Gasification is a thermo-chemical process that breaks down coal – or virtually any carbon-based feedstock – into its basic chemical constituents. In a modern gasifier, coal is typically exposed to steam and carefully controlled amounts of air or oxygen under high temperatures and pressures. Under these conditions, molecules in coal break apart, initiating chemical reactions that typically produce a mixture of carbon monoxide, hydrogen and other gaseous compounds. The environmental benefits of gasification stem from the capability to achieve extremely low SOx, NOx and particulate emissions from burning coal-derived gases. Sulfur in coal, for example, is converted to hydrogen sulfide and can be captured by processes presently used in the chemical industry. Coal gasification may offer a further environmental advantage in addressing concerns over the atmospheric buildup of greenhouse gases, such as carbon dioxide. If oxygen is used in a coal gasifier instead of air, carbon dioxide is emitted as a concentrated gas stream in syngas at high pressure. In this form, it can be captured and sequestered more easily and at lower costs. By contrast, when coal burns or is reacted in air, 79 percent of which is nitrogen, the resulting carbon dioxide is diluted and more costly to separate. Gasification of fossil fuel is widely used for the generation of electricity but almost any type of organic material can be used as the raw material for gasification and it can be an important technology for renewable energy.