Petroleum coke (often abbreviated Pet coke or petcoke) is a carbonaceous solid derived from oil refinery coker units or other cracking processes. Other coke has traditionally been derived from coal. Calcined petroleum coke (CPC) is the product from calcining petroleum coke. This coke is the product of the coker unit in a crude oil refinery. The calcined petroleum coke is used to make anodes for the aluminium, steel and titanium smelting industry. It is used in friction materials for its low density and mild abrasive effect. The green coke must have sufficiently low metals content in order to be used as anode material. The green coke with too high metals content will not be calcined and is used as fuel.