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 ------- 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. ------- 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 ------- 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 Penalty for Private Use $300 BULK RATE POSTAGE & FEES PAID EPA PERMIT No. G-35 EPA/600/SR-97/115 ------- |