A substantial part of production in Marl, Evonik’s largest location, is based on the formula C4. It stands for liquid gases, the molecules of which contain four carbon atoms. These liquid gases are refined more and more, via a series of steps, at the C4 facilities in Marl and similarly at the Antwerp location. The products of these processes include MTBE (methyl tert-butyl ether), which is used as an antiknock additive to increase the octane value of gasoline and thus improve combustion, DINP (diisononyl phthalate), a plasticizer that turns brittle PVC into a flexible material, and butadiene, which is processed into synthetic rubber for car tires. All of the C4 facilities are connected closely together by material and energy flows. Even the byproducts of a process can be used as raw materials in other facilities, and the waste heat from one process step can supply the energy needed for another.