Synthesis gas production relies on partial oxidation of carbonaceous materials to produce hydrogen and carbon monoxide. Common feedstocks include coal, methane, and biomass. Additionally, waste streams such as sewage waste have been proposed as a starting material. Conversion of solid carbonaceous materials to synthesis gas is driven by high temperature and pressure and proceeds through the stages illustrated below. The reactor design varies depending on production scale, feedstock, and product usage. Applications for synthesis gas are diverse. The product gas can be used directly in combustion to generate electricity; it can be converted to liquid hydrocarbons via Fischer-Tropsch synthesis; and microbes can utilize the product gases to generate complicated chemicals that are not otherwise easily manufactured.