what is the difference between brown coal (lignite) and firewood?
Bituminous: Bituminous coal is a middle rank coal between subbituminous and anthracite. ... Subbituminous: Subbituminous coal is black in color and dull (not shiny), and has a higher heating value than lignite. Lignite: Lignite coal, aka brown coal, is the lowest grade coal with the least concentration of carbon.