Europe's 3 million tonnes of tyre waste per year could be recycled to provide valuable fuel and materials.
Currently 65 to 70 per cent of used tyres end up in landfill, causing environmental damage and a loss of natural resources, but an EU funded project called TyGRE is hoping to tap into their recycling potential.
Tyres have a better heating value than biomass or coal, and they contain a high content of volatile gasses, meaning they can be a source of synthetic fuels according to Sabrina Portofina, a researcher at the Italian national agency for new technologies, energy and sustainable economic development, ENEA, in Portici, near Naples.
The research project consists of two components is investigating the pyrolysis of the tyre material to extract the volatile gasses that form synthesis gas, also called syngas, as well as looking into the use of the char formed to produce other materials, most importantly, silicon carbide, which is used in the manufacture of ceramic materials and electronics.
“To increase the added value of the gasification we decided to include the production of products such as silicon carbide,” says Portofino.
The process being investigated at ENEA involves injecting the scrap, together with steam, into a reactor and heating it up to almost 1000°C to create syngas; a mixture of mainly hydrogen, carbon monoxide and dioxide, and methane.
Though the heating requires energy, it will be recovered by the energy contained in the produced syngas which can be used as a fuel—having a similar heating capacity to natural gas—but also as a starter material for the production of other by-products.
Solid carbon is collected after the gasification and reacts with silicon oxide at high temperature to form the silicon carbide.
Speaking to Italian website youris.com, Valerie Shulman, Secretary General of the European Tyre Recycling Association, ETRA. “Silicon carbide is one of the materials of the future, it is used in metallurgy, in ceramics, and in a variety other products. It is quite expensive to produce but you can get from €1,200 to 3,000 Euro a tonne.
A prototype plant is now under construction at the ENEA facilities in Trisaia in Southern Italy, which is expected to be in operation at the end of March and will process about 30 kg of tyre waste per hour.
But some experts are sceptical regarding the cost effectiveness of this process.
“I think the cost is too high, and you have to use a granulate that is expensive,” says Juan Antonio Tejela Otero, an engineer and sales manager at Renecal, a tyre recycling company in Guardo, in the Palencia province of Spain.