Tires on fire: From toxic soup to an alternative source of energy
by Quamrul Haider
In Bangladesh and elsewhere, one of the weapons used by the guardians of democracy to achieve their goals is hartal (anti-government strike). To enforce hartals, their foot soldiers merrily hurl firebombs at packed buses and other vehicles, setting them alight and burning to death scores of innocent passengers. As the buses and humans burn, with them burn the tires. Setting up roadblocks with piles of burning tires is also a part of the hartal culture. But are the guardians aware of the health and environmental threat associated with burning tires under open sky?
A tire fire is really two types of fire burning simultaneously _ ordinary combustion and pyrolysis. While ordinary combustion takes place at the surface of the tires exposed to the air, pyrolysis slowly melts the unexposed part of the tires in the absence of oxygen at very high temperatures.
Tires are a diverse and complex mixture of hydrocarbons, metals and small quantities of chlorine. The process of pyrolysis breaks the tires down to their components _ petroleum, chlorine, and cancer-causing suspects styrene and butadiene. The chlorine content in tires leads to the creation of two extremely toxic chemicals _ dioxins and furans. In addition, a typical melted automobile tire would yield roughly two-thirds of a gallon of oil contaminated with carcinogenic benzene derivatives and a host of highly toxic metals used in the manufacture of tires. These metals do not incinerate; they get released into the atmosphere as particulates. Some of the metals, such as copper, iron, manganese, nickel and zinc, serve as catalysts for dioxin formation.
Burning tires has a four-fold impact on the environment and humans. First, and most obvious, is air pollution. The pollutants released during burning produce a toxic soup in the form of thick, black fumes which dissipate fairly rapidly into the lower atmosphere. Furthermore, significant amounts of oil produced by melting tires will pollute the soil, surface water and ground water.
Second is the deleterious effect of the polluted air on human health. The mixtures of chemicals in the fume are cancer-causing, even if the individual chemicals are not. When inhaled, other than the usual _ coughing, sore throat and eye irritation _ the particulates in the fume settle deep in the lungs thereby causing serious respiratory problems in children and adults alike. Research shows that frequent exposure to the particulates cause excess mortality and hospitalizations for heart disease and cancer in children.
Dioxins and furans are among the most hazardous chemicals known. Indeed, studies have shown that extremely tiny doses of these toxins have the potential to produce a range of serious health problems, including infertility, learning disabilities, sexual reproductive disorders, birth defects, skin disorders, damage to the immune and endocrine systems, liver problems, disruption of hormones and certain types of cancer.
Third, trying to control and extinguish fire in a large pile of tires is similar to fighting forest fires. Using water and/or foam is often futile. Water will at best prevent adjacent, unburned tires from igniting. The best option is to smother the fire by cement dust, dirt or sand and gravel.
Fourth, the least obvious consequence of a tire fire, the oil spill, is also its most serious and persistent problem. Twenty million burning tires will add up to a potential spill of about 13 million gallons of oil, if all the tires were to pyrolyze. To appreciate the magnitude of the problem, compare this to the environmental havoc caused by 11 million gallons of crude oil spilled by Exxon Valdez into Prince William Sound off the coast of Alaska in1989.
Cleanup of a tire fire site can be time consuming and prohibitively expensive. Contaminated soil has to be removed, contaminated water used to douse the fire has to be pumped and treated, monitoring wells have to be installed, and leachate collection and treatment systems have to be put in place.
Tires are difficult to dispose of because they are not biodegradable. Most of them are dumped somewhere, usually at landfills, where they will accumulate rainwater giving rise to stagnant pools of water, ideal breeding grounds for dengue mosquitoes. They will also make cozy homes for vermin and other undesirable pests. More importantly, discarded tires could be a seemingly endless reserve for the pro-hartal pickets.
Although green is usually not the colour most people would associate with burning tires, yet a more promising use of discarded tires comes from precisely the quality that makes them so hazardous _ their fuel value. Approximately two billion gallons of oil are locked in the rubbery carcasses of three billion tires discarded annually worldwide. Technology to extract oil from discarded tires without producing toxic emissions has been successfully developed and perfected.
There are many advantages of tire derived fuel (TDF) over fossil fuels. First and foremost, TDF is less expensive than fossil fuels because the raw material is a scrap. Tires produce the same amount of energy as oil but 25 percent more than coal. Compared to coal, TDF emits lesser amounts of oxides of nitrogen that are responsible for ground-level smog and acid rain. The ash residues from TDF may contain lower heavy metals content than some coals. Studies show that one million tires used as fuel in place of coal would reduce carbon dioxide emissions by 19.5 percent. Consequently, the use of TDF is considered a viable alternative to the use of fossil fuels.
Our love affair with the automobile isnt going to end anytime soon. According to the 2009 World Bank data, there are three vehicles (motorcycles excluded) per one thousand people in Bangladesh. With a population of at least 155 million, thats a lot of tires and more than a million gallons of hidden oil that could be extracted to produce electricity for the energy-starved nation.
So, stop using tires as weapons to enforce hartals. Instead, turn them into plowshares.
The writer is Professor of Physics at Fordham University, New York.
Photos: Files
