Tyre recycling: Wheels come full circle

Man's love affair with cars has an unfortunate fallout - massive trash heaps of scrap tyres. In Sharjah alone, about 4,000 used tyres are dumped daily by tyre-change shops into the Saja'a landfill off Dhaid Road. The landfill is just one of several in the emirate, where a massive mountain of sand-covered and compacted garbage keeps expanding at a rate of 2,000 tonnes per day. More than eight million discarded tyres are neatly piled across a four-square kilometre patch; not to mention the millions of others in landfills in other emirates. By law, all trash in Sharjah must be dumped and processed through the Bee'ah Waste Management Complex in Saja'a. Now, a multi-million dirham project is turning this heap, which for years was just a sore sight, into something useful. Bee'ah, an award-winning environment and waste management company, is nibbling away into the tyre dump by turning them into rubber crumbs - as asphalt road additives or soft flooring. Its Tyre Recovery Facility (TRF) started operations in June 2010 and uses state-of-the-art cryogenic process to produce rubber tiles that can be used as matting for gyms, playgrounds, stadium playing areas, running tracks and walkways. The potential is huge and the emerging market for crumb rubber is fuelling old and new applications. Article continues below Since the 1980s, the US Navy has started using rubber skin in nearly all modern ships and submarines as sonar wave absorbers. A new generation of special sub-surface irrigation pipes also uses a mix that is 70 per cent made up of recycled rubber and other additives. Boosting road durability When used with asphalt, the rubber crumbs boost road durability and prevent cracking. The heart of Sharjah's $40 million (Dh146.9 million) rubber recycling plant uses liquid nitrogen to flash-freeze the tyres to minus 196 degrees C, where they become as "brittle" as glass and are broken down into tiny, almost sand-like tidbits - as granular as 0.6mm to 4mm in size. Canadian firm RTI Cryogenics has supplied the machine, which churns out up to 4,500kg per hour. Conveyor belts take the raw crumbs through a line of electro magnets to catch bits of steel, which are then deposited in a separate bin for recycling. Nothing beats the benefits of rubber crumbs when mixed with asphalt. Experiments with asphalt-rubber use for roads started in the 1840s, but it was only in the 1960s that asphalt-rubber (A-R) mix started to be used as paving material. David Martin, senior process manager, Bee'ah, said the crumb rubber is non-toxic. "This not only promotes a message of reuse-and-recycle, but also creates a safer and longer-lasting road system." The patents on A-R mixes expired in 1992, which made the material part of public domain. A US study in 1994 proved that total hydrocarbon content of A-R roads were much lower than conventional asphalt. Moreover, it found that non-methane total hydrocarbon emitted by A-R roads was 20 per cent less compared to conventional asphalt roads. A-R roads also lessen the noise generated by tyre friction and improve riding qualities. Sharjah's forays into tyre recycling has been bolstered by a study which shows that A-R saved up to $7 (Dh25.6) per metre compared to conventional asphalt overlays during a road's life cycle. Studies also show that used A-R grindings can be further recycled after a 15-year use to re-pave roads. "Asphalt-rubber is part of the solution to the waste tyre problem," said Najib Faris, communications manager of Bee'ah, "but the asphalt-rubber mix makes sense engineering wise. The fact that it helps solve the puzzle of what to do with waste tyres is just a green bonus." It makes sense, because rubber came from living trees. Used tyres go through several stages of shredding before they are turned into rubberised tiles (bottom right) used as matting for gyms, playgrounds and jogging tracks. They can also be used as asphalt additives