How Does Plastic Get Recycled?

Where does your plastic go after it leaves the recycling bin? 

We already know that paper gets recycled by sorting it, breaking it down and reforming it into new products, and plastic goes through a fairly similar process, too!

Plastic recycling is the process of converting used plastic into new materials and objects. It’s a great alternative to conventional waste disposal that can not only reduce the need to harvest nonrenewable material, but can also help lower greenhouse gas emissions that come as a result of the mining process. 

Plastic recycling centers have been around for a while and, while the process isn’t necessarily perfect yet, advancements in the technology have allowed recycling centers to efficiently process a wide variety of plastics in many different forms. 

Here’s a basic run-down of how most recycling centers process plastics, from the minute you toss that old milk jug in the recycling bin to the moment it becomes a new product entirely!

Steps in the plastic recycling process

Collecting the plastic

The first step is to collect the plastic waste, which can be done through curbside collection, drop-off centers or other methods (like main back recycling programs). 

Depending on where you live and who runs your local recycling center, there may be regulations on what type of plastics you can recycle through curbside collection bins. Be sure to check with your regional recycling center to make sure you’re getting the most out of your curbside pickup!

Sorting the plastic

Once the plastic has been collected and sent to a recycling center, it is sorted by type and color. This is done to ensure that the plastic can be recycled efficiently and will not contaminate other types of plastics.

There are seven main types of plastic, each with a unique resin identification code (RIC):

• PET (polyethylene terephthalate): This is the most common type of plastic and is used for bottles, food containers and other packaging.
• HDPE (high-density polyethylene): This is a strong and durable plastic used for milk jugs, detergent bottles and other containers.
• PVC (polyvinyl chloride): This is a versatile plastic used for pipes, siding and other construction materials.
• LDPE (low-density polyethylene): This is a flexible plastic used for bags, films and other packaging.
• PP (polypropylene): This is a strong and lightweight plastic used for food containers, cups and other items.
• PS (polystyrene): This is a lightweight and foamy plastic used for cups, plates and other disposable items.
• OTHER: This category includes all other types of plastic, such as acrylic, nylon and polycarbonate.

These different kinds of plastics are sorted using optical sensors that are outfitted with infrared lights. Different materials will reflect the light back to the sensor differently, giving the computers information on what the materials are made from. From there, air guns and machine arms separate the different plastics by their type and send them down the appropriate routes. 

Cleaning the plastic

Sorted plastics are then cleaned to remove any contaminants such as food or dirt; this is important to prevent the contaminants from damaging the recycling equipment. 

(This is why cleaning our used plastics before recycling them is so important. If the machines sense any liquid or grime that can’t be removed using automated processes, then the plastic is thrown away entirely!).

The cleaning process can be done manually or by using machines. The manual process involves washing the plastic with soap and water, while the machine process uses a combination of water, air and chemicals to clean the plastic.

Shredding the plastic

The cleaned plastic is then chopped into small pieces using shredders, which come in a variety of sizes depending on the amount of plastic that needs to be shredded and the type of plastic they’re chopping up. Breaking up the plastic makes it easier to melt and will make the reformation process much simpler and more efficient.

Melting and extruding the plastic

The shredded plastic is then melted at high temperatures, breaking down the hardened plastic molecules and making them easier to re-form. This melting process is done by using machines called extruders — large, heated chambers that melt the plastic and then force it through a small opening. 

From there, the long strands of plastic head to a pelletizer, which will use sharp blades to chop the strand into small pellets.  These pellets are then bagged by type and color and sent to a manufacturing plant where they will be remolded into new products!

Re-molding the plastic

The freshly-minted pellets are then bagged by type and color and sent to a manufacturing plant where they will be remolded into new products. All that needs to happen after that is to heat the pellets up and use molding machines to shape and bind the warm plastic into whatever shape and size the manufacturer requires. 

And there you have it. That’s how your old milk jugs, plastic forks, soda bottles and children's toys end up back on the shelf as a brand new product! It takes time, effort and a lot of technological know-how to run and maintain all the machines used to recycle our old items, so understanding how we can help support that process by cleaning our plastics and recycling the correct kinds of materials is  important to supporting that mission.

If you have more questions about recycling centers and processes in your city, just visit your local government’s website to find out who runs your curbside pickup, what they accept and where you can drop off hard-to-recycle items. They’ll have all the information you’re looking for and more, for sure.

Good luck!

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Featured photo courtesy Pixabay/pasja1000