Though an ethane cracker is a pretty high-tech facility, the basic concept is fairly simple: It takes ethane—a petrochemical that is one of the main components of natural gas—and turns it into the building blocks of plastics. There happens to be a lot of ethane mixed in with the natural gas deposits of Pennsylvania’s Marcellus Shale, which is why Shell wants to build the cracker here in the first place.
The facility will heat the ethane to very high temperatures—we’re talking 1,500 degrees. And at that temperature, an ethane molecule actually starts to break apart.
“You can almost imagine it like when you have two kids, and when they hold arms and swing each other around—if they get too crazy and too wild, at some point they just can’t hold onto each other and they fly apart,” says Getz Veser, a chemist at the University of Pittsburgh.
And the result of this reaction is a whole new molecule called ethylene. Ethylene reacts very easily with other chemicals, so it can be strung together in long chains—kind of like Legos that snap together. We call this type of material polyethylene, and it’s used to make everything from plastic bags to PVC pipe.