Fischer–Tropsch plants associated with biomass or coal or related solid feedstocks (sources of carbon) must first convert the solid fuel into gases.  These gases include CO, H, and alkanes. This conversion is called gasification.  Synthesis gas ("syngas") is obtained from biomass/coal gasification is a mixture of hydrogen and carbon monoxide. The H:CO ratio is adjusted using the water-gas shift reaction. Coal-based FT plants produce varying amounts of CO, depending upon the energy source of the gasification process. However, most coal-based plants rely on the feed coal to supply all the energy requirements of the process.