On April 29th, 2018 we learned about

Details and developments in how plastics get can be efficiently recycled

My five-year-old is quite confident that it’s better to when waste goes in the blue bin, instead of the black. Even though it gets hauled away in an identical garbage truck each week, he knows the blue bin items will be recycled, turned into something useful enough to avoid sitting in a landfill. Those last few steps probably get pretty fuzzy, because they’re basically invisible from our perspective. We don’t see the work that goes into sorting recyclables, how they get shipped, and the difficulties in actually making these materials into something new. It’s not quite the magical process many of us may imagine it to be, but researchers are helping us get closer to the promise of recycling everything that goes in those special blue bins.

Sorting recyclables from other refuse

Once a truck hauls away recyclables, the first step at the local waste processing center is to sort what we’ve dumped in our bin. Items that are too dirty, oily or saturated with contaminants may need to be removed, alongside all the materials that shouldn’t have been placed in the recycling bin in the first place. Some items, like Tetra Paks, may technically being made of recyclable materials but are constructed in a way that preclude them from being cost effective to properly disassemble. The overall impact of all these special cases add up- a processing center in New York estimated that around 50 percent of what’s put in a recycling bin has to be sent to a landfill, despite people’s good intentions for their reuse.

That still leaves a considerable amount of goods that can be reused though, although the cost effectiveness of each material can vary greatly. Pulling out items like glass and metal are fairly straightforward, and they can generally be sold as completely reusable materials in manufacturing. Conversely, plastics are a bit harder to manage, as some types can be repeatedly reprocessed, while others aren’t worth working with after one or two manufacturing cycles.

Squashing, scrubbing and shredding

One of the more reusable types of plastic is polyethylene terephthalate (PET). It’s highly compressible, which means that it can be crushed into bales for efficient shipping to facilities that will actually be able to reprocess it into an useful material. Until recently, this may have included shipping those bales to places like China, although those arrangements have now been terminated leaving many cities without a clear destination for their recyclable goods. Within the United States, some companies are equipped to take the next steps in reusing PET plastics, with one facility in California processing over two billion bottles a year.

To reuse a single bottle, it must first be sorted according to color. This sorting is automated, with lasers quickly assessing what types of plastic are running down the conveyor belt at any given moment. Once sorted, the mashed bottles are washed and heated to cleanse them of residual labels, bottle caps and any other organic materials that may be left behind. After that, the bottles are shredded in small flakes, then washed and heated again before they get packaged for manufacturers. If those flakes might be used in food packaging, they require further cleaning testing before being reused. All this preparation obviously requires a fair amount of energy, but the resulting PET flakes can be used in everything from carpet fibers to new bottles.

Making polymers perfectly mutable

Not every piece of plastic is as recyclable as PET, although researchers are working on some very promising alternatives. While PET can be chopped into relatively small bits, the core structure of plastics make them frustratingly durable— even when reduced to pellets, the chains of molecules that plastics are made of, called polymers, don’t break down in most environments, which is part of why a cheap bottle can sit in a landfill for 500 years. Of course, weakening those polymers too much leaves us with unstable products that would become unusable if heated as much as a warm beverage.

One solution may be to add new, reinforcing molecules to softer polymers. Researchers from Colorado State University have found that adding ringed molecules to polymer chains can make them less sensitive to higher temperatures, without making them too difficult to break down by other means. Ideally, these new plastics could be broken down to their original plasticity in a bath of specific chemicals, making them into a highly versatile and cost effective material for manufacturing. The one catch is that the reinforcement has left these plastics a little too stiff, making them brittle. With any luck, they’ll find a happy medium soon enough making recycling a wider range of products more practical in the near future.


My third-grader said: It’s too bad we can’t just stop using plastic.

Plastic is really useful though. It can be incredibly strong, light, and formed into all kinds of products. It’s unlikely to fall out of use any time soon. However, that doesn’t mean we can’t be thoughtful about when we use it, and when we might re-use it. Specifically, single-use products, like a drinking straw, or water bottle, can probably be skipped or replaced by other, more durable items. Avoiding tossing items into either the trash or recycle bin after using it once is one of the easiest ways to avoid contributing to the world’s piles of plastic.

Source: The Violent Afterlife of a Recycled Plastic Bottle by Debra Winter, The Atlantic

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