Coal as a fuel
Bituminous coal is a solid mineral fuel. It is a sedimentary rock formed from dead plants, mainly during the Carboniferous period, around 360-300 million years ago – in the Palaeozoic era. Over time, with heat and pressure, the dead plant material was subjected to coalification, a process which increases the percentage content of carbon (C), and decreases the amount of oxygen, hydrogen and other substances. In a nutshell, bituminous coal is solar energy converted by the process of photosynthesis – a biological process – in to biomass and then stored through the slow geological processes occurring on Earth.