Editing Lignite (section)

== Characteristics ==
[[File:Lignite mining in Western North Dakota.jpg|thumb|left|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 [[Coal assay#Moisture|inherent moisture content]] is sometimes as high as 75 percent<ref name=brit>Kopp, Otto C. [https://www.britannica.com/science/lignite "Lignite"] {{Webarchive|url=https://web.archive.org/web/20190603191844/https://www.britannica.com/science/lignite |date=2019-06-03 }} in ''Encyclopædia Britannica''</ref> and its [[Coal assay#Ash|ash]] content ranges from 6–19 percent, compared with 6–12 percent for [[bituminous coal]].<ref>{{cite book |last=Ghassemi |first=Abbas |title=Handbook of Pollution Control and Waste Minimization |publisher=CRC Press |year=2001 |page=434 |isbn=0-8247-0581-5}}</ref> 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.<ref name="useia"/>

[[File:Garzweiler surface mine, October 2018, -01.jpg|thumb|[[Strip mining]] lignite at [[Tagebau Garzweiler]] in Germany]]

The energy content of lignite ranges from {{convert|10|to|20|MJ/kg|e6btu/ST|0|abbr=unit|lk=on}} on a moist, mineral-matter-free basis. The energy content of lignite consumed in the United States averages {{convert|15|MJ/kg|e6btu/ST|abbr=unit}}, on the as-received basis.<ref>{{cite web |title=Lignite |url=https://www.eia.gov/tools/glossary/?id=coal |website=Glossary |publisher=U.S. Energy Information Agency |access-date=4 May 2021}}</ref> The energy content of lignite consumed in Victoria, Australia, averages {{convert|8.6|MJ/kg|e6btu/ST|abbr=unit}} on a net wet basis.<ref name="victoria-coal-data-sheet">{{Cite book |url=http://new.dpi.vic.gov.au/__data/assets/pdf_file/0006/37518/Brown-Coal-050710.pdf |title=Victoria, Australia: A principal brown coal province |date=July 2010 |publisher=Department of Primary Industries Melbourne |isbn=978-1-74199-835-1 |archive-url=https://web.archive.org/web/20110317032514/http://new.dpi.vic.gov.au/__data/assets/pdf_file/0006/37518/Brown-Coal-050710.pdf |archive-date=March 17, 2011}}</ref>

Lignite has a high content of volatile matter which makes it easier to convert into gas and liquid petroleum products than higher-ranking coals. 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.<ref>{{cite report |last=George |first=A.M. |title=State Electricity Victoria, Petrographic Report No 17. |year=1975 }}</ref><ref>{{cite report |last=Perry |first=G.J. |last2=Allardice |first2=D.J. |work=Coal Resources Conference, NZ 1987 |id=Proc. 1, Sec. 4. |title=Paper R4.1 }}</ref> However, removing the moisture increases the cost of the final lignite fuel.

Lignite rapidly degrades when exposed to air, in a process called ''slacking'' (or ''slackening'').<ref name="principal-na"/>