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A materials dead end? The unraveling of the recycling cycle

03-26 glass recycling

[Image above] Reduce, reuse, recycle—right? Credit: Bill Smith; Flickr CC BY 2.0


Last Thursday, a bulky waste collection truck dutifully crawled down my street, squealing to a stop in front of each house. The truck’s mechanical arm reached up and over the top of the truck, scooping up my blue curbside recycling bin and dumping its contents into the truck’s open top. 

That scene from last Thursday was nothing new. Each week, I collect my discarded and rinsed recyclables into the bin; each week, the truck lumbers up and down my street, whisking my recyclables away so they can be become a whole new generation of materials.

Reduce, reuse, and recycle—right?

But according to a startling 2017 global analysis of all mass-produced plastics to date, 91 percent of the plastics discarded on this planet have never been recycled. That’s some 6,300 million metric tons (Mt) as of a few years ago, a vast majority of the estimated total 8,300 Mt of plastic materials ever generated on the planet.

So perhaps it is no wonder there is a patch of plastic waste that is twice the size of Texas floating in the Pacific Ocean.

According to the global analysis, published in Science Advances, only 9 percent of the discarded plastic on Earth has ever been recycled. About 12 percent has been incinerated, and the rest is polluting the land and sea or buried in landfills. At current rates of production and waste management, the article cites, humankind will have added 12,000 Mt of plastic materials to landfills and the natural environment by 2050.

That’s a 12,000-Mt problem because plastic is one of the most pervasive and persistent man-made materials on this planet, just like concrete—these materials will outlast our lives and the lives of generations to come.

And not only has most of the plastic ever generated never been recycled, but—despite our awareness—the problem is not getting any better.

Bales of plastic waste. Credit: JMacPherson; Flickr CC BY 2.0

When I watched that truck scoop up my blue recycling bin last week, I never would have thought the materials inside might not be recycled into a new generation of materials. And yet, that is the current situation across much of the United States.

China used to import 70 percent of the world’s plastic waste for recycling, some 7 million tons per year. But last year, that recycling stream ground to a halt.

In January 2018, China imposed contamination restrictions on 24 different recycled materials, restrictions so tight they essentially halted the country’s imports of many recyclables. In 2018, China imported less than 1 percent of the recycling imports it accepted in 2016, according to a recent NPR article.

The list of China’s newly restricted materials includes eight kinds of postconsumer plastic, some scrap textiles and papers, and some metal slag. Plus, the country will implement additional import bans on another 16 types of scrap materials come the end of 2019.

With a dried-up Chinese market for recyclable imports, many countries, including the U.S., are left wondering what to do with all the recyclables piling up.

The U.S. has little domestic market for many recyclable materials. So, although recycling bins are still being dutifully picked up curbside in major cities across the U.S., their contents are not being repurposed into new materials. Instead, recyclables are now often either dumped into landfills or incinerated, simply because it makes more economical sense for cities to do so than to pay much higher prices to keep up recycling without China’s help.

(While incinerating plastic waste gets rid of its physical occupation of space, it creates a new pollution problem—harmful chemicals released into the atmosphere when those polymers are burned.)

In essence, we are creating one big linear chain of single-use, disposable materials—what a waste.

While the situation for recyclable plastics is looking dire, you might be thinking that it’s bound to be better when it comes to glass…right?

A glass act

Unlike plastic—for which some formulations can’t be easily recycled and, even if they can, can end up with undesirable properties as a result of using repurposed precursor materials—glass can be recycled with few materials limits.

“Glass is 100 percent recyclable,” says Bob Lipetz, executive director of the Glass Manufacturing Industry Council (GMIC), in a C&EN article about glass recycling. “It has an unlimited life and can be melted and recycled endlessly to make new glass products with no loss in quality.” 

This ease of recyclability is in part why many European countries have achieved glass recycling rates of around 90 percent, according to a GMIC white paper about glass cullet, or crushed glass that can be repurposed into new glass products.

(Beyond just material sustainability, using glass cullet is beneficial for glass manufacturers because it reduces raw materials needs, energy costs, and emissions.)

So, using recycled glass is hardly a materials challenge. And yet the U.S. only recycles about a third of the 10 Mt of glass discarded annually. What is limiting glass in the U.S. from entering a nearly endless recycling cycle?

Mountains of discarded glass—will it be recycled? Credit: Rockman of Zymurgy; Flickr CC BY-NC-ND 2.0

The story, it turns out, isn’t too different from plastic’s tale—it often simply comes down to cost. But unlike plastic, we can’t point blame at another country’s actions.

Producing a high-quality supply of recycled glass cullet requires several processing steps that, in the U.S., often add up to an inefficient and thus costly process. One costly part of this process is how most places in the U.S. recycle materials—single-stream recycling.

Single-stream recycling is a recycling process in which all recyclables are mixed together in one collection bin. While extremely convenient for consumers because all recyclable materials get tossed into the same combined bin, single-stream recycling creates several issues once those bins get emptied.

It is not easy to separate different recyclable materials from one another—there is no magic sorting robot to completely separate milk jugs from beer cans, glass jars, and old newspapers. And while individual mechanized processes—such as magnets to attract metallic waste and air streams to isolate lighter-weight items like paper—can help partially separate mixed recycling streams, there is still a lot of manual separation required.

Plus, when you add to the single-stream mix all the materials tossed in recycling bins that don’t below there, such as coffee grounds, food waste, plastic bags, and other non-accepted materials, the separation issue only becomes messier. 

You can get an idea of how complex and manual single-stream recycling is in this video from Rhode Island’s Material Recycling Facility.

Credit: RIRRC; YouTube

In the end, challenges with single-stream recycling lead to lower-quality individual material streams being separated from the mix. In particular, glass cullet, for which a high-quality supply of consistent and pure materials is critical, single-stream recycling just doesn’t cut it.

Multi-stream recycling systems, in which consumers toss their recyclables into separate bins that are collected and maintained as separate material streams, offers one solution to the contamination problem.

Although multi-stream recycling is not the standard mode of recycling in the U.S., certain areas and cities have implemented multi-stream recycling—in some areas, specifically for glass—which does offer a much higher quality stream of recycled glass cullet, according to the GMIC report.

But although it solves one problem, multi-stream recycling is not a viable solution for all communities.

For one, multi-stream recycling is costly and logistically more complicated to implement than single-stream systems—consumers must be educated about how to properly use the system, and collecting and maintaining separate materials streams necessarily requires greater coordination and resources.

And, once collected, transporting those individual material streams—which in the U.S. often requires transport across relatively large distances—introduces yet another economical challenge.

Cycling back

So what is the solution to the seemingly broken materials recycling cycle?

Unfortunately, there is no easy solution.

But in regard to glass, there are at least several options. According to the GMIC white paper, “Increasing the amount of recycled glass in the U.S. can be considered as a two-fold problem.” Those two problems are that we need

  • Actions to increase the amount and quality of glass entering and passing through the chain of custody,
  • Actions to improve the quality and lower the cost of recycled cullet along with actions to educate organizations in the chain of custody.

Part of the challenge to improving waste collection streams, both in amount and content, is doing so at an economical cost. One potential solution is glass redemption centers, drop-off bins, and deposits for beverage containers (bottle bills), which have been successfully implemented in several areas in the U.S. (and many more areas beyond the U.S.).

Bottle bills or container deposits have an interesting history. While they used to be the norm and are still used in several countries outside the U.S., a combination of technological and materials advances along with social, economic, and political influence have tossed bottle bills out with the trash. Literally.

Another needed solution is improved sorting processes to better separate single-stream recyclables, as that remains the main form of recycling currently in the U.S. Updated high-tech sorting systems that use optical sorting and hyperspectral imaging could help reach higher cullet standards, but again the challenge with these technologies is prohibitive cost.

For additional details on glass recycling, delve into the full GMIC white paper here.

Ultimately, there are no simple solutions—but whether simple or complex, we need solutions now. Our recycling cycle is too often becoming a materials dead end.

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