977.[51]

Resources and Reserves

List of countries by lignite reserves

Top Ten Countries by lignite reserves (2020)[52]
Countries Lignite reserves (millions of tonnes)
Russia 90447
Australia 73865
Germany 35700
United States 29910
Turkey 19320[53]
Indonesia 14746
China 8250
Serbia 7112
New Zealand 6750
Poland 5752


The Latrobe Valley in Victoria, Australia, contains estimated reserves of some 65 billion tonnes of brown coal.[54] The deposit is equivalent to 25 percent of known world reserves. The coal seams are up to 98 metres thick, with multiple coal seams often giving virtually continuous brown coal thickness of up to 230 metres. Seams are covered by very little overburden (10 to 20 metres).[54]

A partnership led by Kawasaki Heavy Industries and backed by the governments of Japan and Australia has begun extracting hydrogen from brown coal. The liquefied hydrogen will be shipped via the transporter Suiso Frontier to Japan.[55]

North America

The largest lignite deposits in North America are the Gulf Coast lignites and the Fort Union lignite field. The Gulf Coast lignites are located in a band running from Texas to Alabama roughly parallel to the Gulf Coast. The Fort Union lignite field stretches from North Dakota to Saskatchewan. Both are important commercial sources of lignite.[9]


Lignite can be separated into two types. The first is xyloid lignite or fossil wood and the second form is the compact lignite or perfect lignite.

Although xyloid lignite may sometimes have the tenacity and the appearance of ordinary wood, it can be seen that the combustible woody tissue has experienced a great modification. It is reducible to a fine powder by trituration, and if submitted to the action of a weak solution of potash, it yields a considerable quantity of humic acid.[38] Leonardite is an oxidized form of lignite, which also contains high levels of humic acid.[56]

Jet is a hardened, gem-like form of lignite used in various types of jewelry.[41]


Germany is the largest producer of lignite,[57] followed by China, Russia, and United States.[58] Lignite accounted for 8% of all U.S. coal production in 2019.[2]

Lignite mined in millions of tonnes
Country or territory 1970 1980 1990 2000 2010 2011 2012 2013 2014 2015
 East Germany261258.1280[lower-alpha 1]
 Germany108[lower-alpha 2]129.9[lower-alpha 2]107.6[lower-alpha 2]167.7169176.5185.4183178.2178.1
 Russia145[lower-alpha 3]141[lower-alpha 3]137.3[lower-alpha 3]87.876.176.477.9737073.2
 Kazakhstan[lower-alpha 4]
 United States542.879.977.671.073.671.670.172.164.7
 Czechoslovakia828771[lower-alpha 5]
 Czech Republic[lower-alpha 6]50.143.846.643.54038.338.3
 Yugoslavia33.764.1[lower-alpha 7]
 Serbia[lower-alpha 8]35.5[lower-alpha 9]37.840.63840.129.737.3
 Kosovo[lower-alpha 10]8.7[lower-alpha 11]9[lower-alpha 11]8.7[lower-alpha 11]8.2[lower-alpha 11]7.2[lower-alpha 11]8.2[lower-alpha 11]
 North Macedonia7.
 Bosnia and Herzegovina3.4117.
 Montenegro[lower-alpha 10]1.922
 North Korea1010.
Source: World Coal Association[59] · U.S. Energy Information Administration[60] · BGR Energiestudie 2016[61] · 1970 data from World Coal (1987)[62]

no data available

  1. East Germany became a part of Germany as a result of German reunification in 1990.
  2. Data prior to 2000 are for West Germany only.
  3. Data prior to 2000 represent the Soviet Union.
  4. Country was a part of the Soviet Union during this time.
  5. Czechoslovakia dissolved in 1993.
  6. Country was a part of Czechoslovakia during this time.
  7. Yugoslavia broke up in a process that concluded in 1992.
  8. Country was a part of Yugoslavia during this time.
  9. 2000 data is for Federal Republic of Yugoslavia.
  10. Country was a part of Federal Republic of Yugoslavia during this time.
  11. Albanians unilaterally declared independence from Serbia, but the country it is not member of UN and its status is heavily disputed.

See also


  1. Kopp, Otto C. "Lignite" in Encyclopædia Britannica
  2. "Coal explained". Energy Information Administration. Retrieved 2020-09-26.
  3. "Lignite coal – health effects and recommendations from the health sector" (PDF). Health and Environment Alliance. December 2018. Archived (PDF) from the original on 2022-10-09.
  4. "Gesundheit: Feiner Staub, großer Schaden".
  5. Ghassemi, Abbas (2001). Handbook of Pollution Control and Waste Minimization. CRC Press. p. 434. ISBN 0-8247-0581-5.
  6. "Lignite". Glossary. U.S. Energy Information Agency. Retrieved 4 May 2021.
  7. (PDF) Archived from the original (PDF) on 2011-03-17. Retrieved 30 June 2022. {{cite web}}: Missing or empty |title= (help)
  8. George, A.M.. State Electricity Victoria, Petrographic Report No 17. 1975; Perry, G.J and Allardice, D.J. Coal Resources Conference, NZ 1987 Proc.1, Sec. 4.. Paper R4.1
  9. Schobert, Harold H., ed. (1995). "Chapter 1 The principal lignite deposits of North America". Coal Science and Technology. 23: 1–50. doi:10.1016/S0167-9449(06)80002-9. ISBN 9780444898234.
  10. "Hazelwood tops international list of dirty power stations". World Wide Fund for Nature Australia. Archived from the original on 2008-10-13. Retrieved 2008-10-02.
  11. "End of generation at Hazelwood". Engie. Archived from the original on 2017-03-31. Retrieved 2017-06-30.
  12. "The Greens Won't Line Up For Dirty Brown Coal In The Valley". Australian Greens Victoria. 2006-08-18. Retrieved 2007-06-28.
  13. "Greenpeace Germany Protests Brown Coal Power Stations". Environment News Service. 2004-05-28. Archived from the original on 2007-09-30. Retrieved 2007-06-28.
  14. Irfan, Ulmair (3 November 2014). "How East Germany Cleaned Up Dirty Power". Scientific American. Springer Nature America, Inc. Retrieved 4 May 2021.
  15. "Liquid fuel revival". Chemistry and Industry. No. 22. SCI. 2009. Retrieved 4 May 2021.
  16. "The history of energy in Germany". Planete energies. Total Foundation. 29 April 2015. Retrieved 4 May 2021.
  17. "Statistics on energy production in Germany 2014, Department of Energy (in german, lignite = "Braunkohle")" (PDF). 2014-10-01. Archived from the original (PDF) on 2015-12-06. Retrieved 2015-12-10.
  18. "Interview zum Kohlekompromiss: "Damit ist es nicht getan"".
  19. "Was der Kohlekompromiss für Deutschland bedeutet". 13 August 2019.
  20. "Teurer Kohlekompromiss". Retrieved 30 June 2022.
  21. "Kommentar zum Kohleausstieg: Der Kohlekompromiss ist ein Meisterstück". 26 January 2019.
  22. "Greece confirms last coal plant will be shut in 2025". 26 April 2021.
  23. "Σκρέκας: Προετοιμάζουμε και σχεδιάζουμε την πράσινη πολιτική της χώρας | ΣΚΑΪ". 18 May 2021.
  24. Francis, Wilfrid (1980). Fuels and fuel technology : a summarized manual (2d (SI) ed.). Oxford: Pergamon Press. pp. 4–5. ISBN 9781483147949.
  25. Thuβ, U.; Popp, P.; Ehrlich, Chr.; Kalkoff, W.-D. (July 1995). "Domestic lignite combustion as source of polychlorodibenzodioxins and -furans (PCDD/F)". Chemosphere. 31 (2): 2591–2604. Bibcode:1995Chmsp..31.2591T. doi:10.1016/0045-6535(95)00132-R.
  26. "Briketts kaufen bei".
  27. "Briketts kaufen bei".
  28. "Braunkohlebriketts 10kg bei REWE online bestellen!". Retrieved 30 June 2022.
  29. "Briketts kaufen bei Bauhaus".
  30. Kim Thi Tran, Cuc; Rose, Michael T.; Cavagnaro, Timothy R.; Patti, Antonio F. (November 2015). "Lignite amendment has limited impacts on soil microbial communities and mineral nitrogen availability". Applied Soil Ecology. 95: 140–150. doi:10.1016/j.apsoil.2015.06.020.
  31. Li, Changjian; Xiong, Yunwu; Zou, Jiaye; Dong, Li; Ren, Ping; Huang, Guanhua (March 2021). "Impact of biochar and lignite‐based amendments on microbial communities and greenhouse gas emissions from agricultural soil". Vadose Zone Journal. 20 (2). doi:10.1002/vzj2.20105.
  32. Lyons, Graham; Genc, Yusuf (28 October 2016). "Commercial Humates in Agriculture: Real Substance or Smoke and Mirrors?". Agronomy. 6 (4): 50. doi:10.3390/agronomy6040050.
  33. Ram, Lal C.; Srivastava, Nishant K.; Jha, Sangeet K.; Sinha, Awadhesh K.; Masto, Reginald E.; Selvi, Vetrivel A. (September 2007). "Management of Lignite Fly Ash for Improving Soil Fertility and Crop Productivity". Environmental Management. 40 (3): 438–452. Bibcode:2007EnMan..40..438R. doi:10.1007/s00267-006-0126-9. PMID 17705037. S2CID 1257174.
  34. Patti, Antonio; Rose, Michael; Little, Karen; Jackson, Roy; Cavagnaro, Timothy (2014). "Evaluating Lignite-Derived Products (LDPs) for Agriculture – Does Research Inform Practice?". EGU General Assembly Conference Abstracts: 10165. Bibcode:2014EGUGA..1610165P. Retrieved 4 May 2021.
  35. Jones, Richard; Petit, R; Taber, R (1984). "Lignite and stillage:carrier and substrate for application of fungal biocontrol agents to soil". Phytopathology. 74 (10): 1167–1170. doi:10.1094/Phyto-74-1167.
  36. "Youngs, R.W. & Frost, C.M. 1963. Humic acids from leonardite – a soil conditioner and organic fertilizer. Ind. Eng. Chem., 55, 95–99" (PDF). Archived (PDF) from the original on 2022-10-09. Retrieved 30 June 2022.
  37. Gong, Guanqun; Xu, Liangwei; Zhang, Yingjie; Liu, Weixin; Wang, Ming; Zhao, Yufeng; Yuan, Xin; Li, Yajun (3 November 2020). "Extraction of Fulvic Acid from Lignite and Characterization of Its Functional Groups". ACS Omega. 5 (43): 27953–27961. doi:10.1021/acsomega.0c03388. PMC 7643152. PMID 33163778.
  38. Mackie, Samuel Joseph (1861). The Geologist. Original from Harvard University: Reynolds. pp. 197–200.
  39. Elgibaly, A.; Farahat, M.; Abd El Nabbi, M. (1 December 2018). "The Optimum Types and Characteristics of Drilling Fluids Used During Drilling in The Egyption Western Desert". Journal of Petroleum and Mining Engineering. 20 (1): 89–100. doi:10.21608/jpme.2018.40453.
  40. Qi, Ying; Hoadley, Andrew F.A.; Chaffee, Alan L.; Garnier, Gil (April 2011). "Characterisation of lignite as an industrial adsorbent". Fuel. 90 (4): 1567–1574. doi:10.1016/j.fuel.2011.01.015.
  41. Neuendorf, K. K. E. Jr.; Mehl, J. P.; Jackson, J. A., eds. (2005). Glossary of Geology (5th ed.). Alexandria, Virginia: American Geological Institute. p. 344.
  42. "Venus figures from Petersfels". Archived from the original on 29 September 2016. Retrieved 9 August 2016.
  43. Allason-Jones, Lindsay (1996). Roman Jet in the Yorkshire Museum. The Yorkshire Museum. pp. 8–11. ISBN 0905807170.
  44. Muller, Helen (1987). Jet. Butterworths. pp. 59–63. ISBN 0408031107.
  45. Schweinfurth, Stanley P.; Finkelman, Robert P. (2002). "Coal – A complex natural resource". U.S. Geological Survery Circular. 1143. doi:10.3133/cir1143.
  46. "Coal types, formation, and methods of mining". Eastern Pennsylvania Coalition for Abandoned Mine Reclamation. 2016. Retrieved 5 May 2021.
  47. Ibarra, JoséV.; Muñoz, Edgar; Moliner, Rafael (June 1996). "FTIR study of the evolution of coal structure during the coalification process". Organic Geochemistry. 24 (6–7): 725–735. doi:10.1016/0146-6380(96)00063-0.
  48. Turgeon, Andrew; Morse, Elizabeth (22 December 2012). "Coal". National Geographic. Retrieved 25 September 2021.
  49. "Reclamation Process". Mining Lignite Coal for our Energy Future. BNI Coal. Retrieved 25 September 2021.
  50. "Mining Process". Mining Lignite Coal for our Energy Future. BNI Coal. Retrieved 25 September 2021.
  51. "Reclamation Bonds". Office of Surface Mining Reclamation and Enforcement.
  52. "Leading countries based on lignite reserves 2020". Statista. February 2022. Retrieved 2022-07-30.
  53. While the Statista review reports 10975 million tonnes for Turkey, the 2005-2019 surveys of the Mineral Research and Exploration General Directorate of Turkey has almost doubled this value. "Kömür Arama Araştırmaları" [Coal Surveying Studies] (in Turkish). MTA Genel Müdürlüğü. Retrieved 2022-07-30.
  54. Department of Primary Industries, Victorian Government, Australia, ‘Victoria Australia: A Principle Brown Coal Province’ (Fact Sheet, Department of Primary Industries, July 2010).
  55. "Kawasaki Heavy says liquefied hydrogen carrier departs Japan for Australia". Asia Pacific. Reuters. 24 December 2021. Retrieved 24 December 2021.
  56. Tan, Kim H. (22 April 2003). Humic Matter in Soil and the Environment: Principles and Controversies. CRC Press. ISBN 9780203912546. Retrieved 30 June 2022 via Google Books.
  57. "Deutschland ‒Rohstoffsituation 2015" (PDF). Bundesanstalt für Geowissenschaften und Rohstoffe (in German). 1 November 2016. Archived from the original (pdf) on 6 July 2019. Retrieved 6 July 2019.
  58. Appunn, Kerstine (7 August 2018). "Germany's three lignite mining regions". The Clean Energy Wire. Archived from the original on 26 November 2018. Retrieved 5 July 2019. Germany has been the largest lignite producer in the world since the beginning of industrial lignite mining. It still is, followed by China, Russia, and the United States. The softer and moister lignite (also called brown or soft coal) has a lower calorific value than hard coal and can only be mined in opencast operations. When burned, it is more CO2 intensive than hard coal.
  59. "Resources". World Coal Association. 2014. Retrieved 2015-12-22.
  60. "Production of Lignite Coal". U.S. Energy Information Administration. 2012. Retrieved 2015-12-23.
  61. "Archived copy". Archived from the original on 2017-10-20. Retrieved 2017-04-19.{{cite web}}: CS1 maint: archived copy as title (link)
  62. Gordon, Richard (1987). World coal: economics, policies and prospects. Cambridge: Cambridge University Press. p. 44. ISBN 0521308275. OCLC 506249066.
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