A feedstock is raw material (unprocessed material) for a processing or manufacturing and which is an asset that is critical to the production of other products. For example, natural gas and crude oil are feedstock raw materials that provide finished products in the fuel industry. The term raw material is used to denote material in an unprocessed or minimally processed state, such as raw natural gas, crude oil, coal, shale oil, or biomass. However, coal, oil shale, and biomass tar sand are complex carbonaceous raw materials and are possible future energy and chemical sources but, like all feedstocks for petrochemical production, they must undergo sometimes lengthy and extensive processing before they become suitable gases and liquids that can be used for the production of the petrochemicals. They will, however, be synthesis gas (Chapter 5) which can be used as a precursor to a range of petrochemical products (Chapter 10).