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Circular Economy, Advanced Recycling, and Plastic

Historically, the US has a poor record for recycling its plastic waste. Could a circular economy solve this conundrum?

This past spring, the environmental groups The Last Beach Cleanup and Beyond Plastics published a report with discouraging data about plastic recycling. Already abysmally low, the rate for 2021 was about 5 to 6 percent, down from 8.5 percent in 2018.

As expected, the media’s response was frustration, dismay, and anger. Environmental groups responded in kind, placing the plastics problem at the feet of the hydrocarbons industry (rightfully so) while demanding an end to plastics of any kind.

Disheartening, to be sure, but doom and gloom it is not. Why? Because despite all the noise and hype surrounding plastics, we are in the early phases of a paradigm shift as we evolve from a linear economy to a circular economy that benefits us and the world at large. And it has everything to do with plastics.

Strange bedfellows

Billiards was originally a lawn game played in northern Europe in the 15th century. Enjoyed by nobles and common folk alike, the game evolved into using ques (sticks), pockets, and balls. Before colonization and trade introduced ivory, the earliest balls were stone and wood. More durable than wood but also expensive, ivory balls tended to yellow with age and cracked in humid climes or if struck forcefully. Despite these downsides, ivory balls became the biggest rave at the expense of elephant herds in Africa and Asia, whose populations plummeted.

In 1869 the pool table manufacturer Phelan and Collender offered a $10,000 prize for anyone who could replace ivory with a similar material that was just as robust but that didn’t rely on a finite and seemingly unsustainable natural resource. In stepped celluloid, the first synthetic polymer. Made from compressed nitrocellulose (sourced from wood and cotton fibers), camphor, and alcohol, celluloid replicated all the features of ivory and then some. It was also unstable and known to explode during transit or play.

Bakelite, created in the early 1900s, solved this problem. Crafted out of phenol and formaldehyde, it was intended to be a synthetic hardening resin for wood, similar to shellac. However, because it was moldable and less expensive to manufacture than celluloid, chemists and engineers found new ways to use it. Over the next four decades, Bakelite filled consumers’ homes with kitchenware, jewelry, and electronics, to name a few.

Ever since, we’ve created more kinds of plastics for just about everything under the sun. Broadly speaking, there are seven types of plastic. The reality is that because of their versatility and flexibility, there are thousands of different plastics, and more appear every year.

Humble pellets

Unfortunately, their chemical makeup also means plastics don’t degrade quickly. Because they’re impenetrable to air, water, acids, and other solvents, they require hundreds of years to break down. And despite their durability, they also shed microplastics, another problem that’s only getting bigger.

Molecularly, plastics consist of polymers, chains of chemical compounds that imbue them with traits like flexibility or rigidity, depending on the chain length. These polymers come from petroleum and natural gas, which refiners process into several products, particularly ethane (from petroleum) and propane (from natural gas). These gasses are piped to crackers, which apply pressurized heat that chemically alters them into ethylene and propylene monomers. The next step, polymerization, adds catalysts that bind the molecules, transforming them into polymers called resins—in this case, polyethylene and polypropylene. After cooling, the resins are chopped into small pellets (or nurdles) and shipped to manufacturers.

Understanding the numbers

Despite thousands of different types of plastics, we regularly interact with only seven, as denoted by the resin identification number (aka Chasing Arrow symbol):

Polyethylene terephthalate (PET/PETE) PET is lightweight, rugged, and commonly transparent. The fourth-most produced synthetic globally, it’s used in food packaging and clothing. Examples include water bottles, condiment containers, and polyester clothing. PET contains antimony trioxide, a known carcinogen, so it’s commonly downcycled into fibers for carpets and clothing, fiberfill, rope, car bumpers, and pallet strapping.

High-density polyethylene (HDPE) Taken as a whole, polyethylene is the most widely produced synthetic plastic on Earth. Why? Unlike other plastics, its molecular structure enables various densities, like linear low, low, medium, high, and ultra-high. HDPE is different from PET at the molecular level because its polymer fibers are longer and thicker; the result is a denser, more durable plastic, making it an ideal material for containers, bags, pipes, and benches.

Polyvinyl chloride (PVC/vinyl) Accounting for about 20 percent of plastics produced worldwide, PVC is versatile and blendable with other plastics. It resists chemicals, weathering, and germs and doesn’t conduct electricity—characteristics that make it ideal for construction, medical, and high-tech gadgetry. A curious fact about PVC is that its base materials are salt (58 percent) and ethylene (43 percent), so unlike other plastics, it’s less demanding of hydrocarbons.

Low-density polyethylene (LDPE) LDPE is less dense than HDPE because its polymers vary in length and fan out like tree branches. This structure makes it pliable while maintaining strength and durability. Typical uses are packaging and agricultural film, bags, squeeze bottles, and household wares.

Polypropylene (PP) Second to polyethylene in global production, PP is more hardy and customizable, which is why some consider it the “steel” of the plastic industry. One aspect of that strength is fatigue resistance, as demonstrated in the ordinary hinge cap on condiment bottles. Other familiar applications are screw-cap lids, to-go food containers, and food-grade film, like the kind grocery stores use to package meat products.

Polystyrene (PS) PS has the unique distinction of being discovered twice. The first was in 1839, when Edward Simon, a German pharmacist, isolated an oily substance from storax, a tree resin, that he called styrol. Despite a few tweaks here and there, styrene, as it came to be known, wasn’t commercialized until the 1930s. Toward the end of that decade, Ray McIntire, a Dow Chemical engineer, mixed styrene with isobutylene under pressure, hoping to create a rubber-like polymer. When he released the pressure, he instead found foam polystyrene—better known as Styrofoam. Highly stable, PS is inexpensive, an excellent insulator, and widely used in construction, shipping, and food packaging. These features also make it challenging—but not impossible—to recycle.

Other This is the catch-all for plastics that don’t fit into the other six groups or because they are layered or mixed with other plastics. Examples include nylon, polycarbonate, fiberglass, and acrylic. It also contains polylactic acid, a compostable bioplastic. Some #7s are recyclable, and some aren’t.

From linear to circular

So what do plastics have to do with moving from a linear to a circular economy? Plenty. Current estimates suggest we produce 380 million metric tons of plastic annually. And most of this plastic will be landfilled instead of recycled because once it has served its purpose—as a water bottle, pair of sunglasses, a grocery bag, or diapers—its value is negligible.

With this setup, the real value of plastics is sourcing their primary ingredients and transforming them into something usable. This is called a linear economy, which follows a path of taking raw materials from the environment, using them to make products, and disposing of those products at the end of their useable life. This model strives to produce more to sell more.

In contrast, a circular economy follows a reduce-reuse-recycle approach with the endgame of drastically minimizing the volume of landfilled waste. In this model, waste becomes the raw materials to make more products. When products reach the end of their useful life, we disassemble them for reuse or repair, and we recycle any leftover materials. And when new products are remanufactured, we design them to be repaired and repurposed again and again.

This might sound quixotic, but the movement toward circularity began with recycling programs in the 1970s. Back then, the thinking was that if we recycled as much of our waste as possible, the demand for raw materials would diminish. It seemed like a no-brainer. And theoretically, it was. Recycling programs took in paper, cardboard, metals, and plastic and sent that material to facilities for sorting and further processing.

The reality, then and now, is that recycling programs struggle to find outlets for their recyclables, and when they do find one, operational costs often morph any revenues. As many communities, large and small, have realized, landfilling their waste is cheaper than recycling it. So these programs come and go, and for those that manage to hold on, they usually collect paper, metal, glass, cardboard, and maybe plastic, but only certain kinds, like #1s and #2s.

Mechanical vs. advanced recycling

Until recently, the only way to process plastic was via mechanical recycling, which grinds, melts, and reprocesses plastic into pellets to make more plastic products. It’s an efficient way to repurpose plastic waste, and because it requires minimal inputs of energy and chemicals, its production of greenhouse gasses is also minimal.

Mechanical recycling also has its downsides, which exemplify why this kind of recycling, though practical, has failed to lessen the ever-growing glut of plastics. Specifically, it:

Requires clean materials Post-consumer plastic is dirty. Though consumers are supposed to rinse their recyclables, many forget or choose not to. So, although containers mucked up with steak sauce, peanut butter, or sesame seed oil end up in recycling bins, recyclers discard them. And unfortunately, this happens to many #1s and #2s. Oils, dyes, or chemicals can also contaminate plastics. The oil gums up the conveyor belts and grinders, while the chemicals are ground up with the plastic and thus taint the next generation of products. This means mechanical recyclers reject lots of plastic, like quart-sized motor oil bottles, agriculture and industrial films and containers, and take-out packaging.

Processes only #1s and #2s The lower the number, the easier plastic is to recycle. This is primarily due to molecular structure, with #1s and #2s the best suited for this type of recycling. But economics also comes into play. Mechanical recycling facilities have processed these grades for decades, so there’s an existing infrastructure. As such, #1s and #2s have a strong commodity market and have far higher recovery rates than the other grades.

Degrades materials Over time, the polymer chains break down, impacting the quality of new plastics. Shorter chains mean less strength, which translates into decreased durability. Dyes cloud the plastic, while other contaminants like toxins limit their use. At best, plastics like #1s and #2s go this route maybe four to seven times before their value and structural strength are such that landfilling or downcycling are the only options.

As its name implies, the only direction for downcycled plastic is down. So water bottles become carpets or fleece, which become plastic lumber, car parts, railroad ties, and such. The next step is landfilling or incinerating when delaying the inevitable becomes impossible.

Mechanical recycling has its strengths, but its weaknesses are many. This is where advanced (or chemical) recycling steps in. By utilizing over 100 technologies, like dissolution, enzymolysis, and pyrolysis, advanced recycling repeatedly converts used plastics into new products with no loss in quality or function. And it excels in processing hard-to-recycle plastics like #3s through #7s and dirty and contaminated materials. The technologies involved depend on the desired goal—some break polymers apart while others combine. But in either case, plastic is modified at the molecular level so that polymers separate from toxins and other contaminants. This enables them to be processed into a circular oil comparable to virgin crude, except for how it’s sourced—recycled plastics vs. fossil fuels.

Our reality, warts and all

Within the next decade, we can expect more humans, plastic, fossil fuel demand, pollution, and climate issues. Dismal and realistic, it also foretells something else: fossil fuels won’t last forever. Oil and natural gas fields are drying up—some industry pundits suggest we reached peak fossil fuel production in 2015 or 2018, while others think peak rates are years away. But this should come as a surprise to no one. We’re pumping millions of barrels of oil out of the ground every day; the faster we consume it, the faster it will dry up.

We can stay the course and reach the inevitable. Or we can search for solutions that delay the inevitable and maybe even mitigate some parts of climate change. Shifting to a circular economy could be one of those solutions. And given the role that plastics play, mechanical and advanced recycling could help get us there.

The challenges before us are manifold. Globally, plastic collection is not scaled to our level of use, and the plastic collected is limited to just a few forms. Our recycling infrastructure is woefully in disrepair; overhauling it will be costly. Consumers need better education about recycling. We also need to change plastic itself. Instead of over-engineering it to withstand extreme temperatures and stories-high falls, we should design plastic so it’s reduced, reused, and recycled more easily.

Doing so would give plastic waste more value and make recycling beneficial at all levels. For communities large and small, recycling waste will be more profitable than landfilling. For the middle players—recyclers, waste management companies, material recovery facilities, and brokers—a vast, mostly untapped market will offer them opportunities to increase services and profits. For the manufacturers, using circular oils instead of virgin crude will lessen their demand for fossil fuels and their production of greenhouse gasses while keeping shareholders and consumers happy—never an easy task.

The reality is that reducing, reusing, and recycling won’t become a thing until we find ways to profit from them. When we do, society will change—recycling will be easy, waste will be repurposed and recycled, and unrecyclable waste will be disposed of properly.

I acknowledge the previous paragraph has lots of will-be’s. I might as well have said: If pigs could fly…

My point is that this might happen in fits and starts. If it does, it won’t be easy. But change never is.

Further reading

Advancing Sustainable Materials Management: 2018 Tables and Figures.” US Environmental Protection Agency, November 2020.

Baheti, Payal. “How Is Plastic Made? A Simple Step-By-Step Explanation.” British Plastics Federaation, 2022.

Beckman, Eric. “The World of Plastics, in Numbers.” The Conversation, August 9, 2018.

Circular Economy.” Nederland Circulair, no date.

History and Future of Plastics.” Science History Institute, 2022.

It’s All Downcycled From Here.” Freshkills Park Alliance, February 5, 2020.

Johnson, Anne. “Advanced Recycling Technologies and a Circular Economy for Plastics.” Circularity Concepts, April 2022.

Makower, Joel. “Is Advanced Recycling the Answer to Plastic Waste?” GreenBiz, August 1, 2022.

Mechanical Recycling.” Royal Society of Chemistry, August 24, 2021.

Plastics 101.” National Geographic, no date.

The Real Truth about the US Plastics Recycling Rate.” The Last Beach Cleanup and Beyond Plastics, May 4, 2022.

Taylor, Liam. “What Is the Linear Economy and Why Do We Need to Go Circular?” Planet Ark, October 14, 2020.

Wolberg, Cailyn. “The Performance of Recycled Plastics vs Virgin Plastics.” Oceanworks, 2022.

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