United States
Environmental Protection
Agency
Air and Energy Engineering
Research Laboratory
Research Triangle Park NC 27711
Research and Development
EPA/600/S2-89/054 Jan. 1990
4>EPA Project Summary
Characterization of
Emissions from the Simulated
Open Burning of Scrap Tires
Jeffrey V. Ryan
Discarded automobile tires have
become a serious health concern,
largely because the growing number
of stockpile fires has focused
attention on the potentially harmful
products of incomplete combustion
(PICs) emitted into the atmosphere
from burning scrap tires. This small-
scale combustion study was
designed to collect, identify, and
quantify products emitted during the
simulated open combustion of scrap
tires. Fixed combustion gas, volatile
and semi-volatile organic, participate,
and airborne metals data were
collected under two burn conditions
that varied by the size of tire material.
Burn rates, varied by material size,
were used to estimate potential
emissions of identified products.
Total estimated emissions of semi-
volatile organics ranged from 10 to 50
g/kg of tire material burned. Mono
and poly aromatic hydrocarbons were
the main emission products
identified. Benzo(a)pyrene (BAP) In
participate extracts is of particular
concern because it is a known
carcinogen. The presence of zinc in
gaseous particulate collection was
also verified and quantified. Several
trends were evaluated relating
emission products with burn rates.
This Project Summary was
developed by EPA's Air and Energy
Engineering Research Laboratory,
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
Approximately 240 million vehicle tires
are discarded annually. Although viable
methods for reclamation exist, less than
25% are re-used or re-processed. The
remaining 170 million scrap tires are
discarded in landfills, above-ground
stockpiles, or illegal dumps.
Many landfills are refusing to accept
tires because they present not only
disposal but also health-related problems.
After burial, tires often float to the surface
and become partially filled with water.
Cutting the tire in half or in pieces can
reduce this tendency. It is very costly to
cut or shred tires into a condition suitable
for landfill; in any event, many sites lack
the necessary equipment. Steel-belted
radials which comprise the majority of the
nation's discarded tires, are particularly
difficult to cut and/or shred. Often, they
are simply stockpiled or illegally dumped.
These stockpiles and dumps can become
a breeding ground for many insects,
especially mosquitos, where water
collects in the tires and creates an ideal
breeding habitat. The introduction and
spread of several mosquito species has
been directly attributed to the presence
of refuse tires.
The growing incidence of tire fires
creates another potential health hazard.
More tire stockpiles and illegal dumps
are coming into existence, and with them
the occurrence of tire fires. These fires,
often started by arson, generate a huge
amount of heat making them extremely
difficult to extinguish. Some of these tire
fires have continued for months. For
example, the Rhinehart tire fire in
Winchester, Virginia, burned for nearly 9
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months, potentially exuding large
quantities of harmful compounds.
The EPA's Control Technology Center
(CTC) received numerous requests from
state and local agencies nationwide for
information pertaining to tire fires and
their effects. Because very little
information on the open burning of scrap
tires was available, the steering
committee felt a study investigating this
potential problem was warranted. Guided
by the Combustion Research Branch
(CRB) of EPA's Air and Energy
Engineering Research Laboratory
(AEERL), Acurex conducted a study
which identified and quantified organic
and inorganic emission products
produced during the simulated open
combustion of scrap tires.
Experimental Approach
The project consisted of a parametric
study to collect organic and inorganic
emissions from the simulated open
combustion of scrap tires. Small
quantities (10-20 Ib, 4.5-9.0 kg) of scrap-
tire material were burned under two
controlled conditions determined by the
size of the material. The conditions were
evaluated in duplicate on successive
days. An existing burn hut used for
similar projects was modified to
accommodate this task. A separate
outbuilding housed the required organic
and particulate sampling equipment.
CRB's Hazardous Air Pollutants Mobile
Laboratory (HAPML) was used to monitor
fixed combustion gases. Organics were
collected using the Volatile Organic
Sampling Train (VOST) and a semi-
volatile collection system using XAD-2
and particulate filters. Particulate was
also collected to assess airborne metals.
The organic constituents were analyzed
both qualitatively and quantitatively by
GC/MS, GC/FID, HPLC, and gravimetric
methodologies.
Representative scrap truck and
passenger car bias ply tires were
obtained from local tire dealers. Bias ply
tires were chosen due to difficulties
encountered attempting to cut steel
belted radial tires. The tires were cut into
two sizes in order to vary initial surface
area and therefore combustion rate. The
"CHUNK" condition represented a
quarter to a sixth of an entire tire, while
tire material cut into 5.08 cm (2 in.)
squares represented the "SHRED"
condition. Tire material approximating the
equivalent weight of two passenger car
tires (30 Ibs, 13.6 kg) was placed in a
small burn pit and combusted. A platform
scale under the burn pit monitored the
weight of tire material combusted. An air
system designed to deliver nominally
1,200 cfm (34.0 ms/min) was used to
simulate rapid dilution and cooling of
combustion products.
An insulated duct transported the
gaseous sample to an adjacent sampling
shed for collection of volatile and semi-
volatile organics, particulate, and fixed
combustion gases. Common combustion
gases, 02, CO, C02, S02, and total
hydrocarbons (THC) were monitored
continuously throughout the burn period.
Volatile organics were collected using the
Volatile Organic Sampling Train (VOST).
Semi-volatile organics and particulate
were collected using applicable modified
sampling systems. During the sampling,
tire material weight differentials were
recorded to determine burn rates.
The VOST samples collected were
analyzed by gas chromatography/mass
spectrometry (GC/MS). Compounds were
identified through spectral library
searches and matching, along with
investigator interpretation. The identified
compounds were quantitated using the
system response to toluene. Individual
compound responses were not
determined. Semi-volatile organics were
collected on both particulate filters as
well as the XAD-2 organic sorbent
material. The organics were retrieved
from the collection media by soxhlet
extraction with dichloromethane. Both the
particulate extracts and the XAD-2
extracts were analyzed for total
chromatographable organics (TCO) and
GRAV—organic compounds with boiling
points of 100-300°C, and > 300°C,
respectively. The XAD-2 extracts were
analyzed by GC/MS to identify
compounds found in the TCO range.
Again, compounds were identified using
library spectral matching and investigator
interpretation. Identified compounds were
quantitated using the same response
used for TCO quantitation. Individual
identified compound responses were not
determined. The organic extracts were
also analyzed for polycyclic aromatic
hydrocarbons (PAHs). Separately
collected particulate matter was also
quantitated for specific metals common
in tire ash residues.
Data and Results
The size of tire material was varied to
change combustion conditions and gain
insight into the mechanisms governing
burn rate. Burn rates were calculated by
dividing the amount of tire material
burned over a given period by that time
in minutes and normalizing to a mass per
hour basis. A higher burn rate was
observed during CHUNK tests than in
SHRED tests. Roughly double the
amount of tire material was combusted
during the same time. In both burn
conditions, an initial high burn rate was
observed and led to a gradual leveling off
until the burn rate was steady.
Combustion gases were monitored
continuously throughout the test. High
emissions of CO, S02, and THC were
observed at high burn rates.
The identification of unknown volatile
organics using the MS proved to be
highly successful. More than 50
compounds were identified from the
VOST samples collected. Most of these
compounds are aliphatically, olefinically
or acetylenically substituted aromatics.
Cyclic and chained alkanes, alkenes and
dienes were also identified. Several
sulfonated and nitrogenated compounds
were also identified in samples.
Thiophene, substituted thiophenes,
isocyanobenzene and benzodiazine were
isolated in multiple samples. Following
quantitation of identified compounds,
average gaseous concentration and
emissions were estimated.Of particular
interest are the emission rate estimations.
The estimated emissions are based on
several variables and were obtained by
relating the amount of tire material
combusted during the sampling period
with the average gaseous concentration.
It was assumed that the dilution air added
to the burn hut was constant.
It is difficult to isolate consistent trends
in the types and amounts of specific
volatile organic compounds formed
during the combustion of scrap tires
under varied burn rates. A trend appears
that, as burn rate decreases, the amount
of organics potentially emitted tends to
increase with respect to the amount of
tire material combusted.
As with the volatile organic analyses,
the MS analysis of the XAD-2 extracts
identified the same types of compounds.
Table 1 lists the 60 compounds identified
and indicates that substituted mono and
poly aromatics were the predominant
products of incomplete combustion.
Table 2 presents the average gaseous
concentration and estimated emissions of
the quantitated identified compounds
from the four test conditions. The
estimated emissions of many compounds
increase with decreased burn rate. Table
3 summarizes the semi-volatile organic
emission data from the four test
conditions. The total organics from
respective boiling-point-based analyses
are presented for each component of the
sampling media. The estimated emis-
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Table 1. Compounds Identified by GC/MS from XAD-2 Extracts
Compound Identified
Formula
Compound Identified
Formula
Compound Identified
Formula
Methyl Benzene
Cyclopentanone
Dimethyl Cyclohexene
Ethenyl Cyclohexene
Ethyl Benzene
Dimethyl Benzene
Hexanenitrile
Ethynyl Benzene
Styrene
Nonane
Propenyl Cyclohexane
Methylethyl Benzene
Propyl Benzene
Benzaldehyde
Trimethyl Benzene
Phenol
Cyanobenzene
Propenyl Benzene
Methyl, Ethenyl Benzene
Methyl, Methylethyl Benzene
C7H8
CgH12
£-8^70
CgHg
CgH20
CgH,2
C7H60
CgH72
C6H60
C7H5N
Limonene
Dihydro Indene
Hydroxy Benzaldehyde
Indene
Tetramethyl Benzene
Ethyl, Dimethyl Benzene
Methyl Phenol
Methyl Benzaldehyde
Methyl, (Methylethyl) Benzene
Propenyl, Methyl Benzene
Undecane
(Dimethylpropyl) Benzene
Dimethyl, (Methylethyl) Benzene
Butynyl Benzene
Methyl Indene
Azulene
Naphthalene
Benzo[b]th!ophene
Benzisothiazole
Hexahydro Azepinone
C7H602
CgHg
C7H80
CgHaO
C,jH24
CgHgS
C7H5NS
CgH^NO
Dihydro, Methyl Naphthalene
Butyl,Trimethyl Benzene
Methyl Naphthalene
Biphenyl
Dimethyl Naphthalene
Dihdro Acenaphthalene
Acenaphthalene
(Dimethyl, Hexenyl), Methyl Benzene
Pentadecane
1,1' Biphenyl,Methyl
Isocyano Naphthalene
Naphthalenecarboxaldehyde
Propenyl Naphthalene
Trimethyl Naphthalene
1H Fluorene
Dimethyl Biphenyl
Dibenzothiophene
Phenanthrene
9H Fluorene, Methylene
Phenylnaphthalene
C12H12
C12H10
C12Hg
C13H12
C,,H7/V
C,,H80
C12H10S
C14H-,Q
C 14^10
sions data presented show that 12-50 g
of semi-volatile organics can be emitted
for every kilogram of tire burned. A trend
does seem evident when relating the
amount of organics emitted to burn rates.
It appears that, as burn rate decreases,
the amount of organics emitted,
particularly in the TCO range, increases.
There did not seem to be any significant
variation in GRAV range organic
emissions when related to burn rate. A
PAH analysis was performed on the XAD-
2 and particulate filter extractions. Of
particular importance is the presence of
benzo(a)pyrene (BAP) in all particulate
portions. BAP is a reported carcinogen
and a highly scrutinized compound when
evaluating combustion processes.
A separate particulate collection
system was operated to verify and
quantitate the presence of metals
collected from ambient emissions. The
results of the analyses were marginal for
many of the targeted metals. Many of the
results were at or near instrument
detection levels. It did seem evident that
lead and particularly zinc were found to
be collected from gaseous emissions.
Conclusions
The primary goal of this project was to
characterize potentially harmful
emissions from the simulated open
burning of scrap tires. The simulation was
necessarily crude, because it woujd be
extremely difficult to match the burning of
the equivalent of two tires with a 6 million
tire, full-scale, stockpile fire. Neverthe-
less, the study allowed the investigators
to identify and measure gaseous
emissions and directly relate this
information to a mass burn rate. This task
was accomplished by accurately
measuring dilution volumes, sample
volumes, and weights of tire material
combusted.
It is not known how well the concentra-
tions obtained from this study represent
those at an actual tire fire. The dilution air
added to the burn hut was used not only
to control known volumes introduced, but
also to simulate ambient condition's.The
same types of compounds identified
during this study are probably emitted
during an actual fire, but whether the
average gaseous concentrations and
estimated emissions are comparable is
uncertain. A comparison with limited data
collected at the Winchester, Virginia, fire
by NIOSH, indicates that reasonable
agreement exists within several
measurement areas. Many of the same
compounds were identified in actual
plume samples. Particularly good
agreement exists in PAH plume
measurements. NIOSH reported ambient
concentrations of total PAHs are gener-
ally within the same order of magnitude
as average gaseous concentrations
obtained during testing. Measurements of
CO and metals also indicate similar
agreement. Both the lead and zinc
measurements show similar values both
in concentration and relative
concentration between the two metals. It
may be reasonable to assume that the
estimates obtained during this study may
be within an order of magnitude of
emissions realized from actual stock-pile
fires.
The results of this study pose a variety
of pertinent topics and questions
regarding tire fires. How far does the
particulate from a stockpile fire carry?
Are evacuation procedures for
populations near stockpile fires
sufficient? Is it good policy to continue to
let tire fires burn themselves out? A
greater potential for harmful organic
emissions seems to exist at lower burn
rates; thus a smoldering tire fire may be
more harmful than one that is burning out
of control. The identification of significant
quantities of benzo(a)pyrene in the
particulate extracts warrants serious
concern. High emissions of other noxious
compounds, particularly benzene, with
concentrations often exceeding 1 ppm,
suggest that uncontrolled scrap tire
combustion poses significant health risks.
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Table 2, Quantitation and Emission Summary of Compounds Identified in
Day 1 CHUNK Condition
Vol Samp = 12,98 m3
Burn Rate =2.3 kg/h
Compound Identified
Methyl Benzene
Ethyl Benzene
Dimethyl Benzene
Ethynyl Benzene
Styrene
Methylethyl Benzene
Propyl Benzene
Benzatdehyde
Trimethyl Benzene
Phenol
Cyanobenzene
Trimethyl Benzene
Methyl, Methylethyl Benzene
Limonene
Indene
Tetramethyl Benzene
Ethyl, Dimethyl Benzene
Methyl Benzatdehyde
Ethyl, DimeVtyl Benzene
Propenyl, Methyl Benzene
Methyl Indene
Methyl Indene
Naphthalene
Benzo[B]thiophene
Benzisothiazole
Hexahydro Azepinone
2-Methyl Naphthalene
1 -Methyl Naphthalene
Biphenyl
Dimethyl Naphthalene
Acenaphthalene
1,1' Biphenyl, Methyl
Isocyano Naphthalene
Propenyl Naphthalene
Trimethyl Naphthalene
1H Fluorene
Phenanthrene
Totals
Average
Gaseous
Concentra-
tion (mg/m3)
0,716
0.074
0.000
0,185
0.419
0,000
0.000
0.111
0.000
0.190
0.095
0.127
0.000
0.000
0.325
0.000
0,000
0,000
0.000
0.000
0.000
0.000
1,230
0.099
0.000
0.000
0.164
0.124
0.083
0.000
0.390
0.025
0.021
0.053
0,000
0.087
0,152
4,670
Estimated
Emissions
(mg/kg TIRE)
634.8
65.8
0.0
163.6
371.5
0,0
0.0
98.6
0.0
168.3
84.3
112.8
0.0
0.0
288.5
0.0
0.0
0.0
0.0
0.0
0.0
0.0
1,090.4
87.6
0.0
0.0
145.6
109.9
73.5
0.0
345.6
22,1
18.7
46.6
0.0
76,9
135.0
4,140.4
XAD-2 Extracts' •*
Day 2 CHUNK Condition
Vcrf Samp = 12.76 mg/m3
Burn Rate = 1.7 kg/h
Average
Gaseous
Concentra-
tion (mg/m3)
1.500
0.289
0.513
0.325
0.795
0.081
0.000
0.327
0.000
0.473
0.305
0.256
0.215
0.094
0.602
0.000
0,000
0,000
0.000
0.000
0.188
0.000
1.931
0,000
0.000
0.126
0.466
0.463
0.290
0.069
0.773
0.000
0.000
0.000
0.000
0.288
0.194
12,672.8
Estimated
Emissions
(mg/kg TIRE)
1,799.5
347.1
615.3
390.0
953.3
97.4
0.0
392.1
0.0
566.9
365.5
307.6
258.1
113.2
722.0
0.0
0.0
0.0
0.0
0.0
225.6
0.0
2,315.9
0.0
0.0
151.4
559.4
555.3
347.8
83.0
927.0
0.0
00
0.0
0.0
346.0
233.2
9.367
Day 1 SHRED Condition
Vol Samp = 13.77 mg/m3
Burn Rate = 1.1 kg/h
Average
Gaseous
Concentra-
tion (mg/m3)
0.731
0.192
0.554
0.078
0.332
0.142
0.136
0.343
0.156
0.360
0.307
0.195
0.926
1.402
0.156
0.094
0.000
0,089
0.162
0.537
0.223
0.000
0.516
0.000
0.179
0.345
0.202
0.122
0.180
0.183
0.217
0.000
0.000
0.000
0.169
0,141
0.000
17,362.2
Estimated
Emissions
(mg/kg TIRE)
1,354.9
355.0
1,026.1
144.2
614.6
263.5
251.2
635.3
289.9
667.2
569,3
361.5
1,716.1
2,599.2
289.9
174.8
0.0
164.7
300.0
996,2
413.7
0.0
957.2
0.0
330.9
638.9
373.9
225.7
333.6
338.8
402.2
0.0
0.0
0.0
312.9
260.8
0.0
9.633
Day 2 SHRED Condition
Vol Samp = 12.43 mg/m3
Burn Rate = 1.3 kg/h
Average
Gaseous
Concentra-
tion (mg/m3)
0.911
0.203
0.532
0.150
0.433
0.122
0.118
0.000
0.351
0.470
0.292
0.199
0.704
1.316
0.251
0.000
0.154
0.000
0.000
0.000
0.114
0.132
0.843
0.000
0.000
0.555
0.313
0.146
0.208
0.000
0.430
0.000
0.000
0.000
0.203
0.230
0.251
15,108.7
Estimated
Emissions
(mg/kg TIRE)
1,429,0
318.3
834.2
235,2
679.8
191.0
184.6
0.0
549.9
736.8
458.6
312.2
1,104.9
2,064.5
393.9
0.0
241,8
0.0
0.0
0.0
179.2
207,3
1,322.8
0.0
0,0
869.9
490.5
229,7
326.3
0.0
673,8
0.0
0.0
0.0
319.1
361.2
394.2
10,566
1 Concentrations determined using system response to TCO calibration mix.
2 Average gaseous concentrations and estimated emissions are based on controlled dilution of pit emissions. It is not known how well this dilution
represents ambient air exchange under actual conditions.
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Table 3. Organic Emission Summary
Average Gaseous
Concentration
Sample Portion
Sample
Time (min)
Weight
Change (kg)
Avg
Rate
Bum
(kglh)
Volume
Samp (m3)
TCO
(mg/m3)
GRAV
(mglm3)
Estimated Emissions
TCO
(mglkg
GRAV
TIRE)
XAD-2
Filter 1
Filter 2
Filter Total
KAD-2
Filter 1
Filter 2
Filter Total
XAO-2
Filter
140
11
129
140
152
42
110
152
182
182
5.4
1.7
3.7
5.4
4.3
2.4
1.8
4.3
3.2
3.2
2,3
9,4
1.7
2.3
1.7
3.5
1.0
1.7
1.1
1,1
Day 1 CHUNK Condition
12.98
0.93
12.05
12.98
6.067
0.043
0.066
0.065
Day 2 CHUNK Condition
12.78
3.3
9.45
12.76
11.398
0,018
0.53
0.398
Day 1 SHRED Condition
13.77
13.77
20.658
0.141
Day 2 SHRED Condition
0.698
33.634
•J.S23
6,888
Total
0,749
18.498
10.219
12.359
Total
0.89
6.822
Total
5,379
9
79
58
5,436
13,671
11
1,081
477
14,148
38,292
261
38,554
619
7,298
5,785
6,106
6,725
898
10,776
20,837
14,824
15,722
1,SSO
12,646
14,295
12,161
25,870
52,849
XAD-2
Filter
183
183
4.0
4.0
1.3
1.3
12.43
12.43
15.65
0,173
1,099
8.77?
Total
24,546
271
24,819
1,724
13,757
15,481
40,299
Results from the airborne metals
portion of the study were inconclusive.
Maximum values were presented, often
based on detection levels. Emissions of
lead and zinc may reach significant
quantities. Reported chemical analysis of
tire ash residues reveals that zinc
comprises nearly 50 percent of the total
residue. Evidently, the other metals
known to be contained in tires remain in
the ash residue. Although no attempt was
made to analyze ash residue, significant
quantities of metals present in the ash
could potentially be leached out into
groundwater systems, posing another
major problem.
The values obtained by the on-line
analyzers for normal combustion gases
showed that as burn rate increased, the
amount of CO, SO2, and unburned
hydrocarbons also increased. High burn
rate conditions were not fully evaluated,
so greater quantities of these gases,
particularly SOg, may be emitted during a
stockpile fire. Tires contain a significant
amount of sulfur, so high emissions of
SOa, while likely only a minor contributor
to the acid rain problem, could have
significant local consequences.
This study was designed to identify the
potential chemical hazards from tire fires
on a small-scale, simulation basis. The
study reveals the potential for the
emission of great amounts of organic
compounds, primarily aromatics, some of
which may be extremely harmful.
Although the estimates of average
gaseous concentrations and emissions
are crude, the trends presented for burn
rate may be helpful in directing further
research and control efforts. That the
"SHRED" condition resulted in a lower
burn rate indicates that the gaps between
the tire material provide the major avenue
of oxygen transport. Oxygen transport
appears to be a major if not the con-
trolling mechanism for sustaining the
combustion process. This fact could have
advantageous implications for those
attempting to combat tire fires. It may be
possible to fill the gaps between tires
with a foam inhibitor, potentially suffo-
cating the fire from within.
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J. V. Ryan is with Acurex Corp., Research Triangle Park, NC 27709.
Paul lit Lemieux is the EPA Project Officer (see below).
The complete report, entitled "Characterization of Emissions from the Simulated
Open Burning of Scrap Tires," (Order No. PB 90-126 0041 AS; Cost: $17.00,
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 and Energy Engineering Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
United States Center for Environmental Research
Environmental Protection Information
Agency Cincinnati OH 45268
Official Business
Penalty for Private Use $300
EPA/600/S2-89/054
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