Tyres on the table

The post was prepared by Dr. Liina Joller-Vahter from the University of Tartu and Power Algae

For tackling the circularity challenge several perspectives are needed, the helicopter view for grasping its whole societal scope, as well as deep dive into the niches. The challenge of increasing circularity in the vehicle tyres is one such niche. The European Tyre and Rubber Manufacturers’ Association (ETRMA) is the voice of the tyre industry in Europe, its corporate members represent 59% of global sales, and provides first insights into the sector.

The tyres are sold to final consumers as an integral part of a vehicle, or as replacements. According to the ERTMA statistics the tyre sector strongly correlates with overall economic and logistics trends. For example, the drop during the first Covid wave is clearly visible. The 2023 full year is not published yet, but most recent quarterly data on consumer tyres reflects decline of -6% from Q3 2022 to Q3 2023 (from 58 037 000 to 54 291 000 units). The decline was even deeper in the bus, truck, agricultural, and moto segments.

Table. ERTMA members’ tyre sales in Europe (Source: ERTMA press releases 2012-2023)

The useful lifetime of a vehicle exceeds the tyres manifold. With a mileage of 200 000 km-s, a passenger car will have used 4-10 tyre sets. Whereas the OE tyres directly correlate with vehicle sales, the demand for replacement tyres is what is more interesting from the circularity perspective. In the CIRCOMOD project we are particularly interested in the end-of-life (ELT) tyres.

Based on the circular economy framework used in the CIRCOMOD project, which builds on the works of Bocken et al. 2016 and Potting et al. 2017, the most feasible and viable paths for tyres are in the centre, among the ‘slow the loop’ models. The high-impact and generally in CE most anticipated ‘narrowing the loop’ can only happen along the radical changes in the transport sector and overall patterns in the cities and societies, e.g. human geography, international trade & value chains, etc., but for these tyre sector they remain external. The low-hanging ‘close the loop’ patterns are certainly better than dumping to the landfill, but their positive environmental impact is still quite limited. Already in 2010 ETRMA witnessed positive trend in the management of end-of-life tyres (ELTs) in Europe with a recovery rate of 96%. Nowadays dumping is very rare, as at least energetic value can be recovered from most of the waste types in all European countries.

Figure. CIRCOMOD framework for circular technologies and business models (based on Bocken et al., 2016 and Potting et al., 2017)

The niche of car tyres also possesses a crucial dilemma – how to reduce environmental impacts from tyres while ensuring high standards for safety-related performance. Therefore the ‘reuse’ after designated exploitation is also out of the game, and even legally sanctioned. However, the ‘slow the loop’ model includes two groups of approaches retreading and repurposing, which have proven their feasibility and viability in practice.

Retreading has been on the market already since the 1950s. Retreading ranks the highest among the circularity technologies and business models that with current technologies do not compromise passenger safety. Retreading is a re-manufacturing process for tyres, which, in short, means replacing the tread on worn tyres. A video by Wolf Tyres excellently explains the process.

 

Already in 2016 Ernst & Young published a report for estimating the impacts of truck tyre retreading in Europe. They showed that retreading reduces carbon emissions, natural resource extraction, water consumption, air pollution, and land use. Among other things, they pointed out that in case of tyres the solution to a global problem must be local. This comes from estimations widely used in secondary resource economics that transporting secondary resources is roughly viable in a 500-1000 km radius. As a result, side to the reduction of negative environmental impact from the tyre sector, applying retreading provides new local job opportunities. E&Y estimated that already in 2015, 30% of truck tyres sold in the EU 5 largest economies were retreaded, but the consumer segment was lagging behind.

Repurposing is another already quite common application, ranging from DIY playgrounds to the professionally manufactured outdoor sports facilities. However, the need for these is marginal compared to the annual inflow of end-of-life tyres. Cement industry is another focus in the CIRCOMOD project, and interestingly, we can see overlapping applications between these two. At least two recent academic publications have investigated the opportunities, Valente et al. 2022 for using tyre fractions in cement, and Shariati et al. 2024 have reviewed studies on its applicability more broadly in civil engineering.

A premium tyre designed for retreading can be retreaded up to two times, and the need for such material in playgrounds will be met, hence, the majority of the end-of-life tyres requires an industrial solution. One such industrial unit that specialises in the first phase – shredding the used tyres, is in planning in Estonia by Ragn-Sells. The rubber scrap can be further used in the chemical industry, and the products may include, for example, pyrolysis oil or asphalt. Alternatively, it can be mixed together with the plastic waste that is too dirty or damaged to be recycled, and made into heating oil so that at least energetic value is recovered.

In practice the estimation and evaluation of the state of the circularity in the European tyre sector possesses several challenges. The puzzle can be put together from data from manufacturers, re-sellers, recyclers, Eurostat’s international trade statistics as well as waste accounting. When modelling the paths to increased circularity we can rely on the data about past, and the current patterns of production and consumption, however the extrapolation needs to consider also technological advancements, for example technologies that are in the piloting or market entrance phase. In the world of tyres exciting developments are being made in non-pneumatic tyre technology that uses unconventional polymers like polyurethanes and thermoplastic elastomers to create innovative tyre designs for better durability and sustainability (e.g. the new concept of Michelin’s Uptis airless tyre). As the rubber end-of-life tyres can be used in other applications, from producing oils for chemical industry to mixing into cement, to name a few, estimation of the overall circularity potential and impact is an interesting yet challenging task.

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