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New Vegetable Based Plastics: What they are... and are not By
Elizabeth
Ferry, Coop
Food Stores, Plastics
are everywhere in our lives. They are in the clothes we wear, the buses
we ride
or the cars we drive, and they surround many of the foods we eat.
Petroleum
plastics are not biodegradable; they may break down into ever-smaller
pieces,
but they are not absorbed back into the environment. For decades,
environmentalists have warned the public about mounds of plastic waste
creating
a mountain of solid waste that someday will become too big to ignore. So, when I
saw an advertisement for corn-based plastic containers, I was excited.
The
words “corn-based,” though only half of the name, jumped to the
forefront. I
envisioned a product that was non-toxic, biodegradable, and made from a
renewable resource. It seemed like an answer to consumer requests for
the most environmentally
sensitive packaging option available. My reaction
was just what the product promoters — the makers of petroleumbased
plastic —
would have hoped for: a “green” consumer assuming that “corn plastics”
have a
positive effect on the environment. But when I gathered more
information, I
found that some of the industry’s selling points for these alternative
plastics
were misleading to consumers. Let’s take a closer look. How
Plastics Are Made All plastics
are created in the laboratory. One way of defining them is by their
molecular structure. Plastics
are manufactured in a process known as polymerization. Polymerization
is a
chemical reaction in which two or more molecules combine to form larger
molecules.
These larger molecules are characterized by repeating structural units. The vast
majority of plastics are derived from petroleum. However, the long
polymeric structures
that define plastics can be made from other substances as well.
Recently, scientists
have experimented with other materials, including plant-based sources
such as
corn and potatoes. Success- ful developments include corn-based plastic
packaging
and potato-based disposable plates, which look more like thick paper
than like
plastic. The Product
and What It Can Do Corn-based
plastics are the first non-petroleum plastic to reach the broader
market. For
example, they were used at the 2002 Olympic Games at Add Heat
and They Degrade However,
corn-based plastics are heat sensitive. They melt if filled with hot
food or placed
in a microwave — qualities that limit their usefulness at this stage of
development. One might expect that, being made from plant-based
materials, corn
plastics would be biodegradable. While supporters promote them as
biodegradable,
the claim is somewhat misleading. The polymerization process changes
the corn
molecules so that, unlike the corn from which they are derived,
corn-based
plastics will not degrade in an ordinary compost bin or municipal
landfill.
Rather, they must be transported to special incineration sites and
heated in
order for decomposition to take place — often consuming greater amounts
of
petroleum products than were saved by using corn as the primary
material. How
“Green” Is My Corn Plastic? Plastic
developed from corn has some “green” qualities. It is made from a
renewable resource.
It does not emit toxic fumes when it burns. Further, it can biodegrade,
albeit
with the addition of heat. However, it is misleading for advertisers to
promote
this product as reducing |
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