Processing plastics for recycling
The plastics recycling industry works with both post-consumer and post-industrial plastic waste. Too little plastic gets recycled, so the industry needs to grow. But recycling alone won’t solve our plastic problem. The supply of new plastic needs to shrink.
Typical American households have access to single-stream recycling programs. That means we comingle paper, metal, glass, and plastic of various kinds. Everything goes to a materials recovery facility (MRF) for sorting.
Regarding plastic recycling, MRFs can easily sell two kinds of plastic, those with codes 1 and 2. No. 1 (polyethylene terephthalate or PET) is used for water bottles and soda bottles. Clear no. 2 (high density polyethylene or HDPE) is used for milk jugs. Colored HDPE is used mostly for laundry detergent and other non-food items.
So MRFs separate and bale PET, clear HDPE, and colored HDPE. Everything else becomes mixed plastic, and it doesn’t bring a good price. China used to buy it, but not anymore. But it’s not junk further sorting could make much of it into valuable commodities. China’s decision had the effect of forcing the rest of the world to take responsibility for its own plastic waste.
More and more consumer product companies, including Coca-Cola and Unilever, have announced ambitious plans to make more of their packaging—not just nos. 1 and 2––from recycled plastic. And not without controversy.
Unfortunately, MRFs are unlikely to sort mixed plastic further until there’s a market for the various kinds. And the plastics recycling industry won’t provide a market for it without a dependable supply. Help is on the way, but it’s coming slowly.
MRFs cannot handle plastic bags and other plastic film, by the way. These are mostly no. 4 (low density polyethylene (LDPE). Grocery stores and others collect whatever customers bring them.
Plastic recycling methods
Pyrolysis
Plastic recycling mostly uses five different methods:
- Mechanical recycling requires separation of different kinds of plastic. It cleans shreds, and melts plastic and turns it into pellets that can be used to make new plastic objects. In practice, it uses only PET and HDPE. Over time, the quality of the plastic degrades, which limits how often it can be recycled. And it’s hard for mechanically recycled resins to satisfy requirements for food safety and become new food packaging.
- Gasification turns plastic and other wastes into carbon monoxide and hydrogen. These gases have many applications, but gasification is very expensive. It can play no major role in recycling until it becomes more economically viable.
- Pyrolysis subjects plastic to very high temperatures in the absence of oxygen. Plastic breaks down into simpler hydrocarbons such as diesel fuel and naphtha. Naphtha can be used as a building block for making new plastic.
- Depolymerization returns plastic to its constituent monomers. Unfortunately, it now mostly works with PET, which is one of the plastics most successful for mechanical recycling.
- Solvent processes for plastic purification dissolve plastics in a form that allows impurities to be filtered out. Projects to purify polypropylene and polystyrene in this way have started.
Collectively, the last four are various methods of chemical plastics recycling. Many in the plastics recycling industry look to chemical recycling to boost plastic recycling and keep more plastic out of landfills and oceans.
As of 2020, chemical recycling processes accounted for a negligible portion of plastic recycling. By 2030, they will account for a third of plastic recycling. Other innovations in plastic recycling are also on the horizon.
No. 3 polyvinyl chloride (PVC) recycling
PVC inflatable swimming pool / How Stuff Works
PVC, one of the most widely used of all plastics, presents special recycling problems.
It comes in many varieties, each with different additives. It is not conducive to mechanical recycling without more sophisticated sorting than yet exists. So with post-consumer waste, it is too difficult to predict and control the output of the process. It appears unlikely that MRFs will get a good price for PVC any time soon.
PVC mechanical recycling can work, however, with post-industrial waste where the composition of the PVC is known.
But there’s another complication. PVC’s high chlorine content means that it can’t undergo the same chemical recycling processes as other plastics. It requires a separate step to remove the chlorine. Recycling it is, therefore, more expensive than recycling other plastics. Researchers are looking for ways to perform chemical recycling and remove the chlorine in a single step.
Nonetheless, the plastics recycling industry does recycle PVC. A recycling process called RecoVinyl has operated successfully in Europe since 2003.
No. 5 polypropylene (PP) recycling
Polypropylene bottles / SABIC, PR058 via Flickr
Many foods come packaged in polypropylene (PP): yogurt and cottage cheese are but two examples. Shampoo bottles are among other common uses for PP.
About 90% of Americans have access to a recycling program that accepts PET and HDPE. Only about 60% can recycle PP. It’s still a majority, but much less. But the recycling stream may actually contain more PP than HDPE.
The Recycling Partnership has recently launched the Polypropylene Recycling Coalition to improve prospects for recycling PP. Coalition members include the Walmart Foundation, The Kroger Co. Zero Hunger, Campbell Soup, Procter & Gamble, and the American Chemistry Council.
It has granted almost $2 million to encourage four MRFs (one each in New York, New Jersey, Pennsylvania, and Ohio) to purchase sorting equipment to separate PP from mixed plastic. Presumably, buyers for the PP exist near these MRFs, although I haven’t seen any named.
A California initiative shows another way PP recycling can grow. The Plastic Recycling Corporation of California started by buying PET at a loss in order to assure MRFs of a market for their output. Six PET reclaimers now buy everything that California MRFs can send them. They need more of it.
The program has been successful enough to start the same tactic for HDPE and PP.
One reclaimer has licensed a technology called PureCycle, developed by Procter & Gamble to recycle PP. It will open its first plant in 2022 and hopes to build from an initial output of 100 million pounds of PP to an eventual one billion pounds annual capacity.
So PP recycling will become profitable for MRFs once these small initiatives scale up and become more common. Here’s a hopeful sign: Some companies that have long made virgin plastics have started to move into the plastics recycling industry.
No. 6 polystyrene (PS) and expanded polystyrene (EPS) recycling
A mountain of Styrofoam
/ Some rights reserved by David Gilford
Polystyrene (PS) presents two different problems for recycling, depending on whether it’s rigid or foam. Rigid polystyrene has many of the same uses as PP and raises similar issues for recycling. That is, it’s easy enough to separate from other plastics, but there’s no point in doing so without a market and no market can exist while it’s difficult to obtain.
Expanded polystyrene (EPS), better known by the brand name Styrofoam, is mostly air. It easily breaks into little pieces in MRF equipment—or, for that matter, long before it gets to the MRF. It only gets into bales of everything else and contaminates them.
Little bits of EPS as litter cause numerous issues. If it gets into a waterway, eventually it joins one of the large gyres of plastic in the oceans. Fish, birds, and other animals eat it. If they don’t excrete it, it can fill their stomachs until they can’t eat anymore. Then they starve. And whatever gets into the bloodstream bioaccumulates. That is, it enters the tissue and stays there.
Predators who eat food contaminated with microplastics simply absorb all that plastic in their own bodies. We humans, as apex predators, have plenty of microplastics in our own bodies. The monomer styrene has been identified as a possible human carcinogen.
Although EPS makes up less than 1% of the total weight of the waste stream, it makes an outsized share of the volume. That volume means that trash cans with a lot of it have to be emptied more often. And it makes transporting it quite expensive.
I have earlier written about recycling EPS and described several machines that remove the air and therefore reduce the volume. Using this technology can reduce these disadvantages.
Recycling Taco Bell sauce packets
Composite lumber / Wikimedia Commons
The packaging industry wants more recycled plastic than it can get from MRFs. Taco Bell and Terracycle teamed up in 2021 to collect emptied Taco Bell sauce packets. TerraCycle operates internationally. To begin with, however, the Taco Bell partnership is available only in the US.
It is only the latest project in which a corporation pays to have consumers collect its packaging and send it to TerraCycle for recycling. TerraCycle will use the packets to make composite lumber. It will sell it to companies that make such products as outdoor furniture or decks.
How big a deal is it? American Taco Bell locations give out 8.2 billion packets of sauce every year.
American consumers can create an account at TerraCycle if they don’t already have one. Then they start collecting the packets in whatever box they have. They don’t have to wash them, just squeeze as much sauce as possible out of them.
When the box is full, they log into their account, download a shipping label, and ship the box to TerraCycle by UPS. Taco Bell pays for the shipping. Participating consumers earn points, 100 points per pound of plastic shipped, and apply them to a variety of charities, including the Taco Bell Foundation.
Each point is worth one cent. It may not seem like much, but each packet weighs enough to be worth 1.5 points. A decent-sized box of them can be very helpful to the designated charity, and TerraCycle members can contribute to any number of different recycling projects. The company helps the plastics recycling industry extend its reach.
But this initiative brings up a problem. Using sauce packets for composite lumber doesn’t reduce and amount of virgin plastic used for single-use packaging.
Controversial aspects of the plastics recycling industry
The plastics and packaging industries have pushed plastics recycling as a solution for about 30 years now. The environmentally better advice to use less plastic in the first place works against the plastics industry’s economic interests.
As the world turns more and more from burning fossil fuels to renewable energy, petrochemical companies depend on manufacturing plastic to remain profitable. They need a whole new business model if they’re to have any place in a sustainable economy. That will be easier said than done.
Plastics industry advocacy of plastics recycling makes many environmentalists suspicious. The industry, they say, shows no interest in actually producing less virgin plastic. And the industries that use packaging show little interest in using less packaging or changing to something else besides plastic. Industry has invested much more money into expansion of plastic production than into chemical plastics recycling.
Environmentalists especially criticize pyrolysis. Some appear to think that pyrolysis is a kind of combustion, which is incorrect. Others claim that it is used mostly to make fuel for burning. Still more point to the amount of energy pyrolysis uses.
To the extent that industry pushes plastics recycling without actually planning to make and use less plastic, plastics recycling amounts to greenwashing. It seems too cynical, however, to dismiss it entirely.
Environmental advantages of chemical plastics recycling appear not only in industry-sponsored studies, but also independent ones.
Argonne National Laboratory determined that low-sulfur fuel made from waste plastic accounts for 14% less greenhouse gas emissions than conventional diesel.
CE Delft, a Dutch think tank, examined depolymerization. It determined that every metric ton of recycled plastic saves 1.5 metric tons of carbon dioxide when compared to ordinary plastic. And so if the plastics recycling industry is no environmental hero, it can make a positive contribution to cleaning up the planet.
Promises and pitfalls of chemical plastics recycling
Mountain of plastic trash / Shafiu Hussein via Flickr
It would appear that chemical plastics recycling presents a massive opportunity to reduce waste plastic. The industry is in its infancy, however. Many startups will fail, and for various reasons. Too many entrepreneurs never master the mechanics of running a commercially successful operation.
Sometimes new technology doesn’t work as well as its creators anticipate. Sometimes they can’t raise the money they need to scale up production. And new products from new technology tend to cost more than established alternatives. Sometimes much more. Startups in the plastics recycling industry need to find a way to profitability while their products are still expensive.
Eastman Kodak, for example, developed a chemical process for recycling X-ray film to use for new film products in the 1980s. It shut the process down because it couldn’t find a market for the output.
Now, Eastman, spun off from Eastman Kodak in 1994, has returned to the same processes, the same machinery, and even some of the same employees. In November 2019, it started recycling such materials as old polyester carpet. Some of its processes produce the monomer dimethyl terephthalate, which it intends to use to make reusable PET water bottles.
So while a lot of chemical plastics recycling projects will fail, some will succeed and become (or be bought by) large, respected companies helping to reduce plastic waste.
We need to increase all kinds of plastics recycling. Advances in the plastics recycling industry can help accomplish it. Unfortunately, we can’t recycle our way out of an economy that produces and uses too much plastic in the first place.
Sources:
Coalition goes after polypropylene plastic, expanding recycling to 4 million people / Jeff Kart, Forbes. December 16, 2020
Companies are placing big bets on plastics recycling. Are the odds in their favor? / Alexander H. Tulio, Chemical & Engineering News. October 11, 2020
Everything you need to know about PVC recycling / Michelle Rose Rubio, BioEnergy Consult. January 2, 2021
Recycling of EPS foam packaging / Michelle Rose Rubio, BioEnergy Consult. November 1, 2020
Taco Bell® sauce packet recycling program / TerraCycle
Trends and action around PP, PET, and HDPE / Arlene Karadis, Waste 360. July 8, 2021
What’s gone wrong with plastic recycling / Kevin Loria, Consumer Reports. April 30, 2020
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