In the tiny town of Ashley, Ind., a factory is about to be built that could help change how American companies dispose of plastic waste.

RES Polyflow plans to break ground early next year on the first commercial-scale plant creating petroleum blends from nonrecycled plastic trash. A multimillion-dollar investment from Brightmark Energy and a possible bond sale will finance the construction of the $200 million plant, which will employ 136 people, RES Polyflow said Nov. 9.

To date, economic...