All About Plastic

We get a LOT of questions about plastics here at Recycle Smart MA, and we understand why. There’s a lot of confusion about which plastics can go in the recycling and which can’t. There’s also a fair amount of confusion about why some plastics are a yes and others are a no. And finally, there’s the whole question about whether plastics get recycled at all (read The Truth About Plastics Recycling for answers).

This month, we’re taking a deep dive into how plastics are sorted at material recovery facilities and how that process determines which plastics can and can’t be recycled. There’s a method to the madness – we promise!


Who/What/How/Why – Decisions About Recyclability

Most of us agree that recycling is good for the planet, but it’s also a science and a business. Despite our fervent wish that everything could be recycled (where’s a genie when you need one!), safety, chemistry, mechanics, and markets must all be taken into consideration. To boil it down, the Material Recovery Facility (MRF) operators use three criteria to determine whether a material is acceptable.

The three criteria are:

Understanding these criteria can shed some light on why we can’t recycle everything made of plastic (or metal, glass, & paper) despite what some package labels suggest. Let’s dig a little deeper.

Criterion 1 – Safety

This is kind of the no-brainer criterion. If the material can explode, cause a fire, physically harm a worker, or is in any way potentially hazardous to the staff or MRF equipment, it should not go in the recycling. Period. 

Criterion 2 – MRF Technology

If you’ve ever taken a tour of a MRF (take a virtual one here!) you know that the mechanical engineering involved is pretty cool. There are conveyor belts, magnets, optical sorters, people sorters (called pickers), and blowers, all used to move 3D and 2D objects into the right buckets before they are crushed into 2,000 pound cubes (called bales) and sold to recyclers.

Here’s how the sorting process works at a typical MRF (note: sorting processes vary).

1. Trucks dump what they’ve picked up from residents or businesses on the tip floor at the MRF.

If it’s single-stream collection, the trucks will have paper, plastics, glass, cardboard, and metal recyclables all together. 
If it’s dual-stream collection, paper and cardboard are picked up separately from plastic, glass, and metal (sometimes in dual-chamber trucks) and the loads are tipped on separate tip floors at the MRF.(For a primer on single-stream and dual-stream, check out our Recycling Road Map and click on “Collection.”) 

2. A front end loader moves the material from the tip floor into a drum feeder where it is fluffed (this process loosens up the materials that were squished together in the truck). From there it moves onto a conveyor belt where pickers manually remove contaminants like plastic bags, trash,and bulky items.

3. In single-stream MRFs, cardboard is usually separated first. Star screens, optical sorters, magnets, eddy currents, and belts sort the remaining glass, plastic, and metal containers, as well as paper. The same sorting technology is used in dual-stream MRFs. The difference is, in dual-stream MRFs cardboard and paper (fiber) are never mixed with containers (glass/plastic/metal) because they are sorted in different parts of the MRF.

4. Plastics are sorted into different resin types by optical sorters or pickers. Optical sorters work within a fraction of a second. By using reflected light, they can determine the chemical make-up of an object on the belt. A puff of air then separates different types of plastic.

For example, if the optical sorter is looking for PET, every time a water bottle (or other PET container) goes by, a puff of air shoots out and pushes it into a different sorting stream, while the rest of the plastics fall onto the next sorting belt or into a bunker. Here’s a video showing the optical sorter in action (thanks, Casella!). Some MRFs still rely on manual labor to sort plastics by resin type. 

5. The end product of all that sorting are 2,000 pound bales of colored HDPEnatural HDPE, PET, PP, and mixed plastics that are then sold to plastics recyclers. 

Why Can't They Sort Every Plastic, No Matter the Shape/Color/Size?

The answer is in the mechanics. MRFs are engineered to sort the most common types of plastics for which there are strong and consistent markets. Sorting equipment can run into the millions and is built to last 10+ years. Meanwhile, the packaging used for our food and household products is constantly evolving. 

Not too long ago, metal cans and glass bottles and jars were commonplace on store shelves. Now, multi-layer, shelf-stable boxes (aka aseptic packaging) hold everything from soup to wine, and plastic pouches have become ubiquitous. While there are environmental advantages to making packages smaller and lighter, packaging designers aren’t necessarily keeping the realities of MRF sorting equipment in mind, and MRFs simply can’t adapt to all the new types of packaging in real time.   

Putting the RIGHT stuff in your recycling bin helps the MRF run smoothly and ensures they produce a product they can sell, which in turn, supports the circular economy. That’s why criterion 2 – MRF Technology –  is a vital part of the equation. 

Criterion 3 – Recycling is a Business

Some plastics are simply not economical to recycle. Low value plastics such as polystyrene and complex packaging like pouches are not a desirable feedstock for making new products because of their chemical and physical characteristics. There are currently no markets for those materials in MA so they end up in the trash. That said, the vast majority of the plastic containers holding our food, beverages, personal care products and household cleaners (i.e., the stuff pictured on the Smart Recycling Guide 😉) are made of high-density polyethylene (HDPE),  polyethylene terephthalate (PET), or Polypropylene (PP) which are high quality plastics with consistent markets.

Market values cycle up and down according to supply and demand, but the operative word in criterion 3 is “consistent.” The reason the MRFs are engineered to sort and capture specific types of plastic is because there has been consistent demand for those plastics for many years. Fun fact: In the past few years, demand for PP, or polypropylene, (found in tubs, lids, and certain plastic take-out containers) has strengthened in the eastern U.S. That’s why MRFs in Massachusetts are almost all sorting this plastic, while in other parts of the country, these containers are not accepted for recycling.

US Companies Want Our Recycling!

Currently, Massachusetts MRFs sell sorted plastic to recyclers right here in the USA.  Companies like Aaron IndustriesEFS PlasticsKW PlasticsUnifi and Trigon Plastics buy, clean, flake, or pelletize plastic into a raw material for making new consumer products, packaging, automotive parts, construction materials, and even 100% recycled Adirondack chairs. If you’d like to see the process, this quick video shows how recyclers create a raw material that can then be used to create new products. It’s pretty neat!

How To Easily Identify Acceptable Plastics

The easiest way is to check the Smart Recycling Guide. The plastic containers pictured there meet all three criteria for recycling. If you want to check something not pictured, search the Recyclopedia (use generic terms like “plastic jar,” “plastic envelope,” or “single-use plastic container”). Click around on some of the options that auto-populate and look at the pictures. If you don’t see what you’re looking for, chances are, it’s trash. (But you can always email recyclesmartma@mass.gov if you want to triple check).

We get a lot of questions about the numbers on plastics. Our advice: Forget about the numbers, think about the shape. If it’s a hard plastic bottle, jar, jug, or tub, it can be recycled. But a few exceptions were added to the “acceptable” list since we started RSMA (aka, “recycling miracles”). Some irregularly-shaped but still acceptable items include: clear plastic cupssalad greens tubs, and deli/fruit containers.

Whew, that was a long one!

Thanks for sticking with us and for your efforts to recycle smart. Please share what you’ve learned, and when in doubt, reach out – we’re here to help!

Partner Spotlight: Habitat for Humanity of Greater Plymouth ReStore

We love seeing reuse promoted throughout the state, and this month’s spotlight focuses on an RSMA Partner and Reduce, Reuse, Repair Micro-Grantee that’s doing it right. The Habitat for Humanity of Greater Plymouth ReStore is a retail outlet that sells donated home goods to anyone looking for good-quality secondhand items to furnish their abodes. 100% of the ReStore’s profits benefit Habitat for Humanity of Greater Plymouth, which builds affordable homes in the region, and keeps perfectly good items from ending up in the trash.

This past summer and fall, the Habitat ReStore used their grant money to purchase a tent display to promote their work at public events. They also partnered with local businesses as part of a recent “Recycling & Energy Drive.” During that event they collected thousands of pounds of usable goods – enough to fill their retail floor and two storage containers with inventory for 3+ months.  And, they made a great TikTok about it! 

The ReStore has plans for more outreach and we can’t wait to see them grow as a community resource!

📚 What We're Reading

Wishing you a #WasteFree 2023,

The Recycle Smart Team at MassDEP