Ever wondered what happens to the recyclables you carefully sort and place in your bin? For years, recycling has been a crucial part of our efforts to reduce waste and protect the environment.

Recycling is hard. Most Americans don’t know what should go into their recycling bins — and when they guess, they often guess wrong and gum up the works of recycling facilities in the process.

Crisscrossing the massive space is a highway of conveyor belts snaking in and out of devices that grind, toss and sort the plastic from paper from glass from cans. Standing over the conveyor belts ...