Coal is a
combustible black or brownish-black
sedimentary rock, formed as
rock strata called coal seams. Coal is mostly
carbon with variable amounts of other elements; chiefly
hydrogen,
sulfur,
oxygen, and
nitrogen. As a
fossil fuel burned for heat, coal supplies about a quarter of the world's
primary energy and two-fifths of its
electricity. The largest consumer and importer of coal is
China.
China mines almost half the world's coal, followed by
India with about a tenth.
Australia accounts for about a third of world coal exports, followed by
Indonesia and
Russia. Coal is largely held in the Earth in areas that it needs to be
mined from, and is generally present in coal
seams.
Estimation of proved reserves Unlike "resources", which is the amount that could technically be extracted, according to BP in 2019 "total proved reserves of coal" is "generally taken to be those quantities that geological and engineering information indicates with reasonable certainty can be recovered in the future from known reservoirs under existing economic and operating conditions". Unlike the internationally traded commodities hard or soft coal,
lignite is not traded far from the place where it is mined because of its low value relative to transport costs, so it does not have a national price. For example lignite costs within India vary greatly. The
IEA does not define “reserve” or
proven reserves for coal, only for oil and gas. However the
EIA defines US “recoverable coal reserves”. == List (2023) ==