Making rubber sustainable
Waste Management Expo 2020 MAR 12&13 BIEC, Bengaluru, India

Making rubber sustainable

11:28 AM, 9th February 2017
Rubber Trees
Rubber or scrap tyres are one of the major sources of environment pollutant today.

We want the best in class tyres to have the smoothest drive. But has it ever concerned you as to what happens to these tyres after it is discarded? We have to bear the burden of millions of discarded tyres dumped every year. However, more and more companies are coming up with innovative measures to lighten this burden. 

By Debarati Das

The robust rubber industry is driven by the ever growing tyre manufacturing across the globe. According to the Global Industry Analyst, Inc report, the global tyre market is estimated to reach 2.5 billion units by 2022!! 

But what about the number of tyres that are discarded? The Rubber Manufacturers  Association (RMA) estimates that about 4038 thousand tonnes of tyres were generated in the US alone in 2015. World Business Council for Sustainable Development(WBCSD)points out that every year, a total of 1 billion end-of-life tyres are generated.An estimated four billion tyres are currently piled up in landfills and stockpiles worldwide.

These heaps of scrap tyres are one of the major sources of environment pollutant today, simply because: 

  • It is a sheer wastage of huge amount of fossil fuels and other raw materials used to produce the tyres 
  • They consume valuable space with their large volumes which consist 75 percent void space
  • Tyre fires release harmful toxins into the air, soil and water. 
  • Tyre piles are ideal breeding ground for mosquitoes and other pests spreading life-threatening diseases 
  • Illegal dumping of scrap tyres pollutes the environment 
  • Due to their heavy metal and other pollutant content, tyres pose a risk for the leaching of toxins into the groundwater when placed in wet soils.

Given the alarming number of tyres being dumped every year, tyres are banned from landfills in the European Union, 38 states in the US and three Canadian provinces. However, this has not stopped the menace completely as a significant number of scrap tyres are still being dumped illegally or stored in stockpiles. 

The next option is to responsibly recover and recycling waste tyres. Many developed countries joined hands with tyre manufacturers. RMA estimates that the end-use markets consumed 87.9 percent by weight of the scrap tyres generated in the US in 2015.

However, the story isn’t the same everywhere. WBCSD reports that South Africa has an estimated 800 million tyres in stockpiles in the Western Cape region while the numbers in Mexico is approximately 1-2 billion.

The solution 

Innovative rubber furniture and various tyre art from scrap tyres, turning end-of-life tyres into rubber crumb and incorporating them in running track paving, sports, playing fields and playgrounds, weightlifting plates, acoustic barriers etc- rubber are witnessing a wide range of innovative transformations. But this takes care of just a fraction of the millions of scrap tyres piling up across the globe. Acknowledging the grave danger of piling up waste tyres, various industry associations, tyre manufacturers and research institutes are coming up with novel ideas and solutions to put these scrap tyres to better use.

Reclaiming the tyres: More and more tyre manufacturers, distributors and retailers are voluntarily participating in tyre recycling programmes. Manufacturers are focusing on a casing of the tyres wherein when the tread is worn, but the casing is still functional, the tyre is retreaded. Manufacturers are trying to come up with tyres which can go through up to four to five retreading cycles. 

In case the tyres are worn beyond repair, manufacturers themselves come up with solutions to dispose of waste tyres in an ethical and environmentally friendly manner. Along with various innovative measures to manufacture sustainable tyres, Bridgestone also observes various recycling programmes including creating rubber crumb that is used in everything from playground and road surfaces to tile adhesives and compound for new tyres.

Making sustainable tyres: It takes about 80 litres of crude oil to make one truck tyre. In its research, Continental Tires found that with low rolling resistance rubber, each tyre uses 200 litres of oil during its life fitted to a car before it reaches its end of life.The key here is to make tyres more sustainable so as to bring down the fuel consumption. 

“Sustainable tyres must take in a whole host of elements. At Continental we examine the environmental considerations around the tyre such as the materials used, the energy and manufacturing techniques that go into making the tyre and our efforts to minimise those and how the tyre is disposed of or recycled,” said David O’Donnell, senior vice president research and development tyres, Continental Tire.

“The tyres must still have low rolling resistance and therefore help give good fuel economy, be safe in all weathers, be durable yet quiet and still affordable. So all the ingredients that go into producing a sustainable tyre make for a pretty complex recipe,” he added.

Experts from various tyre manufacturing companies are constantly working towards minimising the rolling resistance of a tyre, lowering the amount of rubber used and various other measures to reduce the overall carbon footprint. 

Natural alternatives to rubber: Natural rubber is used to make over 40,000 different products. The burden of rubber extraction is in South-East Asia, which produces around 90 percent of the world’s natural rubber supply. More and more research is happening around the world to find a cheaper yet natural alternative to rubber. There has been a new excitement around ‘Russian dandelions’ – an undemanding plant from which a rubber-like material can be produced from its white milky fluid. 

A research team headed by Münster University and the Fraunhofer Institute for Molecular Biology and Applied Ecology IME (Munster branch), has identified proteins which play a key role in the production of rubber in the plant. The milky fluid containing the rubber is produced in special cells in the dandelion due to a protein complex, called the rubber transferase activator. This protein plays a key role in the formation of the long polyisoprene chains. These so-called polymers give the rubber its typical properties of elasticity and resilience.

“Dandelions have become well-known recently in particular as a result of applied research. We have been able to identify no fewer than two key components of rubber biosynthesis. It has not so far been possible to manufacture natural rubber by biotechnological means. But the possibility has been brought a step closer,” said Dr Christian Schulze Gronover, IME, Munster branch.

DRIVE4EU-‘Dandelion Rubber and Inulin Valorization and Exploitation for Europe,’ a demonstration project, is doing similar work in the European Union for the development of the production chain of natural rubber and inulin from dandelions to become less dependent on the import of natural rubber and at the same time to respond to the threat of a global rubber shortage. 

Making new tyres from old ones: US-based green materials company, Lehigh Technologies, came up with a novel way of producing new tyres from waste tyres. The company buys shredded tyres from waste recyclers and, using its turbo mill technology, turns it into micronized rubber powder (MRP), resembling the consistency of flour. It then sells this as an additive to go back into new tyres (making up 5 to 7 percent of all the rubber in new tyres), reducing raw material costs.

“We are seeing a strong market reception for MRP as companies learn that micronized rubber powder delivers a strong value proposition,” said Dr Alan Barton, chief executive officer of Lehigh Technologies.

From tyres to fashion: While scrap tyres are being converted to rubber artefacts, manufacturer and distributor, Omni United, teamed up with fashion brand, Timberland, to convert scrap tyres to become a part of haute couture. These tyres are recycled to be used in Timberland shoes. “We make lots of shoes, and therefore we use lots of rubber,” said Stewart Whitney, president, Timberland. “For some time now, we have been seeking a consistent source of recycled tyre rubber that meets our stringent quality and environmental standards.”

Making stronger infrastructure: Rubber tyres have been used in construction. While sometimes, entire homes can be built with whole tyres by ramming them full of earth and covering them with concrete, known as Earthships, they are also used in various civil engineering applications like sub-grade fill and embankments, sub-grade insulation for roads, septic system drain fields etc. 

Now, a team of researchers from University of Surrey, UK, and Aristotle University of Thessaloniki, Greece, have come up with a new method of protecting bridge infrastructure in disaster-prone regions using used tyres that may otherwise be sent to landfill. 

“Bridges are important infrastructure assets, which are costly to construct and maintain. In developing countries especially, there is a need to build bridges using simple and inexpensive methods. This had led to a type of bridge known as an integral bridge becoming increasingly popular which is a simple frame structure with no extra parts such as bearings or expansion joints, it is maintenance-free but has limitations meaning that they can only be used over short lengths,” said Dr Stergios Mitoulis, lead author, University of Surrey.

“Where the bridge meets the land the soil moves and shifts and in times of stress this can lead to extended damaged or collapse. The longer the bridge, the greater the risk of collapse,” added Mitoulis.

The researchers used old tyres to create an aggregate that effectively provides double with the performance of conventional designs when movements due to earthquakes or temperature changes are simulated. The new design will eventually allow for safer and sturdier bridges. 

Despite awareness, the tyre recycling industry is still constantly struggling to find customers with end users. Amidst millions of scrap tyres, these are just tiny steps taken around the world which, when aggregated, can one day take a big leap towards a sustainable world.

© Chemical Today Magazine

See the Feature in Chemical Today magazine (Pg. 36)

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