Pet coke is the solid carbon byproduct of cracking units such as the the FCC and coker unit.

In an FCC, coke forms on the catalyst and is burned off as fuel for the FCC process, resulting in no net production of coke as a product.

In a delayed coker, resid is thermally cracked to produce lighter more desirable products. In the process a significant portion of the feed (~15% of volume) is converted into elemental carbon called petroleum coke. Refiners separate the coke from the other coker products and sell it as a product.

The primary end use for pet coke is as a solid fuel, used as a substitute for coal in furnaces and boilers. The value of the coke as a product is typically far below the cost of the crude oil used to produce it.