How Plastic Is Recycled

Mar 10, 2000 - © Kenneth Friedman

Really old tennis players remember the days when tennis balls came in a three-ball can. Those days are gone. So are the cans. Since 1978 when plastic bottles came into use, tennis balls and an increasing number of other products have been packaged in containers made from recycled plastic. Today it's hard to decide whether the triangular recycling symbol on the bottom of a plastic container means the container is recyclable or was recycled already. (It's the former.) The technical name for the plastic in tennis ball and soft drink containers is a mouthful: polyethylene terephthalate. PET is easier to say.

The other big recycled plastic is HDPE (milk, detergent, shampoo), which made up more than 50 percent of the recycled bottles in 1998. Together, PET and HDPE accounted for more than 99 percent of the recycled bottles.

I searched and searched and despite finding many, many web sites on recycling plastics, I couldn't find one that described what takes place when plastic is recycled. So, I'll tell you how it "used" to be done for PET.

Although the process must vary from recycler to recycler, it probably is about the same, give or take the order. As with other recycling activities, the process begins when consumers put their plastics into the recycling system at a centralized collection facility or at curbside. Then the plastics may or may not be separated by color, flattened and baled for delivery. Today maybe they even have a way to separate by type. You know, by soda bottles, milk bottles, yogurt containers, pudding cups and what-have-you.

In addition to the main plastic bottle, you've got plastic and aluminum caps, paper labels, plastic labels that you can't rip off with a pliers, and glue strong enough to hold the nose tiles on the space shuttle Challenger during re-entry. Some soda containers come with a plastic bottom called a cup. Recyclers like it when the bales come separated by type and color (mostly clear or green) because it makes further separation easier.

Upon arrival, bales are split open and then may be flattened. One way of handling the bottles is to shred them to reduce them to odd-shaped flakes of about a half-inch or less. Once shredded, the plastic flakes can go to an air machine that blows off and separates label paper and plastic from the flakes. Then the flakes are washed again so that the heavier "cup" bottom plastic sinks while the flakes float. Another wash tank removes glue, and then the flakes are dried. After drying, flakes go through a separator where an electrostatic charge "pushes" the aluminum from caps away from the plastic.

After all this processing, the flakes are ready to be sold as a product or to be melted and drawn or extruded into thin, spaghetti-like strands. These are cooled in a water bath and then dried and cut into bead-like pellets, which are sold as raw PET to manufacturers.

Manufacturers then use the raw PET for a great number of products, such as tennis ball containers, horse bridles, park benches, floating docks, picnic benches and landscape ties, to name only a very few.

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