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

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