Overview of Scrap Tire Disposal and Recycling Options
Prepared for
Border Environment Cooperation Commission
Submitted by
Houston Advanced Research Center
December 2003
For more information about the Houston Advanced Research Center, please contact:
Tom Carroll
Houston Advanced Research Center
4800 Research Forest Drive
The Woodlands, Texas 77381
Phone: (281) 367-1348
Fax: (281) 363-7914
Email: tcarroll@harc.edu
Website: http://www.harc.edu
Overview of Scrap Tire Disposal and Recycling Options
Prepared for the Border Environment Cooperation Commission
Submitted by the Houston Advanced Research Center
December 2003
Abstract
Whereas markets now exist in the United States for 72% of the scrap tires generated annually, in Mexico only 7%
of scrap tires are reused in some way. The lack of markets in Mexico for scrap tire disposal and recycling options,
including combustion for energy recovery, civil engineering uses, and ground rubber applications, combined with
the import of used and scrap tires from the United States, has led to the accumulation of scrap tires in vast
stockpiles along the U.S.-Mexico border. The serious health and environmental hazards posed by these scrap tire
piles suggest that an appropriate scrap tire management strategy for the BECC would be to use all available
opportunities to coordinate and develop projects aimed at eliminating tire piles. Most scrap tire disposal options,
including tire-to-energy incineration and civil engineering and ground rubber applications, have the potential to
meet the baseline BECC project certification criteria. An examination of the approach taken by other countries,
including the United States, indicates that tire-to-energy projects might be the most immediate and economically
feasible solution. The civil engineering or ground rubber options represent the most sustainable solutions from an
environmental and health perspective; however, the economic and technical feasibility of such projects must be
carefully examined.
Credits
This report was prepared by the Houston Advanced Research Center. The project team members included:
Valerie Cook
Marilu Hastings
Ginny Jahn
Lisa Gonzalez
Dan Matisoff
Cover photo of the Centro de Acopio in Ciudad Juárez, 2001, courtesy of the U.S. Department of Energy, National Border
Technology Partnership Program
Executive Summary
Industrialized countries such as the United States generate approximately one scrap tire per
person per year. As passenger tire retreading has declined dramatically in the U.S. marketplace
since the 1980s and scrap tire stockpiling has subsequently increased, various disposal and
recycling solutions have been developed to address the scrap tire problem.
Mexico’s scrap tire problem today resembles that of the United States in the mid-1980s. On the
Mexican side of the U.S.-Mexico border, the scrap tire problem is particularly acute. Mexican
law permits one million used tires to be imported each year into Mexicali and Chihuahua, and
Baja California permits a recycling company to import 500,000 scrap tires annually.
Municipalities estimate, however, that millions more enter the country illegally. In part, this
importation is of used tires, which have been discarded primarily by consumers in the United
States but which are still usable. These used tires wear out faster than new tires, however, and
contribute to the rapid growth of Mexico’s scrap tire problem. Because of the inflow of used
tires from the United States and because of undeveloped markets in Mexico for scrap tires,
Juárez and Mexicali are believed to have the worst scrap tire problem in the country.
Scrap tire stockpiles can cause significant public health and environmental problems. The piles
serve as breeding grounds and havens for mosquitoes and other vermin, which are vectors for a
number of serious human diseases such as dengue fever, yellow fever, encephalitis, and malaria.
The piles also are a fire hazard; once ignited by arson or lightening strike, tire fires are difficult
to extinguish and can cause serious air and water pollution. The threats associated with tire piles,
the compaction problems that tires can cause in landfills, and the market value of recoverable tire
materials have all contributed to the development of an array of tire disposal and recycling
options in the public and private sectors.
Apart from landfilling, three main categories of tire disposal options exist. The most common in
the United States and Mexico is the use of tires as a supplemental fuel in cement kilns, paper
mills, and power plants. The second most common is the use of tire chips in civil engineering
projects such as infrastructure fill and landfill lining. A variety of ground rubber applications
also exist, including recreational surfaces and bound rubber mats. There are other, less common
uses for scrap tires, including retreading, pyrolysis, and gasification. Retreading tires is no
longer a common practice in the United States in the passenger car market, but it nonetheless
remains the method that recovers the most value from a used tire. Today in the United States, all
federal agencies, some state agencies, most airlines, and many trucking operations use retreaded
tires. Pyrolysis and gasification are related thermal technologies that reduce tires into solid,
liquid, and gaseous components, but these technologies are not currently financially viable.
Scrap tire incineration can be controversial because of the potential health and environmental
effects. Open-air tire fires emit carbon dioxide, nitrogen oxides, sulfur dioxides, particulate
matter, volatile organic compounds, dioxins, and furans. The use of tires for energy recovery,
however, is a controlled process and generally emits less pollution than do other solid fuels such
as coal and wood. In a controlled environment with the appropriate scrubbers and particulate
matter traps, tire-to-energy incineration should not result in increased emissions and in some
instances can result in decreased emissions of some pollutants compared with other solid fuels.
i
Executive Summary
In the United States, scrap tires are regulated as a municipal solid waste under the Resource
Conservation and Recovery Act, but regulations are generally enforced at the state level. Nearly
all states have some form of scrap tire regulation, typically involving restrictions on the
landfilling of scrap tires as well as a tire disposal fee levied at the time of tire or car purchase.
Tire incineration is regulated in the same manner as other types of incineration; all projects
involving incineration for energy purposes are required under the Clean Air Act to comply with
the Act’s Title V permit program.
In Mexico, scrap tire disposal is regulated less stringently than in the United States. The
Mexican government regulates tire incineration but delegates oversight of other scrap tire
disposal technologies to the states. In most states, scrap tires are generally either landfilled or
monofilled. Scrap tires are also burned for energy by four cement kilns in Mexico. The Norma
Oficial Mexicana NOM-040-ECOL-2002 was passed in 2002 and specifies emissions levels for
the use of alternative fuels, including scrap tires.
The serious hazards posed by scrap tire piles suggest that the BECC’s overall strategy regarding
the issue of scrap tire management should be to coordinate and develop projects aimed at
eliminating tire piles. Most scrap tire disposal options, including tire-to-energy incineration and
civil engineering and ground rubber applications could meet the baseline BECC certification
criteria. The current lack of markets for the civil engineering or ground rubber options, however,
suggests that energy recovery projects might be the most financially feasible. On the other hand,
compliance with some of the other criteria, particularly those in the Human Health and
Environment; Community Participation; and Sustainable Development categories could require
additional effort by tire-to-energy project sponsors because of public skepticism regarding tire
incineration. The civil engineering and ground rubber applications represent the most
sustainable uses for scrap tires and would likely be less controversial, but these could fall short
of the Financial Feasibility criteria unless more innovative financing options, such as a
combination of public and private funds, are utilized.
The array of potential disposal and recycling options provides the BECC with an opportunity to
establish and support a variety of markets for tire disposal. Nonetheless, the opportunity for the
BECC to assist in the market development of the most sustainable solutions must be balanced
with the human health and environmental imperative to reduce scrap tire stockpiles
expeditiously.
ii
Table of Contents
Section
Title
Page
Executive Summary
Table of Contents
i
iii
I
Scrap Tire Overview
A. Scrap tire generation
B. Scrap tire markets in the United States, Mexico, and Europe
C. Tire composition and combustion characteristics
D. Scrap tire disposal and recycling methods
1
1
3
6
8
II
Overview of Potential Human Health and Environmental Effects of
Scrap Tire Piles and Tire Incineration
A. Introduction
B. Hazards of open air tire piles
C. Air emissions associated with scrap tire combustion
D. Potential effects for incinerator-exposed populations
E. Risk management and minimization
27
27
27
28
36
37
III
International and U.S. Regulatory Framework
A. International framework for tire disposal
B. U.S.-Mexico border agreements
C. U.S. laws and regulations governing tire disposal
D. State regulations and permitting programs
E. U.S. border state regulations and permitting programs
39
39
39
41
46
47
IV
Mexican Regulatory Framework
A. General environmental laws
B. Tire incineration regulations
C. State regulations
54
54
55
58
V
Tire Disposal Projects in the Context of the BECC’s Certification
Criteria
A. Introduction
B. General Certification Criteria
C. Human Health and Environment Certification Criteria
D. Technical Feasibility Certification Criteria
E. Financial Feasibility and Project Management Certification
Criteria
F. Community Participation Certification Criteria
G. Sustainable Development Certification Criteria
60
References
60
60
60
61
62
62
63
69
iii
Table of Contents
Tables
Table 1.
Table 2.
Table 3.
Table 4.
Table 5.
Table 6.
Table 7.
Table 8.
Table 9.
Table 10.
Table 11.
Table 12.
Table 13.
Table 14.
Table 15.
Table 16.
Table 17.
Table 18.
Table 19.
Table 20.
Table 21.
Table 22.
Table 23.
Table 24.
Table 25.
Table 26.
Table 27.
Table 28.
Table 29.
Table 30.
Table 31.
Table 32.
Table 33.
Table 34.
Stockpiled tires in border cities
Estimated total U.S. scrap tire market in 2001
What happens to scrap tires in Mexico and Texas
Material composition of a passenger tire
Energy released by the combustion of different fuel types
Tires processed into TDF in the United States
Summary of TDF use in cement kilns
Summary of TDF use in power plants
Summary of TDF use in pulp and paper mills
Summary of TDF use in steel mills
Millions of tires used in the United States per industry, per year
Ambient and cryogenic rubber processing
Life cycle cost analysis of conventional asphalt and asphalt rubber
Summary of scrap tire management methods
Laboratory simulated air emissions from open burning of chunk and shredded tires
VOC and PCDD/PCDF emissions from laboratory simulated rotary kiln combustion of TDF and
natural gas at varying rates
Metal emissions from laboratory simulations of rotary kiln combustion of TDF and natural gas at
varying rates
Comparative fuel analysis by weight
Maximum 1-h, 24-h, and annual concentrations computed at ground level for both modes of kiln
operation (coal or coal and tires)
Average annual emissions by source category for U.S. EPA Criteria Pollutants in 2001
Greenhouse gas emissions associated with various solid fuels
Criteria pollutants measured under the Clean Air Act
Hazardous air pollutants
Summary of U.S. laws pertaining to scrap tires
Clean Air Act (Title V) implementation by border states
Summary of U.S. border state legislation
Permitting processes for scrap tire processing, storage, transportation, and disposal
State tire disposal laws and regulations
Mexican emissions regulations for cement kilns using alternative fuels
Mexican emissions regulations for cement kilns: maximum permissible levels of emissions
Mexican laws pertaining to scrap tire incineration
Energy consumption required to produce tire rubber compared to energy recovered through tire
incineration
Sustainability ranking of tire disposal and recycling options
Tire disposal options and the BECC certification
Figures
Figure 1.
Figure 2.
Figure 3.
Figure 4.
Scrap tire disposal and recycling in the United States and European Union
Construction of a tire
Ambient scrap tire recycling system
Cryogenic scrap tire recycling system
Boxes
Box 1.
Box 2.
Tire processing for tire-derived fuel
Cement kilns and their use of TDF
iv
I.
Scrap Tire Overview
A. Scrap tire generation
In developed countries approximately one scrap tire is generated per person per year.
Accordingly, about 280 million scrap tires are generated each year in the United States (RMA,
2002a). Scrap tire stockpiling only became an acute problem in the United States in the last 15
years, when markets for scrap tires diminished due to the emergence of cheaper substitutes for
retreaded tires and other rubber products (Snyder, 1998). The development of other end uses for
scrap tires has led to the gradual depletion of tire stockpiles, and the most recent data estimates
that as of 2001 approximately 300 million tires remained stockpiled in unmanaged, unpermitted,
unlawful piles in the United States (RMA, 2002a).
Landfilling of tires is a poor disposal option for a number of reasons. First, tires are bulky, do
not biodegrade, and take up valuable landfill space. Second, tires’ low density and ability to trap
gases results in their tendency to “float” to the top of landfills after being buried, disrupting the
landfill compacting process and often breaking through landfill closure caps. Third, scrap tires
contain a significant amount of energy and rubber, both of which have economic value that is
lost when a tire is landfilled. Finally, placing whole or processed scrap tires in landfills can also
have a direct and negative effect on the markets for scrap tires, because the low disposal fees at
landfills limits the tipping fees that tire processors can charge for accepting the tires and also
restricts the supply of scrap tires that are available to the processors. For these reasons, the
landfilling of tires is gradually being legislated out of the range of options for tire disposal in the
United States. In 38 states the landfilling of whole tires is banned, 17 states allow processed tires
to be placed into “monofills” exclusively for tires, and 11 states ban tires in any form (whether
whole, cut, or shredded) from landfills (RMA, 2002b).
Because there is less regulation governing scrap tire disposal in Mexico, and because much of
the tire trade in Mexico takes place in informal markets, more limited data exists on the
generation and disposal of scrap tires in that country. Estimates range for the number of scrap
tires generated per year in Mexico. The Secretaría de Medio Ambiente y Recursos Naturales
(SEMARNAT), Mexico’s environmental agency, estimates that the country generates 40 million
scrap tires per year (SEMARNAT, 2003b). To understand the situation in Mexico, it is
important to first understand the distinction between used (or second-hand) tires and scrap (or
waste) tires. Used tires are those which have been used on cars but which still have some utility
left.1 Scrap tires are those tires that have no useful life remaining. A substantial market exists in
Mexico and in some U.S. border cities for used tires, which are sold and re-used until they are no
longer road worthy. While a new tire can cost as much as $100, used tires sell for less than half
that price. These second-hand tires wear out faster than new tires, however, further accelerating
the accumulation of scrap tires in Mexico.
Mexican law allows the limited importation of about one million used tires per year into
Mexicali and Chihuahua. Baja California also permits one tire recycling company to import
about 500,000 scrap tires annually (Castillo, 2003a). The extensive scrap tire problem in Mexico
is therefore due in large part to the demand for used tires and to the informal or illegal
transportation of used tires across the border from the United States. “Tire jockeys” or llanteros
1
SEMARNAT considers used tires to be those with more than 15/32" tread remaining (Castillo, 2003a).
1
Overview of Scrap Tire Disposal and Recycling Options
play a large role in the scrap tire problem in Mexico. Llanteros transport tires into Mexico in
part to satisfy the demand for used tires, and also because they can charge a “tipping fee” in the
United States for accepting scrap or used tires, which are sometimes then dumped in illegal
stockpiles on the Mexican side of the border (Cappiello, 2003).
The scrap tire problem in the border region is much more severe than in interior Mexico. The
population boom, brought about by NAFTA, on the Mexican border has resulted in increased
demand for tires. When Texas abandoned its scrap tire incentive program in 1998, the flow of
tires to the border further increased. It is believed that the largest tire piles in the country exist in
two border cities, Ciudad Juárez and Mexicali (Blackman & Palma, 2002:2).
A report from the non-profit research institute Resources for the Future analyzes the scrap tire
situation in Ciudad Juárez and provides a snapshot of one border metropolitan area that may be
extrapolated to characterize the situation in other border areas. The researchers report that a
2001 consulting study found that Juárez generates approximately 828,000 scrap tires per year, or
0.69 scrap tires per person per year. This figure does not include the flow of used tires from the
United States into the city. The largest scrap tire pile in Juárez is a secured monofill called
Centro de Acopio that is managed by the city and contains approximately 1 million tires, or more
than one-third of the total 3 million tires estimated to be stockpiled across the metropolitan area.
There are two other large tire piles in the city, each with over 10,000 tires, and numerous smaller
tire piles. In contrast, El Paso generates 879,000 tires per year, or 1.56 tires per person, but the
one officially secured pile, Tres Pesetas, contains fewer than 5,000 tires. The El Paso site
accepts almost 2,000 tires per day but ships them almost immediately to end users (Blackman &
Palma, 2002:3). It is estimated that Juárez contains about 100 times as many scrap tires as El
Paso for two reasons. As discussed above, there is a steady flow of American used and scrap
tires across the border. In addition, El Paso’s private-sector scrap tire facility has found end uses
for most of its tires (Blackman & Palma, 2002:18).
Table 1 provides estimates of tire stockpiles in some of the Texas-Mexico border cities.
Table 1. Stockpiled tires in border cities. Sources: Compiled from Cappiello (2003),
CCBRES (2003), and Foro Binacional (2003).
México
Estimated tires in piles
Mexicali
5,000,000
Ciudad Juárez
3,000,000
Matamoros
800,000
Reynosa
500,000
Nuevo Laredo
100,000
Piedras Negras
50,000
Ciudad Acuna
50,000
Texas
El Paso
75,000
The Border Environment Cooperation Commission (BECC) is charged with certifying for
financial assistance infrastructure and clean-up projects that would benefit communities and the
2
I.
Scrap Tire Overview
environment along the border. Under the BECC’s mandate expansion in 2000, waste reduction
and recycling projects were included among those that could potentially meet its certification
criteria for environmental infrastructure projects. The BECC expects that scrap tire incineration
projects will be submitted to it for certification in the future and is working to discern whether
projects of this type could be addressed under its criteria.
Included in this report are an overview of scrap tire incineration processes; a summary of
statistics regarding the use of tire incineration in various countries; and a discussion of the use of
tires as fuel, as well as other methods of tire disposal and recycling. Regulations concerning tire
incineration and other forms of tire disposal are explored for both the United States and Mexico,
and the potential public health and environmental effects of tire incineration are examined.
Finally, these disposal options are evaluated against the BECC’s project certification criteria to
determine whether such projects would meet the criteria, and how the criteria might be
interpreted to better address tire disposal options.
B. Scrap tire markets in the United States, Mexico, and Europe
Of the approximately 280 million scrap tires generated annually in the United States, about 78%
are reused. Of these, about 41% are used for energy generation, representing the largest end use
for scrap tires. The second most common use for scrap tires is in civil engineering applications,
which use chipped tires in myriad ways, including structural fill material and landfill lining. Of
the remaining 63 million tires that are generated annually, it is estimated that 25 million of those
are legally disposed of in a monofill or landfill (RMA, 2002a). The disposal route for the
remaining 38 million tires is unknown, suggesting that these scrap tires are illegally stockpiled or
exported. Table 2 provides statistics for scrap tire use in the United States.
3
Overview of Scrap Tire Disposal and Recycling Options
Table 2. Estimated total U.S. scrap tire market in 2001. Source: RMA (2002a:8)
Millions of tires
Percentage of tires
Number of
consumed
consumed
facilities
Tire-derived fuel
Cement kilns
53
19%
39
Pulp and paper mills
19
7%
14
Electric utilities
18
6%
9
Dedicated tires-toenergy
14
5%
2
Industrial boilers
11
4%
16
Total fuel use
115
41%
Other uses
Civil engineering
40
14%
Ground rubber
33
12%
(including rubbermodified asphalt)
Export
15
5%
Cut/punched/stamped
8
3%
Misc./agriculture
7
2%
Total use
218
78%
Total scrap tires
generated annually
281
It should be noted that the figures in Table 2 are for “scrap tires” only; tires which are suitable
for retreading or reuse are accounted for separately in the United States. According to the
Rubber Manufacturers Association, about 16.4 million retreadable tire casings were retreaded in
the United States in 2001. A rough estimate for the “used tire” market in the United States is that
10-12% of the total number of worn tires removed from vehicles, or 30 million tires, are resold.
In contrast, the vast majority of scrap tires that are generated in or transported into Mexico end
up in stockpiles or landfills. Table 3 compares the end uses for tires generated in Texas and
Mexico. The table shows that, in contrast to markets in the United States for 72% of scrap tires,
markets in Mexico currently exist for less than 7% of the country’s scrap tires. For purposes of
comparison, the septic system and landfill drainage uses mentioned below would generally fit
into the civil engineering category.
4
I.
Scrap Tire Overview
Table 3. What happens to scrap tires in Mexico and Texas. Source: Cappiello (2003)
What happens to scrap tires …
… in Mexico
… in Texas
Disposed of in piles
91%
0%
Retreaded
5%
0%
Burned for fuel2
2%
44%
Shredded and disposed of
0%
9%
Used for filtering septic systems
0%
3%
Used for landfill drainage
0%
20%
Used for fill
0%
18%
Other uses
0%
7%
Sources: SEMARNAT; Texas Commission on Environmental Quality, Division of Border Affairs
Note: Numbers may not add to 100% due to rounding.
Figure 1 presents similar information comparing scrap tire usage in the United States and the
European Union. Although Europe is frequently perceived as being more progressive in
terms of environmental regulation and recycling, it has in fact lagged the United States in its
recovery of scrap tires for fuel or rubber recycling. As Figure 1 illustrates, countries in the
European Union still landfill 30% of their scrap tires, and their usage of tire-derived fuel is
just 22%, about half that of the United States (Reschner, 2003).3 New European Union laws
that come into effect over the next three years will ban tires in any form from landfills, which
should dramatically increase the utilization of other methods of disposal.
Figure 1. Scrap tire disposal and recycling in the United States and European Union.
Source: Reschner (2003)
United States
European Union
Used tire export Misc.
5% 3%
Civil engineering
14%
Misc.
16%
Energy recovery
41%
Energy recovery
22%
Used tire export
8%
Civil engineering
8%
Rubber recycling
15%
Landfilling/
stockpiling
22%
Rubber recycling
16%
Landfilling &
stockpiling
30%
In summary, markets for scrap tires vary greatly from country to country and even from region to
region. In the United States, a market exists for about 72% of scrap tires, and in the European
2
SEMARNAT’s website states that 2% of scrap tires are used for fuel or are disposed of in a managed facility;
therefore, the percentage of tires used for fuel could be even less than 2% (SEMARNAT, 2003).
3
Sources for Figure 1 include the European Tyre Recycling Association and the U.S. Rubber Manufacturers
Association.
5
Overview of Scrap Tire Disposal and Recycling Options
Union there is a market for at least 46% of scrap tires. In Mexico, on the other hand, current
markets exist for only 7% of scrap tires.
C. Tire composition and combustion characteristics
Tires are composed of as many as 200 different kinds of raw material, primarily carbon black,
synthetic and natural rubber, oils, fabric, and steel. The typical materials that comprise a tire
include the following: (RMA, 2003d).
ƒ
ƒ
ƒ
ƒ
ƒ
ƒ
ƒ
ƒ
ƒ
ƒ
ƒ
ƒ
Natural rubber
Sulfur and sulfur compounds
Silica
Phenolic resin
Oil: aromatic, naphthenic, paraffinic
Fabric: Polyester, Nylon, etc.
Petroleum waxes
Pigments: zinc oxide, titanium dioxide, etc.
Carbon black
Fatty acids
Inert materials
Steel wire
The rubber portions of the tire are actually comprised of a number of different compounds,
which are described in more detail in Table 4.
Table 4. Material composition of a
passenger tire. Source: RMA (2003d)
Material
% of total weight
Carbon black
28%
Synthetic rubber
Fabric, fillers,
accelerators, antizonants,
etc.
Steel
Natural rubber
Average weight
27%
16-17%
14-15%
14%
New 25 lbs, scrap 20 lbs
6
I.
Scrap Tire Overview
Figure 2 illustrates how a passenger tire is constructed from these materials.
Figure 2. Construction of a tire. Source: RMA (2003c)
Because of their material composition, tires have similar combustion characteristics to other
carbon-based fuels. Table 5 compares the energy released by tires and other types of fuel.
Table 5. Energy released by the combustion of different fuel types. Source: Snyder
(1998:48)
Fuel
Pine wood
Bituminous coal
Coke
Tire chips
Fuel oil
BTU/lb
9,100
11,000 – 14,000
14,000
14,000 – 15,000
18,000 – 19,000
Tire combustion generally produces similar waste products and emissions to other solid fuels.
Since SO2 is regulated under the Clean Air Act, the use of tires instead of coal can assist a
facility in complying with emissions standards. In comparison with coal, the fuel most
commonly supplemented with tires, tires contain less sulfur—approximately 2% (Blumenthal,
2003b), compared with Midwestern soft coals that can contain as much as 4% sulfur. Tire
combustion also produces CO2, although for the amount of energy produced, tires emit less CO2
than coal (Snyder, 1998).
The metals that are also present in tires can have both positive and negative effects on their use
as a fuel. Tires contain significant amounts of zinc (approximately 1.5%), which is not present
in coal. After tire combustion, zinc is found in the ash and as a particulate in the stack gases. As
much as 14-15% of a tire’s total weight is in steel. The amount of steel remaining depends on
the amount removed when the tire was processed into tire-derived fuel (TDF). In a coal boiler,
7
Overview of Scrap Tire Disposal and Recycling Options
this steel also burns and contributes to the energy generation, leaving iron oxide in the ash
(Snyder, 1998). When tires are burned in cement kilns, the iron oxide that is produced is actually
recycled as an ingredient in the cement making process.
Despite the generally favorable emissions profile of tires when compared to coal, the combustion
of tires for energy nonetheless can also present air pollution and related human health impacts.
Emissions from tire combustion are similar to those from burning coal, although the levels of
SO2 and CO2 are lower. In general, supplementing traditional fuels such as coal or wood with
TDF will still satisfy emissions limits, and facilities that are designed to burn tires exclusively
can have much lower emissions than traditional solid fuel facilities, especially if particulate
controls are added (EPA, 1997).
In summary, the following material and combustion properties of tires contribute to their
attributes as an energy source (Blumenthal, 2003b).
ƒ
ƒ
ƒ
ƒ
ƒ
ƒ
ƒ
14,000 – 15,000 BTU’s per pound of tires
Contain less than 1% moisture, resulting in hotter, quicker, and more complete
combustion than fuel sources such as coal or wood
Lower fixed carbon ratio than coal, resulting in lower CO2 emissions
Less nitrogen than coal, resulting in lower NOx emissions
Less sulfur than coal, resulting in lower SO2 emissions
Virtually no chlorine
Virtually no mercury
D. Scrap tire disposal and recycling methods
As discussed earlier, the landfilling of whole or chopped tires is an undesirable disposal method.
Whole tires trap gases and tend to rise to the top of landfills, disrupting the compaction process.
Disposing of chopped or shredded tires is also a poor solution because of the value of the tires as
an energy source or as a source of rubber and steel.
This section provides an overview of the range of scrap tire disposal and recycling options,
including combustion for energy recovery, civil engineering applications, ground rubber
applications, pyrolysis, retreading, and the use of recycled rubber granules in new tires. These
options vary in their usage and economic feasibility in the United States and Mexico. In both
countries, the use of tires for energy is the most developed market for scrap tire use, although
even this market is still nascent in Mexico. In Mexico, the 2% of tires that are burned for energy
are used primarily in the cement industry. The use of TDF in other Mexican industries such as
paper mills, utilities, and industrial boilers is rare (Blumenthal, 2003a; Alvarez, 2003).
8
I.
Scrap Tire Overview
Tire incineration methods for energy recovery
Depending on the combustion process, tires can be burned
whole or as tire-derived fuel (TDF), whereby the tires are
chopped or shredded and some of the tire cord and wire is
removed. Tire processing varies greatly depending on the
end use for the rubber particles. The general process for
making TDF is described in Box 1.4
Several factors have influenced the increased use of TDF. In
2001 the American Society for Testing and Materials
International (ASTM), a provider of industrial standards
worldwide, released ASTM D6700-01, a set of standards for
the production and use of TDF (ASTM, 2001). The
development of these industry standards, combined with
improvements in the second and third generation TDF
processing systems, has increased the consistency and
quality of TDF and thereby facilitated its use. The high cost
of natural gas has also resulted in the increased use of TDF
as a replacement fuel.
Table 6 shows the number of tires being made into TDF
annually in the United States. The slowdown in the rate of
growth of number of tires going to TDF is the result of the
development of other markets for tire recycling.
Table 6. Tires processed into TDF in the
United States. Source: Blumenthal (2003b)
Year
# tires into TDF
1990
24 million
1992
46 million
1994
101 million
1996
115 million
1998
114 million
2001
115 million
Box 1. Tire processing for
tire-derived fuel
Tire-derived fuel, or TDF, is a term
describing tires that are burned for
energy recovery. These tires can
either be whole (“whole TDF) or
chopped or shredded (“processed
TDF”). Processed TDF can be
chopped into particles ranging in size
and metal content. TDF is generally
used as a fuel supplement in boilers
that use another solid fuel such as coal
or wood as the primary energy source.
Different processes are used to
produce processed TDF depending on
the size of rubber particle needed. For
the largest sizes, machines that cut the
tires into pieces are sufficient.
Different types of shredders will
produce particles of different sizes and
properties. Often, several successive
chopping operations and different
types of equipment are needed (Snyder
1998:19-39).
The amount of tire wire included in
processed TDF also ranges from no
wire removed, to only bead wire
removed, to relatively wire free. The
amount of wire that can be removed
depends on the chopping process, and
the amount of wire that a combustion
facility can tolerate depends on the
facility type (ASTM, 2001).
Using tires as fuel
Tires were first used as a supplemental fuel in Germany in the mid-1970s, where they were used
in cement kilns. The use of TDF in the United States began in 1979 in pulp and paper mills in
the Northwest. The first U.S. cement kiln to use TDF occurred in 1985.
The usage of TDF as a supplemental fuel is complex, because rubber contains substantially more
energy and has lower moisture content than other commonly used solid fuels such as coal or
4
The term TDF is sometimes used to refer to any tires that are used for fuel, regardless of whether they are whole,
chopped, or shredded.
9
Overview of Scrap Tire Disposal and Recycling Options
wood. Two factors must be kept in mind when TDF is used as a supplemental fuel. Boiler
facilities that are constructed to use a certain type of fuel can absorb only so much heat, after
which the boiler begins to melt. The grate that holds the fuel over the fire can also melt or clog.
For these reasons, TDF usage is generally limited to blend ratios in the 10-30% range, depending
on the primary fuel source (ASTM, 2001), and the TDF must be well-mixed with the other fuel
before it is placed on the grate (Porter, 2003).
The amount of processing that a tire must undergo in order to be used as a supplemental fuel in
different industries is indirectly correlated with its economic feasibility as a fuel source. As a
tire is processed into smaller pieces, the processing equipment required and the amount of energy
used diminishes the economic value of the scrap tire as an alternative fuel source. Also, although
the steel can be separated from the tire with sufficient processing, in general the market value of
that scrap steel would not alone justify the tire processing costs (Blumenthal, 2003a).
Dedicated tire-to-energy facilities
The first dedicated tire-to-energy facility was owned by Gummi-Mayer, a retreaded tire
company. Gummi-Mayer designed and built a small steam plant that used the tire casings that
were not suitable for retreading as fuel, producing all of the steam necessary for the retreading
process as well as half of the facility’s electric needs.
Whole tire industrial boilers have also been built and operated by Goodyear in Jackson,
Michigan, and in Wolverhampton, England. Both facilities were small and were intended as
supplementary energy facilities. Even so, the operators found that the supply of tires that could
be provided at an acceptable price on an ongoing basis was inadequate, and neither facility is
currently in operation (Snyder, 1998:50).
As of the end of 2001, there were only two dedicated tire-to-energy facilities operating in the
United States (RMA, 2002a:15). The Chewton Glenn Energy facility in Illinois consumes three
million scrap tires per year and generates 20 MW (SNC Lavalin, 2003). The Exeter Energy
Limited Partnership facility in Connecticut consumes 10-11 million scrap tires per year,
generating 26 MW and serving as a major market for scrap tires in lower New England (SNC
Lavalin, 2003). Five percent of scrap tires were used in dedicated tire-to-energy facilities in the
United States in 2001. There are no dedicated tire-to-energy facilities in Mexico.
Energy facilities designed to combust solely whole tires or TDF are rare for several reasons.
First, a high initial capital investment is necessary for dedicated tire-to-energy facilities
compared to standard coal-fired boilers, and the uncertainty about a sufficient tire supply further
complicates this investment, as banks are reluctant to finance a facility whose fuel supply is
insecure. Second, high transportation costs5 for tires require that a dedicated tire combustion
plant be located close to the tire source. It follows that the limited supply of tires at any
particular location restricts the size of the plant that can be constructed. For instance, the Oxford
Energy facility in Westley, California, was located next to the largest pile of scrap tires in the
United States and was a 14.4 MW unit, compared to modern 500 MW coal-fired power plants.
5
It costs one dollar to transport a new tire 100 miles, and presumably transporting a scrap tire would cost nearly as
much. For this reason, scrap tires are somewhat anchored geographically to their original disposal site (Snyder,
1998).
10
I.
Scrap Tire Overview
(Snyder, 1998:51). A dedicated facility producing 227 MW per hour would require 66,000 scrap
tires per day to meet its fuel demands. This level of demand could strain a region’s ability to
supply the tires, thereby putting the fuel supply at risk (ASTM, 2001).
Cement kilns
The manufacture of cement is energy intensive, requiring approximately 500 lb. of coal to
produce one ton of cement. The cost of cement is closely tied to the cost of its fuel source, and
TDF has become a popular supplement to coal to lower fuel costs (Snyder, 1998).
Two steps are involved in making cement. In the first step, limestone (CaCO3) is heated to
remove the CO2, resulting in lime (CaO). In the second step, the lime is mixed with sand,
calcium sulfate (CaSO4), and small amounts of iron oxide (Fe2O3) and other ingredients. This
mixture is heated to temperatures above 1,500ºC for approximately 24 hours during passage
down a long kiln. Once the material has been finely ground, the resulting product is cement. It
is important to note that two of the minor recipe ingredients for cement are iron oxide and sulfur,
which can be furnished by tires. When tires are used as a supplemental fuel, the burning steel is
converted to iron oxide, and the sulfur dioxide (SO2) is scavenged by the hot lime and converted
to calcium sulfate before it can escape (Snyder, 1998:53-54). Box 2 outlines the process of
making cement and the types of cement kilns.
11
Overview of Scrap Tire Disposal and Recycling Options
Box 2. Cement kilns and their use of TDF
A cement kiln is a large, rotating furnace that is slightly angled down, allowing the materials to pass through the
kiln by gravity. The upper end of the kiln is the “cold” or back end where the raw materials are fed; the lower
end is the “hot” end where the fuel combustion produces temperatures exceeding 1,500°C (EPA, 2000). Three
types of cement kilns exist. Each requires a different feeding method for whole and processed TDF.
Straight kiln (wet or dry)
In a wet process kiln, the raw materials are ground and mixed with water to form a slurry. A greater amount of
energy is needed during the cement-making process to evaporate this additional water. Only straight kilns can
employ the wet process. In the dry straight kiln process, the raw materials are ground into a dry powder before
being fed into the kiln (EPA, 2000).
Either whole tires or shredded tires can be fed into a straight kiln. Whole tires require using a tire kiln injector,
which is done at 15 to 50 feet uphill from the kiln drive gear. Shredded tires are fed in by insufflation (blowing
tire shreds into the discharge end of kiln). Because of their short residence time in the kiln, the tire particles must
be small to be completely consumed prior to entering the kiln’s clinker cooler (Weatherhead, 1991).
Preheater kiln
In a preheater kiln, the raw materials are heated prior to entering the kiln. This allows for a shorter kiln and
lower combustion fuel use (EPA, 2000).
Preheater kilns are the most promising for the use of whole tires. Tire feeding is done at the riser duct from the
feeder end of the kiln and the preheater vessel through a double tipping valve. Burning whole tires may increase
the kiln’s production rates due to the increased rate of calcination when burning whole tires (Weatherhead, 1991).
Preheater/precalciner kiln
In a preheater/precalciner kiln, the additional step is taken to heat the raw materials to the point where they begin
to calcinate before entering the kiln, further lowering the fuel consumption (EPA, 2000).
Preheater/precalciner kilns can use whole or shredded tires, or both. Shreds can be fed in with the coal in a
precalciner. Whole tires or shreds can be fed in between the 4th, 5th, or 6th stage of the preheater and the kiln at
riser duct of the feed end of the kiln (Weatherhead, 1991).
Cement kilns are currently the most economic disposal route for scrap tires, especially stockpiled
tires, for several reasons. As noted above, tires provide iron and sulfur, two minor but key
ingredients in producing cement. The tires can be burned whole, so no energy or expense is
required to shred the tires. Also, cement kilns are an attractive disposal option for stockpiled
tires, which are typically dirty and therefore not good candidates to be processed into ground
rubber for recycling applications (Blumenthal, 2003a).
Traditional cement kilns must be modified to use scrap tires as a supplemental fuel. Generally, a
conveyor, scale, and metering system must be added in order to utilize the tires. Costs for these
modifications vary widely, from US$100,000 to US$1 million, and depend on the configuration
of the kiln and on the quality of the components purchased (Blumenthal, 2003a). Cement
companies in both the United States and Mexico typically charge a “tipping fee,” or a fee for
accepting the scrap tires. A feasibility study conduced by a cement plant in Ciudad Juárez
concluded that TDF would be an economically attractive alternative to coal if (1) a steady supply
of scrap tires existed within 300 km of the plant; and (2) the plant were paid the tipping fee
currently being paid for scrap tire disposal (Blackman & Palma, 2002:17).
12
I.
Scrap Tire Overview
The costs associated with burning TDF are similar to those of other technology upgrades in a
cement plant. The project balance sheet would include capital expenditures and debt service, as
well as a revenue line (if whole tires are used) and a coal savings line. Labor costs might
increase depending on the level of automation of the tire feeding system. Maintenance costs
would remain the same, with the exception of coal mill maintenance costs, which should
decrease.
The cement industry is the one industry in the United States that has increased its usage of TDF
as a supplemental fuel in recent years and is expected to continue doing so. The reasons for this
are varied. In 1998 the EPA called for states to develop plans to reduce the emission of nitrogen
oxides from fuel combustion, and the use of TDF can help to reduce NOX emissions (RMA,
2002). Also, the recent economic downturn lessened the demand for cement, and the lower
production caused kiln managers to institute cost-cutting measures such as using TDF to reduce
their energy costs. The increase in natural gas costs has also led to plant conversions to use tires
as a supplemental fuel.
The cement industry in the United States is the largest end user of scrap tires. Cement kilns in
the United States consumed 53 million tires in 2001 and a similar number in 2002; it is projected
that cement kilns will have used as many as 55 million tires by the end of 2003.
Four cement kilns in Mexico currently use tires as a supplemental fuel. Three are CEMEX
facilities, in Ensenada, Baja California; Monterrey, Nueva León; and Colima, Colima. The
fourth, operated by Holcim Apasco, uses tires in its facility in Apaxco, México. (Wilson, 2003).
Table 7 summarizes the benefits and limitations of the use of tires as a supplemental fuel in
cement kilns.
Table 7. Summary of TDF use in cement kilns. Source: Blumenthal (2003b)
Benefits of TDF to cement kilns
• Lower cost of energy
• Lower NOx emissions
• Steel in tires reduces iron ore needs
• Expedites calcination process
• Use of whole tires reduces wear and maintenance costs on coal roller mills
Limitations on use of TDF in cement kilns
• Total zinc cannot exceed 4,000 PPM
• Zinc limitation restricts fuel replacement to 25-30%
• Amount of excess oxygen can limit the use of TDF
Power Plants
Tire-derived fuel is also a feasible fuel supplement for utilities, although the amount of TDF used
as a percentage of total fuel is still relatively low (1-3%). Some of the benefits of using TDF as a
supplemental fuel in a utility boiler are that it reduces the amount of ash produced, and it lowers
NOx emissions in instances where the primary fuel is a solid fuel such as coal. One limiting
factor in the use of TDF in power plants is that excess wire in the TDF causes blockages in the
feeding system and allows slag to build up on the grate. While TDF can be processed so that
13
Overview of Scrap Tire Disposal and Recycling Options
most of the wire is removed, this processing makes the TDF more expensive and diminishes its
cost competitiveness.
From a technological standpoint, TDF is an acceptable supplement for coal in stoker-fired
boilers, since TDF can be processed to be similar in size to stoker coal. Older stoker-fired
facilities have benefited most from using TDF as a coal supplement. Apart from these older
facilities, however, in the United States the use of TDF as a fuel supplement by utilities has been
on the decline for several reasons. Most new facilities have been designed to use powdered coal
or have entered into long-term contracts to purchase low-sulfur coal. TDF is not compatible with
powdered coal, as TDF cannot be processed to that size at an economic cost. The emissions
profile of TDF also does not compare as favorably against low-sulfur coal, and most utilities are
not willing to use a fuel that contains more sulfur than their primary fuel. The industry in
general is moving away from solid fuels and in particular fuels that are perceived as “dirty,” such
as coal and by association, TDF (RMA, 2002a).
In 2001, 6% of scrap tires were used for fuel in power plants in the United States (RMA, 2002a).
Scrap tires are not typically used as a fuel source by utilities in Mexico (Blumenthal, 2003a;
Alvarez, 2003).
The guidelines for use of TDF in smaller scale industrial boilers are like those for utilities.
Industrial boilers typically operate at similarly high temperatures and have similar pollution
control equipment. Four percent of scrap tires generated in the United States were burned in
industrial boilers in 2001 (RMA, 2002a). Again, in Mexico the use of scrap tires in industrial
boilers was rare (Blumenthal, 2003a; Alvarez, 2003).
Table 8 summarizes some of the benefits and limitations of the use of tires as a supplemental fuel
in power plants and industrial boilers.
Table 8. Summary of TDF use in power plants. Source: Blumenthal (2003b)
Benefits of TDF to power plants
• Lower NOx emissions and sometimes SOx emissions
• Reduces the quantity of ash
Limitations on use of TDF in power plants
• Excess wire in TDF causes plugging of the feeding
system and slag build up on grate
Pulp and paper mills
TDF is an accepted fuel supplement in the forest products industry, which frequently uses its
own wastes such as bark, branches, and sawdust as a primary fuel in pulp and paper mill
processes. The use of TDF is in part limited by its supply and pricing, as the industry is able to
use its forest product waste at what is essentially a negative cost. Other factors that limit the use
of TDF in this industry are the inability of many systems to deal with the zinc and wire found in
TDF. Pulp and paper mills that do use TDF can realize benefits such as improved energy content
of the fuel mix and lower emissions (Blumenthal, 2003b).
14
I.
Scrap Tire Overview
The use of TDF by the pulp and paper industry declined in the United States from 1998 to the
end of 2001 for several reasons. Many mills closed due to excess manufacturing capacity in the
industry. Other mills ended their use of TDF due to poor quality, such as excess wire in the
TDF, which increased boiler maintenance costs. Finally, industry consolidation resulted in new
parent companies that lacked experience in TDF use and discontinued it. In 2001, 7% of scrap
tires were used for fuel in the pulp and paper industry in the United States (RMA, 2002a). Scrap
tires are not typically used as a fuel source by the pulp and paper industry in Mexico
(Blumenthal, 2003a; Alvarez, 2003).
Table 9 summarizes some of the benefits and limitations of the use of tires as a supplemental fuel
in pulp and paper mills.
Table 9. Summary of TDF use in pulp and paper mills. Source: Blumenthal (2003b)
Benefits of TDF to pulp and paper mills
• Increases BTU content of fuel mix
• Lowers NOx emissions and sometimes SOx emissions
• Reduces ash
• Reduces particulate matter emissions
Limitations on use of TDF in pulp and paper mills
• If no gas scrubber, use of TDF is limited to 10%
• If mill has a wet scrubber, zinc concentration builds
up in effluent
• Excess wire in TDF can plug the ash sluicing systems,
feeding system, and slag can build up in the grate
Steel mills
The use of TDF as a supplemental fuel in steel mill boilers is a recent development. The Rubber
Manufacturers Association projects that steel mills will use six million tires, or 2% of scrap tires
generated, as TDF by the end of 2003. Although this number is small in comparison to the use
of TDF by other industries, there is also potential for increased use of TDF by the steel industry.
The use of tires as fuel by the steel industry in Mexico has not yet been developed (Blumenthal,
2003a).
Nucor Corp., the most profitable U.S. steelmaker, has begun a program in its Auburn, NY, plant
that melts tires in its electric-arc furnace. The facility began using scrap tires as fuel in 2002 and
has saved about $1 million in coal and scrap steel costs in its first 18 months of operation. The
plant is now using 1 million tires per year to replace approximately 8,000 tons of coal. In
addition, the plant is able to derive roughly 1,000 tons of scrap steel from the 1 million tires used
each year. The company is also investigating whether the tires can be used as an alternate carbon
source (Recycling Today, 2003).
The benefits for the steel industry are similar to those for the cement industry. In addition to
scrap tires providing a source of steel for the industry, their combustion can also lower the cost
of energy and reduce NOx emissions. As with other tire-to-energy efforts, the economics of tires
as a replacement fuel depend on supply and transportation costs as well as on the primary fuel
costs.
15
Overview of Scrap Tire Disposal and Recycling Options
Table 10 summarizes some of the benefits and limitations of the use of tires as a supplemental
fuel in steel mills.
Table 10. Summary of TDF use in steel mills. Source: Blumenthal (2003b)
Benefits of TDF to steel mills
• Lowers cost of energy
• Lowers NOx emissions
• Source of steel
Limitations on use of TDF in steel mills
• N/A
To summarize, Table 11 provides an historical perspective of the use of tires as fuel in the United
States in the industries discussed above. A projection of the number of tires that will be used by
various industries during 2003 is also included.
Table 11. Millions of tires used in the United States per industry, per year. Source:
Compiled from Blumenthal (2003b)
‘90
‘92
‘94
‘96
‘98
‘01
Cement kilns
6
7
37
39
38
53
Paper mills
13
10
27
24
20
19
4.5
15
15
15
16
14
Dedicated tire-toenergy facilities
Utilities
1
5
12
21
25
18
Industrial boilers
0
9
10
16
15
11
Steel mills
0
0
0
0
0
0
Total used
24.5
46
101
115
114
115
16
‘03E
55
25
14
18
15
6
133
I.
Scrap Tire Overview
Civil engineering applications
Tire chips are lightweight, low density, durable, free draining, and provide good thermal
insulation. These properties make them an excellent material for use as fill in infrastructure
projects. Tire chips have been used in retaining walls, for erosion control, crash attenuation, and
as structural fill material. Because of their low density, tire chips used as fill exert lower
horizontal pressure, often resulting in lower construction costs because walls can be made
thinner and with less steel reinforcement.
The use of tire chips as structural fill has been problematic, however. In 1995, three fill projects
in the United States experienced a catastrophic internal heating reaction and had to be torn down.
The heating reaction was believed to have been caused by oxidation of the exposed steel and
rubber; microbial activity also might have played a role (RMA, 2003b). In response, the ASTM
D6270-98 standards6 were developed in 1998 for the use of tires in civil engineering, specifying
that chip layers should not exceed 10 ft. in depth (multiple layers can be separated by layers of
other material, however, such as soil) (Humphrey, 2003).
The use of tire chips to construct landfills is one of the most widespread and fastest growing
engineering uses; the chips can be used as a liner to protect the geotextile layer and to provide
drainage, and can also be used on the sloping sides of a landfill and as a landfill cover (Snyder,
1998).
Tire chips can also be used in various ways in the municipal sewage treatment process and in
septic system drainage fields. Tire chips can also be substituted for wood chips in the treatment
of municipal sewage as a bulking agent for the composting process, resulting in not just cost
savings compared to the wood chips but also in improved composting. In the United States,
several hundred municipal sewage treatment plants now compost sewage sludge, but despite the
cost and process advantages of using tire chips, adoption of this alternative has been slow
(Snyder, 1998).
Another engineering use for whole tires is to construct artificial reefs for recreational purposes,
an idea first developed and promoted by the Goodyear Tire and Rubber Co. The scrap tires are
filled with concrete to overcome their buoyancy, bundled together, and then sunk in warm,
shallow coastal waters. The tires become encrusted with barnacles and other marine growth that
effectively cements them together. These tires then serve as a refuge for young fish from their
predators, increasing the population of adult game fish in subsequent seasons. By 1985 it was
concluded that the use of scrap tires in fishing reefs is not economically feasible, although some
projects have continued with local subsidies (Snyder, 1998:114).
Metal leaching from tire chips used in civil engineering is a concern, as the leachate can contain
relatively high levels of metals, particularly iron and manganese. The ASTM D6270 also
6
The full name of the specification is “ASTM D6270-98 Standard Practice for Use of Scrap Tires in Civil
Engineering Applications.” This practice provides guidance for testing the physical properties and gives data for
assessment of the leachate generation potential of processed or whole scrap tires in lieu of conventional civil
engineering materials, such as stone, gravel, soil, sand, or other fill materials. In addition, typical construction
practices are outlined (ASTM, 2001).
17
Overview of Scrap Tire Disposal and Recycling Options
contains guidelines to prevent this from occurring. Patrick Sheehan, a toxicologist with the
engineering consulting firm Exponent, studied the effect of tire chip leachate on aquatic species,
from civil engineering applications both above and below the water table. He found no effect on
aquatic species in applications above the water table. However, for below-water-table
applications he did find a small effect on fish, and larger effects on the survival and reproduction
of aquatic invertebrates. Sheehan has developed guidelines for the distance that below-watertable applications must be from open bodies of water in order to avert leachate concerns (2003).
Potential leachates from scrap tires are discussed further in Section II.
Civil engineering uses comprised 14% of the U.S. scrap tire market in 2001 (RMA, 2002a). No
such market exists in Mexico at this time (Cappiello, 2003).
Ground rubber applications
Ground rubber, also called crumb rubber, applications comprised 12% of the U.S. scrap tire
market in 2001 (RMA, 2002a). No ground rubber market currently exists in Mexico, although
some applications, such as a rubber-modified asphalt project in Los Cabos, Baja California, may
have been tried on a test basis (Foro Binacional, 2003).
Ground rubber is produced by putting tires through a series of machines that first shred the tire
and then grind it into decreasing particle sizes. Such processing is generally done in ambient or
cryogenic environments. To prepare the tires, processors generally first shred scrap tires into
chips of approximately five centimeters (two inches) in size. This reduces the space
requirements of the tires to about ¼ of that for whole tires, therefore reducing shipping costs.
The most common tire shredding machines are rotary shear shredders with two counter-rotating
shafts. Most shredders have a capacity of two to six tons per hour, depending on the input
material and the size of the chips produced (Reschner, 2003).
In ambient tire processing, all of the size reduction steps take place at or near ambient
temperatures. Tires are typically at room temperature when they enter the processor, and their
temperature subsequently rises as a result of the friction generated as the rubber is torn apart.
While there is a limited market for rubber granules that are about one centimeter (⅜ inch) in size,
most applications require finer material in the 10-30 mesh range (30 mesh means that material
has been sized by passing through a screen with 30 holes per inch). Tires can be economically
processed down to 20 mesh using ambient grinding (Reschner, 2003). Figure 3 provides an
example of an ambient scrap tire processing system.
18
I.
Scrap Tire Overview
Figure 3. Ambient scrap tire recycling system. Source: Scrap Tire News (2003b)
In cryogenic tire processing, liquid nitrogen is used to cool tires to a temperature below -80°C.
Below this “glass transition temperature,” the rubber becomes brittle and can be crushed into
even finer mesh sizes. Cryogenic size reduction requires fewer pieces of machinery and less
energy than ambient processing, and liberation of the steel and fiber is easier, leading to a cleaner
rubber product. However, the cost of liquid nitrogen means that this method is only economic if
clean, fine mesh rubber powder is required (Reschner, 2003).
To prepare tires for the cryogenic process as well as the ambient process, the tires are first
debeaded and pre-shredded down to a two-inch size. In the cryogenic process, the two inch
particles are cooled in a freezing tunnel and then dropped into a hammer mill, which shatters the
chips down to a 30 mesh size or smaller (Reschner, 2003). Figure 4 provides an example of a
cryogenic scrap tire processing system.
19
Overview of Scrap Tire Disposal and Recycling Options
Figure 4. Cryogenic scrap tire recycling system. Source: Scrap Tire News (2003b)
In both ambient and cryogenic tire processing, the tire steel is separated from the rubber by
magnets, and the fiber is removed by aspiration and screening. Several proprietary wet-grinding
processes are also in use today in the United States for producing fine and super-fine grades of
crumb rubber.
Table 12 summarizes the ambient and cryogenic methods of tire processing.
Table 12. Ambient and cryogenic rubber processing. Source: Reschner (2003)
Parameter
Ambient processing
Cryogenic processing
Operating temperature
Ambient, max. 120°C
Below -80°C
Size reduction principle
Cutting, shredding, shearing
Breaking cryogenically
embrittled rubber pieces
Particle morphology
Spongy and rough
Even and smooth
Machinery maintenance costs Higher
Lower
Electricity consumption
Higher
Lower
Liquid nitrogen (LN2)
n/a
0.5 – 1.0 kg LN2 per kg tire
consumption
input
Rubber-modified asphalt
Scrap tire rubber has been added to asphalt since the mid-1960s; this is the single largest use for
ground rubber in the United States, providing a disposal route for 12 million tires per year
(RMA, 2002a). Rubber is most frequently used as part of the asphalt binder, and it can also be
20
I.
Scrap Tire Overview
used as an aggregate substitute, as a seal coat to cover the existing road, or as a joint and crack
sealant.
ASTM in 2002 published the “D6114-97(2002) Standard Specification for Asphalt-Rubber
Binder” which provides standards for the use of rubber in the asphalt binder. The specification
notes that at least 15% rubber by weight of the total blend is necessary to provide the benefits of
rubber-modified asphalt.
The advantages of rubber-modified asphalt include the following (Reschner, 2003):
ƒ
ƒ
ƒ
ƒ
Ability to withstand both hot and cold temperature extremes, reducing both thermal
cracking (due to cold temperatures) and rutting (due to hot temperatures);
Lower lifecycle costs compared to conventional asphalt pavement, due to lower
maintenance costs and increased durability;
Increased traffic safety due to increased skid resistance, shorter breaking distances,
better deicing properties, and fewer road construction sites; and
Decreases traffic noise by 4 – 6 decibels, resulting in lower construction costs for
highway sound barriers (ADOT, 2003).
Rubber-modified asphalt is used extensively in Arizona, Texas, California, and Florida (Rubber
Pavements Association, 2003). Although not widely used in Mexico, 10 miles of asphalt rubber
road has been constructed from the Arizona border into Nogales, Mexico (EPA, 2003h).
Arizona is the national leader in the use of rubber-modified asphalt, and currently uses 1.5
million scrap tires in 400 miles of pavement resurfacing per year. A total of 15 million scrap
tires have been used in paving 3,000 miles of highway since the state began the program in
earnest in 1988 (Zareh, 2003). Currently, a large project is underway to do a one-inch overlay of
asphalt rubber to reduce road noise; the project will coat 150 miles of concrete pavement
surrounding Phoenix. The state uses a pavement that is 18 – 20% by weight of rubber blended
with the asphalt binder, which is then mixed with 8 – 10% by weight with the paving aggregate
(ADOT, 2003). The binder is one that has been developed to withstand hot and cold temperature
extremes (Zareh, 2003).
Two studies conducted in Arizona and Texas on the performance of rubber-modified asphalt
may indicate how such projects would fare in Mexico. Researchers from Arizona State
University and the Arizona Department of Transportation conducted a life cycle cost analysis of
conventional asphalt compared to rubber-modified asphalt, comparing two adjacent four-mile
stretches of highway. The asphalt rubber blend used in Arizona is approximately 20% rubber.
The study evaluated both agency costs (initial construction, rehabilitation, and maintenance) and
user costs (travel time delays and vehicle operating costs). Over a 25-year period that began
with the construction of the roads, the asphalt-rubber pavement was found to be less costly than
conventional pavement in terms of both agency costs and user costs. In this case, the initial
construction costs were lower overall for the asphalt rubber pavement. Although the unit costs
of asphalt rubber pavement were higher, the total initial cost for the conventional pavement was
higher due to the difference in the thickness of each layer. After five years, the data showed little
difference in the maintenance costs of the two roads; after 10 years, the maintenance costs for the
21
Overview of Scrap Tire Disposal and Recycling Options
conventional pavement became much higher; and after 15 years a difference in user costs began
to be found (Jung, 2002). Over a 25-year period, the study calculated a 40% lower life-cycle
cost for the asphalt rubber. Table 13 summarizes these results.
Table 13. Life cycle cost analysis of conventional asphalt and asphalt rubber.
Source: Jung (2002)
Year
Conventional asphalt Asphalt rubber
MC$
UC$
MC$
UC$
0 1,515,008
875,776
5
1,844
12,296
1,317
12,325
10
7,477
12,705
4,295
12,288
15
10,471
13,288
5,853
12,890
20
11,998
13,981
6,471
13,172
25
12,649
14,800
6,683
13,565
Key: MC = maintenance costs; UC = user costs
In Texas, rubberized asphalt has been used since 1976, and a study was conducted in 2001 for
the Rubber Pavements Association by Pavetex Engineering and Testing. Due to the limited
number of asphalt rubber applications in Texas, the study examined all applications regardless of
their age. The study results are described below (Tahmoressi, 2001).
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Projects using rubber asphalt in Porous Friction Course projects performed the best of
any type of rubber asphalt application, exhibiting high resistance to cracking and
raveling. From the cost-benefit standpoint, this PFC projects are the best use for
rubber asphalt.
Most asphalt rubber hot-mix projects exhibited satisfactory performance and showed
better resistance to cracking than traditional asphalt.
Chip seal coat projects that utilized grade 3 (5/8” maximum) size chips had excellent
resistance to cracks and chipping. Projects that used a smaller chip size (grade 4),
however, experienced some bleeding problems.
Obstacles to the wide-spread use of rubber in asphalt are a greater upfront cost and a lack of
training and education on the part of paving companies and local decision-makers. Asphalt
rubber programs also require time and resources to institute (RMA, 2002a). Nonetheless, from
1995 to 1999 the use of rubber in asphalt approximately doubled in the United States.
(Reschner, 2003).
Playgrounds and athletic surfaces
Ground rubber is used for stadium playing surfaces, running tracks, and playground surfaces.
Depending on the type of surface use, rubber can be packed and sealed or can be spread loosely
on the ground. It can also be mixed with sand and used as a base for artificial grass, an
application commonly used on European soccer fields and increasing in use in the United States
(RMA, 2002a).
22
I.
Scrap Tire Overview
Molded, bound, and stamped rubber products
A wide range of products made from ground rubber using compression molding are available. A
fast-growing U.S. market for ground rubber is rubber mats or poured rubber for surfaces such as
playgrounds. The use of rubber mats in agricultural applications has also been successful. The
low thermal conductivity of rubber makes these livestock mats a warm bed for animals, and in
the case of cattle the use of these mats generates economic value through increased milk
production (Snyder, 1998). The compression molding method is also used to make railroad
crossings, removable speed bumps, and athletic mats.
Scrap tires also can be used in roofing materials in two ways. Roof shingles can be stamped out
of tire sidewalls and can be processed to have a slate-like appearance. These shingles provide
superior insulation compared to traditional asphalt shingles and can be more resistant to weather
damage. Tires also can be processed into a sealant for roofing and flooring.
New tire manufacturing
As the quality and quantity of ground rubber has improved in recent years, an increasing number
of tire manufacturers are adding ground rubber to new tires. Currently, newly manufactured tires
in Mexico contain between 2 - 5% recycled ground rubber (Foro Binacional, 2003). Adding 5 15% crumb rubber to the virgin rubber component of a new tire lowers material costs and
improves plant efficiency due to reduced curing times (Reschner, 2003).
Scrap steel markets
In addition to the ground rubber uses, markets also exist for the tire wire and beads that are
liberated from the rubber part of the tire during processing. The Institute of Scrap Recycling
Industries has published the specifications for scrap tire wire and beads in the “Scrap
Specifications Circular 2003.” The specifications describe 15 different types of tire steel, based
on the steel grade, the form in which it comes, and the type of tire from which it was derived
(ISRI, 2003).
Retreaded tires
Retreading tires represents perhaps the most sustainable but one of the least used tire recycling
solutions. Whereas producing one new tire requires about 22 gallons of oil, only seven gallons
are needed to retread a tire. Another advantage is that retreading tires reduces the rate of scrap
tire generation. However, the use of retreaded tires has declined dramatically in the United
States since the mid 1980s. The primary reasons for the decline of passenger tire retread markets
were (1) the decline in use of snow tires, a high percentage of which were retreads; (2) the
increased use of radial tires, which are more difficult to retread; and (3) competition from lowcost, imported new tires (Snyder 1998:xiv-xv). The retread market has also been damaged by
the perception that retreaded tires are less safe than new ones, largely because of the truck treads
that can be found along the highway. However, a study conducted by the Tire Debris Task
Force, an industry association representing trucking companies, retreaders, new tire companies,
and governmental agencies found that only 1% of the 1,070 treads that they collected from nine
sites across the United States were from retreaded tires. Moreover, retreaded tires receive similar
warrantees and mileage recommendations as new tires, indicating similar safety and performance
records (TRIB, 2003).
23
Overview of Scrap Tire Disposal and Recycling Options
Significant public and industrial markets remain for retreaded tires. Currently, there are 1,175
retreading companies in North America, although none of these operations produces retreaded
tires for passenger cars. Since 1993, an executive order has required that all U.S. agencies use
retreaded tires on their vehicle fleets. The State of California also requires the use of retreaded
tires on all state vehicles. All commercial and military aircraft in the United States use retreaded
tires. Trucking companies are a large consumer of retreaded tires; nearly 23 million light,
medium, and heavy truck tires were sold in 2002 (TRIB, 2003).
There are no official estimates for the number of tires retreaded in Mexico. About 200 retreaders
are believed to be in business around the country, one-third of them around Mexico City. As in
the United States, the retread market in Mexico has been negatively affected by an increase in
the use of radial tires and low prices for new tires (Retreading Business, 2003).
Emerging technologies
Pyrolysis
Pyrolysis is a process whereby tire chips are heated to temperatures above 315ºC in an oxygenfree environment, decomposing the tires so that the components are separated but are not
allowed to combust. Pyrolysis produces the following products:
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40% carbon black
25% pyrolysis oil
20% hydrocarbon gases
15% steel
The carbon black comes out of the process in a powdered form and is reprocessed before being
sold. The pyrolysis oil is a heavy oil similar to No. 6 fuel oil and can be used for similar
purposes, including as a rubber extender in manufacturing. The gases, containing hydrogen and
methane, are used primarily to fuel the process. The steel can be collected and sold as scrap.
Although markets exist for these products, their economic value is typically low, both because of
the low quality of the products and the greater value for using tires as a combustible energy
source. Currently, no significant market exists for this recycling option in the United States or
Mexico (Professional Engineering, 2000).
Gasification
Gasification is another thermal process that is somewhat similar to pyrolysis. Rather than the
oxygen-free environment of the pyrolysis reactor, wherein gaseous hydrocarbons and liquid oils
are produced from only part of the organic feedstock, gasification uses partial oxidation of the
fuel necessary to convert all of the carbon to light gases including: H2, CO, CH4 and CO2. The
final products are known as either “producer gas” (containing nitrogen) or “syngas,” (when pure
oxygen is used as the oxidant, eliminating nitrogen). Producer gas has heating values ranging
from 160 – 250 BTU/standard cubic foot (SCF). Syngas has heat values of up to 348 BTU/SCF
(DOE, 2003). A range of organic material can be used as feedstocks including tires, biomass and
municipal solid waste, leaving only an inert ash as a by-product.
24
I.
Scrap Tire Overview
In 2004 the U.S. Department of Energy’s National Border Technology Partnership Program
(NBTPP) plans to conduct a demonstration project of a mobile gasification unit with power
generation capability in the El Paso/Juárez area. The system will use scrap tires as the feedstock.
The purpose of the demonstration project is to highlight the capability to produce electrical
energy via gasification of tires and to obtain baseline operating parameters necessary to enable
the design of a scaled-up stationary gasification power system (Phillips, 2003).
A primary benefit of gasification systems over pyrolysis is that the systems convert more of the
fuel in the carbon to usable gases. Another benefit is that the syngas product can be used for
various purposes, including not just power generation (including fuel cells) but also for fuels
production and chemical applications including the production of hydrogen. In the future
gasification technology could be an economically viable disposal option for scrap tires,
depending on the system location and size, the valuation of the feedstock, and the price of
conventional sources of energy (Phillips, 2003).
Financial viability of tire recycling options
The economics of various tire disposal and recycling options are highly specific to the
technologies involved. However, there are several overarching factors that should be considered
when evaluating the financial feasibility of a particular solution. The financial viability of a
proposed tire disposal or recycling project would be highly dependent on these regional factors,
as well as on the project’s technological and operational costs. These factors include the
following:
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Supply—the number of tires available;
Location—the distance of the tires from the disposal or recycling center, as well as
the distance of regional stockpiles from each other;
Labor—the labor costs associated with handling, transporting, and processing the
tires varies from region to region yet; and
Condition—the longer a tire has been stockpiled outside, the dirtier and more
degraded it becomes, limiting its use for some retreading, civil engineering, and
ground rubber applications.
25
Overview of Scrap Tire Disposal and Recycling Options
Table 14 summarizes the scrap tire management methods discussed in this section.
Table 14. Summary of scrap tire management methods
Tire
Management
Method
Areas of
Use
Advantages
Disadvantages
Financial
viability
Tire-derived fuel
Widespread
• Inexpensive fuel source
• High-energy fuel
• Burns well with
traditional fuels
• Produces less SO2 and
CO2 than coal
• Requires a large
stockpile for continuous use
• TDF is perceived as a
“dirty” fuel compared to
fuels like natural gas.
• Inconsistent TDF quality
• Lack of community
acceptance
• Economics depend on
required facility
modifications and regional
TDF supply.
• Facilities are typically
paid a “tipping fee” to
accept the tires.
• Dedicated tire-to-energy
facilities have a long
payback period to recover
capital investment.
Civil engineering
United States
• “Hot spots” can develop
when ground tires are used
as structural fill.
• Leaching can occur in
below-water-table
applications
• Tire chips can be more
expensive than traditional
fill materials such as gravel,
but overall construction
costs can be less.
Roofing material
United States
• Limited number of tires
used
• Limited market
Rubber-modified asphalt
Primarily in the
southern U.S.
states
• Increased upfront costs
• Political obstacles and
resistance to new technology
• Lower life cycle costs
but higher upfront costs
compared to traditional
asphalt
Athletic facility applications
United States
and Europe
United States
• Preferable to crushed
gravel as a liner for landfills
• Superior sound
absorption when used in
highway barriers
• Cheap and lightweight
fill for construction
• Resilient to weather
damage
• Good insulating
properties
• Lower life cycle costs
• More durable road
surfaces
• Lower maintenance
costs
• Safer roads
• Reduced road noise
from traffic
• Improved safety and
durability
• A large number of
rubber products, such as
agrimats and flooring
material, provide human
and animal benefits.
• Tires are melted into
their constituent materials,
which can be sold.
• Limited number of tires
used
• Most of these products
represent niche markets
whose growth might be
limited.
• Limited market
• The quality of the
pyrolysis products is low
compared to other
alternatives.
• Perceived safety issues
• The value of a tire as
TDF exceeds the value of
its pyrolytic products.
Other rubber products
Pyrolysis
United States
and Europe
Retreaded tires
United States
and Europe
• Retain the most value
from the scrap tire in terms
of energy and materials
26
• Limited market
• Undeveloped retread
market for passenger tires
II. Overview of Potential Human Health and Environmental
Effects of Scrap Tire Piles and Tire Incineration
A. Introduction
Scrap tire piles present significant health and environmental hazards. As discussed in Section I,
tires are highly combustible, and tire piles can ignite as a result of arson or lightning strike. The
combustion of tires in an open air fire results in considerable air, water, and soil pollution. Tire
piles also provide a breeding ground for disease-carrying vectors including mosquitoes and rats.
Compared with the threat of an open air tire fire, the tire disposal and recycling options discussed
in Section I, including energy recovery and civil engineering and ground rubber applications,
would be preferable to tire stockpiling.
Nonetheless, the use of scrap tires for energy continues to generate controversy, and a debate
persists in some circles over the risk to public health posed by emissions from facilities that use
scrap tires as a fuel source. Conflict exists between the general public and those who wish to
utilize TDF as an economically viable fuel source. Some members of the general public,
particularly when the use of TDF is proposed for a facility in their area, believe that TDF poses
an unacceptable risk to nearby communities. In turn, entities that wish to use TDF assure the
public that emission controls are in place to protect the health of surrounding communities.
Governmental agencies and the scientific community attempt to provide answers by conducting
studies to determine the emissions from scrap tire combustion. The answers are not easily
determined, and insufficient data on scrap tire emissions adds to the uncertainty regarding
incineration.
This section summarizes the available research on health and environmental impacts related to
scrap tire piles and tire incineration. Several categories of tire incineration are discussed,
including open air (uncontrolled) tire burning, the use of tires as a supplemental fuel, and the use
of tires as a fuel source in small and fully dedicated operations. A comparative analysis of air
emissions from other power sources will also be examined and discussed.
B. Hazards of open air tire piles
Scrap tire piles attract a number of disease vectors that are hazardous to human health. Tire piles
can become habitat for rats and other rodents when the piles are located near a food source, as
the tires provide shelter from their predators. Rodents are known to carry diseases such as rabies,
hantavirus, lyme disease, and the plague.
Regardless of how a tire is placed in a pile, whole tires collect rainwater and block the
penetration of sunlight, thus serving as a ready breeding ground for mosquitoes, which can carry
potentially dangerous diseases. Mosquitoes are of particular concern due to their ability to carry
diseases such as yellow fever, dengue fever, malaria, encephalitis and the West Nile virus. The
two mosquito species commonly found in the Southern United States and Mexico are the Asian
tiger mosquito (Aedes albopictus) and the Yellow Fever mosquito (Aedes aegypti). Both of these
species are invasive, or introduced, from Asia and Africa, respectively. Not only do scrap tire
piles serve as prolific mosquito breeding grounds, but the interstate transport of scrap tires can
also act as a pathway of distribution for these invading species (Moore, 1988).
27
Overview of Scrap Tire Disposal and Recycling Options
Tire piles present a significant fire hazard, with about 20 major tire fires occurring each year in
the United States (DOE, 2003). While not subject to spontaneous combustion and not easily
ignited, tires burn readily once ignited. Fires in large tire piles are very difficult to extinguish,
and such uncontrolled tire fires pose serious environmental and health threats. The U.S.
Environmental Protection Agency (EPA) has developed a list of 34 compounds released in open
air tire fires that present a high potential for inhalation health impacts; these impacts are
described extensively in Section C below. Moreover, the heat from a tire fire causes pyrolysis of
those tires which are not themselves on fire but are adjacent to burning tires. Pyrolysis refers to
the chemical changes in tires when heat (590 - 815ºC) is applied in an oxygen-deprived
environment. Pyrolysis produces substantial quantities of low-grade petroleum oil, whose runoff
can contaminate not only the soil but also can enter neighboring streams or percolate through the
soil and contaminate the ground water (Snyder, 1998: 2-3). Tire fires result in costly and lengthy
firefighting efforts, as well as substantial clean up problems. Soil that has been contaminated by
the pyrolytic oil or tire fire ash contains large amounts of steel, zinc oxide, and carbon char that
must be remediated.
Even in the absence of a fire incident, scrap tire piles are also associated with ground water and
surface water quality degradation and soil contamination. Contaminants of concern include
aluminum, barium, chromium, iron, lead, manganese, zinc, volatile organic compounds (VOCs)
and semi-volatile organic compounds (SVOCs). A five-year study by Humphrey and Katz
(2001a) was conducted to discern the water quality effects of tire shreds placed above the water
table (i.e., the effects on surface water). With the exception of manganese and iron, the authors
found levels of potential contaminants to be in trace amounts. A four-year study conducted by
the same authors (Humphrey and Katz, 2001b) to determine water quality effects of tire shreds
placed below the water table (i.e.. the effects on ground water and soils) found elevated
concentrations of iron, zinc and manganese. Tire shreds also exhibited a release of low levels of
1,1-dichoroethane, 4-methyl-2-prentanone (MIBK), benzene, acetone, 1,1,1-trichloroethane, 1,1dichloroethene, xylenes, toluene, trichloroethene, 2-butanone (MEK), and chloroethane
(Humphrey and Katz, 2001b). As mentioned in Section I, the possibility of leaching must also
be considered in civil engineering projects that use tire shreds.
C. Air emissions associated with scrap tire combustion
Air emissions are closely related to the compounds that comprise the combustion material, so it
is important to understand the chemical composition of the fuel source. Automotive tires are
manufactured using a synthetic rubber that is generally referred to as styrene-butadiene rubber
(SBR). The list of chemicals found in automotive tires is extensive and is detailed in Section I,
but the four main compounds used in the manufacture of tires are styrene, 1,3-butadiene,
extender oils, and carbon black. Other compounds found in scrap tires include nitrogen, sulfur,
ash, cadmium, chromium, iron, lead, and zinc (Reisman, 1997).
A report produced for the EPA by Joel Reisman in 1997 compiled data describing emissions
sampled from laboratory simulations of uncontrolled tire combustion, tire fire events, rotary kiln
simulators, and emissions tests of industrial TDF facilities. The findings of that report are
discussed below.
28
II. Overview of Potential Human Health and Environmental
Effects of Scrap Tire Piles and Tire Incineration
Open burning of scrap tires
As discussed in Section A above, one of the greatest hazards to human health and the
environment posed by scrap tire piles is the threat of ignition by lightning strike or arson.
Reisman compiled data describing air emissions from the simulated open burning of scrap tires
for the EPA and the U.S.-Mexico Border Information Center on Air Pollution (1997). In the
EPA report, Reisman estimated that open burning of scrap tires is 16 times more toxic than
residential wood combustion and 16,000 times more toxic than coal-fired utility emissions with
appropriate combustion efficiency and pollutant reduction controls.
According to Reisman, chemicals found in emissions of uncontrolled tire fires include four of the
six EPA criteria pollutants— carbon monoxide, particulate matter, nitrogen dioxide, and sulfur
dioxide. Open tire fire emissions are also known to contain EPA-classified hazardous air
pollutants (HAPs) such as benzene, dioxins and furans, hydrogen chloride, polynuclear aromatic
hydrocarbons (PAHs), and polychlorinated biphenyls (PCBs). Other compounds found in the
plumes of uncontrolled tire fires are arsenic, benzene, cadmium, chromium, mercury, nickel,
vanadium, zinc, and other volatile organic compounds (VOCs).
Reisman summarized data from an EPA simulation test program (Ryan, 1989; Lemieux & Ryan,
1993). Table 15 shows the emissions data from laboratory-simulated open tire fires. The highest
emissions of VOCs included benzene, methyl benzene, and naphthalene. A main ingredient of
the rubber used in automotive tires, 1,3-butadiene, was also present. Of the semi-volatile organic
compounds, methyl benzene and styrene, another main ingredient of automotive tires, constituted
those compounds with the highest concentrations. PAHs with the highest concentrations were
acenaphthylene and naphthalene. In smaller amounts, but still important to note were
benzo(a)pyrene (a known carcinogen) and anthracene (commonly found in emissions from the
combustion of coal). Particulate matter (PM) was also observed.
The study found that PM emissions decreased with decreasing burn rates (i.e., capacity-pounds
incinerated per hour). Also interesting to note is PM10, a class of particulate matter less than 10
microns in diameter. Their small size allows the particles to become lodged in the lung if
inhaled. Depending on whether chunk or shredded tire was burned, anywhere from 227 to 298
lbs of PM10 respectively was estimated to be emitted for every ton of tire burned. Reisman
looked at emissions test data obtained from individual power plants burning a variety of fuel
sources. In many instances, PM emissions were higher for operations using 100% coal than for
those operations using a combination of coal and TDF.
Reisman also summarized monitoring data sampled near actual tire fires. He noted that benzene,
toluene, styrene, xylenes, and ethyl benzene were found in the highest concentrations at less than
1,000 feet from the fire, and that lower concentrations were found more than 1,000 feet
downwind of the fire.
29
Overview of Scrap Tire Disposal and Recycling Options
Table 15. Laboratory simulated air emissions from open burning of chunk and shredded
tires. Source: Reisman (1997)
Chunk tire
Shredded tire
(1/4 to 1/6 of a tire)
(5 cm x 5 cm pieces)
Emission factor
Emission factor
(lb/ton of tire)
(lb/ton of tire)
Volatile Organic Compounds (VOCs)
Benzene*
Methyl benzene
Naphthalene
Ethenyl benzene
Dimethyl benzene
Ethenyl methyl benzene
1,3-Butadiene*
Pentadiene
Limonene
4.313
3.210
2.260
1.880
1.559
1.061
0.610
0.388
0.055
4.410
2.260
1.650
1.223
2.156
0.517
0.320
2.330
1.790
3.396
2.424
1.320
1.267
0.732
0.610
0.112
2.261
2.870
1.291
1.062
1.400
1.870
4.691
Semi-volatile Organic Compounds
Naphthalene
Methyl benzene
Styrene*
Acenaphthylene*
Phenol*
Dimethyl benzene
Limonene
Polynuclear Aromatic Hydrocarbons (PAHs)
Acenaphthylene*
Naphthalene
Acenaphthene*
Fluorene
Phenanthrene
Benzo(a)pyrene*
Anthracene
1.722
1.632
0.581
0.521
0.475
0.170
0.113
1.124
0.920
4.891
0.374
0.505
0.228
0.099
Particulate Matter
Organic particulates
Metal particulates
PM10
* Known carcinogens
1,940
210
227
147
129
298
30
II. Overview of Potential Human Health and Environmental
Effects of Scrap Tire Piles and Tire Incineration
It is widely recognized that the ignition of large stockpiles of used tires poses a potential threat to
the health of nearby residents. To avoid the uncontrolled burning of scrap tires, governmental
agencies work to reduce both legal and illegal stockpiles of used tires.
Air emissions from tire-derived fuel
Scrap tires are increasingly recognized as a plentiful, cost-effective and efficient source of fuel.
Entities that use scrap tires as a fuel source include cement kilns, pulp and paper mills, electrical
utilities, and industrial boilers. As discussed in Section I, TDF is typically used as a supplement
to traditional solid fuels such as coal, wood, and coke.
Reisman (1997) reported results of pilot-scale emissions testing conducted by the EPA. The
tests utilized a 250,000 BTU/hour rotary kiln incinerator simulator (a scaled-down version of a
full-size rotary kiln incinerator). The EPA used the data it obtained from the simulator to
develop permitting guidelines and to aid in the review of permit applications. It should be noted
that emissions factors from the simulator could not be directly linked to emissions from full-scale
rotary kiln incinerators due to scaling issues and equipment-specific factors. The simulated
emissions data also could not be directly related to emissions from other TDF combustion
equipment such as boilers due to inherent differences between the devices. The EPA did note,
however, that the data is useful in understanding emissions phenomena associated with TDF
combustion (Reisman, 1997).
TDF used in the tests consisted of crumb-free (i.e., containing no granulated rubber) pieces less
than 0.25 inches in size. TDF was used as a supplementary fuel to natural gas with fuel ratios
varying from 0% TDF and 100% natural gas to 20% TDF and 80% natural gas. Emissions data
were collected from the exhaust prior to contact with add-on pollution control equipment. The
intent was to measure for VOCs , metals, particulate matter, polychlorinated dibenzo-p-dioxins
(PCDD), and polychlorinated dibenzofurans (PCDF). PCDD and PCDF, also known simply as
dioxins and furans, are unwanted by-products of industrial processes and are known to be highly
toxic (Reisman, 1997).
As seen in Table 16, VOC concentrations varied little, with concentrations remaining nearly the
same regardless of the TDF to natural gas fuel ratio. VOC emissions associated with natural gas
alone were not much lower than those with increased amounts of TDF. PCDD/PCDF emissions
were measured at 0% TDF and 17% TDF. No PCDD/PCDF emissions were found in either case
(Reisman, 1997).
31
Overview of Scrap Tire Disposal and Recycling Options
Table 16. VOC and PCDD/PCDF emissions from laboratory simulated rotary kiln
combustion of TDF and natural gas at varying rates. Data are expressed in units of
lb/MMBtu (pounds per million British thermal units). Source: Reisman (1997)
0% TDF
7% TDF
17% TDF
(natural gas (steady
(steady
19% TDF
15% TDF
only)
state)
state)
(ramp)
(batch)
Benzene
1.56E-06
2.91E-07
2.91E-07
1.71E-05
5.09E-05
Carbon disulfide
4.95E-07
7.98E-07
5.35E-07
5.21E-07
2.19E-06
Xylene
1.56E-06
9.70E-07
2.47E-06
6.14E-07
4.14E-06
Styrene
6.12E-07
1.83E-06
1.67E-06
1.63E-06
1.81E-06
Toluene
9.23E-0
1.1E-06
1.08E-06
8.90E-07
3.00E-06
PCDD/PCDF
0.00
-0.00
--As seen in Table 17, metal concentrations associated with 100% TDF were found to be slightly
higher than those of 100% natural gas. The only exception was zinc, whose concentrations were
three times higher with TDF than with natural gas. Zinc concentrations were several orders of
magnitude greater than other metals.
Table 17. Metal emissions from laboratory simulations of rotary kiln combustion of TDF
and natural gas at varying rates. Data are expressed in units of lb/MMBtu. Source:
Reisman (1997)
0% TDF
Metals
(natural gas only)
100% TDF
Arsenic
1.12E-06
2.17E-04
Cadmium
4.09E-07
6.21E-06
Chromium
6.46E-07
2.27E-05
Lead
8.02E-07
3.86E-04
Nickel
6.98E-07
2.05E-05
Zinc
2.86E-04
2.08E-01
Particulate matter increased appreciably with increased feed rates of TDF in rotary kiln
applications. Total PM (PMtot) concentrations were measured at 0 mg/Nm3 (Nm3 is a cubic meter
of gas at 0ºC and 1 atmosphere pressure) with a rotary kiln fuel source of 100% natural gas. At a
ratio of 15% TDF to 85% natural gas, PMtot concentrations measured 95.26 mg/Nm3. A fuel
ratio of 20% TDF and 80% natural gas gave PMtot concentrations of 132.95 mg/Nm3.
Reisman (1997) also presented data on criteria pollutant concentrations from 22 field emissions
tests at industrial facilities including two cement kilns, one pulp and paper mill, and 19 industrial
boilers using TDF, coal, wood, and coke as fuel sources. Reisman reported that properly
designed solid fuel combustors can supplement with 10-20% TDF and maintain emissions rates
similar to those of traditional solid fuels. He also stated that well-designed dedicated tire-toenergy facilities can produce lower emissions than those of traditional solid fuel-fired
32
II. Overview of Potential Human Health and Environmental
Effects of Scrap Tire Piles and Tire Incineration
combustors. However, particulate matter is a concern for facilities using TDF. Venturi
scrubbers used commonly by industry to remove fine dusts and aerosols tend to be ineffective.
Proper particulate removal requires fabric filters or electrostatic precipitators. Of particular
importance is the fact that there is no data describing emissions for antiquated or poorly designed
combustion facilities.
Important to note is that while data derived from controlled tests as described above are useful in
understanding air emissions relating to TDF, one must consider that actual combustion facilities
using TDF may see dissimilar emissions numbers, especially during periods of startup,
shutdown, and equipment malfunctions.
A comparison of air emissions from various fuel sources
Information describing air emissions of scrap tire combustion versus other fuel types is difficult
to clarify. Substantial amounts of information describing emissions are available for older,
established fuel types such as coal, oil and natural gas. Unfortunately, less emissions
information is available regarding newer fuels such as biomass, municipal solid waste, and scrap
tires. A comparison of emissions data is further complicated by the fact that emissions numbers
are often reported in different units and are calculated using various methodologies.
TDF is typically compared to coal in terms of its use as a fuel source due to similarities in terms
of emissions and due to their combined use as an energy source (e.g., in cement kilns). As seen
in Table 18, TDF can generate higher heating values and contains lower moisture content than
coal. TDF also produces higher carbon and hydrogen content and less oxygen, nitrogen, ash and
moisture content than coal. Sulfur content of TDF is similar to that of a medium-sulfur coal
(Reisman, 1997).
Table 18. Comparative fuel analysis by weight. Source: Reisman, 1997
Fuel
Composition (%)
Carbon Hydrogen Oxygen Nitrogen Sulfur Ash Moisture
TDF 83.87
7.09
2.17
0.24
1.23
4.78 0.62
Coal 73.92
4.85
6.41
1.76
1.59
6.23 5.24
Heating value
kJ/kg
Btu/lb
36,023 15,500
31,017 13,346
Carrasco et al. (2002) studied gaseous emissions of coal and scrap tires at a cement kiln that
produced one million tons of cement per year (see Table 19). When scrap tires were used in
combination with coal, they observed a 12-24% increase in particulate matter, a 31-52% increase
in carbon monoxide, a 22-34% increase in sulfur dioxide, a 39-52% increase in hydrochloric
acid, a 12-27% increase in iron, a 3-8% increase in aluminum, a 30-37% increase in zinc, and a
270-885% increase in lead. Alternately, they found a decrease of 8- 13% in nitrogen oxides, a 913% decrease in polycyclic aromatic hydrocarbons, a 6-7% decrease in naphthalene, a 32-39%
decrease in chlorobenzene, and a 32-45% decrease in dioxins and furans. Overall, although the
authors saw increases in certain compounds, they still believed emissions to be within
environmental guidelines (Carrasco et al., 2002).
33
Overview of Scrap Tire Disposal and Recycling Options
Table 19. Maximum 1-h, 24-h, and annual concentrations computed at ground level for
both modes of kiln operation (coal or coal and tires). Source: Carrasco et al., 2002)
Maximum concentrations
Annual
1-h Concentration 24-h Concentration
concentration
Coal
Coal and
Coal
Coal and
Coal
Coal and
Pollutant
tires
tires
tires
PM (ug/m3)
--92.0
102.7
14.8
18.4
Metals (ug/m3)
Fe
9.1
10.8
1.4
1.6
0.2
0.3
Al
9.9
10.0
1.5
1.5
0.2
0.3
Zn
637.8
844.0
97.3
126.1
15.9
21.8
Pb
50.0
185.5
7.7
29.2
0.5
4.6
Cr
44.0
173.5
23.3
29.3
3.8
4.8
Hg
22.8
16.3
3.6
2.8
0.3
0.4
Mn
274.1
300.6
41.8
44.0
6.7
7.9
Cu
11.8
35.0
6.3
5.3
1.0
0.9
3
Gases (ug/m )
Nox 1,402.2
1,224.4
163.1
149.5
7.3
6.6
SO2
533.3
715.2
64.5
82.8
2.8
3.4
CO
118.5
179.9
14.3
20.4
0.6
0.8
HCl
--0.9
1.4
--Organics
PAH (ng/m3)
64.9
56.3
7.8
6.9
0.3
0.3
3
Naphthalene (ng/m )
59.3
55.1
7.1
6.7
0.3
0.3
3
Chlorobenzene (pg/m )
--160.7
98.1
6.9
4.6
Dioxins and furans (fg/m3)
--94.8
51.8
4.0
2.7
On a yearly basis, the EPA publishes the National Emissions Inventory (NEI), which contains
average emissions rates for criteria pollutants organized by fuel type. Data are organized by
major fuel source. As seen in Table 20, the categories are broad; however, it gives a general idea
of the emissions of major fuel sources. Emissions information for alternative fuels (including
scrap tires) is not included in the EPA NEI Report.
34
II. Overview of Potential Human Health and Environmental
Effects of Scrap Tire Piles and Tire Incineration
Table 20. Average annual emissions by source category for U.S. EPA Criteria Pollutants in
2001 (Emissions are reported in short tons). Source: U.S. EPA (2003g)
Source category
CO
NOx VOC PM-2.5 PM-10
SO2
Fuel combustion – electric utilities
Coal
246
4,169
30
503
595 9,955
Oil
31
163
5
18
19
525
Natural gas
103
364
14
20
21
199
Other
36
41
2
4
4
81
Internal Combustion
75
154
12
23
23
61
Fuel combustion - industrial
Coal
130
547
11
30
77 1,268
Oil
47
162
9
25
36
444
Natural Gas
380
965
57
113
117
398
Other
334
122
31
70
79
136
Internal Combustion
290
842
60
19
20
16
Fuel combustion - other
Commercial/Institutional Coal
14
31
1
9
18
126
Commercial/Institutional Oil
18
79
4
20
25
242
Commercial/Institutional
Natural Gas
88
250
16
34
35
12
Miscellaneous Fuel Combustion
(Except Residential)
40
34
6
9
10
5
Residential Wood
2,526
33
895
342
342
5
Residential Other
233
641
30
77
81
159
The U.S. Department of Energy’s Energy Information Administration reports data on greenhouse
gas emissions (i.e., CO2) associated with various sources of solid fuel. As Table 21 shows, the
use of TDF emits less CO2 than most commonly used solid fuels. TDF ranks third, just behind
motor gasoline and just before municipal solid waste in terms of the least amount of CO2 emitted.
Table 21. Greenhouse gas emissions associated with various solid fuels. Source: Energy
Information Administration (2003)
Fuel
Pounds CO2 per million BTU
Liquefied petroleum gases
130.04
(LPG)
Motor gasoline
156.43
Tires/TDF
189.54
Municipal solid waste
199.85
Bituminous coal
205.30
Wood and wood waste
221.94
Anthracite coal
227.40
In summary, compounds such as VOCs, semi-volatile organic compounds, PAHs, and metals are
found in high concentrations in the smoke resulting from open burning of scrap tires. When
35
Overview of Scrap Tire Disposal and Recycling Options
TDF was analyzed in a laboratory setting simulating conditions found in rotary kilns, these same
compounds were found at emissions concentrations similar to those of natural gas. With the
exception of zinc emissions, potential emissions from TDF are not expected to differ
significantly from those of other conventional fuels, as long as combustion occurs in a device
that is well-designed, well-operated and well-maintained (Lemieux, 1994; Reisman, 1997).
Particulate control devices such as electrostatic precipitators or fabric filter can manage
particulate matter resulting from TDF combustion.
Compared to fossil fuels that have been used for centuries, the use of scrap tires as an energy
source is a relatively new development. Decades of research have investigated the
environmental impacts of energy derived from fossil fuels. It is important to note that research
regarding the environmental impacts of scrap tires as a fuel source is continuously evolving.
Many technical considerations under the Clean Air Act that affect tire fuel industries are under
development. Testing protocols and emissions standards have not been developed for all
potential emissions (CIWMB, 1996).
D. Potential effects for incinerator-exposed populations
When tires are burned in an uncontrolled environment, many of the combustion by-products (see
Table 15) have the potential to threaten human health through air emissions and contamination of
surface and ground water supplies. Depending on the length and degree of exposure, residents
living near uncontrolled tire fires and emergency responders can suffer acute and chronic health
effects including irritation to skin, eyes and mucous membranes; respiratory effects; central
nervous system depression; and cancer (Reisman, 1997). In addition to the primary products of
combustion, secondary chemicals (e.g., dioxins and furans) may also be released under
uncontrolled conditions.
For facilities utilizing TDF as an energy source, three contaminants have the highest potential to
impact nearby populations: particulate matter, zinc, and dioxins and furans. Elevated levels of
particulate matter and zinc have been associated with TDF (Reisman, 1997). Dioxins and furans
are so toxic to humans, that even trace amounts can cause irreparable harm.
Of the criteria pollutants associated with TDF emissions, particulate matter is of specific
concern. Particulate matter is categorized in terms of particle size. Larger particles (100
microns in diameter) are usually expelled by the body through respiratory system clearing
reflexes such as coughing and sneezing. Particulate matter monitored in air emissions is
classified as PM10 (less than 10 microns in size) or PM2.5 (less than 2.5 microns in size). Because
of their extremely small size, PM10 and PM2.5 can become lodged deep in the lungs of people
who inhale the small particles of dust or aerosols. The EPA has identified a variety of health
effects associated with particulate matter such as premature death, acute respiratory symptoms,
asthma, chronic bronchitis, decreased lung function/shortness of breath, and straining of the
heart.
The health effects of particulate matter inhalation may not be immediately noticed and can be
exacerbated by continuous exposure. Additionally, toxic compounds such as heavy metals can
36
II. Overview of Potential Human Health and Environmental
Effects of Scrap Tire Piles and Tire Incineration
bind to particulates. Once in the respiratory system, the toxins can enter the blood stream and
affect other organs such as the liver or kidneys.
The economic impacts related to the health effects associated with particulate matter include the
increased incidence of respiratory-related hospital admissions and emergency room visits (e.g.,
asthma attacks), and work and school absences. Populations at highest risk of adverse impacts
from particulate matter are the elderly, children, asthmatics, and persons with existing heart or
lung problems.
As mentioned previously, zinc that can enter the atmosphere through the combustion of TDF.
Zinc is an element that is essential for human health. But when inhaled in dust or fumes, large
amounts of zinc can lead to an acute condition known as “metal fume fever.” This short-term
condition is thought to be an immune system response and affects lung function and body
temperature. Laboratory studies involving rats have linked zinc to skin irritation, infertility, and
low birth weights. Long-term effects of zinc inhalation are unknown (ATSDR, 1995).
Dioxins and furans are two closely related classes of chemicals (often referred to collectively as
dioxin) that are highly persistent in the environment, are extremely toxic, and are known
carcinogens. Dioxin is not intentionally manufactured, but is a byproduct of the combustion of
chlorinated compounds.
Exposure to dioxin can result in a painful and disfiguring skin disease known as Chloracne.
Other human health effects include liver damage; changes in glucose metabolism; changes in
hormone levels; weakening of the immune system; weight loss; nervous system disorders;
reproductive damage; and birth defects. Dioxin is also recognized by the World Health
Organization as a human carcinogen (UNEP, 1999).
The UNEP (1999) estimates that more than 90% of the human intake of dioxin occurs through
contamination of food (dairy products, meat, eggs, and fish). Dioxins build up in fatty tissue and
accumulate substantially up the food chain; i.e., livestock consume contaminated feed, and the
dioxin then becomes available to humans who consume the contaminated dairy products and
meat. Trace amounts of dioxins present in the air emissions of a TDF facility could conceivably
enter the food chain through the contamination of downwind food crops and livestock pastures.
Health officials have also recognized the contamination of human breast milk by dioxin.
Researchers estimate that an infant consuming breast milk for one year can have six times as
much dioxin in their system as an infant fed on formula for one year. Over a lifetime of 70
years, individuals breast fed during infancy were estimated to have an accumulated dose 3-18%
higher than individuals who had not been breast fed (Lorber and Phillips, 2002).
E. Risk management and minimization
With so much still unknown regarding the environmental and human health effects of tires as a
fuel source, risk management should include a variety of mitigation strategies. Among the most
important are the following approaches:
37
Overview of Scrap Tire Disposal and Recycling Options
ƒ
ƒ
ƒ
ƒ
ƒ
ƒ
ƒ
ƒ
Public participation and inclusion in decision- making from the outset, beginning with
public comment on proposed projects and continuing through to the monitoring of
daily operations. A lack of inclusion could result in public opposition to the project
or in the development of a project without necessary environmental and health
safeguards.
Fire prevention planning and training implemented for all major tire stockpiles.
Emergency control strategies ready for deployment to address accidental tire.
stockpile fires as well as uncontrolled or fugitive emissions during TDF combustion
Use of best available technologies for the combustion system to ensure efficient and
complete combustion of TDF to minimize emissions and ensure maximum utility of
the fuel.
Use of best available technologies for the control system, including the use of fabric
filters and electrostatic precipitators, to ensure complete entrapment of particulate
matter and metal emissions. Particulate matter and zinc emissions are of special
concern when burning tires for energy, and installing control equipment specifically
for these emissions would help to safeguard public health and establish public
support.
Baseline testing and trial burns to measure emissions to determine concentration and
composition of VOCs, metals, particulate matter and products of incomplete
combustion. Establishing a baseline would ensure that the emissions are at the
expected levels and indicate any future failures of control equipment.
Regular monitoring of emissions of compounds recognized as a priority for TDF
ambient air quality monitoring, including criteria pollutants, metals, volatile and
semi-volatile organics, and dioxins/furans.
Unannounced site visits and monitoring to ensure compliance and to build public
confidence.
38
III. International and U.S. Regulatory Framework
A. International framework for tire disposal
The rate of scrap tire generation in industrialized countries is approximately one passenger car
tire per capita per year (Reschner, 2003). Many countries have adopted regulations to deal with
tire disposal and the problems that scrap tire piles can cause. While legal guidelines vary from
country to country, the main purpose of these regulations is to provide for the environmentally
safe disposal of tires, to limit the number of tires stored at any given location, and to encourage
the use of tire-derived products.
Several countries, including Canada, Korea, Sweden, and Switzerland, lead the way in scrap tire
recycling programs, and all have implemented programs that place recycling responsibility on
the tire producers or retailers. In Canada, every province with the exceptions of Ontario and
Newfoundland has implemented a scrap tire program. As part of these programs, consumers pay
environmental fees of about $2-4 per tire, and scrap tires are sent back to retailers. These
programs generally recover 90% of scrap tires for recycling or energy recovery through
incineration. In Korea, tire manufacturers have organized industry associations that take
responsibility for collecting and recycling tires. The manufacturers charge a deposit fee to fund
these operations. Sweden and Finland passed laws in 1995 and 1996 that require tire producers
to collect and recycle scrap tires, with the goal of establishing nationwide collection systems and
the recycling of 80-90% of all scrap tires. Tire suppliers formed non-profit producer
responsibility organizations to administer the contracts covering all tire collection and recycling
operations, and consumers pay a fee to fund the program. Importers as well as tire
manufacturers are subject to these recycling requirements (EPA, 2002).
The European Union, which historically has landfilled more tires than the United States, has
begun to attack the problem aggressively. A recent EU Landfill Directive bans whole tires from
landfills by the end of 2003. By 2006, tires in any shape or form will be banned from landfills in
EU member states (Reschner, 2003).
B. U.S.-Mexico border agreements
While there have not been agreements, regulations, or policies specifically concerning the
management of scrap tires along the border, a long history of environmental cooperation exists
between the United States and Mexico, and several treaties govern U.S.-Mexico environmental
relations. The 1983 Agreement on Cooperation for the Protection and Improvement of the
Environment in the Border Area (the “La Paz Agreement”), for example, empowers the federal
environmental authorities in the United States and Mexico to undertake cooperative initiatives
and is implemented through multi-year bi-national programs.
The La Paz Agreement defines the U.S.-Mexico border region as extending more than 3,100
kilometers (approximately 2,000 miles) from the Gulf of Mexico to the Pacific Ocean, and 100
kilometers (approximately 62.5 miles) on either side of the border. The bi-national border region
also contains multiple jurisdictions including 10 states, numerous local governments, and U.S.
Tribes.
39
Overview of Scrap Tire Disposal and Recycling Options
Specifically, the agreement addresses border sanitation concerns between San Diego, California,
and Tijuana, Mexico; discharges of hazardous substances along the border; trans-boundary
shipments of hazardous wastes and substances; trans-boundary air pollution due to copper
smelters along the border; and trans-boundary urban air pollution. The treaty also seeks to
harmonize air pollution and ambient air quality regulations along the border.7 The EPA and
Mexico’s Secretaría de Medio Ambiente y Recursos Naturales (SEMARNAT) serve as national
coordinators for these programs (EPA, 2003b).
Following the legal precedent of the La Paz Agreement, the United States and Mexico have
continued to improve environmental cooperation along the border. In 1990, the two countries
developed the Integrated Border Environmental Plan (IBEP), which focused on trade-related
environmental impacts. In 1995, the EPA developed the Border XXI program to bring binational work on border environmental issues under one guiding framework.
More recently, the United States and Mexico have sought to increase environmental cooperation
along the border through the Border 2012 program. Established in 2002, the Border 2012
program seeks to reduce water contamination, air pollution, and land contamination; improve
environmental health; reduce exposure to chemicals; improve environmental compliance and
enforcement; and promote environmental stewardship. Among other issues, the Border 2012
program specifically addresses the need to develop domestic and/or bi-national policies to target
scrap tire piles along the border while working with tire manufacturers and vendors. It
emphasizes a bottom-up approach, anticipating that local decision-making, priority setting, and
project implementation will best address environmental issues in the border region. In its
Regional Issues section, Border 2012 specifically acknowledges the issues of land pollution due
to used tires between Arizona and Sonora, and the need to resolve that problem (EPA, 2003c).
State initiatives along the border include the 1998 Chihuahua, New Mexico and Texas Strategic
Environmental Plan, which calls for environmental cooperation and coordination along the
border (TNRCC, 1999). Additionally, the Cal/BECC (Border Environmental Cooperation
Committee) was created in 1994 to focus on environmental issues along the California, Baja
California, and Baja California Sur borders.
BECC initiatives aimed at scrap tire disposal include co-sponsorship of the first annual binational scrap tire forum in April 2003, in Ciudad Juárez (Foro Binacional, 2003:2). Some of
the forum’s conclusions included the need for a better quantification of the scrap tire problem in
Mexico, perhaps by surveying the municipalities. This shows recognition of the insufficient
nature of legislation regarding scrap tires in Mexico, and the acknowledgement that development
of market solutions for scrap tires is critical for ameliorating the problem.
Also in 2003, the BECC invited Michael Blumenthal, Senior Technical Director for the Rubber
Manufacturer’s Association, to teach a course titled, “Market and Management Solutions to
7
These regulations include air pollution control standards under the New Source Performance Standards in the
United States, and the Limites de Emisión para Fuentes Nuevas in Mexico. Ambient air quality standards were
established in the United States under the Clean Air Act National Ambient Air Quality Standards, and in Mexico
under the Norma Mexicana de Calidad del Aire.
40
III. International and U.S. Regulatory Framework
Waste Tire Disposal (Blumenthal, 2003c).” Blumenthal revealed lessons from scrap tire
management in the United States including facts such as, in the United States more than 100
million tires would be sent to landfills each year if tires were not incinerated for energy recovery.
He also noted that scrap tires will ultimately be disposed of in the least expensive manner
available. He identified the rubber-modified asphalt industry as holding great potential for scrap
tire recycling.
C. U.S. laws and regulations governing tire disposal
National Initiatives
Public recognition of the scrap tire problem in the United States began in the early 1980s and
was influenced by the growing scrap tire piles around the country, and in particular by the 1983
tire fire in Winchester, Virginia (Snyder, 1999). In Winchester, a pile of five to seven million
tires measuring over four acres and 80 feet deep at some points was ignited by an arsonist. Once
the oil runoff from the burning tires was contained, the decision was made to let the fire burn
itself out. The Winchester fire burned for three months.
Because of the emergence of scrap tires as a national environmental problem (though more acute
in some states than others), the EPA studied scrap tires and scrap tire piles at great length. In
accordance with its own criteria, however, the EPA could not justify piles of scrap tires as
“hazardous waste” (to the extent of needing national regulation), 8 despite their unsightly
appearance, potential as a fire hazard, and the fact that tire piles serve as breeding grounds and
refuges for disease vectors such as mosquitoes and rats.
The management of scrap tires in the United States is best explained within a historical context.
U.S. regulations treat scrap tires similarly to other non-hazardous municipal solid waste. Passed
by Congress in 1965, the Solid Waste Disposal Act (SWDA) established grant programs to
support improved disposal methods and the development of solid waste disposal plans by states
and/or interstate agencies. Additionally, it set minimum safety requirements for local landfills.
Even with the SWDA, however, trash still overflowed from landfills and dumps.
Partly in response to what was becoming an intractable waste problem, the EPA was created in
1970. An Office of Solid Waste was formed within the agency to examine the problems caused
by the generation and disposal of wastes. The EPA worked with the states and industry to collect
and analyze information on resource recovery, waste types, and volumes. It examined the risks
posed by waste and the likelihood of harm to human health and the environment. By 1974, it
had become clear that the SWDA was not sufficient to address the dangers posed by the
increasing volume of solid and hazardous waste.
In October 1976, waste management fundamentally changed when Congress passed the
Resource Conservation and Recovery Act (RCRA). The goals of the RCRA were to ensure that
wastes are managed in a manner that protects human health and the environment; to reduce or
8
The EPA’s criteria for hazardous waste are ignitability, corrosivity, reactivity, and toxicity.
41
Overview of Scrap Tire Disposal and Recycling Options
eliminate the amount of waste generated; and to conserve energy and natural resources through
waste recycling and recovery (EPA, 2002: 1-2).
RCRA was a departure from the “end-of-the-pipe” pollution controls previously enacted. It was
intended to be a pollution prevention measure and to manage waste from cradle to grave. Dumps
were to be replaced by regulated landfill facilities. Stringent restrictions on waste disposal were
intended to encourage recycling. Additionally, RCRA was a joint federal and state venture. The
federal program provided basic requirements that gave consistency to waste management
programs implemented by states and local governments.
Since 1976, RCRA has been regularly updated and amended, most recently in 1996, but no
specific legislation pertaining to scrap tire disposal has ever been included. Parts of RCRA,
however, specifically acknowledge the scrap tire problem in the United States. In the U.S. Code,
Title 42 “The Public Health and Welfare,” Chapter 82 “Solid Waste Disposal” pertains to nonhazardous waste and contains specific provisions for scrap tires. These provisions were included
in Subchapter II, Section 6914, which made available grants for the purchase of tire-shredding
facilities during 1978 and 1979. These grants were for 5% of the purchase price of tire
shredders, including portable shredders that could be attached to tire collection trucks. The
grants were available to public and private entities as well as public-private partnerships. Also
included was Subchapter VIII, Section 6982, which provided for a study to examine possible
problems in the collection of discarded motor vehicle tires, as well as the recovery of resources
and the use of these tires (Legal Information Institute, 2003).
Scrap tire incineration is governed under the Clean Air Act (CAA), which regulates air quality in
the United States and contains provisions that apply to scrap tire incineration, in that it gives the
EPA authority to regulate emissions from all forms of combustion. While the EPA regulates
solid waste incineration, as described in Title 42, Chapter 82, Subchapter I, Part A, Section 7429,
waste tire incineration used for small power production or cogeneration purposes (i.e., as a
primary fuel supplement) is specifically excluded (Legal Information Institute, 2003).9
Should the EPA decide to develop regulations governing such dedicated facilities, it has the
authority to do so under Sections 111 and 112, which do not contain the Section 129 exemption.
Section 111 grants the EPA authority to develop regulations for any new source of common, or
“criteria,” air pollutants (which include ozone, nitrogen dioxide, particulate matter, sulfur
dioxide, carbon monoxide, and lead). Section 112 provides the EPA with authority to develop
regulations for any source of hazardous air pollutants (Porter, 2003). At this time; however, no
specific federal regulations govern tire incineration, and facilities that burn tires as a
supplemental fuel would be subject to regulations governing their primary fuel, often coal or
wood.
The 1990 amendment to the CAA did establish the Title V Permit Program; however, which
covers all major sources of air pollution. Any facility, whether it would burn tires exclusively or
as a fuel supplement to a material such as coal or wood, must apply for a Title V permit if total
9
Section 129 of the Clean Air Act describes the exclusion of scrap tire incineration. In U.S. Code, it is contained in
Title 42, Chapter 82, Subchapter 1, Part A, Section 7429.
42
III. International and U.S. Regulatory Framework
emissions of criteria air pollutants could potentially exceed 100 tons/year; if total emissions of
hazardous air pollutants such as mercury, or cadmium would exceed 25 tons/year; or if the
emission of any single hazardous air pollutant could exceed 10 tons/year. An operating permit
lasts for five years. The use of tires as a fuel supplement typically would not pose any regulatory
roadblocks, however. Since tire incineration produces less SO2 than most forms of coal,
facilities can actually use tires to lower their overall emissions. The CAA delegates enforcement
of the Title V permit program to the states (Porter, 2003).
If a state does not have a permitting program, then a federal permit can be obtained; EPA-issued
New Source Review (NSR) permits do not have a fee and take six months to a year to obtain
approval. Additionally, as part of the CAA, NSR rules dictate that any new facility or facility
undergoing renovation or modification that will be subject to Title V requires a NSR permit.10
NSR permits require the installation and maintenance of pollution control devices. Large sources
in polluted areas must reduce emissions or buy credits from another company that has reduced its
emissions.
Due to the complexity of Title V regulations, the EPA has created a Title V policy and guidance
database that can be downloaded at:
http://www.epa.gov/region07/programs/artd/air/title5/title5pg.htm
Table 22 details the six criteria pollutants measured under the Clean Air Act and their health
effects.
10
The New Source Review rules were relaxed in August 2003 so that facilities undertaking modifications or
renovations costing less than 20% of the total equipment replacement value do not have to install improved pollution
controls.
43
Overview of Scrap Tire Disposal and Recycling Options
Table 22. Criteria pollutants measured under the Clean Air Act. Source: EPA (2003e)
Criteria pollutant
Carbon Monoxide
(CO)
8-hour average
1-hour average
Nitrogen Dioxide
(NO2)
Annual arithmetic
mean
Ozone (O3)
1-hour Average
8-hour Average
Lead (Pb)
Quarterly average
Particulate (PM10)
(Particles with
diameters of 10
micrometers or less)
Annual arithmetic
mean
24-hour Average
Particulate (PM2.5)
(Particles with
diameters of 2.5
micrometers or less)
Annual arithmetic
mean
24-hour average
Standard value*
Standard type**
Health and environmental impacts
Is easily absorbed by the body, can lead to
unconsciousness and death.
9 ppm (10
mg/m3)
35 ppm (40
mg/m3)
Primary
Primary
Causes ground-level ozone, can react to form
acids (i.e., acid rain)
0.053 ppm (100
µg/m3)
Primary &
Secondary
0.12 ppm (235
µg/m3)
0.08 ppm (157
µg/m3)
Primary &
Secondary
Primary &
Secondary
1.5 µg/m3
Primary &
Secondary
50 µg/m3
Primary &
Secondary
Primary &
Secondary
150 µg/m3
15 µg/m3
65 µg/m3
Principal component of smog, can cause
impaired lung function, can damage trees and
plants, can reduce visibility.
Can cause seizures, mental retardation, and/or
behavioral disorders. Young children are
especially susceptible to low doses.
Small particles travel deep into the lungs,
causing irritation and damage to the sensitive
tissue. Can cause wheezing and coughing, can
trigger asthma attacks and lead to premature
death.
Primary &
Secondary
Primary &
Secondary
Can cause lung irritation and coughing. Can
trigger asthma attacks in sensitive individuals.
Can cause painful irritation of eyes, nose,
mouth, and throat. Can form sulfuric acid (acid
rain) and reacts with particles to form other
toxic compounds.
Sulfur Dioxide
(SO2)
Annual arithmetic
mean
24-hour average
0.030 ppm (80
Primary
µg/m3)
0.14 ppm (365
Primary
µg/m3)
3-hour average
0.50 ppm (1300
Secondary
µg/m3)
* Parenthetical value is an approximately equivalent concentration.
** The Clean Air Act established two types of national air quality standards. Primary standards set limits to
protect public health, including the health of "sensitive" populations such as asthmatics, children, and the elderly.
Secondary standards set limits to protect public welfare, including protection against decreased visibility, damage
to animals, crops, vegetation, and buildings.
44
III. International and U.S. Regulatory Framework
Table 23 lists the Chemical Abstract Service (CAS) Number and the chemical name of
hazardous air pollutants that are relevant to open burning and TDF incineration and are regulated
under the Clean Air Act.
Table 23: Hazardous air pollutants. Source: EPA (2003f)
CAS Number
Chemical Name
71432
Benzene
106990
1,3-Butadiene
75150
Carbon disulfide
132649
Dienzofurans
100414
Ethyl benzene
91203
Naphthalene
108952
Phenol
100425
Styrene
1746016
2,3,7,8-Tetrachorodibenzo-p-dioxin
108883
Toluene
1330207
Xylenes
Arsenic compounds*
Cadmium compounds*
Zinc compounds*
Mercury compounds*
Lead compounds*
Selenium compounds*
* These listings are defined as including any unique chemical
substance that contains the named chemical as part of that
chemical’s infrastructure.
Table 24 includes a summary of the major U.S. laws that pertain to scrap tire incineration, the
year they were enacted, and their key provisions.
Table 24. Summary of U.S. laws pertaining to scrap tires. Source: EPA website
U.S. Law
Year Enacted
Key Provisions
Solid Waste Disposal
Act (SWDA)
1965
Resource Conservation
and Recovery Act
(RCRA)
Clean Air Act
1976 (most
recently amended
in 1996)
1970
Established grant programs to support application of
improved disposal methods and the development of solid
waste plans by the states and/or interstate agencies
Amends the SWDA. Governs municipal waste disposal
and landfills; no specific regulation for tire disposal
1990 amendment contains Title V Permit Program for
sources of air pollution. Governs air quality standards and
major sources of pollution; depending on emission
amounts large incineration units must receive permit from
states
45
Overview of Scrap Tire Disposal and Recycling Options
D. State regulations and permitting programs
To a great extent, the federal government has left states to manage their own scrap tire problems
and to seek their own legislative remedies. In 1985, the State of Minnesota, an early adopter of
tire regulation, attempted to establish a repository for scrap tire collection and chopping in
Minneapolis/St. Paul. Due to political pressure, however, the depot was built far from the Twin
Cities, and it became more cost effective to ship tires out of Minnesota into neighboring
Wisconsin, which lacked regulation. As similar import/export scenarios played out across the
country, state legislatures became involved, and most states now have regulations governing
scrap tire disposal. Surprisingly, despite population and demographic variations among the
states, most states have established very similar regulations.
Today, 49 of the 50 states currently have regulations for scrap tire disposal, with the exclusion of
Alaska (Alabama, the most recent state to act, passed scrap tire legislation in June 2003). Thirtyseven states ban whole scrap tires from landfills; nine of these ban scrap tired in any form from
landfills; 34 require a fee, primarily collected at the point of purchase by tire retailers or by the
state through vehicle registrations (RMA, 2003b; Goodyear, 2000). Most states specify scrap
tire storage methods, often defining the maximum pile size and the requirement for surrounding
berms or fences. States usually prescribe recordkeeping on the origins of the tires accepted and
the license provisions for the storage site, including fees. To prevent the appearance of new
illegal tire piles, most states license all haulers of scrap tires and some states require them to keep
manifests of their deliveries.
Control of existing tire piles and the means by which they grow is a necessary first step in scrap
tire management and has been sufficient for some state programs. In other states, legislation
provides for the elimination of existing tire piles and often offers market incentives to scrap tire
processors for the effective use of chopped tire products through grants or loans to purchase tire
chopping equipment, or through direct subsidies to the users of chopped tires. Additionally,
permitting is generally based on the size of tire piles, and permits are often contingent on
meeting guidelines for pest control as well as safety requirements.
In Wisconsin, now one of the most progressive states in terms of scrap tire management, the state
pays a subsidy of $20 per ton for users of Wisconsin scrap tires if the tires are used for fuel, and
an additional subsidy of $20 per ton for other commercial uses of scrap tires. Wisconsin recently
modified its program to reward both the processors and the users of scrap tire products. The tire
processors and the end users can each collect a subsidy of $40 per ton. The scrap tires must have
originated in Wisconsin, but payments can be made to processors outside of Wisconsin.
Likewise, Virginia now reimburses users of scrap tire products at $20 per ton.
To fund tire programs, most states have utilized existing tax or fee collection mechanisms. The
most popular funding device has been the simple increase of $1 or $2 on the retail sales tax on a
tire. A handful of states, however, use vehicle-titling fees to generate the funds. For example,
Minnesota charges $4 on vehicle title transfers to generate $4 million per year, of which twothirds goes into tire stockpile clean up, and the remainder goes into grant and loan programs for
scrap tire recyclers and users. Wisconsin chose to put a $2 per tire tax on new vehicles to
46
III. International and U.S. Regulatory Framework
generate $3 million per year. Likewise, Michigan has placed a $0.50 per tire disposal surcharge
on vehicle registrations, and New Mexico added a charge of $1 to the vehicle registration fee.
E. U.S. border state regulations and permitting programs
The EPA’s “State Scrap Tire Programs: A Quick Reference Guide - 1999 Update” outlines the
state regulations for the U.S.-Mexico border states of Arizona, California, New Mexico, and
Texas (EPA, 1999:v-xlv). Below is a summary of these regulations as they relate to scrap tire
disposal or incineration for energy recovery.
Arizona
Arizona’s original Scrap Tire Law was passed in 1990, and the state now has a comprehensive
set of scrap tire disposal regulations. Both whole and shredded tires are banned from landfills,
although scrap tire monofills are allowed. A number of fees are collected on new tires to fund
scrap tire programs. The state charges a 2% additional sales tax on new tires, and car dealerships
charge $1 per tire with the purchase of a new car. Retail tire sellers are required to accept used
tires from customers. Both retailers and scrap tire collection sites are required to keep manifests
documenting tire disposal. State-funded tire collection sites must accept tires from customers
and retailers at no fee. Funds collected through Arizona’s scrap tire program enable counties to
contract with private scrap tire processing and collection facilities.
Tire collection sites are subject to a variety of regulations. The Arizona Department of
Environmental Quality must approve all sites as solid waste facilities. Facilities storing over
5,000 tires must have financial assurance and are responsible for self-certification. Facilities that
contain between 500 and 5,000 tires must comply with scrap tire best management practices.
Facilities holding between 100 and 500 tires are subject to specific storage conditions. A facility
with fewer than 100 tires is regulated by local zoning and fire codes (EPA, 1999).
Permits are also required for sites using TDF. If emissions from a TDF site can be shown to be
equal to or lower than emissions from other accepted fuels, and if the site meets the requirements
of Title I of the Clean Air Act, “Air Pollution and Control,” which sets air quality standards and
emissions limits, the site can be permitted to use tires as a fuel source. Title V permits under the
Clean Air Act regulate permitting of such sites. Currently, only one cement kiln site in Arizona
uses TDF as a supplemental fuel (RMA, 2003).
The use of scrap tires in civil engineering projects is approved in the State of Arizona. No
market incentives exist, however, to promote scrap tire recycling.
California
California began developing regulations and programs for scrap tires in 1989. The California
Integrated Waste Management Board (CIWMB) was charged with establishing regulations for
the state purchase of retreaded tires, which today are required on most state vehicles. Also in
1989, regulations regarding the permitting of scrap tire collection facilities were passed, a
recycling program was established, and a feasibility study of tire use as fuel was launched. The
47
Overview of Scrap Tire Disposal and Recycling Options
permit and recycling programs have been in place since 1993. The feasibility report concluded
that the use of TDF in place of coal would mitigate the scrap tire problem and reduce air
pollution. The California Department of Transportation and CIWMB are charged with
determining bid specifications for the use of recycled products, including tire shreds, in paving
materials. Since 1990, fees have been applied to new tires, currently amounting to a $1 point-ofsale per tire fee. The fee generates $3-$4 million annually for the California Tire Recycling
Management Fund (EPA, 1999).
Since 1993, whole tires have been banned from landfills in California, and the state has
established several incentive programs to promote the recycling of scrap tires. A 5% price
preference exists for state-purchased products using material from recycled scrap tires. The
CIWMB manages a grant and loan program to encourage tire recycling, with the power to offer
grants or loans to companies engaged in a variety of energy recovery or recycling measures as
well as grants and loans for the end-product users (CIWMB, 2003b). The CIWMB is also
engaged in the stabilization and remediation of scrap tire sites; conferences to promote recycling;
collection of data on emissions from facilities using TDF; civil engineering investigations; local
fire authority training; and several other measures. No state emissions requirements exist for tire
incineration facilities, but these facilities must meet all local and pollution district emissions
requirements (CIWMB, 2003a).
California also requires permits for tire storage facilities. Small facilities (between 500 and
5,000 stored tires) are required to provide a completion of operation plan, environmental
information, and an emergency response plan in order to obtain a permit. Large tire facilities
(over 5,000 stored tires) additionally must meet requirements for fire prevention, security and
vector control measures, tire pile size and height limits, closure and pile reduction plans, and
operating liability coverage. Cement kiln facilities are allowed to maintain three months of tire
fuel supply without obtaining a storage permit. Currently, five cement kiln facilities exist in
California, consuming six million tires per year. Additionally, a dedicated tire-to-energy facility
in California burns five million tires annually (RMA, 2003).
New Mexico
New Mexico’s tire regulations are relatively moderate in comparison to those in the other states
discussed here, although new regulations for scrap tire management are currently being
developed. For the purposes of disposal, tires are treated as any other municipal solid waste and
can be disposed of at landfills.
Tire haulers must register with the state’s environmental department. Facilities processing or
recycling more than 1,000 tires per year can apply for funding from the state’s Tire Recycling
Fund, which funds tire pile mitigation and recycling projects. Currently, Southwest Tire
Processors is the only permitted tire recycling center. Facilities that store more than 250 scrap
tires at a time or firms that use more than 250 tires in a civil engineering application must
register with the environmental department and obtain a storage permit.
48
III. International and U.S. Regulatory Framework
The state does have programs creating market incentives for the use of rubber-modified asphalt
and recycled tires. In 1994, the New Mexico State Legislature enacted the “Tire Recycling Act,”
which provides for the recycling and disposal of scrap tires and the creation of the rubberized
asphalt fund. This fund covers any additional expenses incurred by municipalities and counties
when rubber-modified asphalt is used in road construction projects. A law passed in 1997 also
provides for a 5% price preference for the purchase of products containing recycled materials.
Texas
In 1998, the State of Texas determined that market-based incentives were no longer needed to
encourage tire recycling and other forms of re-use. As a result, those incentives were removed.
The state’s regulatory framework for scrap tires; however, remains fairly robust. Texas does not
permit landfilling of whole tires and requires manifests and permitting for facilities that deal with
more than 500 tires at a time. Within 60 days of their arrival at a disposal site, scrap tires must
be at least quartered. Storage sites must also be managed and monitored to prevent fires and
control disease vectors. Scrap tire facilities including incineration units must register with the
Texas Commission on Environmental Quality (TCEQ) and submit an annual report. If a facility
stores more than 500 tires, it must also be registered as a storage site.
In 2001, the State of Texas for the first time re-used, recycled, or disposed of legally in landfills
more tires than it generated. That year, approximately 25.5 million scrap tires were consumed or
disposed of, whereas the tire industry estimates that approximately 24 million scrap tires were
generated (amounting to slightly more than one tire generated per person) (Castillo, 2003b).
49
Overview of Scrap Tire Disposal and Recycling Options
State implementation of the Clean Air Act
The Clean Air Act is implemented individually by state. Table 25 explains how the Clean Air
Act is implemented in the border states and contains website links to each state’s permitting
regulations.
Table 25. Clean Air Act (Title V) implementation by border states. Compiled from state
environmental agency websites
Applications issued by Arizona Dept. of Environmental Quality; applications vary by industry
Arizona
California
New Mexico
Texas
and can be obtained online at http://www.adeq.state.az.us/environ/air/permit/general.html.
Counties have authority to set own criteria and approve applications; currently, Maricopa, Pima,
and Pinal counties have their own regulations. Permit approval takes from 124 days to 479 days,
depending on type of permit, complexity, and whether a public hearing is held; fees are
determined based on industry and quantity of emissions.
State is divided into 34 air districts, each of which issues its own permits and has its own
regulations. The Air Resources Board oversees districts; New Source Review and operating
permit applications are submitted to the appropriate air district for approval; NSR permit approval
takes up to 180 days; operating permits last five years. Each county’s air regulations can be
downloaded at http://www.arb.ca.gov/drdb/drdb.htm.
New Mexico Environmental Department oversees permitting process and has a universal
application for NSR and for operating permits; these can be obtained at
http://www.nmenv.state.nm.us/aqb/app_form.html
TCEQ oversees permitting process; all sources of air pollution must obtain NSR permits; Large
sources of air pollution must also obtain operating permits; Applications for NSR and operating
permits vary based on industry and size and can be obtained at
http://www.tnrcc.state.tx.us/permitting/airperm/index.html#nsr
50
III. International and U.S. Regulatory Framework
Table 26 highlights the U.S. border state laws that affect scrap tire disposal methods.
Table 26. Summary of U.S. border state legislation. Source: EPA (1999)
State
California
Tire Recycling Act,
Assembly Bill 1843
Year Enacted
Provisions
1989
Establishes the following scrap tire programs: $1/tire fees
collected at point-of-sale effective 7/1/90; permit program
(through CIWMB) for major and minor scrap tire facilities
effective 1992; whole tires banned from landfills effective
1/1/93; recycling program
Establishes permit and manifest system for haulers; must
register with CIWMB
Waste Tire Hauler
Register Program
Senate Bill 744
Solid Waste: Tire
Recycling, Senate
Bill 1026; Waste
Tires: Cement
Manufacturing Plant
Assembly Bill 1071
Tire Recycling
Enhancement Bill,
Senate Bill 876
Arizona
The Scrap Tire Law
House Bill 2687
Chapter 389
Amendment to the
Scrap Tire Law
Senate Bill 1252
Amendment to the
Scrap Tire Law
Senate Bill 1024 and
1228
New Mexico
Tire Recycling Act
Senate Act 1978
Texas
Senate Bill 1516
1993
Waste Tire
Recycling Program
Senate Bill 1340
Amendment to the
Waste Tire
Recycling Program
Senate Bill 776
1991
1995
Allows use of scrap tires for fuel at cement kilns; allows
kilns to maintain three-month supply without storage
permit
1999
Expands original scrap tire program with higher fees and
expanded coverage; authorizes funding of market
development for recycled tire products.
1990
Establishes the state’s scrap tire law with an additional
sales tax on tires
1991
Amends scrap tire law; whole tires cannot be landfilled
1997
Amends scrap tire law to extend program
1994
Tire disposal fee established, rubberized asphalt fund and
tire recycling fund established
1989
Scrap tires must at least be quartered within 60 days at
disposal site.
Tire fee established to fund scrap tire processors
1995
Established/amended comprehensive regulations for
program; established a grants program that expired in 1997
51
Overview of Scrap Tire Disposal and Recycling Options
Each state also has different permitting regulations regarding scrap tire disposal. Table 27
explains the permitting requirements for each border state, with links to more detailed
information.
Table 27. Permitting processes for scrap tire processing, storage, transportation, and
disposal. Compiled from state environmental agency websites
California
Waste Tire Facilities
(WTF)
Waste Tire Hauler (WTH)
Arizona
Waste Tire Collection
Facilities (WTCF) / Waste
Tire Processing Facilities
(WTPF)
New Mexico
Solid Waste Facility and
Tire Recycling Facilities
must obtain permit. Any
person or facility that
stores more than 250
scrap tires at a time, uses
250 scrap tires in a civil
engineering project, or
processes 1,000 scrap
tires in a year must obtain
permit.
Texas
Scrap tire generators;
transporters; facilities;
storage sites;
transportation facilities;
land reclamation projects
using tires; and landfills
All WTFs must complete permit application, operating plan, environmental
information, and emergency response plan; major WTFs (over 5,000 tires) must
complete closure plan, reduction/elimination plan, financial assurance mechanism; see
http://www.ciwmb.ca.gov/Tires/Facilities/Permit.htm for applications.
WTHs are required to complete registration application and purchase surety bond;
WTHs must comply with scrap tire manifest program.
All WTCFs that store over 500 tires must register with the Arizona Department of
Environmental Quality; see http://www.adeq.state.az.us/comm/download/waste.html
for forms; all WTCFs must comply with manifest program.
The following procedure is uniform to all permitting processes, including those related
to scrap tires, in New Mexico:
1. Facility applies for permit
2. Application evaluated for completeness
3. Filing fees collected
4. Develop plan for evaluation of application
5. Determine need for public notice
6. Determine need for public hearing
7. Accept public input
8. Conduct evaluation to include testing and inspections
9. Disapprove or approve with stated conditions
10. Exercise signature authority
11. Inform requester
12. Process appeal of denial
13. Forward for compliance monitoring
All must register with the TCEQ and are subject to various specific regulations;
regulations and permit application are available at:
http://www.tnrcc.state.tx.us/permitting/r_e/eval/we/tires/#gen
Table 28 details state disposal laws and restrictions for each of the U.S. border states.
52
III. International and U.S. Regulatory Framework
Markets Establish to
handle Annual
generation?
Comments
None
None
State
recently
depleted
fund of
almost
$5 M to
clean up
two largest
piles.
Provides
funds to
counties to
contract with
private scrap
tire collectors
/ processors.
None
Grants and
loans
available for
scrap tire
operations.
5%
purchase
price
preference
for state
purchased
products
made with
tire
derived
materials.
Requires
the use of
retreads
on state
vehicles.
Yes
$0.50 of
the $1.50
collected
goes to the
state's
general
fund
Yes
Market
Incentive
Yes
Subsidies/
Grants/
Loans
5% price
preference
for state
purchases
of
products
containing
recycled
materials.
Yes
Active Clean-Up
Program?
Yes
No
No
Yes
Stockpile Clean-Up
Program Exist?
Yes
Yes
Yes
Yes
Monofills Allowed?
Yes
Yes
Yes
Yes
Yes
No
No
Cut/Shredded Tires
Banned from Landfill?
53
No
Whole Tires Banned from
Landfill?
No
Yes
Yes
Yes
Storage/Disposal Reg. Or
Permit Required?
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
CA Tire Recycling Management Fund
created. CIWMB administers the fund.
Waste Tire Fund
created
Yes
12/31/1997
12/31/2002
Collection /
Transportation Reg. Or
Permit Required?
Prohibit Collection of
Other Fees?
Fee Account
Tire Recycling Fund
created.
Fee Sunset Date
Fee Collected by
State
n/a
n/a
Tire Dealer
Fee Basis
Vehicle Registration
n/a
n/a
Per Tire
Number of Tires in
Stockpiles (millions)
Fee Collected
$1.50
None
1.82
0.24
58
0
None
$1.00
(EPA 9)
Californi
a
2
(EPA 9)
Arizona
20.85
(EPA 6)
Texas
5.13
(EPA 6)
New
Mexico
33.87
(EPA
Region)
State
Annual Generation
(millions)
Table 28. State tire disposal laws and regulations. Source: RMA (2003b)
State provides
Rubberized
Asphalt Fund
and cost
reimbursemen
t for tire
recycling
centers.
IV. Mexican Regulatory Framework
A. General environmental laws
At the top of the hierarchy of Mexican laws, rules, and standards regarding the environment is
the Ley General de Equilibrio Ecológico y Protección al Ambiente (LGEEPA)—the General Law
for Ecological Equilibrium and Environmental Protection—originally enacted in 1988. With this
law, Mexico brought most environmental issues, including the management of hazardous wastes
and solid wastes, under one regulatory scheme. The LGEEPA defines hazardous waste, sets
general policy goals, and outlines the obligations and requirements of the federal government.
Additionally, the LGEEPA establishes policies for the export and import of hazardous waste as
well as requirements for generators and facilities that manage hazardous wastes.
The LGEEPA has been amended regularly since its original passage, including revisions in 1996
and 2000 dealing with waste management. The 1996 revisions established a system to
differentiate the hazardousness of wastes into categories, leaving the management of some lowgrade hazardous wastes to states (RMALC and Texas Center for Policy Studies, 2000).
Additionally, the revisions emphasized waste minimization policies, recycling, and secondary
materials recovery. Revisions in 2000 left the federal government with the power of jurisdiction
over categories of its choosing. Again, the federal government divided the jurisdiction over
wastes between the federal government and the states, leaving states in control of low-grade
hazardous wastes and municipal wastes (Alvarez, 2003).
While the LGEEPA establishes overall environmental policy and strategy, Normas Ofíciales
Mexicanas (NOMs)—Mexican Official Standards—are specific standards intended to allow the
federal environmental agency (SEMARNAT) to fulfill its obligations contained in the LGEEPA.
The process for adopting a NOM is intensive. The Municipal Waste, Hazardous Waste and
Material Standard Subcommittee of SEMARNAT submits policy recommendations to the
National Consultative Standards Committee. The National Consultative Standards Committee
may approve the regulations, and after a 60-day public comment period, the comments and NOM
are sent back to the Subcommittee, where the final decision concerning the adoption of the new
regulations is made. Both the Subcommittee and the National Consultative Standards
Committee are comprised overwhelmingly of industrial associations, chambers of commerce,
and governmental officials, with little representation from university representatives and
virtually no representation from non-academic, non-governmental organizations (RMALC and
Texas Center for Policy Studies, 2000).
Proposed NOMs may amend or replace earlier standards or may involve new issues not currently
covered by Mexican regulations. In 1995, a subcommittee approved a draft of the NOM
establishing maximum emission standards for the incineration for hazardous, industrial, and
municipal waste in incinerators and cement kilns. However, by 1998 the NOM had yet to be
approved by the larger National Consultative Standards Committee, in part because the cement
industry considered the standards too tough to meet. Instead, a different NOM was proposed,
relating specifically to the burning of “alternative fuels” in cement kilns (RMALC and Texas
Center for Policy Studies, 2000). A version of this NOM was eventually passed in December
2002.
54
Overview of Scrap Tire Disposal and Recycling Options
When there is no specific NOM for a particular topic, Mexican law defers to the most applicable
standards and regulations. For example, while regulations have been devised for the incineration
of scrap tires in cement kilns, in practice, these regulations govern any facility burning scrap tires
and also serve as the basis for regulations for municipal waste incineration. When there is no
related national regulation, Mexican law then defers to international standards and practices.
Additionally, a lack of regulation has not meant “no regulation;” instead, projects tend to be
evaluated on a case-by-case basis by SEMARNAT in accordance with overall Mexican
environmental policy (Alvarez, 2003).
As in the United States, scrap tires are classified as a solid waste by Mexico, and the governance
of scrap tires has been left primarily to the states. In 2002, however, federal regulations
regarding scrap tire incineration were passed, formalizing and strengthening the existing
practices employed by cement kiln operators. While states still govern scrap tire disposal and
storage, scrap tire incineration is governed by the federal government.
A new solid waste law, Ley General para la Prevención y Gestión Integral de los Residuos—
General Law for the Prevention and Special Management of Wastes—was passed in Mexico in
October 2003. The law reclassifies solid waste into three categories: (1) residuos sólidos
urbanos (municipal solid waste); (2) residuos de manejo especial (special-management waste);
and (3) residuos peligrosos específicos (hazardous waste). Under the new law, every major
generator of waste, including municipalities and industrial facilities, will be required to develop
integrated waste management plans. A guidance document explaining how to develop these
management plans is expected to be released in April 2004. Waste produced by transportation
sources is specifically mentioned in the new law, and management plans will be required for
scrap tires as a type of “special-management waste” (Wilson, 2003b).
B. Tire incineration regulations
The Norma Oficial Mexicana NOM-040-ECOL-2002, Protección Ambiental-Fabricación de
Cemento Hidráulico – Niveles Máximos Permisibles de Emisión a la Atmósfera (Mexican
Official Standard - Environmental Protection – Hydraulic Cement Production – Maximum
Permissible Levels of Emissions to the Atmosphere), was passed in December 2002 and set
emission limits that specifically regulate the use of alternative fuels in cement production
(SEMARNAT, 2003).11 The standard creates emissions limits to monitor various particulates
and gas emissions, based on type of cement produced and location of the kiln. Additionally,
each emissions target is broken into three levels, with different monitoring requirements for each
pollutant, ranging from annual to continuous monitoring. The allowable emissions level and
monitoring requirements are based on the amount of conventional combustibles that the
alternative fuel is replacing and the type of alternative fuel to be used. Each type of alternative
fuel is organized into one of three categories: scrap tires; recoverable combustibles, including
oils and other combustibles; and formulated combustibles. Formulated combustibles include
hazardous and non-hazardous materials (excluding certain bio-hazardous, radioactive, and dioxin
wastes) that, while typically not good fuel sources, have been specifically blended with more
combustible materials to burn in a kiln. Tables 28 and 29 detail the permissible emissions levels
11
NOM-040-ECOL-2002 is now titled NOM-040-SEMARNAT-2002, due to internal reorganization within
SEMARNAT.
55
IV. Mexican Regulatory Framework
from cement kilns. Table 29 correlates the level of monitoring with the percentage of alternative
fuel that has been substituted for conventional fuel. Table 30 details the emissions limits and
monitoring frequency for each level. For example, a cement kiln burning 20% scrap tires in
place of traditional combustibles would be subject to level 1 emissions monitoring, whereas a
cement kiln burning more than 30% scrap tires would be subject to level 2 emissions monitoring.
Emissions limits for some pollutants also vary depending on the type of cement produced and the
location of the facility.
Table 29. Mexican emissions regulations for cement kilns using alternative fuels.
Source: SEMARNAT (2003)
Percentage of alternative
fuel substituted for
conventional fuel (%)
Tires
Recoverable
combustibles
Formulated
combustibles
0-5
None
None
Level 1
5-15
Level 1
Level 1
Level 2
15-30
Level 1
Level 2
Level 3
> 30
Level 2
Individual validation
56
Overview of Scrap Tire Disposal and Recycling Options
Table 30. Mexican emissions regulations for cement kilns: maximum permissible levels of
emissions (1). Source: SEMARNAT (2003)
Emission Type
Emission Limits
Monitoring Frequency**
mg/m3
Level 2
Level 3
CO (2)
3000-4000*
Annual
Continuous
HCl
70
Bi-annual
Continuous
NOx (2)
800-1600*
Annual
Continuous
SO2 (2)
400-2500*
Annual
Continuous
HCt (such as CH4)
70
Bi-annual
Continuous
Particulates
80-100*
Annual
Annual
Sb, As, Se, Ni, Mn
0.7 (3)
Annual
Bi-annual
Cd
0.07
Annual
Bi-annual
Hg
0.07
Annual
Bi-annual
Pb, Cr, Zn
0.7 (3)
Annual
Bi-annual
Dioxins and Furans
0.2 (µg EQT/m3)
Biennial
Annual
* Exact limits depend on type of cement being produced.
** All level 1 compliance levels are monitored yearly
(1) Based on normal, dry, conditions, corrected with 7% Oxygen (O2) by volume.
(2) Exact limits vary based on the location of the firm.
(3) Sum of all heavy metals.
NOM-040-ECOL-2002 requires that facilities that wish to burn tires or other alternative fuels
must retrofit their kilns to meet emissions standards and apply to SEMARNAT for a permit.
They are then offered a temporary permit in order to test burn a sample of tires or other
alternative fuel. If regulations are met, then the permit becomes permanent and is subject to
monitoring set out by the regulation (Alvarez, 2003).
Four cement kilns in Mexico currently use tires as a supplemental fuel. Three are CEMEX
facilities, in Ensenada, Baja California; Monterrey, Nueva León; and Colima, Colima. The
fourth, operated by Cementos Apasco, uses tires in its facility in the State of Hidalgo (Wilson,
2003). Another Hidalgo company, Llanset, SA DE CV, processes tires to make ground rubber
for such products as paving tiles and speed bumps (Construcción y Technología, 2003).
Apart from its use in cement kilns, TDF is also used for one other industrial activity—traditional
brick making in Ciudad Juarez. Juarez has about 400 rudimentary adobe kilns that are smallscale, low-tech, and highly polluting. Each kiln employs an average of six workers, is fired
twice a month, and uses a variety of cheap, dirty fuels. The vast majority of brick makers do not
use any emissions control devices (Blackman and Palma, 2002). Since the early 1990s, firing
57
IV. Mexican Regulatory Framework
brick kilns with TDF has been illegal in Chihuahua; the Mexican federal government has a
formal agreement with brickmakers in which they have agreed not to burn garbage, oil, and tires.
The vast majority of fuel is sawdust, wood, and periodically propane, depending on price.
Nevertheless, enforcing these prohibitions is difficult, and some brick makers continue to burn
tires surreptitiously. Collectively, brick kilns in Ciudad Juarez probably burn no more than 500
tires per year (Marquez in Blackman and Palma, 2001). In other areas, however, such as Saltillo,
Coahuila, open kiln burning of tires for tile making is more common. According to a survey,
55% of fuel used in open kilns in Saltillo was tires, with the remainder being primarily wood
(COMIMSA in TNRCC, 2002). Recently, these kilns have begun to switch to used oil (Castillo,
2003a).
C. State regulations
Mexican Law currently permits one million used tires to be imported across the border each year
into the states of Baja California, Sonora, and Chihuahua, though reportedly millions more enter
the country illegally each year (Wilson, 2003). Unfortunately, no accurate quantification exists
for the total number of scrap tires entering the country (Foro Binacional, 2003). Most states
prohibit the importation of scrap tires but permit a limited number of used tires that still have
retail value to be imported. The exception, Baja California, permits one company engaged in
recycling to import scrap tires across the border, totaling about 500,000 used tires per year.
Llanteros, or used tire dealers, can obtain special permits to allow them to import tires across the
border. Some states and municipalities have experimented with taxes on new tires and with
taxes on tires entering the border, but these measures have been largely unsuccessful, in the
former case because most tires sold are used tires, and in the latter because so many of those tires
enter the country illegally (Alvarez, 2003).
While states have the power to regulate scrap tire storage and disposal, aside from incineration,
most states have not implemented any specific laws addressing these issues. Most states in
Mexico landfill or mono-fill scrap tires. Some private landfills have experimented with tire
shredding. Some public landfills, such as those in Ciudad Juárez, are following more rigorous
standards for tire disposal that are similar to those of the Texas Commission on Environmental
Quality, despite the lack of official regulation requiring them to do so (Alvarez, 2003).
Efforts are underway to issue a Norma that would provide regulatory guidance to state and
municipal jurisdictions on the management and final disposal of scrap tires. The Norma would
reinforce shared responsibility among the authorities, manufacturers, distributors, and users
(Foro Binacional, 2003). The draft version of this Norma should be available for public
comment sometime during 2004.
58
Overview of Scrap Tire Disposal and Recycling Options
Table 31 summarizes the Mexican laws that govern scrap tire incineration.
Table 31. Mexican laws pertaining to scrap tire incineration
Mexican law
Year enacted
Key provisions
Ley General de Equilibrio
Ecológico y Protección al
Ambiente (LGEEPA)
Revisions to LGEEPA
NOM-040-ECOL-2002
(Protección ambientalFabricación de cemento
hidráulico-Niveles
máximos permisibles de
emisión a la atmósfera)
1988
Establishes authority of federal government to manage wastes;
sets general environmental policy and strategy
1996, 2000 and
others
Amends LGEEPA, orienting its strategy towards recycling,
reuse, and energy recovery; sets hazardous waste categories
and gives some jurisdiction over less hazardous wastes to
states
Sets emissions limits and monitoring requirements for cement
kilns burning alternative fuels; divides alternative wastes into
categories; regulates emissions based on type of waste and
percentage used
2002
59
V. Tire Disposal Projects in the Context of the BECC’s
Certification Criteria
A. Introduction
As discussed in Sections I and II, open-air tire piles present significant human health and
environmental hazards. Tire piles provide breeding grounds for a number of disease vectors,
most notably mosquitoes and rodents. They are also a fire hazard, and open-air tire fires produce
dangerous air, water, and soil pollution. For these reasons, the primary goal of any scrap tire
management strategy should be to eliminate or, in the case of stockpiles to supply tire disposal or
recycling projects, to minimize tire piles.
Given the public health and environmental hazards posed by large tire piles, a variety of tire
disposal options may be viable under the BECC’s certification criteria. Scrap tire uses can be
organized into three main categories: tire-derived fuel; civil engineering; and ground rubber
applications. Most likely, sponsorship of these projects would derive from a public/private
partnership or from the private sector. Tire recycling projects often require innovative financing
through a hybrid of private investment and public loans.
In this section, the range of applications for scrap tires is evaluated against each of the six
categories of criteria: General; Human Health and Environment; Technical Feasibility; Financial
Feasibility and Project Management; Community Participation; and Sustainable Development.
Specific information that could assist in the evaluation of a tire disposal project is suggested, and
additions to the criteria that might enable the BECC to fully evaluate such projects are also
proposed.
B. General Certification Criteria
A project involving any of the above-mentioned scrap tire uses, including tire-to-energy, civil
engineering, or ground rubber applications, would likely comply with the BECC’s General
Criteria. All would meet the BECC’s goal of solid waste reduction. Tire-to-energy incineration
projects as well as gasification projects also would meet the key objective of eliminating waste
material through a waste-to-energy project. Moreover, the locations of such energy-related
projects could be highly appropriate, as the border has both large tire stockpiles and burgeoning
energy needs. The vast piles of scrap tires along the border and the transportation costs
associated with shipping tires could necessitate that economically viable scrap tire disposal
projects be located within the required zone of 100 km of the border. Provided that emissions
controls, particularly for forms of particulate matter and zinc, are implemented at a tire-to-energy
facility, such a project should be able to conform to the relevant U.S. and Mexican regulations
and international treaties and agreements.
C. Human Health and Environment Certification Criteria
Because of the health and environmental hazards that scrap tire piles pose, most tire disposal
projects would meet the BECC’s requirement that “all projects address a human health and
environmental need.” Tire-to-energy projects should be able to comply with applicable
environmental resource regulations, provided that the proper emissions controls are in place.
60
Overview of Scrap Tire Disposal and Recycling Options
Compliance of tire-to-energy projects with the Human Health and Environment Certification
Criteria depends on the interpretation of the criteria. As noted earlier, with the proper pollution
control equipment TDF combustion emits less air pollution (with the exception of particulate
matter and zinc) than other commonly burned solid fuels such as coal, wood, or coke and should
therefore fall within legal emissions limits. However, TDF combustion emissions are typically
higher than those from natural gas combustion. Although the incineration of tires for energy
recovery would likely conform to all U.S. and Mexican regulations, some could contend that
these regulations do not offer the “high” level of protection as required by the BECC’s criteria.
Therefore, any additional guidelines that the BECC develops for tire incineration should
emphasize that such projects be optimized for energy recovery, with consistent and high
temperatures, and that the best available technologies be utilized to minimize emissions.
This criteria category also requires an environmental assessment. In addition to the standard
environmental assessment, a tire-to-energy project also could result in transboundary pollution
and might necessitate the completion of an environmental assessment of potential cross-border
impacts. Accordingly, Mexican and U.S. regulatory authorities might consider developing
specific air quality requirements for tire-to-energy projects to ensure that such projects, even if
they meet the basic emissions standards, would not degrade the regional air quality.
Special attention should be focused on rudimentary or outdated incineration facilities. Without
system upgrades or modifications, these facilities might not have the appropriate pollution and
particulate matter controls and might not be able to maintain the high temperatures necessary to
ensure complete and clean TDF combustion.
Other tire disposal and recycling options, ranging from shredding projects to civil engineering
applications to ground rubber applications such as asphalt-modified rubber, should be able to
meet the BECC’s health and environment criteria. These solutions would also provide a higher
level of protection to human health and the environment compared to tire incineration projects.
Provided that the leaching and self-heating issues in civil engineering applications are managed,
these applications appear to pose little or no health or environmental risk.
D. Technical Feasibility Certification Criteria
All of the tire disposal options discussed in this report should generally be able to comply with
the BECC’s Technical Feasibility Certification Criteria. Facilities that propose to use tires as a
supplemental fuel to coal will need to make some system modifications, including adding a
conveyor, scale, and metering system to deliver tires into the incinerator. Provided that a blend
of no more than 20% TDF is used, standard boilers and emissions controls should be adequate.
Facilities other than those that were designed to burn coal, such as natural gas facilities, may
require additional modifications.
In the event that a dedicated tire-to-energy facility is proposed, the issue of adequate resource
inputs, as required by the Technical Feasibility criteria, could pose a barrier. The large quantity
of tires required for even a small dedicated facility would require assurance that an adequate and
economic supply of scrap tires is available locally or could be secured from outside the
community.
61
V. Tire Disposal Projects in the Context of the BECC’s
Certification Criteria
In the case of other tire disposal options that require tire processing, either for civil engineering,
ground rubber, or tire-derived-fuel applications, system flexibility is critical so that the system
can grow or adjust to meet new market needs. A basic tire processing system can be set up in the
initial phase of the project, and additional processing systems to produce smaller and cleaner tire
granules can be added as markets emerge. The training of locally available labor should also be
discussed in the project plan, since local operators and communities may be unfamiliar with
some of the technologies and systems. It is important to note that some tires that have been
stockpiled along the border may be too dirty or degraded to be processed into ground rubber.
Such projects would therefore fail to meet the Technical Feasibility criteria.
E. Financial Feasibility and Project Management Certification Criteria
Of the tire disposal options, tire-to-energy projects using tires as a fuel supplement would be
most able to comply with the Financial Feasibility criteria. Civil engineering projects might also
be able to achieve compliance with these criteria. Other markets for scrap tires are still
immature, and with the ground rubber applications in particular, the industry is fragmented and
not yet highly lucrative. Pyrolysis and gasification projects are still in demonstration phase and
are not yet viable in the open marketplace.
As with the technical criteria, tire-to-energy facilities should be evaluated differently for
supplemental TDF projects versus dedicated TDF projects. Projects using TDF as a fuel
supplement might only need to make modest system modifications and might not be required to
take on significant financial risk. However, dedicated tire-to-energy facilities as well as some
other tire disposal projects could involve large capital outlays and, in the case of tire-shredding
machinery, large maintenance budgets. These factors could pose financing challenges, as
traditional lenders might be reluctant to provide loans if the supply of a required resource such as
tires might not exist for the amortized life of the facility. It is difficult to conceive of a ground
rubber project in Mexico today that would be financially viable without some form of public
support, such as grants or subsidies. The Financial Feasibility criteria would therefore be the
most challenging for such projects to meet.
F. Community Participation Certification Criteria
The community participation category contains criteria that could be somewhat challenging for
tire disposal projects, particularly tire-to-energy projects, to meet. Despite efforts on the part of
the EPA and scientific community to provide answers, debate continues over the risk to public
health and the environment posed by emissions from facilities that process tire-derived fuels.
The actions of some cities and even countries around the world to ban forms of incineration
indicate continuing public skepticism. Communities not currently dealing with scrap tire piles
might also be concerned about introducing new tire stockpiles for tire disposal facilities. For
these reasons, many in the general public could believe that the use of TDF poses an
unacceptable risk to nearby communities.
62
Overview of Scrap Tire Disposal and Recycling Options
Other tire disposal options such as civil engineering and ground rubber applications could also be
somewhat controversial for safety and political reasons and because they might be perceived as
new technologies. However, community concerns regarding these applications would not likely
be of the same magnitude as for tire-to-energy projects.
The following information should be provided to the public as part of the project sponsor’s
public participation plan:
ƒ
ƒ
ƒ
ƒ
ƒ
ƒ
ƒ
ƒ
Potential emissions;
Ash disposal and recovery;
Number of tires used;
Number of tires to be stored on site, and whether those tires will be whole,
chunked, or shredded;
Expected increases in truck traffic from delivery and/or collection of used tires;
Expected increases in noise or odors from proposed facilities;
Pest control measures for tire piles; and
Use of the best available technologies for combustion and control systems.
It is paramount that the relationship between the project sponsor and the affected community be
transparent. Any tire-disposal project sponsor seeking the BECC certification should commit to
a substantial public education effort to communicate the risks, costs, and benefits of the project.
Public meetings should be held early in the planning process and in the community where the
facility would be located as well as in communities downwind or downstream of the facility. At
these meetings and in the appropriate written materials, all of the alternatives should be
discussed, including other options for scrap tire disposal and the “no action” alternative. Also,
any mitigation measures that are proposed to offset a project’s negative impacts should be
closely related to the potential impacts and to community needs. The BECC could consider
instituting a 30- or 60-day public comment period for scrap tire projects, during which it would
receive and review comments before a project is approved or rejected for certification.
G. Sustainable Development Certification Criteria
Fundamentally, the range of tire disposal options, from tire-to-energy incineration projects to a
re-use project such as retreaded tires, could all meet the sustainable development criteria.
Because of nuances in the definition of the term “sustainable development,” however, an
analysis of tire disposal options against these criteria is complex.
The more value a tire disposal project is able to re-capture from the original product, the closer
that project would come to being truly sustainable. Conversely, the more energy that is lost in
the tire disposal process, the less sustainable that option would be. Table 32 examines the tireto-energy option, comparing the energy required to make the original tire with the energy
captured through incineration.
63
V. Tire Disposal Projects in the Context of the BECC’s
Certification Criteria
Table 32. Energy consumption required to produce tire rubber compared to energy
recovered through tire incineration. Source: Reschner (2003)
Energy needed to manufacture a tire
32 kWh/kg
Energy needed to produce tire rubber
25 kWh/kg
Energy released when incinerating scrap tires
9 kWh/kg
As Table 32 shows, only a fraction of the energy required to make a tire is recaptured through
tire incineration. It is suggested that the BECC’s overall scrap tire management strategy should
be to promote projects that would eliminate scrap tire piles and the hazards that they represent,
while maximizing the value recaptured from the tire and minimizing the environmental and
health impacts of scrap tire disposal.
Table 33 organizes the primary tire disposal and recycling options according to their adherence
to the sustainable development criteria, with a ranking of “1” being the most sustainable and “8”
being the least sustainable.
64
Overview of Scrap Tire Disposal and Recycling Options
Table 33. Sustainability ranking of tire disposal and recycling options
Sustainability
Disposal or recycling option
Health and environmental
ranking
effects
1
Retreaded tires
None. Retreaded tires are
believed to be as safe as new
tires.
2
3
4
Civil engineering applications
(i.e., structural fill, backfill for
retaining walls, landfill liners,
etc.)
Note: From environmental and
health standpoints, civil
engineering and ground rubber
applications are generally similar
in terms of their sustainability.
However, the market for civil
engineering applications is larger
than that for ground rubber
applications.
Ground rubber applications (i.e.,
rubber-modified asphalt,
recreational facilities, new tires,
flooring and roofing tiles, etc.)
Whole tire TDF incineration
Low. The formation of hot
spots in tire chips used for
fill, and the possibility of
water contamination from tire
chip leachate can be avoided
or mitigated by following
engineering guidelines set by
ASTM International.
No known harmful
environmental or health
effects
Moderate. Tire incineration
emissions are generally
similar to those of other solid
fuels, with the exception of
higher particulate matter and
zinc emissions.
65
Economic viability
Advantages
Disadvantages
Low to moderate. Outside
of public sector vehicles,
airplanes, and commercial
trucks, the market demand
for retreaded tires is
currently limited.
Moderate. Tire chips can
be more expensive than
traditional fills such as
gravel, but their low
density can decrease
overall construction costs.
Recovers the most value
from the original tire
ƒ
Moderate. Tires that have
been stockpiled along the
border may be too dirty
for ground rubber
applications. Processing
ground rubber from tires is
expensive, but the life
cycle cost of many ground
rubber applications is
lower than that of
traditional materials.
High. Facilities that can
burn whole tires (such as
cement kilns) are often
able to secure this fuel at a
lower or even negative
cost compared to
traditional fuels. System
modifications may be
required in order to feed
tires into the facility.
ƒ
Can lower construction
costs in some
applications
ƒ
ƒ
ƒ
More expensive
than some new
tires
ƒ Perception that
retreads are less
safe
ASTM guidelines must
be followed so that
leaching and hot spots
do not occur.
Lower life cycle
cost of pavements
resulting from less
maintenance,
longer life
Reduces braking
distance and traffic
noise
Higher upfront costs for
some projects
Most developed
market for scrap
tires world wide
Produces less SO2
emissions than coal
Produces air emissions
similar to those of coal,
except that emissions of
particulate matter and
zinc are higher
V. Tire Disposal Projects in the Context of the BECC’s Certification Criteria
Table 33 (cont.)
Sustainability
ranking
5
Disposal or recycling option
Shredded TDF incineration
Health and environmental
effects
Moderate. Tire incineration
emissions are generally
similar to those of other solid
fuels, with the exception of
higher particulate matter and
zinc emissions.
Economic viability
Advantages
Disadvantages
Moderate to high.
TDF is cheaper than other
sources of solid fuel, but
processing tires into TDF
is costly.
ƒ
ƒ
ƒ
Most developed
market for scrap
tires world wide
Produces less SO2
emissions than coal
ƒ
6
7
8
Landfilling shredded tires
Landfilling whole tires
Gasification
Moderate to high.
Landfilling shredded
tires uses valuable
landfill space
ƒ Leaching must be
guarded against
Low. No marketable
product is created, and
valuable landfill space is
used.
ƒ
Moderate to high.
Landfilling whole tires is
difficult because the tires
resist compaction and
tend to rise to the top.
ƒ Leaching must be
guarded against
Low. The products, primarily
a syngas, are recovered.
Low. Whole tires utilize
valuable landfill space.
ƒ
ƒ
ƒ
ƒ
ƒ
Low. The value of the
gases produced is
currently less than the
production expense.
ƒ
ƒ
ƒ
9
Pyrolysis
Low. Most of the product
outputs are recovered, and the
methane gas produced is used
to fuel the process or is sold.
66
Low. Most product
outputs are low grade and
have lower market value
than the original tires.
Immediate disposal
option
Fire and vector
dangers inherent to
tire stockpiles can
be centrally
managed
Immediate disposal
option
Fire and vector
dangers inherent to
tire stockpiles can
be centrally
managed
Little pollution
Many feedstocks,
including tires and
biomass, can be
used
Can generate fuel,
power, and
chemical products
Little pollution, as most
of the products are
recovered
ƒ
ƒ
Produces air
emissions similar
to those of coal,
emissions of
particulate matter
and zinc are higher
Processing tires
before incineration
reduces the
financial
advantages
No value is
recovered from the
scrap tire
Cost of processing
tires is not
recovered
No value is recovered
from the scrap tire
ƒ
ƒ
Expensive
Requires a large
supply of tires
ƒ
ƒ
Expensive
Requires a large
supply of tires
Overview of Scrap Tire Disposal and Recycling Options
Each of the scrap tire disposal and recycling methods described above—tires-to-energy, civil
engineering applications, and ground rubber uses—has the potential to meet the BECC’s
certification criteria. Tradeoffs among the criteria will nonetheless be required when evaluating
projects for certification. For example, tire-to-energy projects could be perceived as weaker
according to the Human Health, Community Participation, and Sustainable Development criteria.
These energy projects may be the only ones, however, that could meet the Financial Feasibility
and the Technical Feasibility criteria because the market for tires as a fuel supplement is the most
developed. Conversely, ground rubber and civil engineering projects would earn high marks
with the Human Health, Community Participation, and Sustainable Development criteria but
might not be financially or technically feasible given current market realities in Mexico.
The opportunity that Mexico has to bypass the incineration option as some other countries have
done for various forms of waste incineration is appealing. The argument could be made that the
air quality in some Mexican cities is already so poor that incineration options should not be
considered sustainable in those areas. Nonetheless, if markets in Mexico develop as they have in
the United States and other industrialized countries, tire-to-energy markets would be among the
first to mature and might be only feasible market for scrap tires in the short term.
67
V. Tire Disposal Projects in the Context of the BECC’s
Certification Criteria
Table 34 summarizes the various tire disposal options discussed in this report, and reviews how
they would fit under the BECC certification criteria.
Table 34. Tire disposal options and the BECC certification
Supplemental fuel
Cement kilns
Pulp and paper mills
Electric utilities
Industrial boilers
Steel mills
Dedicated tires-to-energy
Civil engineering
Structural fill
Landfill lining
Sewage composting
Artificial reefs
Ground rubber
Rubber-modified asphalt
Recreational facilities
Roofing materials
Floor mats
New tires
Retreading
Gasification
Pyrolysis
General
√
√
√
√
√
√-
Human health
& environment
√
√
√
√
√
√
Technical
feasibility
√
√√√√√-
Financial
feasibility
√+
√√√√√-
Community
participation
√√√√√√-
Sustainable
development
√√
√
√
√
√
√
√
√
√-
√
√
√
√-
√
√
√
√
√
√
√
--
√
√
√
√
√
√
√
√
√
√
√
√
√
√
√
√-
√+
√+
√+
√+
√+
√+
√+
√
√√√√√√
√
√-
√√√√√√
√--
√+
√+
√+
√+
√+
√+
√+
√
√+
√+
√+
√+
√+
√+
√+
√
Key: √+ exceeds criteria
√ meets criteria
√- meets criteria to a limited extent
-- does not meet criteria
68
References
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http://cisat1.isciii.es/tfacts60.html. Accessed 8/1/03.
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Matisoff. 9/2/03.
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practice for use of scrap tires in civil engineering applications.
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waste handling and disposal. Title 14 Chapters 3-7.
http://www.ciwmb.ca.gov/regulations/title14/ch3a55.htm. Accessed 8/13/03.
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[CIWMB] California Integrated Waste Management Board. 2003b. Energy recovery from tires
grants. http://www.ciwmb.ca.gov/tires/grants/energy. Accessed 8/13/03.
Cappiello, D. 2003. Treading on dangerous ground. Houston Chronicle. 9/7:1A.
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scrap tires in cement manufacturing. Journal of Environmental Quality. 31(5):1484-1490.
Castillo, J. 2003a. Texas Commission on Environmental Quality, Division of Border Affairs.
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Castillo, J. 2003b. Texas Commission on Environmental Quality, Division of Border Affairs.
Summary of findings from the Texas-Mexico Border Waste Tire Stakeholder Group.
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