SHOULD WE DO WITH OLD RUBBER TIRES?
by Whit Gibbons
June 1, 2008
of the United States is approximately 300 million people, a number exceeded
only by China and India. But this column is not about human population,
where we rank third. It's about our automobile tire population, where
we rank first. Each year we discard more than 270 million tires, which
weigh more than 3.5 million tons. The average person adds a tire or so
to the scrap pile every year.
the quality of tires on cars when I was a kid, my guess is that even in
a good year each driver added two or three tires to the world supply.
Back then, old tires were used for three things. We rolled them down hills
to see how far they would go. We burned them outside while standing around
talking on a cold night. And we made tire swings. As my childhood progressed,
people who lived at the bottom of hills gradually discouraged the first
idea. The second idea was squelched by people without completely blocked
sinuses who decided it was better to be cold than to smell burning rubber.
Tire swings lived on. I even put one up in the backyard for my own children.
numbers for scrap tires having been stacked to absurdly high levels, ideas
for new ways to dispose of or recycle old rubber are understandably proliferating.
How about just discarding the tire at the city dump? In the majority of
states you might consider that if the dump happens to be at the bottom
of a hill so you can roll the tire down to it--and if it's nighttime so
no one is watching you. Because in more than thirty states, taking old
tires to a landfill is illegal. The rest of the states are likely to have
similar restrictions soon.
are we supposed to do with this ever-growing supply of hard rubber circles
that would almost reach the moon if they were stacked on top of each other?
Turns out that between 5 and 10 percent of our excess tires are exported
to other countries. Let's not even try to guess why another country would
want tires without cars attached to them, but those are the facts. Maybe
they have a lot of people with head colds who spend lots of time outside
talking on cold nights.
burning rubber is not out of the question as a recycling mechanism. Old
tires have provided an alternative source of fuel for U.S. industries
in which water must be heated to run power plants, pulp mills, and cement
plants. As many as 40 percent of our discarded tires are used this way
in some years.
promising use of discarded tires is a true recycling venture that creates
walkways, playground pads, and other forms of ground or floor covering
from old tires. Some people maintain that a pad made of shredded rubber
has the potential to catch on fire from a burning cigarette or dropped
match, but mixing in a nonflammable substance could solve that problem.
Another use of shredded rubber tires is to supplement asphalt used for
paving streets, a fitting final resting place for an old tire.
One of the
most controversial uses of recycled tires is to make mulch for landscaping
and gardening. In a steel-belted radial tire for a passenger car, the
steel itself makes up as much as 10 percent of the tire's weight, and
the steel fibers are often coated with zinc to retard the rate of rusting.
The metals are in the discarded tires, and excessive zinc can hinder plant
growth. Whether the zinc level in an average tire is something to be concerned
about for plants in a landscaped lawn or, more importantly, in an agricultural
situation, has yet to be determined. Studies should be undertaken to assure
that tire recycling efforts can proceed safely.
Meanwhile, we always have the option of making tire swings from the remaining
surplus. We have enough tires for every man, woman, and child to have
a personal swing. Anything else we use old tires for will be a bonus.
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