Tires have posed a tough problem for recyclers for years.
They seem to last forever.
And who would want old tires anyway?
Some Georgia blueberry growers and researchers have found a
way to use tires that may
surprise you.
"We’re
just entering our second year of this research using tire chips
as a mulch," said
Gerard Krewer, a horticulturist with the University of Georgia
Extension Service.
Krewer, county extension agents and UGA researchers saw a
real need for a
cost-effective mulch, particularly on blueberry and Christmas
tree farms. Mulches help
control weeds and keep the soil cool and moist.
Most landfills won’t accept used tires, and communities were
looking for a way to use or
dispose of the tires. Krewer and his colleagues put the needs
together and started
studying how the tires would work as a mulch.
"They’ve
been performing about the same as a standard mulch — pine bark -
– which was what we were
hoping for," he said.
All tires are made of vulcanized rubber. The vulcanization
process makes tires more
durable. But it also adds zinc. Plants need a little zinc to
grow normally, but very high
levels can be toxic.
Tests that mixed tire chips with soil in potted plants
focused on whether, and how
much, the zinc affected the plants. Krewer said his field
studies show slightly higher
zinc levels in the soil, but no significant increase in the
plant.
"So far, we’re very pleased with the results," he
said.
The new mulch costs about three times as much as the pine
bark nuggets, which run about
a penny a pound, he said. Tire nuggets sell for about the same
cost per pound, but it
takes more of them, since they’re heavier.
But tire chips last nearly forever. "They won’t need
replacing in four
years like the pine bark," Krewer said.
The tire chips on top of the mulched area may become brittle
over time, but that
shouldn’t affect
their longevity or mulching ability.
For slightly more money (six to eight cents per pound), a
higher grade of tire mulch
called crumb rubber provides a more attractive look. Processors
remove the metal cables.
That changes the look from metal-studded rubber to black lava
rocks.
Krewer said he’s seen very little effect of the tire chips on
soil. During the first
year of his study, he found higher levels of zinc and iron in
soil under the mulch. The
excess iron came from rusting metal belts in the tire chips.
Other extension and research engineers are working on more
ways to use waste tires.
They can help improve drainage in wet areas and prevent erosion
along waterways, including
on the edges of drainage ditches.
"We’re
all hoping tire chips will prove useful in commercial
settings," Krewer said. The
Extension Service doesn’t recommend using tire chips as mulch
yet. But the nod could come
in three to five years.
"The studies are continuing," he said. "We’re
all still looking at how
beneficial and safe this material is as a mulch. So far, the
results are quite
positive."
