MANY OF THE PRODUCTS THAT WE USE EVERY DAY ARE made of plastic, a material that can have a variety of shapes and comes in nearly every possible color. One of the most common such products is plastic bags. They are made of a
type of plastic that is surprisingly thin, yet sturdy enough to carry heavy
loads of groceries from the store. But where do they go after they are
When plastic bags are discarded, they are so light they can easily
become airborne. They can be blown everywhere, earning the nickname
“urban tumbleweeds.” Plastic litter is accumulating on land, in waterways, and in the oceans. It is estimated that plastic can take between
500 years and 1,000 years to break down, so most of the plastic that
has ever been made still exists somewhere.
Because many plastic bags become litter, wild animals can become
tangled in the bags or swallow them, confusing them for food. A plastic
bag can block an animal’s digestive tract, which prevents food from
passing through and causes some animals to starve to death.
Also, the impact of plastic litter is being felt in remote parts of the
world, namely in the middle of the oceans. Plastic bags—along with
other forms of plastic—are blown into rivers and streams after being
discarded on land. The waterways carry this litter into the oceans,
where it is caught up in circular ocean currents called gyres. The circular motion of these currents draws debris into the center, where it
becomes trapped, creating an enormous collection of trash floating on
the ocean (Fig. 1).
So, what can we do to eliminate the effects of wayward plastic bags
on the environment? One solution is to recycle them.
Making plastic bags
Before we discuss how plastics and plastic bags are recycled, let’s
take a look at what plastics are made of. The material that makes up
plastic is known as a polymer—a chemical compound that consists of
single units (or monomers) linked together in long chains. Plastics are
mostly made from fossil fuels—crude oil, coal, and natural gas, which
form deep under the Earth’s surface as a result of the decomposition of
plants and animals over millions of years.
Natural gas and oil are complex mixtures of organic compounds,
among which are the raw materials that are used to produce plastics. It
takes a tremendous amount of energy to extract these raw materials out
of the ground and isolate them.
Plastic polymers are made from different components in fossil fuels.
As you may have noticed, there are chasing-arrow symbols on recyclable plastic materials, with a code number inside the symbol indicating
the type of polymer.
Most plastic bags are made of high-density polyethylene (HDPE),
which is a type of polyethylene. Polyethylene is formed by linking
thousands of ethylene molecules (C2H4), as follows:
n C2H4 ; [C2H4]n
where n = 50,000–100,000 monomer units
Bags By Kathy De Antonis
Figure 1. The Great Pacific Garbage Patch is a collection of marine debris
in the North Pacific Ocean that spans roughly from the West Coast of North
America to Japan.