Given what scientists already know how to do, the future could bring a greener, more fool-proof system. Right now, she said, she and other scientists are starting to develop ways to recycle mixtures of plastics — a tough job because many plastics repel one another like oil and water. One of the reasons China imported recycling was that it was possible there to hire cheap labor to sort the different plastic types by hand. (Worth noting: Over that same span in which recycling streams have become more contaminated, labor in China has also become scarcer and more expensive.)