Coaltoliquids

Coal-to-liquids (CTL) describes processes that convert coal into liquid hydrocarbon fuels. The predominant approach is indirect CTL: coal is gasified to produce synthesis gas (a mixture of carbon monoxide and hydrogen), the gas is purified and adjusted, and then the Fischer-Tropsch synthesis converts the gas into long-chain hydrocarbons that are upgraded into gasoline, diesel, or jet fuel. Direct CTL also exists, wherein coal is hydrogenated at high pressure and temperature to produce liquids directly, but has seen less commercial deployment than indirect CTL.

Commercial CTL has been deployed primarily by South Africa's Sasol, notably at the Secunda complex, which has supplied large volumes of liquid fuels for decades. China and some other countries have pursued CTL projects at various scales, including pilot plants and proposed commercial schemes, but many have faced economic and policy hurdles related to oil prices, carbon costs, and water use.

Environmental and energy considerations include higher lifecycle greenhouse gas emissions compared with conventional fossil fuels, particularly if coal is not coupled with carbon capture and storage. CTL is energy and capital intensive and dependent on coal prices; water consumption and air emissions are also concerns. Proponents cite energy security and domestic fuel production, while critics point to climate and resource risks. In some policies, CTL deployment is contingent on carbon pricing or CCS availability.