Pittsburgh’s Jana Thompson takes her recycling pretty seriously. She’s even been known to pry the unrecyclable spouts off otherwise recyclable dishwashing detergent bottles. And check out her recycling bin, and those clear plastic salad tubs are stacked as neatly as a set of Russian dolls.

“Well, I do nest,” Thompson says, laughing. “But if you put two of those [in there], and you don’t nest, there’s no room left—even in a big garbage can.”

Still, despite all the care she puts into it, when it finally comes time to lug her recycling bin out to the curb, she admits sometimes a certain nagging little doubt creeps into her mind.

“Is it somehow just all going into the garbage? Because who are they paying to break apart shopping receipts from soda cans?”

The idea that all of this stuff can be separated once it’s jumbled up in one pile does seem sort of mind boggling. In fact, Kyle Winkler, the city of Pittsburgh’s recycling director, says he hears questions about this all the time.

“Single stream recycling made life more convenient for folks,” Winkler says. “But because people don’t understand how the technology works to sort it, there’s that perception that it doesn’t get sorted.”

And Winkler says that perception is a largely a result of the sorting process being taken out of our hands and put behind a Wizard of Oz-like curtain of mystery. Back in the early days of recycling, during World War II, there was an extreme degree of sorting at the household level.

“Somebody told me the other day that there used to be a guy who would come around and pick up rags,” Winkler says. “He was the rag man. Source-separated rag collection was a thing, which just blows my mind today.”

Eventually, though, the rag man disappeared. And in his place came a dual-stream recycling culture.

“So your containers—your glass, metal, plastic—were separated from your newspaper, your mixed paper and your cardboard.”

But eventually, even that system was abandoned—mostly because waste haulers didn’t like it. Dual-stream trucks kept the paper and cardboard separate from the other recyclables, but each side of the truck didn’t always fill up at the same time, leading to more routes and greater costs. As a result, we got the modern single stream system, where we don’t sort anything on the household end. It all just goes into one bin, gets dumped into one truck, and then gets sorted somewhere else.

And yes—it does get sorted.

“This is the very beginning of the whole process,” shouts Russell Holby, standing in front of a mountain of unsorted recycling fresh off the truck. It’s Holby’s job to oversee the operation which untangles the contents of Pittsburghers’ recycling bins at a sorting facility in Hazelwood.

“Just to give you an idea—our facility is on eight acres. So you’re looking at about 50 yards of material here, 20 feet high.”

A front-end loader will scoop up piles of this material all day long. It then gets fed in one end of a long train of machines designed to pick out specific materials, one by one, until there’s just one kind of material left at the very end. Cardboard, for instance, gets pulled off on the first set of machines.

“We call them star screens,” Holby says. “So what this is trying to do is pull all the larger cardboard out. And actually all the glass and everything will fall down in between these stars and hit two separate infeed belts to the next section.”

The star screens—despite the name—are actually pretty low-tech. They’re basically just a giant mechanical sifter. But some of this stuff is pretty amazing. The machine for separating aluminum cans, for instance, uses what’s called an Eddy current. It gives aluminum, which is not magnetic, a temporary charge that makes aluminium cans literally pop up in the air.

“You can actually see how it will throw any aluminium cans over that separator there. Anything else will fall directly down. It’s pretty wild.”

A couple dozen workers work quality control at various stages to pick out what the machines miss. But most of the process is automated. Huge magnets, for instance, pull out steel cans. And a system called Eagle Vision can actually separate three kinds of plastic at a time. It’s uses a camera to identify different types of plastics, and then jets of compressed air blow things right off the conveyer belt.

“The first time I saw it, I was like, ‘It’s magic.’ But it isn’t magic. It’s physics and science.”

It should be said that the system doesn’t get everything. It only recovers about 90 percent of what comes in on the trucks. And it’s kind of impossible to keep every shred of paper out of a pile of broken glass. But that’s the essence of the single stream system. It’s not about getting every last item. It’s about percentages. It’s a social contract, where we tolerate a certain amount of waste to get some added convenience so that more people will recycle. And like it or not, it’s the system that’s here to stay.

This story is part of the Citizen Q series, where The Allegheny Front answers your everyday questions about the environment.