Coal is as variable as the conditions in the mire, during and after peat accumulation. Many classification systems have been developed so that the coal is used appropriately. Traditional coal classification schemes, such as the rank-based system of ASTM D388 (ASTM, 1996a) or the original ISO (United Nations Economic Commission for Europe) International Classification of Hard Coals by Type, were developed using one type of coal, specifically, vitrinite-rich coals. The goal of international codification systems has always been to provide a uniform basis for the understanding of the range of coal properties while accounting for the differences between coals of different origins, such as between the Carboniferous Laurasian (Northern Hemisphere) and the Permian Gondwana (Southern Hemisphere and India) coals.
The United Nations Economic Commission for Europe endorsed a codification for bituminous- and anthracite-rank coals in 1988 (United Nations, 1988). While not quite satisfying all of the needs of the major Gondwana exporters (Australia and South Africa) owing to the dependence upon vitrinite properties, the system is more universal than any previous codification. The international system codifies coals by means of a 14-digit number based on eight coal-quality parameters (Table 10):