October 17th, 2014

Burning rubber: the problem of tyre-fuelled kilns

5 minute read

by Catherine Hansen

 

The decorative arts of ceramics and pottery have a long and honoured tradition. Whilst we cannot know exactly when the first kilns were built and the first clay fired, some very early examples of pottery have been unearthed in the Middle East, with the most ancient pottery fragments found at Catal Huyuk in Turkey dating from as long ago as 6500BC.

Since then, the development of kilns has occurred in several stages over time: key changes have included building a firing chamber around the pots and adding chimney stacks to better control air flow. More recently, modern technology has brought highly efficient electric, natural gas, and propane fuelled kilns. Unfortunately, these options come with a high price tag when it comes to the industrial scale production of ceramics and other fired products. Thus, much of the ceramic industry’s firing needs, especially in the developing world, are met through cheaper alternatives such as fuelling kilns by burning tyres and other potentially polluting materials.

 

This wheel’s on fire

Whilst some areas of the world such as India are grappling with the harmful effects of coal fired kilns, in Morocco and other Northern African countries tyres and other rubber materials are being used as a primary energy source for kilns giving rise to still bigger problems.

Unfortunately tyres provide a cheap and abundant source of energy. Even where they are not the primary energy source, scrap tyres are often used as a supplement fuels such as coal or wood because of their high heating value. Typically, each pound of scrap tyre rubber burned provides 15,000 BTUs of energy and a single tyre can burn for up to 50 minutes, a yield around 25% greater than from coal.

However, the black fumes emitted from burning tyres contain heavy metals and other harmful pollutants that linger in the air and can lead to acute to chronic health hazards. According to the U.S. Environmental Protection Agency (EPA):

Open tyre fire emissions include ‘criteria’ pollutants, such as particulates, carbon monoxide (CO), sulphur oxides (SOx), oxides of nitrogen (NOx), and volatile organic compounds (VOCs). They also include ‘non-criteria’ hazardous air pollutants (HAPs), such as polynuclear aromatic hydrocarbons (PAHs), dioxins, furans, hydrogen chloride, benzene, polychlorinated biphenyls (PCBs); and metals such as arsenic, cadmium, nickel, zinc, mercury, chromium, and vanadium.”

Both criteria and non-criteria pollutants can cause significant short and long term health effects. The EPA again tells us:

“depending on the length and degree of exposure, these health effects could include irritation of the skin, eyes, and mucous membranes, respiratory effects, central nervous system depression, and cancer”,

and suggests that any unprotected exposure to these emissions should be avoided. Furthermore, uncontrolled tyre burning has been proven to be 16 times more mutagenic – capable of inducing genetic mutation – than traditional residential wood combustion in a fireplace, and “13,000 times more mutagenic than coal-fired utility emissions with good combustion efficiency and add-on controls”.

Especially troubling is the exposure to which children and other at-risk groups such as the elderly, asthmatics, and immune suppressed individuals living within these communities are inadvertently being subjected. Pollutants inhaled by nursing women can be transferred to their babies through the fat in breast milk.

 

Kiln

All too often, where there’s smoke there’s tyres: using tyres as fuel harms both human health and the environment. Photograph by Eastman Johnson

 

Scrap tyres may present a cheap way to fuel kilns, but should not take precedence over public health. Unfortunately in those small villages and other underdeveloped areas where tyre-burning kilns sustain much of the local economy, current practices make widespread and long-term exposure to toxins inevitable.

 

Earth, wind and tyre

In addition to the negative effects the fumes emitted by tyre burning have on human health, the practice also gives rise to water and soil pollution.

According to the EPA: “for every million tyres consumed by fire, about 55,000 gallons of runoff oil can pollute the environment unless contained and collected.” If uncontained, this runoff can then be carried away by rainwater to local water sources contaminating them. The New Zealand Ministry for the Environment has stated that the remaining residue: “can cause two types of pollution; these are immediate pollution by liquid decomposition products penetrating soil, and gradual pollution from leaching of ash and unburned residues following rainfall or other water entry”.

While the burning of tyres is not considered to be recycling, there has been some argument around whether it is worse to landfill tyres or combust them to recover energy. While even in the United States the EPA recognises that the use of tyre-derived fuels is a viable alternative to the use of fossil fuels, there are other factors that need to be considered. For instance, in more developed areas of the world regulations such as the Clean Air Act are in place to minimise the emissions being released by businesses and technologies are employed to help clean and filter emissions before release into the air.

On the other hand, in less developed areas of the world environmental regulations and technology of this kind rarely exist to the same degree, and in the worst cases citizens may be exposed to the environmental and health effects of uncontrolled tyre burning. While the environmental arguments around energy recovery from tyres may be more nuanced in the developed world, for many Middle Eastern and North African nations the issue is more clear-cut. Current practice may help keep the price of ceramics down, but only at the cost of impairing the health and the safety of entire communities.

 

Catherine Hansen

 

Catherine Hansen

 

We are grateful to EcoMENA for the opportunity to publish this article, a version of which will also appear on their site. EcoMENA is a website focused on raising awareness of renewable energy, sustainability, waste management, environment protection, energy efficiency and resource conservation in the Middle East and North Africa (MENA) region. 

 

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