The Petroleum Coke category consists of two substances; green coke and calcined coke. These two substances are grouped together in a category based on their similarity of manufacturing processes which results in similar physical chemical characteristics and chemical composition. The principal difference is the amount of residual hydrocarbon (also termed volatile matter) in the two products. Both substances are a black-colored solid produced by the high pressure thermal decomposition of heavy (high boiling) petroleum process streams and residues. Green coke is the initial product from the cracking and carbonization of the feedstocks to produce a substance with a high carbon-to-hydrogen ratio and undergoes additional thermal processing to produce calcined coke. The additional processing removes volatile matter and increases the percentage of elemental carbon, which results in a lower potential for toxicity for calcined coke.
To meet the HPV Challenge, the Testing Group has thoroughly evaluated the substances within Petroleum Coke category and has made all of the reliable human health and ecological hazard data available to the public. The hazard potential for the petroleum coke category has been characterized by evaluating existing data, testing green coke to fill data gaps, then “reading across” the green coke results to the other category member, calcined coke. This is justified because green coke contains higher levels of volatile matter, and therefore, it is considered to have more potential to cause human or environmental hazards in comparison to calcined coke.