Researchers at RISE are investigating the possibility of manufacturing fuel from old tyres. So far, results are looking promising and, thanks to this process, it may be possible to reduce both waste and the use of fossil resources.
Two processes are required to produce fuel from tyres; firstly, oil is formed from the rubber in the tyres using a process known as pyrolysis and then petrol or diesel is manufactured from the pyrolysis oil in an upgrading process. The aim of the project is to evaluate three different types of upgrading process, both from a benefits and an economic perspective. One of the processes is already demonstrating good results.
“We have tested hydrogenation and, so far, this appears to be a promising alternative. When the project is complete, we hope to be able to demonstrate that it is possible to produce fuel from tyres; however, we also want to show that it actually profitable for the petrochemical industry to recycle oil from tyres,” explains Linda Sandström, project manager at RISE.
Several advantages to recycling
Some pyrolysis oil is currently manufactured from tyres, although only on a small scale. One of the obstacles to commercialisation has been finding profits in the recycling process. Even if Sweden is at the forefront of recycling old tyres, globally there is a massive problem with tyres ending up in landfills instead of being recycled.
“This has generated large amounts of waste worldwide. Large landfills represent a fire risk and are also home to many insects due to the considerable collection of water. Recycling the materials from tyres has many benefits; waste is reduced, worn tyres are reused and fossil oil consumption is reduced. After the project, we hope that industry will be able to recycle tyres on a larger scale,” says Linda Sandström.
Emulate a refinery
A vehicle tyre contains several types of rubber and, depending on how much natural rubber the tyre contains, pyrolysis oil can be more or less renewable. A high percentage of natural rubber provides more bio-based oil.
“As yet, we do not have any figures on the amounts of fossil resources we can save by recycling tyres; however, that is something we will be calculating,” says Linda Sandström.
Within the project, researchers are also studying various blends of fossil oil and renewable oil.
“We have upgraded the mixture of tyre pyrolysis oil and fossil oil in different concentrations and obtained products with diesel-like qualities. The reason we are looking at mixtures is that we want to emulate a refinery, where a substream of pyrolysis oil is added to the process,” explains Linda Sandström.
The project is managed by RISE and will continue until the end of 2018. Scandinavian Enviro Systems and Ragn-Sells Tyre Recycling are also participating in the project, which is being funded by Vinnova. The three processes being studied are hydrogenation, hydrogenation followed by fluid catalytic cracking (FCC) and slurry hydrocracking (SHC).
What is pyrolysis and hydrogenation?
Pyrolysis is a process in which material is exposed to high temperature in the absence of oxygen, causing chemical and physical separation without incineration. Among the ingredients of tyres is rubber, which during pyrolysis is released in the form of pyrolysis oil.
A tyre also contains carbon black, a fine carbon powder added to strengthen the tyre. Carbon black is recyclable and can be reused in the rubber industry.
Hydrogenation is a chemical reaction in which hydrogen is added to a chemical compound. The reaction is often used as an upgrading process, i.e. a process in which the energy value and quality of a fuel is increased.