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What is "Tire Derived Fuel" and why is it dangerous?
As of 2003, about 290 million tires are discarded in the U.S. every year (roughly one per person). Nearly 45% of these scrap tires (130 million) are used as "Tire Derived Fuel" (TDF), which often involves burning the (usually shredded) tires alongside conventional fuels like coal (usually no more than 10-25% TDF is used when co-firing with coal). At the end of 2003, 89 U.S. facilities burned TDF on a regular basis, about half of which (43) are cement kilns with the rest being pulp/paper mills (17), coal-fired power plants (13), and other industrial boilers or waste incinerators (15). Only two dedicated tire incinerators are currently operating in the U.S. (Exeter in Sterling, CT and a smaller one in Ford Heights, IL). Another used to operate in Westley, CA but closed after a major fire. Another was proposed for Preston, MN, but was stopped in 2005. Currently, a giant (800 ton/day) tire incinerator is planned for Erie, PA. The number of facilities burning TDF is increasing. More cement kilns are beginning to use TDF and electric arc furnaces (EAFs) are starting to burn tires.1
Tire manufacturers, Tire Derived Fuel producers (tire shredders) and TDF users (burners) and government agencies promote burning TDF as a solution to the dire problem of waste tires. What they fail to mention in their promotional materials is that tire incineration under any circumstance creates pollution that makes the air dangerous to breathe.
It is common knowledge that burning tires in the open is extremely harmful to human health and the natural environment. The fumes emitted are packed with the many toxic chemicals that tires contain (including volatile organic compounds such as benzene, metals such as lead, polycyclic aromatic hydrocarbons such as benzo(a)pyrene, and synthetic rubber components such as butadiene and styrene). Additionally, the chlorine content in tires leads to the creation of dioxins and furans (which are extremely toxic chemicals) when tires are burned.
Yet, users of Tire Derived Fuel are confident that their machinery (which usually is not even designed for burning tires) and the combination of tires with traditional fuels (like coal) will render the incineration process harmless. According to the Auburndale Recycling Center, Inc, a Wisconsin-based for-profit corporation that sells tire chips for incineration, "Most individuals are confused about the difference between a "burning tire" which emits black smoke and damages the environment, and the use of scrap tires as a fuel source for power companies."
Citing government approval of Tire Derived Fuels, Auburndale ignores the scathing critiques that reputable scientists like Dr. Neil Carman and Dr. Seymour I. Schwartz have written in response to the "junk science" and stacked statistics behind the rubber-stamp approval of tire derived fuel. These experts, along with other scientists, ecologists, and public interest groups, have uncovered the truth behind the propaganda -- that tire incineration by any method is NOT safe.
Problems with Test Data
Supporters of Tire Derived Fuel claim that substituting 10-25% TDF for coal or natural gas in incinerators/boilers does not significantly alter the chemical content of the emissions. To justify their claims, TDF advocates point to government studies like the Environmental Protection Agency's 1997 report "Air Emissions from Scrap Tire Combustion" 2, which states that:
However, there are many problems with this. First of all, the test data is not an accurate measure of the actual day-to-day emissions of a given plant. As reported by Greenpeace, "Trial burns are generally considered a poor indicator of operation on a daily basis: during trial burns when regulatory authorization is at stake and government officials are at the site, variables such as wastefeed, temperature, oxygen flow, and pollution control device efficiency are carefully maintained to optimize performance. On a day-to-day basis, emissions may be considerably higher." 3 Dr. Neil Carman confirms this:
"But during stack tests of TDF, cement kilns will do several things to make emissions and combustion look good-to-decent for such facilities:
Apart from this it should be kept in mind that facilities naturally wear down with use. It is unlikely that any incinerator could continuously operate for a long period of time at the same level of performance as it did during the initial testing period.
Another disturbing aspect of tire incineration, particularly in cement kilns, is the occurrence of serious "upsets." As Dr. Carman explains,
Aside from all of this, it should be noted that a number of tests conducted by or on behalf of the Tire Derived Fuel industry and its supporters have been notoriously shoddy in terms of scientific method, vision, language, and conclusions. As mentioned earlier, such reports have been repeatedly blasted by a number of reputable scientists and organizations. These experts raise very serious concerns and cast a shadow of doubt over much of the "official science" behind tire incineration.
Tire Incineration in Paper Mills
The aforementioned EPA test was not even performed on an actual operating plant but rather on a scaled-down simulator. Such devices are obviously bound to be more stable than large industrial incinerators that are used on a daily basis over a period of years. Importantly, the EPA simulator isn't even designed to represent the type of incinerators typically used in paper mills, which often use Tire Derived Fuel.
Tire incineration in paper mills poses special concerns. The North Carolina Division of Pollution Prevention and Environmental Assistance, a government agency that is generally uncritical of tire incineration as a whole, still has this to say about tire incineration in paper mills:
What we don't know can hurt us.
Another major concern about Tire Derived Fuel is the enormous lack of knowledge about a wide range of potential dangers. This has been painfully apparent even in the pro-TDF reports. What follows is a selection of quotes from the California Air Pollution Control Officers Association (CAPCOA) report. The quotes were originally isolated for analysis by Dr. Seymour I. Schwartz, a professor of environmental science and policy at University of California at Davis.
In his letter to the California Integrated Waste Management Board, Dr. Schwartz also notes that "Virtually nothing is known about the dose-response functions for important categories of health effects, particularly disruptions to the hormone systems of humans, which could produce life long damage in developing infants. Also, virtually nothing is known about the health effects caused by combinations of toxic chemicals that are emitted when burning tires. Without such scientific knowledge, and because some toxic pollutants increase from burning tires, there is no scientific basis for the Board to conclude that burning waste tires in cement kilns is safe." 6
Toxic Pollution from Burning Tire Derived Fuel
So far we have looked at the disturbing unreliability of the existing pro-TDF studies, the special problems posed by burning tires in paper mill boilers, and the alarming lack of knowledge about a wide range of potential dangers that tire incineration may pose to the health and safety of our communities and the environment. This next section will take a closer look at the existing record and find that even based on the limited knowledge that exists, it is already clearly evident that tire incineration is dangerous.
Below is a breakdown of some of the condemning test data, organized by chemical groupings:
Dioxins and Furans
Dioxins are highly toxic and cause serious health problems, including infertility, learning disabilities, endometriosis, sexual reproductive disorders, birth defects, damage to the immune system and cancer. Dioxin is fat-soluble and once it's released into the outside environment, it readily climbs up the food chain, causing average meat and dairy-product consumers to get over 95% of their dioxin exposure through their diet.7 In fact, according to the World Health Organization, the most toxic forms of dioxin are considered to be the most carcinogenic (cancer causing) substances known to science.8 Even a very tiny quantity of dioxins can be dangerous. According to an EPA's Dioxin Reassessment, exposure to dioxins, even at minute levels, poses cancer risks and health concerns wider than previously suspected.9 Deceptively small dioxin emission rates (for example, 0.0236 grams/year for the now-closed tire incinerator in Modesto, California) conceal the harmfulness of these deadly chemicals. Based on the EPA's "risk specific dose" criteria, 0.0236 grams/year is the equivalent of a lifetime maximum acceptable dose for over two million people.3
Dioxins and furans are chemicals that are created by burning chlorine (or other halogens, like fluorine or bromine) in the presence of hydrocarbons and oxygen. Hydrocarbons (the bulk of the TDF itself, as well as coal, wood or gas it's co-fired with) and oxygen (from the air) are readily available when TDF is incinerated. Dioxins and furans are produced by tire incineration because tires contain chlorine. The manufacture of synthetic rubber for tires uses up to 25% aromatic extender oils, a toxic waste product of oil refining which can contain chlorine. Another possible source of chlorine in tires is through the use of the "salt-bath" vulcanization process, a process where the rubber is made more elastic.10 One major source of chlorine in tires is their halogenated butyl rubber liners. The addition of chlorine or bromine (the latter used more widely for truck tires) to the butyl rubber gives liners the air-impermeability required to maintain proper tire inflation.11 A content comparison by the state of California indicates that tires may contain as much as two to five times the chlorine level of western coal, with an average of 0.04 weight percent for western coal, and a range of 0.07 to 0.2 weight percent for tires.12. The largest proponents of TDF burning (the Rubber Manufacturers Association) confirmed this on their own website, when they listed the chlorine content of tires as being 0.149 - 0.150 % by weight.13 An extensive EPA survey of the chemical composition of fuels burned in coal plants found chlorine levels in tires to be 2% higher (1,064 ppm average from 149 samples) than the national average for bituminous coal (1,043 ppm average from 27,352 samples) -- the most widely used type of coal, which also has the highest average concentration of chlorine of any coal type. Since chlorine levels in coal vary throughout the nation, it's possible that the chlorine content of tires could be far higher or lower than coal burned at any specific facility.14
Certain metals present in tires (such as copper, iron, manganese, nickel, sodium and zinc)10 serve as catalysts for dioxin formation, providing a surface on which dioxins can readily form during and after the combustion process.15 The greater chlorine content of tires combined with the presence of these metal catalysts is the likely reason why burning tires with coal has been found to produce more dioxin pollution than burning only coal. Increased dioxin emissions have been found in most of the tests conducted where dioxin emissions at facilities burning 100% coal were compared to those co-firing 4-30% TDF.
Other Chorine-Based Pollutants
Among the halocarbons emitted during tests at TDF incinerators are PCBs, dichlorobenzene, trichlorobenzene, tetrachlorobenzene, hexachlorobenzene, chlorophenol, and dichlorophenol, which are all highly toxic compounds and are all either proven or suspected to be carcinogenic.31
Non-Chlorinated Hydrocarbon Pollutants
Tires also contain petrochemical feedstocks, including butadiene and styrene (the latter being a benzene derivative). The chemicals are both carcinogens. Other carcinogenic benzene derivatives, such as M, P and O-Xylenes are sometimes found in tire derived fuel as well.4
Polycyclic Aromatic Hydrocarbons (also known as Polynuclear Aromatic Hydrocarbons) is a name applied to over 100 chemicals containing multiple benzene rings that are difficult to break down. PAHs are known to cause cancer in rats and "may reasonably be expected to be carcinogens" in humans as well, according to the Department of Health and Human Services.4,32 Approximately 25% of tire contents are PAHs.4 Tire incineration tests have shown increases (compared to only burning coal) in PAHs of between 88% and 23,938% (most are in the several hundreds or thousands), although one test found a decrease of 68%.6,16,17,25,26,28
Tires contain around 20 different metals, none of which can be destroyed by burning them, since they're elements. Metals known to be in tires include aluminum, antimony, arsenic, barium, beryllium, cadmium, chromium, cobalt, copper, iron, lead, magnesium, manganese, mercury, nickel, selenium, silicon, tin, titanium and zinc.2,13,33,34 Zinc is present in particularly high amounts, since zinc oxide is used in the vucanization process. Most of them, including arsenic, lead, mercury, and chromium VI, are quite toxic to humans and can also wreak ecological havoc on aquatic wildlife if even a small quantity finds its way into a body of water. Some metals, like mercury, can accumulate in wildlife. A 2002 test of emissions from a Colorado cement kiln burning TDF with coal found an 8% increase in mercury when TDF was used, leading to nearly 5 pounds of additional mercury pollution per year -- enough to contaminate about 2,000 twenty-acre lakes to the point where the fish cannot be eaten due to methylmercury bioaccumulation.
This evidence clearly demonstrates that tire incineration releases a variety of toxic pollutants into the air, posing a dangerous and potentially deadly threat to human health and the environment.
Alternatives to Tire Incineration