Recovering Commercial Chemicals from Used Tires
Scrap tyres are being turned into valuable oils and green chemicals by a University of Leeds researcher. The process being developed by Paul Williams offers a real alternative, for the first time, to dumping and burying tyres.
With fossil fuels running out, the oil and gas tied up in the millions of waste tyres discarded each year has been targeted as a possible fuel source for decades. Tyres can yield up to 60% of their weight as fuel oil, but the relatively low price of refined crude means it makes little economic sense to use tyre-derived products. Dr Williams believes his process tips the scales towards a greener future for the billions of waste tyres awaiting disposal across the world.
Dr Williams, in the fuel and energy department, has improved on a basic, and largely ignored, technique called 'pyrolysis' to turn scrap tyres into a mixture of valuable chemicals, oils, gases, carbon and steel cord. Tyres break down in this way when they are heated without oxygen.
"Pyrolysis has been around for years," said Dr Williams. "But it hasn't really taken off as there is no commercial interest in the derived products. We have refined the process to produce mixtures of oils and chemicals that have a real commercial value.
"We can recover 20% of the price of a tyre - perhaps £8 -from what is regarded as a waste product, and one that is expensive to dispose of responsibly."
Much of this value comes from a chemical called limonene - a versatile substance that industry cannot get enough of. It can be turned into solvents, resins, fragrances and is even used as a straight, green swap for ozone-destroying CFCs. Dr Williams believes the process will be commercially available within a few years.