Coal assay heating value is based on the moisture content as mined, but without any free water. The ISO has a coal ranking system that also ranks coals; the sub-divisions do not align with the ASTM standard. "Coal Analytical Methods" Blackwell Scientific Press, 1984. Coal assay Coal analysis techniques are specific analytical methods designed to measure the particular physical and chemical properties of coals. These methods are used primarily to determine the suitability of coal for coking, power generation or for iron ore smelting in the manufacture of steel. Coal comes in four main types or ranks: lignite or brown coal, bituminous
Environmental impact of the coal industry This is due to the relaxation of pressure and fracturing of the strata during mining activity, which gives rise to safety concerns for the coal miners if not managed properly. The buildup of pressure in the strata can lead to explosions during (or after) the mining process if prevention methods, such as "methane draining", are not taken. In 2008 James E. Hansen and Pushker Kharecha published a peer-reviewed scientific study analyzing the effect of a coal phase-out on atmospheric CO levels. Their baseline mitigation scenario was a phaseout of global coal emissions by 2050. Under the "Business as Usual" scenario,