Big makers and users of plastic packaging are betting on a recycling technology that has failed for decades to take off, as a public backlash and new rules push them to find ways to cut waste and greenhouse-gas emissions tied to plastic.
Plastic makers like BP PLC and Dow Inc., and packaging users like Coca-Cola Co., Danone SA and Unilever PLC, are testing or investing tens of millions of dollars in the technology, called chemical recycling. The process uses chemicals or heat to break down plastic so it can be turned into…