why the coal with higher percent of carbon is prefeced
Answers
Coal is ranked in six different categories:
1. Peat - not really a coal; it is undeveloped, soft and spongy. It is 20-25% carbon, and was deposited during the last 100 years by decomposed plant remains.
2. Lignite- the first "real" coal. It has a low heating value and is often found near the earth's surface. Lignite coal loses its moisture when exposed to air.
3. Subbituminous - lower in carbon content than bituminous coal. It also loses its moisture when exposed to air. When exposed to wetness it
4. Bituminous - has a high carbon content (65-85%), and a low oxygen content (5-15%). It usually burns with a yellow flame.
5. Semianthracite - a hard coal but softer than anthracite. It has a fixed carbon percentage of 80-85%. It contains more volatile matter than anthracite and also burns more freely.
6. Anthracite - hard, durable, high density. It has low volatile matter and is 85-98% fixed carbon. It ignites slowly and burns with little flame or smoke.
Answer:
because it's a natural limited resource