A sign on an upside-down dumpster spelled the end of Pearl Pai’s long romance with plastics recycling. For years, Pai and her family generated almost no trash. She carefully washed, sorted and bagged hard-to-recycle items and drove them two towns over from her home in Berkeley, California, to the area’s best recycling center. But on a gray morning in late May, when she pulled up with a bag of flimsy plastic clamshell-style containers, yogurt tubs and meat trays, the sign informed her that, “due to poor market conditions”, these items would no longer be accepted for recycling. This is a...