Used tires pose a serious environmental hazard due to damage that can be caused by storage in the environment. From year to year, there are more and more of them in developed countries. Their processing is of great interest and is being stimulated by increasingly stringent regulations from governments around the world. Scientists have figured out how to recycle used tires into fuel using pyrolysis. The research results are published by the journal Renewable and Sustainable Energy Reviews.

The Process Being Used: Pyrolysis

Pyrolysis is an extremely interesting alternative when it comes to recycling tire materials to produce alternative fuels and high value-added petrochemicals. In detail, pyrolysis is the thermal decomposition of organic and many inorganic compounds. In the narrow sense – the decomposition of organic natural compounds with a lack of oxygen. Pyrolysis can be defined as the high-temperature thermolysis of hydrocarbons carried out at low pressure and short duration.

“In this context, pyrolysis involves the destruction of the rubber of a tire by heat in the absence of oxygen. The products and their yield depend on the conditions in which the pyrolysis is carried out,” says Miriam Arabiourrutia-Gallastegui, lecturer in the UPV/EHU’s PROCAT-VARES (Catalytic Processes-Waste Valorization) group.

Can It Really Be Used as Fuel?

The research team analyzed the most important benefits of increasing the value of used tires through catalytic pyrolysis. The main interest in increasing the value of waste tires through pyrolysis is based on the potential of the resulting products: gas, liquid, and solid – such as coal. The yield and composition of each of them depend on the pyrolysis conditions, scientists say.

The liquid is the main product obtained in catalytic pyrolysis. This liquid is of the greatest interest because it can be used as a fuel. Its composition is complex and includes various types of compounds as well as sulfur compounds that limit its direct use as a fuel. Interest in catalytic pyrolysis is usually associated with improving the properties of the output products.

Pyrolysis gases can also be used as a fuel for power generation. And, of course, coal, which is made up of the carbon black present in the tire. It can be reused as carbon black in tire production.

As Arabiourrutia-Gallastegui pointed out, “thanks to all these pieces of work we are gradually adjusting and improving the pyrolysis process to try and bring about a distribution of products with a more suitable composition with a view to their potential application as fuel or raw material to obtain compounds of interest”.

Additional Information About the The PROCAT-VARES Group

The PROCAT-VARES group is involved in proposals, progress and innovation in processes of interest in terms of energy and the environment. The aim is to develop lines of research that are a benchmark on an international level in Chemical Reaction Engineering, are highly topical and focus on sustainable development. This activity involves training researchers and technologists, transferring knowledge to the international scientific and technological community in the form of publications, and collaborating with the industrial sector in matters combining subjects of academic, technological, social and industrial interest.