Synthetic fuels are usually thought of as liquid fuel substitutes for gasoline and diesel fuel made from petroleum sources. In broad context, the source of these synthetics can be any feedstock containing the combustible elements carbon or hydrogen. These include coal, oil shale, peat, biomass, tar sands, and natural gas. Water could be included here because it can be decomposed to produce hydrogen gas, which has the highest heating value per unit weight of any material (excluding nuclear reactions). The conversion of natural gas is treated in a separate article, so this article will emphasize solid feedstocks.

From a practical standpoint, coal, because of its abundance, has received the most attention as a source for synthetic fuels. As early as 1807, a coal-gas system was used to light the streets of London, and until the 1930s, when less expensive and safer natural gas started to flow through...