Pre-combustion capture is carried out in power plants where fossil fuels are utilized in a quite different way. A limited amount of pure oxygen is supplied, with or without steam, to partially oxidize the fuel. Depending on the type of fuel used, the process is referred to as either steam reforming (for natural gas) or gasification (for coal). The product is synthesis gas (syngas) comprised primarily of carbon monoxide, hydrogen and some carbon dioxide. This hot gas mixture contains thermal as well as chemical energy, which are converted to electricity through a steam turbine and a gas turbine, respectively. The whole process, termed integrated gasification combined cycle (IGCC), is more energy efficient than combustion and has simpler emission control. If CO2 capture is desired, the cooled syngas, instead of going straight to the gas turbine, is subjected to a water-gas-shift reaction to convert carbon monoxide into CO2. The CO2/H2 mixture then goes through a separation unit to remove CO2 and produce high purity hydrogen, which can be either combusted to generate power, stored, or transported. The gas mixture has a simple composition, is at high pressure, and contains CO2 in high concentration, making CO2 separation much easier and less energy intensive than post-combustion capture. However, retrofitting power plants for pre-combustion carbon capture is much more difficult than for postcombustion, and the production of pure oxygen for partial oxidation is energy-intensive.