United States
Environmental Protection
Agency
National Risk Management
Research Laboratory
Cincinnati, OH 45268
Research and Development
EPA/600/SR-97/115
November 1997
&EPA Project Summary
Air Emissions from Scrap Tire
Combustion
Joel I. Reisman
Two to three billion (2-3x109) scrap
tires are in landfills and stockpiles
across the United States, and approxi-
mately one scrap tire per person is
generated every year. Scrap tires rep-
resent both a disposal problem and a
resource opportunity (e.g., as a fuel
and in other applications). Of the many
potential negative environmental and
health impacts normally associated
with scrap tire piles, the present study
focuses on (1) examining air emissions
related to open tire fires and their po-
tential health impacts, and (2) report-
ing on emissions data from well de-
signed combustors that have used tires
as a fuel.
This Project Summary was developed
by the National Risk Management Re-
search Laboratory's Air Pollution Pre-
vention and Control Division, Research
Triangle Park, NC, to announce key
findings of the research project that is
fully documented in a separate report
of the same title (see Project Report
ordering information at back).
Introduction
Air emissions from two types of scrap
tire combustion are addressed: uncon-
trolled and controlled. Uncontrolled
sources are open tire fires, which produce
many unhealthful products of incomplete
combustion and release them directly into
the atmosphere. Controlled combustion
sources (combustors) are, for example,
boilers and kilns specifically designed for
efficient combustion of solid fuel. Com-
bustor emissions are much lower and more
often than not, these sources also have
appropriate add-on air pollution control
equipment for the control of particulate
emissions.
Very little data exist for devices that use
scrap tires for fuel, but are not well-de-
signed. These sources include fireplaces,
wood stoves, small kilns, small incinera-
tors, or any device with poor combustion
characteristics. Air emissions from these
types of devices are likely between that of
open burning and a combustor. However,
there is serious concern that the emis-
sions are much more similar to those of
an open tire fire than a combustor.
Open Tire Fires
Air emissions from open tire fires have
been shown to be more toxic, (i.e., mu-
tagenic) than those of a combustor, re-
gardless of the fuel. Open tire fire emis-
sions include "criteria" pollutants, such as
particulates, carbon monoxide (CO), sul-
fur oxides (SOx), oxides of nitrogen (NOx),
and volatile organic compounds (VOCs).
They also include "non-criteria" hazard-
ous air pollutants (HAPs), such as poly-
nuclear aromatic hydrocarbons (PAHs),
dioxins, furans, hydrogen chloride, ben-
zene, polychlorinated biphenyls (PCBs),
arsenic, cadmium, nickel, zinc, mercury,
chromium, and vanadium. Both criteria and
HAP emissions from an open tire fire can
represent significant acute (short-term) and
chronic (long-term) health hazards to
firefighters and nearby residents. Depend-
ing on the length and degree of exposure,
these health effects could include irritation
of the skin, eyes, and mucous membranes,
respiratory effects, central nervous sys-
tem depression, and cancer. Firefighters
and others working near a large tire fire
should be equipped with respirators and
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dermal protection. Unprotected exposure
to the visible smoke plume should be
avoided.
Data from a laboratory test program on
uncontrolled burning of tire pieces and
ambient monitoring at open tire fires are
presented and the emissions are charac-
terized. Mutagenic emission data from
open burning of scrap tires are compared
to other types of fuel combustion. Open
tire fire emissions are estimated to be 16
times more mutagenic than residential
wood combustion in a fireplace, and
13,000 times more mutagenic than coal-
fired utility emissions with good combus-
tion efficiency and add-on controls.
Table 1 lists 34 target compounds rep-
resenting the highest potential for inhala-
tion health impacts from open tire fires.
The list was developed by analyzing labo-
ratory test data and open tire fire data
collected at nine tire fires. The list can be
used to design an air monitoring plan in
order to evaluate the potential for health
risks in future events.
Methods for preventing and managing
tire fires are presented. Recommenda-
tions are presented for storage site de-
sign, civilian evacuation, and fire sup-
pression tactics. For example, tire piles
should not exceed 6 m (20 ft.) in height;
maximum outside dimensions should be
limited to 76 m (250 ft.) by 6 m (20 ft.).
Interior fire breaks should be at least 18
m (60 ft.) wide. Civilians should be
evacuated when they may be subject to
exposure by the smoke plume. Fire sup-
pression tactics are site and incident-
specific and firefighters should have spe-
cialized training to deal effectively with
them.
Other Impacts from Open Tire
Burning
The scope of this report is limited to
airborne emissions. However, significant
amounts of liquids and solids containing
dangerous chemicals can be generated
by melting tires. These products can pol-
lute soil, surface water, and ground water
and care must be taken to properly man-
age these impacts as well.
Controlled Combustion
The results of a laboratory test pro-
gram on controlled burning of tire-derived
fuel (TDF) in a Rotary Kiln Incinerator
Simulator (RKIS) are presented. Natural
gas was the primary fuel, supplemented
by TDF. In all, 30 test conditions were
run, with the TDF feed rate varying from
0 to 21.4% of heat input. The test condi-
tions were achieved by varying kiln firing
rate, combustion air flow rate, and tire
feed rate. The majority of the tests were
conducted with a steady-state feed of
TDF. However, variations in the mode of
TDF feeding were simulated in two tests
to evaluate the impact of transient opera-
tion on air emissions.
Based on the results of the RKIS test
program, it was concluded that, with the
exception of zinc emissions, potential
emissions from TDF are not expected to
be very much different than from other
conventional fossil fuels, as long as com-
bustion occurs in a well-designed, well-
operated and well-maintained combustion
device. However, as with most solid fuel
combustors, an appropriate particulate
control device would likely be needed in
order to obtain an operating permit in
most jurisdictions in the U.S.
Test data from 22 industrial facilities
that have used TDF are presented: 3
kilns (2 cement and 1 lime) and 19 boil-
ers (utility, pulp and paper, and general
industrial applications). All sources had
some type of particulate control. A sum-
mary of criteria emissions data from seven
utility boilers that have burned various
amounts of TDF in addition to their main
fuel supply is presented in Table 2. In
general, the results indicate that properly
designed existing solid fuel combustors
can supplement their normal fuels, which
typically consist of coal, wood, coke,
and various combinations thereof, with
10 to 20% TDF and still satisfy environ-
mental compliance emissions limits. Fur-
thermore, results from a dedicated tires-
to-energy (100% TDF) facility indicate
that it is possible to have emissions
much lower than produced by existing
solid-fuel-fired boilers (on a heat input
basis) with a specially designed combus-
tor and add-on controls.
Depending on the design of the combus-
tion device, some tire processing is usually
necessary before it is ready to be used as
a fuel. Processing includes dewiring and
shredding and/or other sizing techniques.
Some specially designed boilers and ce-
ment kilns have had their feed systems
designed to accept whole tires.
Conclusion
Air emissions have been documented
from open burning of scrap tires and from
TDF in well-designed combustors. Labo-
ratory and field studies have confirmed
that open burning produces toxic gases
that can represent significant acute and
chronic health hazards. However, field
studies have also confirmed that TDF can
be used successfully as a 10 -20% supple-
mentary fuel in properly designed solid-fuel
combustors with good combustion control
and add-on particulate controls, such as
electrostatic precipitators or fabric filters.
Furthermore, a dedicated tire-to-energy
facility specifically designed to burn TDF
as its only fuel has been demonstrated to
achieve emission rates much lower than
most solid fuel combustors.
No field data were available for well-
designed combustors with no add-on par-
ticulate controls. Laboratory testing of an
RKIS indicated that efficient combustion
of supplementary TDF can destroy many
volatile and semi-volatile air contaminants.
However, it is not likely that a solid fuel
combustor without add-on particulate con-
trols could satisfy air emission regulatory
requirements in the U.S.
No data were available for poorly de-
signed or primitive combustion devices
with no add-on controls. Air emissions
from these types of devices would de-
pend on design, fuel type, method of
feeding, and other parameters. There is
serious concern that emissions would
be more like those of an open tire fire
than a well-designed combustor; how-
ever, emissions testing would have to
be conducted to confirm this.
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Table 1. Target Compounds by Criteria
Target Compound
CA
Acenaphthene
Acenaphthylene
Arsenic
Barium
Benz(a)anthracene
Benzene
Benzo(a)pyrene
Benzo(b)fluoranthene
Benzyl chloride
Butadiene
Carbon Monoxide
Carbon Tetrachloride
Chloroform
Chromium
Chrysene
Coal Tar Pitch
Cumene
Dibenz(a,h)anthracene
1,2-Dichloropropane
Dibenz(a,h)anthracene
Ethylene Dichloride
Hexachloroethane
Hexane
Lead
Methylene Chloride
Nickel
Phenol
Styrene
Sulfur Dioxide
SulfuricAcid
Toluene (Methyl Benzene)
1,1,2-Trichloroethane
Trichloroethylene
Vanadium
Xylene, o
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
CA
TLV
RfC
Suspected or Confirmed Human Carcinogen.
Reported Value is 33% of Threshold Limit Value.
Inhalation Reference Concentration.
Criteria
TLV
Subchronic
RfC
Chronic
RfC
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
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Table 2. Summary of Criteria Pollutant Emission Data at Utilities Using TDF
Power Plant
Particulates (Total)
Sulfur Oxides
Nitrogen Oxides
Carbon Monoxide
Facility A
100% Tires
Facility B (Coal)
0% TDF
5% TDF
10% TDF
Facility C (Coal)
0% TDF
7% TDF
Facility D (Coal)
0% TDF
5% TDF
10% TDF
15% TDF
20% TDF
Facility E (Wood)
0% TDF
7% TDF
Facility F (Coal)
2% TDF
g/MJ
9.5 x1Q-7
0.09
0.0064
0.004
0.22
0.06
0.027
0.031
0.0242
0.035
0.0195
0.036
0.133
0.073
Ib/MMBTU
2.2 x 1 0-6
0.21
0.015
0.009
0.52
0.14
0.063
0.0717
0.0564
0.0815
0.0453
0.083
0.31
0.17
g/MJ
6.0 x10-6
0.606
0.774
0.658
0.49
0.37
2.28
2.46
2.46
2.35
2.3
0.009
0.032
2.49
Ib/MMBTU
1.4x10-5
1.41
1.8
1.53
1.14
0.87
5.3
5.73
5.71
5.47
5.34
0.021
0.074
5.78
g/MJ
4.2 x 1 0-5
0.34
0.25
0.13
0.34
0.39
0.258
0.219
0.188
0.191
0.166
0.009
0.054
NT
Ib/MMBTU
9.8x10-5
0.78
0.58
0.3
0.79
0.91
0.601
0.51
0.436
0.443
0.387
0.021
0.125
NT
g/MJ
3.1 x105
NT
NT
NT
0.65
3.12
NT
NT
NT
NT
NT
NT
NT
NT
Ib/MMBTU
7.2 x 1 0-5
NT
NT
NT
1.52
7.26
NT
NT
NT
NT
NT
NT
NT
NT
NT = Not tested or data not available.
Note: Above data taken directly from reference; no adjustment was made to significant digits.
J. Reisman is with E.H. Pechan & Associates, Inc., Rancho Cordova, CA 95742.
Paul M. Lemieux is the EPA Project Officer (see below).
The complete report, entitled "Air Emissions from Scrap Tire Combustion," (Order
No. PB98-111701; Cost: $28.00, subject to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Air Pollution Prevention and Control Division
National Risk Management Research Laboratory
U. S. Environmental Protection Agency
Research Triangle Park, NC 27711
United States
Environmental Protection Agency
Center for Environmental Research Information
Cincinnati, OH 45268
Official Business
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