In 1839, Charles Goodyear accidentally discovers the vulcanization. He puts sulphur and rubber in a hot pan which results in a rubber with high thermal and water resistance. Almost two centuries ago, Mr. Goodyear most likely didn't believe that his discovery would be so widely used, let alone that the recycling of tires would become one of the biggest environmental problems for humanity.
The truth is, nowadays there are landfills of waste tires all over the world. The largest one is in Kuwait, followed by the second largest in the state of Colorado, which continues to expand. When these mountains of tires start to take too much space up, people start to take matters into their hands. In the last 40 years, 28 intentional tire fires have been documented, but in reality, there have been many more. The consequences of fires are adverse for both the environment and human health. They are intentional because the tires cannot be set on fire on their own. It has been proven that in order for a tire to ignite, it must be continuously heated up to 400 degrees Celsius for a long time.
But what is the reason for the formation of mountains of tires? Manufacturers and importers of new tires placed on the market pay a Gate fee, also known as an ‘eco-tax’, which is intended to be used to recycle tires. However, many companies responsible for collecting the eco-tax pile up the tires without recycling them and do not use the money as intended. Another reason for this environmental crime is that the existing ways to recycle used tires are outdated and inefficient. Let's see why:
The best-known way to reduce End-of-Life Tires (ELTs) is to use them as a source of fuel to generate energy in the cement plants. About 40% or 1,370,000 tonnes of used tires in the European Union are burned for this purpose. This process emits almost as much harmful emissions and carbon dioxide as coal combustion. This activity does not contribute to the circular economy and the sustainability of the environment.
Another way to reduce the amount of ELTs is granulation. It is a mechanical grinding that removes the metal and textile from the tires. As a final product are obtained granules, which can be used for building roads. The purpose of these granules is to make the asphalt more flexible, but when too many of ELTs mix with the asphalt, they break down the pavement. ELTs cannot be used in large quantities in this way. At the same time, this process is time consuming and requires a large amount of electricity.
In addition to asphalt, the granules are also used as a filler for flooring of sports fields and playgrounds. In this way, the playgrounds become more durable and more resistant to weather conditions. However, the granules may also contain harmful chemicals as well as polycyclic aromatic hydrocarbons (PAHs), which are classified by the European Chemicals Agency (ECHA) as carcinogenic. Granules also contribute to contamination with rubber microparticles, as they can spread to the environment from the pavement, through rainwater or the shoes and clothes of players and children.
From this we can conclude that these recycling methods do not generally contribute to solving this environmental problem caused by the waste tires. A new approach is needed to drastically reduce the amount of waste tires and to have a zero-carbon footprint.
With the development of technology in recent years, pyrolysis has been used as an innovative method for the treatment of ELTs. This is a thermochemical process in which in the absence of oxygen and under the influence of high temperature certain raw materials are converted into low molecular weight compounds. Pyrolysis of ELTs is currently the only real technology for environmentally friendly recycling, thanks to which carbon black is recovered and pyrolysis oil is produced. The carbon black originally used in the tires is recovered and used again to make new tires. Using 1 ton of recovered carbon black saves 3 tons of carbon dioxide. Pyrolysis oil is a substitute for crude oil in refineries. It is used to make sustainable chemicals, as well as modern biofuels. This contributes to the circular economy.
Many companies all around the world are trying to develop this technology. One of the leading companies that have developed pyrolysis technology for processing ELTs is the Bulgarian company MODUL LTD. Since 2008 it is the first company in Europe to operate a commercial plant with continuously process. The company is currently developing and building such plants throughout Europe.
Author: Silvia Trifonova
Editor: Elitsa Marinova