Coal science in the 20th century

One of the significant changes brought by the industrial revolution required a reliable source of power. As alternative resources of wood, hydro- and wind-powers, drastic increase of production and consumption of coal have been occurred in the last and in this centuries. The value of coal is process heat, electricity, transportation fuels, metals for extracting from their ores and chemicals derived from coal-tar. The industries needs qualification and classification of coal. On the other hand, fundamental investigation of coal has been motivated and initiated at the same periods. In this review, coal science started at the early and middle stages in the 20th century is concerned. Special attentions are put on classification and formation of coal, graphical statistical analysis with coal band, aromatic cluster in coal structure as well as network and molecular association of coal. Probes at the structure analysis and reactions are extracted and discussed. The way to keep the sustainable civilized society in the next century is the efficient utilization of coal as one of the energy and carbonaceous resources. This implies that the enhancement of the research activities on coal even in the 21st century is important.