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Recycling Options
Tire dumps are a growing problem as established in previous sections. However,
scrap tires are also a valuable resource. Many people have become interested
in innovative ideas to capitalize on this cheap abundant material. Several
states have established grants or some form of funding to support the research
and use of new technologies using scrap tires. These programs have generated
many practical ideas. Some of these have been put into use and have achieved
various levels of success. The following table is a compiled list of some
of the uses, we found for scrap tires.
table 1:
coral reefs
sealants
homes or building material
adhesives
live stock fencing
water filter
shoe soles
pumps
ground surfaces
stereo components
carpet overlay
computer accessories
automotive seals
sound barriers
golf courses
pyrolyzes
Tire Processing Technology
These ideas involve using the tires in various forms from whole to finely
powdered. To process the tires , new technology has been developed. Machinery
has been built to produce the consistency needed. For example crumb rubber
has become a popular material. In order get get from a whole tire to crumb
a process must be followed. One example of this process is called ambient
grinding. ³Ambient grinding involves shredding tires at ambient temperatures
into four inch by four inch pieces and then grinding the pieces with a
comminuter into a rubber crumb.²(envirosense) Another technique used
to crumb rubber is cryogenic cracking. This technique has been patented
by the GreenMan technology, which is a new company based on selling recycled
rubber products. This company is also a good example of how rubber recycling
can be profitable. The cryogenic crumbing technique involves freezing the
slit tires with liquid nitrogen and then shatters the frozen rubber to
produce crumbs. Other techniques have been developed using chemical and
mechanical measures however ambient grinding, cryogenic cracking, and slitting
are the most popular.
Tire Derived Fuel and Advantages
The two most successful reuse techniques for scrap tires are TDF and rubberized
asphalt. To define success we considered the advantages, disadvantages,
cost, practicality, and effectiveness at removing the problem of stockpiles.
TDF, or tire derived fuel is now widely used. The most popular uses are
in pulp/paper mills, cement plants and electric plants. Many of these plants
use TDF as a percentage or even full portion of their fuel requirements.
There are several advantages to using tires as a fuel source. Such as their
potential for lower pollution emission levels. In a study done by Toronto
based Proctor & Redfern, emission rate data with TDF were similar to
those of plants using only conventional fuels, and below accepted values
for air emission standards drafted by the Canadian Council of Ministers
of the Environment (CCME). The study was done using five Canadian and two
U.S. cement plants using TDF in cement kilns. The survey measure the emission
for metals (Zn, Thallium, Cadmium, lead, Nickel, Chromium), Co, SOx, NOx,
HCL, dioxin, fuerons. The results showed no significant difference in emission.
Another advantage to TDF is a potential for lower fuel cost. . Government
incentive programs and tipping fees¹ , allow TDF to become a competitive
alternative. For example in Wisconsin, incentives have led to the use of
95% of the states scrap tires produced yearly. (scrap tires) Other states
have developed similar programs, Illinois being one of them. Illinois Power
& Waste Recovery Inc., make use of inch tire chips to produce 5% of
the electrical power generated by the company. (rain trap)Tipping¹
fees for the disposal of scrap tires can subsidize the processing fees
of the tires. Tipping fees make this a more appealing option for private
companies. However, currently without government incentives many of the
plants using TDF would not survive the competitive markets. There is hope
for TDF because scrap tires have the highest BTU, energy content, of all
the alternative fuel sources. Per million BTU produce the cost using scrap
tires would be between $.25- $.75, compared to $2.00 for equal amount of
gas fueled electricity(rain trap). Two other advantages of TDF worth mentioning
are that tire burning is publicly favorable, and that the waste ash can
be used as a traction agent in the winter.
Disadvantages to TDF
There are three disadvantages to using tires as a fuel source. Two of the
disadvantages are cost related. The first is that only certain types of
boilers are suited for burning tires. Comment kilns are the best right
now. Existing boilers can be modified to meet the requirement for such
high temperatures. These modification can be expensive depending on the
model. The second disadvantage is the processing processing fees. The tire
must first be prepared to fit the specific boiler to be used, this could
mean burning the whole tire or a finely ground powder. Finally, unless
the whole tire is burned, there is a certain percentage of waste created.
Until the cost of processing and equipment are lowered the use of TDF will
be limited.
Using Recycled Rubber in Asphalt
The Other popular option, currently being employed, is using scrap tires
in production of asphalt. Research for using rubber in asphalt was first
started by Charles H. McDonald in the 1960¹s. Since then several processes
have been developed using this idea. For example the McDonald process which
uses 25% crumb and 75% asphalt, or the Arco process which uses 18-22% crumb
rubber in hot asphalt cement, and Exxon process composed of 18% finely
pulverized rubber. Advantages to Rubberized Asphalt The advantages of rubberized
asphalt is based its improved performance over normal pavement. The asphalt
containing rubber is more resistant to fatigue and resistant to wear. It
also has strong adhesive and cohesive quality for better traction. Rubberized
asphalt also reduces the noise level produced. Finally, using scrap tires
in the production of pavement on average consumes 1000 tires per mile of
one lane. Disadvantages of Rubberized Asphalt The disadvantages to using
rubber in asphalt are also cost related. The overall cost of production
is 2.4 times greater then regular pavement. It also requires specialized
spraying and surfacing equipment, which lead to more expense. There has
been a growing use of this product throughout the U.S. despite the cost.
The city of Phoenix has a very high percentage of their road system utilizing
this technique. The Government has also added to the incentive through
funding and a Federal Mandate for the use of crumb rubber in 10% of all
federal paving projects in 1996. This is supposed to be increased to 20%
by 1997.
Rain Trap System
Of the other ideas we found for recycling tires we research two that had
the best chance of success based on their practicality and usefulness.
The first idea was developed by a private company and is targeted for private
investment. Their product is call the rain trap system. This system involves
the use of slit tires to form a barrier under the soil of a golf course.
This would reduce the amount of irrigation by keeping the water within
reach of the grass roots. I t would also prevent fertilizers from entering
the ground water. In addition the system reduces the quantity of fertilizer
required because it would be only be dissipating from use not run off.
This solution is aim at private companies building golf courses, it is
not a practical option for government involvement. The purposed plan would
consume 1,231,166 tires per course. In 1994 alone 381 golf courses were
built. This ideas is economically feasible and a practical solution to
problems face by golf courses, especially in arid regions, however it is
a limited use for a growing problem.
Sound Barriers
The second idea we research as a practical solution was using scrap tires
in the production of sound barriers along highways to reduce noise to neighboring
residential areas. Carsonite International has developed a hollow fiberglass
wall supported by concrete or steel beams and filled with rubber crumbs.The
rubber crumbs are purchased from scrap rubber companies and are less a
half inch in diameter. An average wall of tongue-and-groove panels would
consume about 20,000 scrap tires. (May,20) There this system boast three
main advantages. The first being cost, on average the usual sound barrier
can cost between $15-$17 dollars per square foot.. In contrast carsonite
barrier can be produced at as little as $12 per square foot. The second
advantage to using carsonite barrier, is repairability. When a concrete
wall is hit, it takes many of man hours to fix it. The carsonite barrier
can be fixed by replacing or mending the individual panel in very little
time. Not only are the barriers easier to fix, their projected life span
is comparable to that of concrete. Finally, the most impressive advantage
of the carsonite barriers is their effectiveness. In a study done by Riverbank
Acoustical Laboratory in Geneva Ill. , found a noise reduction between
24-42 decibels. The carsonite company indicated the success of their product
and future plans for installation in highways in California, Illinois,
Nevada, Oregon and Virginia. (May,21)
Summary for Recycling
There are many ideas for how to use the mountains of scrap tires existing
and being produced. Government and private funding is sparking the development
of new ideas every day. However the major stumbling block to most of the
projects is cost and effectiveness. Until the cost of recycling is lower
then the cost of dumping tires, people will continue to dump. Recycling
tire involves not only putting the rubber to use it requires transport
and processing. The ideas explored above are currently in use . The results
of their effectiveness are still questioned. However stockpiling is should
not be an option therefore we must continue to support the recycling efforts.
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