In the Netherlands, old car tyres are mainly recycled mechanically into new products, such as stable mats for livestock. Throughout Europe, old car tyres are also frequently used as a coal substitute in cement kilns. RIVM has investigated whether a different method, heating car tyres in the absence of oxygen (a process known as pyrolysis), has potential as a safe and sustainable alternative. The conclusion is that each method carries its own set of advantages and disadvantages, and these should be carefully weighed against each other. RIVM recommends investigating whether soiled stable mats can also be recycled.
The recycling of residual flows plays a pivotal role in realising a circular economy by 2050. However, recycling should also be safe and sustainable. It is therefore important to compare new and existing methods. RIVM has developed a methodology for this, known as Safe and Sustainable Material Loops. This methodology was used to investigate car tyre recycling.
New method: car tyre pyrolysis
Heating without oxygen (pyrolysis) is an innovative new recycling method. Through pyrolysis, a material called ‘carbon black’ is extracted from tyres, which can then be used in the production of new tyres. Additionally, pyrolysis yields gas and oil, which serve as a fuel.
Comparison with existing methods
RIVM compared pyrolysis to two methods currently employed for processing car tyres: mechanical recycling them into stable mats and using them as a fuel in cement kilns. This latter use is common throughout Europe, but is not circular.
Material for new products
Pyrolysis of car tyres yields more useful material than when using them in cement kilns, but less than when mechanically repurposing them into stable mats. However, stable mats become soiled during use, making their reuse potential uncertain. It is therefore possible that the advantage of more useful material disappears over multiple life cycles.
With respect to impact on the climate, the effect of pyrolysis was found to be nearly on par with the process of burning car tyres in cement kilns. Mechanical repurposing into stable mats has a more favourable climate impact.
Material and processing safety
In terms of material composition, it appears that the reclaimed carbon black from pyrolysis is reasonably safe. However, the safety of the oil produced through pyrolysis could not be ascertained definitively.
The conclusion is that each recycling method carries its own set of advantages and disadvantages, and these should be carefully weighed against each other. RIVM recommends investigating the recycling potential of stable mats further.