How a Plastic Bottle Becomes a Shoe

By Allison Tau

If you look at the tag on a piece of clothing, you might see “recycled polyester” listed as one of the materials. Most recycled polyester that we use comes from plastic water and soda bottles! Using recycled polyester is better for the earth than using new polyester. Here’s why.

To make new polyester, you need to start with coal, petroleum, air, and water. These materials have to go through a chemical reaction called polymerization, at extremely high heat. This means that making new polyester uses a lot of energy and natural resources, which isn’t ideal. It also adds greenhouse gases to the atmosphere, which harms the climate.

Using recycled polyester to make new fabric, on the other hand, uses less energy and resources. You use already existing plastic to make the new material, so you don’t need to get coal and petroleum from the earth. 

Plastic water and soda bottles often contain a chemical called polyethylene terephthalate (PET). Using PET bottles to make recycled polyester produces 75% fewer greenhouse gas emissions, compared to making new PET.

You can tell whether a piece of consumer plastic is PET by looking for a number “1” stamped inside the universal recycling symbol. The number you see in the symbol stands for the type of plastic used to make the item. Some types of plastic can be recycled in various ways, but other kinds of plastic cannot be recycled at all. 

Here’s how recycled polyester is made. At the recycling facility, water and soda bottles made with PET are separated from the other plastics. Then, the PET plastic bottles pass through a machine that shreds them into flakes. These flakes are melted down and turned into hard pellets. At another factory, the pellets are melted again, and pushed through tiny holes, like water through a showerhead. The long fibers are pulled and stretched, and then twisted together to make a special kind of yarn. Machines knit or weave the yarns together to make polyester fabric. It takes about 9 plastic bottles to make one T-shirt … and about 11 plastic bottles to make a pair of shoes!

Even though recycled polyester is a useful way to keep plastic bottles out of landfills and the ocean, getting enough PET depends on the choices people make. There are more than enough plastic bottles and containers in the world. However, people must place their PET containers in their recycling bins, instead of their trash cans, or worse, leave them outside. 

Even when used PET ends up at a recycling facility, there is a limit to how many times it can be recycled. Once PET becomes recycled polyester, it cannot be easily recycled any further. Even so, scientists are still coming up with new ideas to reuse the waste we have lying around to keep it from polluting our planet. What other kinds of creative materials could we someday use to create fabrics?

Allison Tau is the Digital Content Manager at the American Chemical Society.