gas mains, lead piping, coal ashes. Cyanide Purifier waste has large amounts of complex ferrocyanides in it. Lampblack Only found where crude oil was used as gasification feedstock. Tar emulsions Coal tar and coal tar sludges are frequently denser than water and are present in the environment as a dense non-aqueous phase liquid. In the UK, a number of former gasworks sites have been redeveloped for residential and other uses (including the Millennium Dome), being seen as prime developable land within the confines of city boundaries. Such development opportunities are now leading to problems associated with planning and the Contaminated Land Regime and have recently been debated in the House of Commons. Environmental impact of modern coal gasification Coal gasification processes require controls and pollution prevention measures to mitigate pollutant emissions. Pollutants or emissions of concern in the context of coal gasification include primarily: Ash & slag Non-slagging gasifiers produce dry ash similar to that produced by conventional coal combustion, which can be an environmental liability if the ash (typically containing heavy metals) is leachable or caustic, and if the ash must be stored in ash ponds. Slagging gasifiers, which are utilized at many of the major coal gasification applications worldwide, have considerable advantage in that ash components are fused into a glassy slag, capturing trace heavy metals in the non-leachable glassy matrix, rendering the material non-toxic. This non-hazardous slag has multiple beneficial uses such as aggregate in concrete, aggregate in asphalt for road construction, grit in abrasive blasting, roofing granules, etc. Carbon dioxide (CO2) CO2 is of paramount importance in global climate change. Mercury Arsenic Particulate matter (PM) Ash is formed in gasification from inorganic impurities in the coal. Some of these impurities react to form microscopic solids which can be suspended in the syngas produced by gasification. Sulfur dioxide (SO2) Typically coal contains anywhere from 0.2 to 5 percent sulfur by dry weight, which converts to H2S and COS in the gasifiers due to the high temperatures and low oxygen levels. These "acid gases" are removed from the syngas produced by the gasifiers by acid gas removal equipment prior to the syngas being burned in the gas turbine to produce electricity, or prior to its use in fuels synthesis. Nitrogen oxides (NOx) (NOx) refers to nitric oxide (NO) and nitrogen dioxide (NO2). Coal usually contains between 0.5 and 3 percent nitrogen on a dry weight basis, most of