Question

why subbtiminous called lowest grade of coal​

Answer 1

Answer:

Subbituminous: Subbituminous coal is black in color and is mainly dull (not shiny). ... Lignite: Lignite coal, aka brown coal, is the lowest grade coal with the least concentration of carbon. Lignite has a low heating value and a high moisture content and is mainly used in electricity generation

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Answer 2

Answer:

Subbtiminous or lignite coal , is a soft , brown , combustible , sedimentary rock. It has a carbon content around 25 to 35 % .... It's relatively low heat content , so ..