The formula is fairly simple. The Marcellus and Utica shale formations, two of the biggest natural gas fields in the United States, largely lie beneath Pennsylvania, Ohio, West Virginia and New York. The surrounding Rust Belt is also home to many of the country's plastics manufacturing factories.
What's missing is the link between the two: the massive plants that turn natural gas byproducts into the inputs needed to manufacture plastic products.
The plants, called crackers, heat natural gas byproducts, like ethane and propane, in order to break them down, or "crack" them, in industry parlance. What comes out is base chemicals, like ethylene and polyethylene, the most widely used plastic, which is shipped in pellets that are then shaped into a range of consumer and industrial goods.
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The Shell facility near Pittsburgh will use ethane produced in the Marcellus and Utica basins to make 1.6 million tons of polyethylene a year. The oil major notes that "more than 70 percent of North American polyethylene customers are within a 700-mile radius of Pittsburgh."
Shell will no doubt seek to tap that domestic market, but the crackers already supplying the region will certainly fight to keep their share, said Steve Zinger, vice president of chemicals at energy consultancy Wood Mackenzie. The result: Much of the new net output will likely be exported, he said.
This is one reason big companies with logistics experience like Shell will continue to drive the petrochemicals expansion, Zinger said. Already, plans for small crackers in the Appalachian region have been scrapped or delayed.
"You really need those economies of scale. You can't just go on the feedstock alone," Zinger told CNBC.
"It's one thing to have the technology to convert ethane into a chemical, but then you have to say, What am I going to do with this chemical? How am I going to move it to market?"