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The Role of Markets
in Recycling
ecycling, along with source
^ reduction, combustion, and
disposal in landfills, is a key
^ component of an integrated
* municipal solid waste man-
agement strategy. Recycling may consist
of several steps, including collection,
separation, processing, remanufacture,
and marketing. A material is not
considered "recycled" until all of these
steps are completed and the "recycling
loop" is closed.
Since materials must be converted
into products and used by consumers to
close the recycling loop, understanding
the markets for recyclable materials and
for goods manufactured from recyclable
materials is key to continued and expan-
ded recycling. Markets for recyclable
materials, like all markets, are influenced
by the laws of supply and demand. As
more and more communities across the
nation implement recycling programs
and more recyclable materials enter the
marketplace, both supply and demand
are affected.
The U.S. Environmental Protection
Agency (EPA) is supporting market
development by promoting the govern-
ment purchase of goods containing
The word recycling as it is used throughout
this booklet encompasses composting as a
form of recycling.
recycled materials; providing assistance
to local governments; and researching,
developing, and evaluating policy
options.
This booklet summarizes EPA's
Markets for Scrap Tires. It describes factors
affecting the current supply and demand
for scrap tires, and provides information
on future market trends. It also explains
how to obtain a copy of the full report.
Used Tire Supply
About 242 million tires (about one
tire per person) are scrapped in the
United States each year. Scrap tire
generation has grown by about 2 percent
per year since 1984. Less than 7 percent
of these scrap tires are recycled as
products; approximately 11 percent are
incinerated for their fuel value. Another
5 percent are exported, and the final 78
percent are disposed of in landfills,
stockpiled, or illegally dumped. A
diagram showing the estimated
destination of scrap tires is presented
on page 2.
Scrap tires that are stockpiled or
disposed of in illegal dumps can create
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Estimated destination for scrap tires in 1990
1. Powei plants
2. Tire plants
3. Cement plants
4 Pulp and paper mills
5. Small package boilers
1 Reefs and breakwaters
2. Playground equipment
3. Erosion control
4 Highway crash barriers
1. Processed rubber products
2. Crumb rubber for pavements
3. Playground gravel substitute
4. Sludge composting
5. Split tire products
43.7
Millions of tires
Percent of whole
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potentially serious health hazards,
including mosquito infestation (with
the potential for spreading dangerous
mosquito-borne disease) and fires
(which create air and water pollution
and are difficult to control and clean up).
Disposing of whole tires in landfills
is problematic since they occupy a large
volume of landfill space, and can collect
gas and harbor rodents. Tires tend to
float or rise in a landfill and come to the
surface, piercing the landfill cover. These
problems have led to extremely high
tipping fees for scrap tires in landfills—
at least twice the fee for municipal solid
waste—or total bans on whole tires.
More than 50 percent of the nation's
rubber is used to make tires. However,
new tires contain no more than 2 percent
recycled rubber. This helps to explain
why the scrap tire problem has become
so large. Several factors, however, serve
to reduce the number of tires that require
disposal:
Improvements in tire manufacturing
over the past 40 years have more
than doubled the useful life of tires.
Currently, steel-belted radial
passenger tires last about 40,000
miles, if these tires are properly-
inflated, rotated, and otherwise
cared for, 60,000- to 80,000-mile
lifetimes may be achieved.
[..-. -.'.• ^ •••: ,«. Frequently,
when one or two tires of a set are
worn out, the entire set is replaced
with new tires. Useful tread may
remain on two or three of the tires
removed. Many tire stores and tire
haulers sort out the reusable tires for
resale. Currently, about 50 percent of
usable tires are being scrapped.
;•• -i •<•..-.;;M:, Retreading is the appli-
cation of a new tread to a worn tire
that still has a good casing.
Currently, over 1,900 retreaders
operate in the United States, but that
number is shrinking because of
declining markets for passenger
retreads. This decline is due to the
relatively low price of new tires and
concerns about the safety of retreads.
Truck tires, however, are often
retreaded three times before they are
discarded, and the truck tire
retreading business is increasing.
Future Trends in the Supply
The federal government is working
to identify and implement strategies to
decrease the number of scrap tires and
the economic and environmental
problems that accompany scrap tire
disposal. For example, in 1989 EPA
promulgated procurement guidelines
that promote the use of retread tires by
government agencies and entities funded
by the government. These guidelines
became effective on November 17, 1989.
If the retread markets could be devel-
oped so that all the passenger and light
truck tires suitable for retreading were
actually retreaded, then about 20 million
fewer new replacement tires would be
needed annually. This would reduce the
number of scrap tires generated per year
by almost 10 percent.
More widespread reuse of partially
worn tires could also help to reduce the
number of tires scrapped each year. An
estimated 10,000 miles of additional life
can be realized out of 25 percent of the
tires removed from vehicles. Reusing all
of those tires would reduce the number
scrapped by about 3 percent. Major
design changes could also significantly
increase tire life; however, these are not
expected to occur in the near future.
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Demand (oi Recovered Tires
The markets for scrap tires include a
of crumb rubber and combustion
faotes that use the tires as a fuel.
About 6.7 percent of scrap ttres are
currently recycled.
Crumb rubber is usually made by
choppTng and grindmg rubber >nto
be used in rubber or plasnc
Fach year approximately 8.6 million
n nercent of the total number
;«tn rubber products (sucn a^
S mudguards, and carpet pad-
ding) and plastic products ^u* a s
floor mats and adhes.x es,
rubbes made by mWng c
Into slabs or bales and s
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manufacturers for use as an alternative
to virgin rubber in tires or in mats and
other rubber products. Because reclaim
rubber tends to lose its elastic properties
during processing, it is no longer exten-
sively used in tires. Due to limited mar-
ket demand, only 50 to 60 percent of the
reclaim rubber industry's capacity is
currently being utilized.
Over 1 million scrap tires per year
are currently used for pavements with
rubber additives. Asphalt pavements
with rubber added have increased
durability and flexibility compared to
ordinary asphalt. They can have twice
the lifetime of ordinary asphalt, but the
initial cost is about twice as high. Two
different processes are currently used to
add crumb rubber to asphalt: the Rubber
Modified Asphalt Concrete (RUMAC)
technique and the Asphalt-Rubber
Binder System. Presently, the equivalent
of 0.8 percent of scrap tires are used in
rubberized asphalt, although their use in
pavement is increasing rapidly (almost
60 percent growth from 1987 to 1989).
In the past 3 years, the use of scrap
tires as a fuel has increased significantly.
Scrap tires make an excellent fuel
because they have a heat value slightly
higher than that of coal, about 12,000 to
16,000 Btu per pound. On a national
basis, they represent a potentially
significant energy source. If all scrap
tires were burned, they would supply
0.09 percent of the nation's energy needs.
Currently, 10.7 percent of scrap tires are
used as fuel and this is expected to
continue to increase. Combustion
facilities that currently use tires as fuel
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include power plants, tire manufacturing
plants, cement kilns, and pulp and paper
mills. The most economical way to use
tires for fuel is to burn them whole;
however, most plants currently burning
tires for fuel do not have the capability
to burn whole tires. Instead, they must
burn tires that have been shredded into
chunks (also known as tire-derived fuel,
or tdf).
At present, only
one company in the
United States
manages a power
plant fueled
exclusively by whole
tires. This company,
located in Modesto,
California, collects
and sorts scrap tires
for fuel and other
applications, with no
tires going to
landfills.
The technology used
at this plant also
allows for recycling
of all the scrap tire by-
products generated
in the process. The
power that is gener-
ated is sold under a long-term agreement
to a regional utility. A second whole-tire-
to-energy plant, which will turn 9 to 10
million tires per year into electricity, is
under construction in Sterling, Connecti-
cut. With the completion of this plant,
there will be capacity in the United
States to turn 14 million scrap tires into
electricity each year.
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Two tire manufacturing plants have
installed pulsating floor furnaces to
combust scrap tires and other solid
wastes. The steam generated during the
combustion process is converted to
energy for use in the tire manufacturing
operations. Each of the combustors has
the capacity to burn approximately
500,000 tires per year; however, one of
the facilities is currently shut down.
Cement kilns can thoroughly
combust scrap tires because they operate
at very high temperatures. In addition,
the cement production can utilize the
iron contained in the tires' steel belts and
beads. Despite these advantages, only
three cement plants in the United States
currently use tdf, consuming a total of
about 6 million tires per year. This is in
sharp contrast to several other countries
(particularly West Germany, Austria,
France, Greece, and Japan) where burn-
ing of scrap tires in cement kilns is more
common. The slower adoption of this
approach in the United States is prob-
ably due to the lower cost of fuel here, as
well as the existence of landfills that will
accept tires at fairly low tipping fees.
In addition, some kiln owners are reluc-
tant to begin using tdf because to do so
would require reentering the permitting
process.
Furnaces at many pulp and paper
mills are designed to burn wood waste
(also known as hog fuel). Often these
furnaces can be fed tdf without any
major capital equipment changes. Hog
fuel boilers can generally use tdf for up
r> -it the OxforH Fnerov > h> ' m
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to 15 percent of their fuel value. At
higher percentages, additional tech-
nology may be needed to control particu-
late emissions. The equivalent of 12
million tires are consumed annually in
hog fuel boilers in the pulp and paper
industry.
The newest use of tires for fuel is in
conventional electricity-generating
power plants. Power companies in
Illinois, Wisconsin, and South Dakota
have tested tdf as a partial substitute
for coal in some types of boilers. Key
considerations are the capabilities for
these plants to handle tdf and ensuring
that any air emissions or other by-
products meet environmental limits.
Pyrolysis of tires involves the
application of heat to produce chemical
changes and derive products such as gas,
oil, and carbon black. Although several
pyrolysis units have operated on an
experimental basis, none has yet sus-
tained commercial operation. The oil
produced by pyrolysis would have to
compete with conventionally produced
oil from crude. The char by-products
often require upgrading before they can
be sold.
Scrap tires are also used to a lesser
extent for a variety of other purposes,
including whole tires for artificial reefs,
breakwaters, erosion control, play-
ground equipment, and highway crash
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barriers; split, punched, or stamped tires
for fabrication into products such as
floor mats, belts, gaskets, shoe soles,
dock bumpers, seals, muffler hangers,
shims, washers, and electrical insulators;
chipped tires for lightweight fill material
where roads cross peat or other soft soils;
chipped tires for playground gravel
substitutes; crumb rubber in railroad
crossings and rubber and plastic
products; and shredded tires for bulking
agents in the composting of wastewater
treatment sludge.
Factors Affecting Demand
Crumb rubber additives for
pavements and combustion are the two
categories of scrap tire utilization that
have the greatest potential for using a
considerable proportion of the scrap tires
generated each year. Both of these uses
are based on proven technologies, and
both have the potential to be used in
many areas of the country. Substantial
barriers remain, however, to expanded
utilization of scrap tires in these areas.
A number of barriers have limited
the use of rubberized asphalt for
pavements, such as the high initial cost
to highway departments. For example,
although the use of rubberized asphalt
usually doubles a pavement lifetime,
it is often difficult for state and local
governments to justify doubling the
initial highway repair investment. Other
barriers include lack of long-term test
results on the performance of pavements
that use these technologies; lack of
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national specifications for pavements
containing rubber; concerns about the
recyclability of pavements containing
rubber; and the existence of limited
expertise in rubberized asphalt. As
experience is gained with the two types
of rubberized asphalt (RUMAC and
asphalt rubber), however, these barriers
may be overcome.
Barriers to expanded use of scrap tire
combustion include limits on the
revenue gained by the tire processor for
electricity or tdf, as well as noneconomic
factors such as environmental concerns,
permitting, and siting. For tire-to-energy
power plants, the key economic factor is
the buy-back rate for electricity granted
by the utility. These plants are feasible
only where the buy-back rate is high.
Generally, these rates are highest in Cali-
fornia and the Northeast, where oil is the
major fuel, and lowest in the Northwest,
where hyclropower is available.
Existing power plants that have been
specifically engineered for the burning
of tires are designed to control air pollu-
tion. They also create by-products that
can be used rather than disposed of.
Public concerns regarding tire storage
and potential environmental pollution,
however, can delay siting, permitting,
and operation of these facilities.
In analyzing the economic feasibility
of a tdf operation, the key issue is the
price of the competing fuel, such as pet-
roleum coke or coal. Because petroleum
coke is a cheaper fuel than tires for
cement plants, tdf cannot capture this
local market. Similarly, tdf often must
compete with coal as the fuel for cement
plants. If tdf is only slightly cheaper, the
additional capital costs needed to burn
tdf are difficult to justify. For pulp and
paper plants already equipped to burn
hog fuel, only minor equipment
modifications are needed to burn tdf.
10
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The annual cost savings can often justify
these minor modifications to handle tdf.
Concerns about regulatory delays,
permitting, or siting can also prevent an
operator from converting to tdf. Cement
kiln operators who switch from coal to
tdf usually must conduct test burns with
air pollution measurements, and the
resulting delays can affect the projected
cost savings from changing fuels.
Similarly, pulp and paper mills that
begin using tdf may need to conduct
test burns under state and local environ-
mental permitting requirements. Since
tdf tends to increase the particulates
emitted from these pulp and paper
plants, the permits sometimes restrict
the percentage of tdf that can be burned.
Future Trends in Demands
Several tire recycling technologies
could substantially reduce the number of
scrap tires requiring disposal each year.
Recycling rubber from tires for use in
asphalt pavements is a promising tech-
nology. Each year the United States
consumes approximately 450 million
tons of asphalt; this is enough capacity
to consume about 10 times the annual
supply of scrap tires. This use may be
expanded significantly if federal, state,
and local governments promote much
broader use and demonstration of
asphalt rubber and RUMAC
technologies.
Recycling whole tires as fuel and
using tdf in cement kilns and the pulp
and paper industry also have the
potential for further expansion. Other
technologies and options are promising
on a smaller scale, but are also important
to an overall solution to the scrap tire
problem. In some areas of the country,
use of chipped tires as road fill material
has potential for recycling a large num-
ber of tires. Other markets for scrap tires,
such as artificial reefs, highway crash
barriers, sludge composting, erosion
control, and playground gravel sub-
stitute, will continue to be small, but
may be important locally in some areas.
Entrepreneurs can work with local
industries to seek creative and innova-
tive applications for scrap tires.
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