Every year, we recycle about half a million tons of plastic bags. If that sounds impressive, it’s only about 5% of all the plastic bags we use. Still, plastic bag recycling gives us some important new products.
“Plastic” refers to a variety of materials made from petroleum. When used for single-use products, it has two major environmental drawbacks. First, oil is not a renewable resource. The amount of oil discarded as waste plastic can never be reused to make something else. Second, plastic is not biodegradable. Not only does it basically last forever, it can harm wildlife.
Plastic bags come from low-density polyethylene, or LDPE. If they have a recycling triangle at all, it has the number 4 in it. We also take LDPE home as bread bags, produce bags, boxes of plastic storage bags, and all kinds of other packaging films.
When we recycle plastic bags, they can become new plastic shopping bags, but that’s not all. A lot of them end up as composite lumber. Nanotech industries have started to find new uses for waste plastic bags.
What happens after you take bags back to the store?
First of all, never put plastic bags out with the rest of your recycling. When they get tangled in sorting equipment, they interfere with the operation of your recycling facility. In most of the country, grocery stores collect used plastic bags in specially designated containers. So take them back to the store. Plastic bag recycling happens somewhere else.
Please remember to remove the paper receipts first. About 20% of recycled plastic shopping bags still have them. A plastic processing company will get the bags from the store. It has to get rid of such contaminants.
Fortunately, it’s easy. The company shreds the bags and plunges them into water. The paper sinks and the plastic floats. Further processing entails drying the plastic and shredding it into smaller flakes. Those flakes become the product the processing company sells to manufacturers.
Because plastic doesn’t degrade, it can be recycled any number of times. And so the company doesn’t have to separate bags made of virgin plastic from bags made of recycled plastic.
Plastic bag recycling isn’t complete till someone makes and sells new products from them. Companies that make plastic bags can use the flake from recycled plastic bags as well as virgin LDPE.
Composite lumber from plastic bag recycling
Composite lumber is a much more important product made from recycled plastic bags. The two biggest manufacturers of it are Trex and Advanced Environmental Recycling. Its two main ingredients are polyethylene and cellulose fiber.
The polyethylene comes to the factory in the form of granules about the size of a grain of rice. The cellulose becomes a fine powder resembling flour. A mixture of these materials, along with some additives, is subjected to high heat and then extruded through a die. That gives it the basic shape. The wood-like grain is imprinted after the composite lumber cools.
All the polyethylene comes from waste. It can be either the plastic bags and other post-consumer waste, or post-industrial waste. Agricultural wastes and scrap wood from flooring factories or cabinet makers provides all the cellulose. In other words, when you buy something made of composite lumber, it has no virgin materials in it.
It can make decks, benches, playground equipment, fences, siding, window frames and more. When made of composite lumber, a 500-square-foot deck uses about 140,000 plastic bags.
7 things you probably didn’t know can be made from recycled plastic / SC Johnson, Mother Nature Network
How to make plastic wood / Craig Webb, ProSales. June 10, 2011
Plastic bags: where they come from and where they end up / David Brand, Global Citizen. February 23, 2018
What happens to plastic grocery bags when they get recycled? / SeattlePi
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