Old tires find new life as cleaner alternative to diesel

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Scrap tires could still help get you around with recycling technology that produces into saleable oil, carbon and steel(Credit: Geronimo/Depositphotos)

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One is an eyesore and a health hazard, the other one is plain dirty. So what do you get when you combine processed scrap tires with diesel fuel? In what might be a case of two wrongs making a right, Australian startup Green Distillation Technologies (GDT) has shown that it is possible to get a cleaner blend of fuel by combining oil derived from old tires with diesel.

Recent attempts to recycle old tires have included coming up with a more energy-efficient way to break them down, using them as mosquito traps and cutting them up so they can be stored more easily. Despite these and various legislative efforts to minimize the hazards posed by scrap tires, they are incredibly hard to get rid of and there are still more of them than people know what to do with. In Australia alone, nearly 48 million end-of-life tires get discarded every year and most end up in landfills and illegal stockpiles.

GDT, which was launched in 2009, has pioneered a recycling technology that it calls destructive distillation to solve this problem. Similar to pyrolysis – the process by which organic materials are broken down by high heat in an oxygen-deprived environment – it reduces whole tires into saleable oil, carbon and steel.

It differs from other recycling methods in that it is the only process in Australia at the moment that turns the rubber from these tires into a different form of energy. Others merely change the shape or appearance of the rubber, points out GDT chief executive Craig Dunn. Apart from heat, the process is emission- and waste-free, and since it processes whole tires, no labor or energy is needed to break them down.

This table shows how much oil, steel and carbon QDT can get from individual tires

While this all sounds well and good in theory, how exactly does the oil produced measure up? According to engineers from the Queensland University of Technology (QUT) who subjected it to a series of rigorous tests, the results are highly promising: not only did it produce a fuel with reduced emissions, there was also no loss of engine performance when blended with diesel.

"We tested the oil which GDT produces from both recycled natural and synthetic rubber tires in 10 percent and 20 percent diesel blends," says Farhad Hossain, a doctoral candidate at QUT who was part of the study, adding that the tire-oil blends were tested in a turbocharged, common rail, direct injection, six-cylinder engine – typical engine types used in the transport industry. "Our experiments were performed with a constant speed and four different engine loads of 25, 50, 75 and 100 per cent of full load."

The researchers found a 30 percent reduction in nitrogen oxide, a greenhouse gas and air pollutant, as well as lower particle mass, which means fewer problems for emission treatment systems. In addition, the oil can also be used as a heating fuel, which is what happens at GDT's facility, and further refined into automotive or aviation jet fuel.

"The process recycles end-of-life tires into oil, carbon and steel, leaving nothing wasted," says GDT chief operating officer Trevor Bayley. "The potential of this source of biofuel feedstock is immense, and it is more sustainable than other bio-oils from plants such as corn or algae."

While one might question whether a 30 percent reduction in pollutants is enough, the fact that the process helps cities get rid of end-of-life matter in an environmentally sustainable manner is a step forward at least.

GDT, which won a bronze award in the resource management or renewable resources category at the Edison Awards last year, has already received offers from at least one company to buy all the eight million liters of oil it will produce at its plant in Warren when it becomes fully operational next year, says Bayley. It is expected to process about 685,000 (19,000 tons) car and truck tires a year – approximately three percent of what ends up being discarded each year.

Talks to build a plant in Tasmania, which currently has 900,000 tires waiting to be processed, are still ongoing, and a mining tire processing plant is also planned for either Queensland or Western Australia.

Source: QUT

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