In concept, single-stream recycling is a marvelous thing.

When everything glass containers, aluminum cans, plastic bottles and spent paper products of all shapes and sizes — can be chucked into a single bin and hauled to the curb, folks who normally balk at the act of recycling are more likely to participate. (Some people really hate sorting, apparently.) In turn, by taking sorting out of the equation and making things simpler for the consumer, household recycling rates go up, municipalities cut costs on the collection/transportation front and, theoretically, less recyclable waste ends up being landfilled.

Yet in reality, single-stream recycling programs — first introduced in the 1990s in California as an alternative to multi-stream recycling, which requires the consumer to sort his own waste prior to collection, and now representing a majority of municipal recycling programs — are far from perfect.

As Sarah Laskow wrote for The Atlantic back in 2014, the problem with single-stream recycling begins largely at material recovery facilities (MRFs). Manned by both humans and high-tech machinery, these expansive and sometimes expensive-to-operate facilities are the first stop commingled recyclables make after being picked up via curbside collection programs.

Provided that recyclables arrive at MRFs as one jumbled mass instead of a neatly pre-sorted heap, the risk for contamination is high. And if one recyclable contaminates another recyclable, both items lose their value. In the world of single-stream recycling, glass containers, by their very fragile nature, are a top contaminant. You see, glass containers are highly vulnerable to breakage — and this can happen anytime between collection and their arrival at an MRF. When these containers shatter and break, they taint the entire load.

"As we often say, you can't unscramble an egg," Susan Collins of the nonprofit Container Recycling Institute explained to NPR last spring, noting that single-stream recycling systems promote volume but not quality. "In terms of preserving the quality of materials so that the maximum materials collected can actually be recycled, single-stream is one of the worst options," she says. Collins adds that a quarter of single-stream recycling is hauled to the dump due to cross-contamination. Glass represents roughly 40 percent of landfilled recyclables.

In turn, many waste-sorting facilities dealing with single-stream systems have begun to turn away glass containers while continuing to accept aluminum cans, newspaper and what have you. While there is special machinery that can help MRFs pluck out broken glass from the stream, it can be prohibitively expensive. And so, with nowhere else to go, perfectly good glass is being landfilled by the truckload across the nation.

There could be worse things to send to the landfill than glass. Unlike other forms of waste (I’m looking at you, plastic) that pose serious environmental threats when landfilled, glass is nontoxic and relatively benign. It’s sand, after all. In addition to being heavy and expensive to transport, the issue with landfilled glass is largely real estate-related. That is, infinity recyclable glass containers take up a lot of space and ultimately stick around for the long-haul (read: 1 million-plus years) before beginning to break down and decompose.

A dirty little secret?

There’s another emerging issue with glass being redirected away from sorting facilities and dumped into landfills: Oblivious to the fact that their recyclables are, in fact, not being recycled, many residents are continuing to dutifully add glass containers and jars to single-stream recycling programs.

While cities such as Baton Rouge, Boise and Harrisburg, Pennsylvania, have either suspended or never even offered glass recycling, other cities such as Denver, Chattanooga and Atlanta continue to collect glass for recycling … and then dump it in landfills.

In the Atlanta metro area, where single-stream recycling dominates, some residents are riled up over this rather hush-hush practice.

“The county should have let people know that they really don’t need to be doing any of this. They didn’t need to be saving the glass at all,” Dekalb County resident Carol Lambert tells the Atlanta Journal-Constitution. “I think a lot of people have come around to doing some sort of recycling, but I don’t like the deception.”

Writes the AJC:

Some recycling companies treat glass like garbage because it can slash more valuable recyclables like cardboard and paper. Shards can also damage recycling machinery or pose an injury risk to workers.

Every county in the core Atlanta area works with companies that reject glass from their recycling streams.

Meanwhile, government officials and environmentalists said they’re wary of telling residents not to recycle glass. They don’t want to send a mixed message after years of efforts to simplify recycling by allowing residents to combine their materials.

Ack. It’s discouraging stuff — and it also begs the question: In cities where glass materials are collected for recycling but ultimately landfilled (Denver and Chattanooga both crush glass and uses it as a landfill cover), are there ways to really recycle glass containers? Or is diverting that old spaghetti jar from the landfill a fruitless effort?

This largely depends on the market for recycled glass where you live. By not adding glass materials into a single-stream recycling system, you’re avoiding the middleman: the MRF. And the operators of facilities not equipped to handle glass will likely thank you for this. However, this often means that curbside recycling is out the question and that you’ll have likely have to haul glass containers directly to a recycler or specialized recycling facility/drop-off location. And in some areas, this is no easy task. So much for easy, breezy and convenient one-bin recycling.

There’s also container deposit legislation to consider. While only on the books in 10 states, bottle bills further encourage recycling and help ensure that glass containers remain out of landfills and in perpetual circulation as they should be.

Matt Hickman ( @mattyhick ) writes about design, architecture and the intersection between the natural world and the built environment.