MONACA, Pa. — Economic “game changer” is not a phrase often used in Appalachia and rarely a phrase proclaimed in unison by politicians from both parties at the same time on any subject. Yet since 2016, when Shell Chemical announced it was building a $6 billion ethane cracker plant here, an economic revolution began that is far from reaching its potential. Mention “cracker plant” in most parts of the country and people think you are making a Nabisco product, but the cracker plant in Beaver County is all about a molecular “cracking,” in which extreme heat “cracks” ethane molecules to form new ones that will eventually produce more than a million metric tons of polyethylene, a type of plastic used in all kinds of common household products. Creating the fertile building blocks for plastic also creates a vibrant market for new jobs, and not just blue-collar ones but also chemists, computer scientists, and engineers, all of whom are needed in this burgeoning energy economy. The gas found here in the Appalachian region of Western Pennsylvania, Eastern Ohio, and West Virginia is low cost and “wet,” meaning it carries highly valued natural gas liquids, or NGLs. When separated and refined, it can become different fuels, such as fertilizer or propane. The project has already created 1,000 new jobs and is expected to top out at 6,000 during the construction and preparation phases over the next decade...