Does single

If you recycle at home, chances are you take advantage of a system called "single-stream" recycling: you mix all your bottles, newspapers, cans and containers together in a roll cart or dumpster, and a truck comes by once a week to pick them up.

But what happens next? Is that jumble of broken glass, paper, metal and plastic really getting recycled?

The short answer is ... mostly, yes. But the system is far from perfect, and some of what could have been recycled ends up in a landfill.

I followed the trail of single-stream recycling in St. Louis. Here's some of what I found out.

What can be recycled through the single-stream process?

How does single-stream recycling work?

Does everyone in the St. Louis area have access to single-stream recycling?

What is a MRF and what happens there?

VIDEO: This optical sorting machine at Republic Services' MRF in Hazelwood, Mo. is programmed to "see" HDPE or #2 plastic, like detergent bottles and milk jugs with its infrared scanner. Air jets propel the plastics off the conveyor belt into a bunker 25 ft. below. The sorting process isn't perfect, and some plastic bags, papers and other items also get blown off the belt. (Video by Emanuele Berry, St. Louis Public Radio)

http://youtu.be/pygA-4X-qZw

Is everything at a MRF done by machine?

VIDEO: Workers sort recycling and remove trash at Republic Services' MRF in Hazelwood, Mo. (Video by Emanuele Berry, St. Louis Public Radio)

http://youtu.be/Q7KQ-YIm6GA

What causes the biggest problems for a MRF?

Where do residential single-stream recyclables end up?

Besides single-stream, what other residential recycling options are out there?

So what's the bottom line — how well is single-stream recycling really working?

On average, about 8 to 10 percent of the residential single stream recycling that comes into a MRF ends up at a landfill.

But according to Susan Collins, the president of the Container Recycling Institute, a non-profit research and advocacy group, the total loss is closer to 25 percent, because materials leaving the MRF are still contaminated. The companies that buy them have to clean them up before they can be reused, and a lot of what could have been recycled gets lost along the way.

Glass — which should be 100 percent recyclable — fares particularly badly in the single-stream process. Bottles and jars end up crushed and contaminated with everything from pieces of ceramics to chicken bones. Collins estimates that only about 60 percent of the "glass" coming out of a MRF can be salvaged and reused.

"In terms of preserving the quality of materials so the maximum materials collected can actually be recycled, single-stream is one of the worst options," Collins said.

Still, single-stream has increased residential recycling in the St. Louis area, although participation varies widely by municipality.

On average, Republic Services' Brent Batliner said about 20 to 30 percent of St. Louis County's residential waste is being diverted from the landfill. "But you can go into some areas where you’re up to 50, 60 percent, for that particular neighborhood," Batliner said. "And you go into other areas where you may be as low as 5 or 10 percent."

In the city, the diversion rate has plateaued at about 10 percent for the past two years.

Republic Services has recycling plants in approximately 70 cities nationwide. Overall, Batliner said, the St. Louis region is "middle of the road" in terms of its success in keeping residential waste out of the landfill using single-stream recycling.

Follow Véronique LaCapra on Twitter: @KWMUScience