During coal gasification the environmentally unfriendly components, sulfur, nitrogen, chlorine and the trace metals, can be released with the tar and gaseous species or retained in the carbonaceous char and ash. The fate of these components is dependent on the type of coal, on the reaction conditions to which they are subjected during gasification, on downstream pollution control devices and on the type of gas turbine used for electricity production. A model has been developed to predict the fate of these components under a range of conditions, so that suitable measures can be devised to minimize their environmental impact, and to estimate their effects for two generic types of gasifier, namely those based on air and on oxygen. The trace metal distribution could be modelled accurately up to 1100 degrees C but uncertainty increased at higher temperatures. Ammonia and hydrogen cyanide were found to be mainly formed from the coal nitrogen and their pathways were followed by kinetic modelling. These compounds can affect the level of NOx produced by the gas turbine.