Continental is making huge strides in using sustainable and recyclable raw materials.

Car tyres are round, black and made of rubber. Look closer, however, and you’ll see that the design of tyres and the interaction of the various materials that go into making them are extremely complex. But for some time now, material experts and tyre engineers at Continental have been bringing about a silent revolution. By 2050 at the latest, all tyres are to be made of sustainable materials. There is still a long way to go until then. But step by step, it is already becoming apparent which raw materials will find their way into tyre construction in the future. These include waste products from agriculture (such as the ash from rice husks), rubber from dandelions, recycled rubber or PET bottles.

Claus Petschick, Head of Sustainability at Continental Tires, is clear about Continental’s mission, saying, “Continental is on the road toward becoming the most progressive manufacturer in the tyre industry in terms of sustainability. We aim to use 100 percent sustainable materials in our tyre products by 2050 at the latest. Our innovative power enables us to break new and even more sustainable ground. This encompasses everything from the origin and sourcing of our materials through to the reuse and recycling of our tyres.”

Already today, around 15-20 percent renewable or recycled materials are used in a standard passenger car tyre from Continental. To further increase the proportion of sustainable materials and conserve valuable resources, Continental continuously analyses and reviews all raw materials used in tyre production.

Perfect material matching for maximum safety 
Depending on the application, season and environment, tyres have to fulfill specific requirements. This can be seen in, for example, the tread design. But in other areas – the composition of the rubber compound, for example – these changes are not so readily visible. Passenger car tyres from Continental consist of as many as a hundred different raw materials.

Their precise composition has a major impact on the tyres and their handling characteristics. The ability to deploy the various materials with their unique properties and interdependencies in specific ways is a complex balancing act for Continental’s engineers and material experts. Only when all the materials are ideally matched to each other can safe, energy-efficient and durable high-performance tyres be created.

Natural rubber still essential due to exceptional properties
Natural rubber is essential for ensuring outstanding tyre performance. This natural product accounts for between 10 and 40 percent of the entire weight of modern high-performance tyres. Its special properties include the high level of strength and durability, which are caused by the strain-induced crystallisation of the rubber. The tyre industry is the biggest consumer of global rubber production, accounting for more than 70 percent. However, Continental considers natural rubber a sustainable material only if it is sourced responsibly. Therefore, the company employs an integrated approach aimed at making the complex and fragmented supply chains for natural rubber more sustainable, including using cutting-edge digital technology, local involvement and close collaboration with capable partners with the goal of improving transparency and traceability along the entire value chain. Meanwhile, with its Taraxagum project, Continental is pursuing an innovative approach to ensure that it can become less dependent on natural rubber grown primarily in southeast Asia. The tyre manufacturer is working alongside partners on industrialising the extraction of natural rubber from specially cultivated dandelion plants.

Sustainable plant-based fillers 
In addition to rubber, fillers such as silica are essential to tyre assembly. Silica, for example, helps to optimise characteristics such as grip, rolling resistance and tyre life. In the future, rice husks will be used as the source material for sustainably-produced silica. Rice husks are a waste product of rice production and cannot be used as food or animal feed. Silica derived from the ash of rice husks is more energy-efficient when used in manufacturing than that obtained from conventional materials such as quartz sand.

Plant-based oils, such as rapeseed oil and resins based on residual materials from the paper and wood industries, already offer an alternative to crude-oil-based fillers in Continental's tyres. Only oils that meet technical quality standards and are not suitable for consumption are used. Oils and resins allow for flexibility in terms of tyre compounds and so improve the material’s grip.

Expanding the circular economy
Continental is aiming for fully circular operations in its tyre production by 2050 at the latest. In addition to the use of renewable materials, the company is working systematically on using recycled raw materials in tyre production. This is intended to ensure that carbon black – another crucial filler in rubber compounds – can be obtained on a large scale in the future. Continental recently signed a development agreement with Pyrum Innovations with a view to further optimising the recycling of materials from old tyres. To do this, Pyrum breaks the old tyres down into their constituent parts in an industrial furnace using a special pyrolysis process. This way, valuable raw materials contained in end-of-life tyres can be extracted and recycled. Both companies are working towards obtaining high-quality raw materials from the pyrolysis oil obtained for Continental's tyre production in the medium-term, in addition to the direct use of high-quality carbon black. In the long-term, the tyre manufacturer and Pyrum are aiming to establish a closed loop circular economy concept for the recycling of old tyres.

Recycled rubber from end-of-life tyres
In addition to pyrolysis, Continental is also making use of mechanical processing of end-of-life tyres. Rubber, steel and textile cord in particular are separated from one another in a highly sophisticated process. The rubber is then prepared for re-use as part of new rubber compounds.

Continental has a long history of working consistently to introduce end-of-life tyres into the circular economy to conserve resources and the environment. A material known as Conti-Reclaim has been obtained as part of the truck tyre retreading process at the company’s plant in Stöcken in Hanover since 2013. It has been used in tyre production at Continental for years. To expand the range of applications for the recycled rubber and optimise the properties for the various fields of application, Continental uses not only Conti-Reclaim but also recycled rubber from other suppliers.

Recycled plastic bottles in tyre casing 
“Recycled raw materials are going to play a big role in making tyres more sustainable. We use recycled materials whenever possible. Comparable quality and material properties to conventional raw materials are crucial for us,” says Petschick.

For example, Continental is working with partners to obtain high-quality polyester yarn for its tyres from recycled PET bottles. PET bottles often end up in incinerators or landfills otherwise. With its ContiRe.Tex technology, the tyre manufacturer has developed a more energy-efficient and eco-friendly alternative that allows it to reuse between nine and fifteen plastic bottles for each tyre, depending on the tyre size. The recycled PET has already replaced conventional polyester in the structures of some tyre casing. The PET bottles used are sourced exclusively from regions where there is no closed recycling loop.

Systematically moving toward greater sustainability
Continental is working to advance innovative technologies and sustainable products and services throughout its entire value chain, from sourcing sustainable materials to recycling end-of-life tyres. The company is aiming to achieve 100 percent carbon neutrality by 2050 at the latest.

Kraton Corporation, a leading global producer of speciality polymers and high-value biobased products derived from by-products of pine wood pulping, has received an International Sustainability and Carbon Certification (ISCC) PLUS certification for its manufacturing facility in Niort, France.

Kraton can now supply 100 percent ISCC PLUS-certified AMS and AMS Phenolics resins using a mass balance attribution approach thanks to the certification. Kraton's dedication to promoting the biobased and circular economy is further demonstrated by the Niort facility's accreditation. Kraton is committed to lowering carbon emissions and accelerating the shift to a more sustainable future by empowering clients to include more environmentally friendly products into their supply chains.

An independent multi-stakeholder project, the International Sustainability and Carbon Certification (ISCC) is a leading certification method that guarantees accurate mass-balancing bookkeeping and reporting of renewable and recycled materials across the supply chain.

Lana Culbert, Kraton Pine Chemicals VP of Marketing, said, “Our SYLVARES™ and SYLVATRAXX™ brands feature a range of high-performance AMS and AMS Phenolics resins used in speciality adhesives and tyre applications. Our ISCC PLUS journey began in 2021 with the certification of our Sandarne, Sweden facility. Earning this certification for our Niort plant marks a significant milestone, further expanding our portfolio of sustainable solutions.”

Sumitomo Rubber Industries, Ltd. has said that it has clarified the process of rubber breakdown, a crucial element that affects tyre longevity, through joint research with Professor Gert Heinrich at Dresden University of Technology (Saxony State, Germany).

In a special session called ‘Combining Physics, Chemistry & Engineering of Rubber: A Symposium in Honor of Charles Goodyear Medalist Gert Heinrich’, which was held in honour of the Professor's medal-winning achievement, the findings were presented in an invited talk at the American Chemical Society, Rubber division, ACS 2025 Spring Technical Meeting held in Orlando, Florida, US, on 6 and 7 March. Professor Heinrich is a member of the Leibniz Institute of Polymer Research Dresden, which took part in the collaborative effort.

Tyre durability is determined by cracking processes, which result in the development of cracks and rips in a rubber substance. The endurance of rubber was previously mostly assessed using tearing tests, but there were still numerous unanswered concerns regarding the microscale structural alterations at the crack tip. This effort identified a factor that determines the start and propagation of cracks in rubber by analysing the force applied to a fracture tip using a simulation approach. In rubber, a crack tip undergoes dilatation deformation to create voids, or microvoids within the item. The fracture gets worse as the voids expand and come together. It was also discovered that the tension focused on the fracture tip is lessened when voids emerge.

The German Rubber Industry Association (Wdk) is advocating for a thorough and legally enforceable regulation of the end-of-waste status for Germany and the whole of Europe. The association is pusing for the circular economy to be strengthened for tyres.

Valuable secondary raw materials are still legally regarded as waste since there are no consistent standards for the end-of-waste status, according to Stephan Rau, Technical Director of the WDW. This restricts the market integration of sustainable recycled materials, impedes investments and creates legal uncertainties. “We call for a comprehensive and binding end-of-waste regulation for Germany and the whole of Europe to strengthen the recycling sector, facilitate investment in modern technologies, and sustainably reduce the CO₂ footprint of the rubber and tire industry,” he said.

In order to adhere to the prescribed waste hierarchy and stop illicit exports, Rau also emphasised that lawmakers must quantitatively and openly document waste tyre flows. He added that waste tyres should only be gathered by approved disposal companies and pre-sorted based on their intended use.

On the important role of mechanically recycled tyre granules and powder, Rau said, "This is an important secondary raw material that is already used in a variety of durable and safe products. A clearly defined end to its waste status must be made more economically viable. To ensure the market success of tyre granules, a risk-based approach to assessing chemical ingredients is essential. Binding limit values ​​must be assessed using a migration analysis, i.e. based on their bioavailability. Second, the use of tyre granule products must become mandatory in the construction industry and infrastructure projects. The goal is clear: Recycling must be economically viable."

Kuraray, a global speciality chemicals company and one of the largest suppliers of industrial polymers and synthetic microfibres, has received ISCC PLUS certification for its thermoplastic elastomers SEPTON and HYBRAR as well as Liquid Rubber produced at the Company’s Kashima Plant at Ibaraki Prefecture.

ISCC PLUS makes sure that certified products, such biomass and recycled raw materials, are appropriately handled throughout their supply chains, including the manufacturing process, by applying the mass-balance technique.

In the five years preceding up to its centenary in 2026, Kuraray is carrying out its medium-term management strategy, PASSION 2026. In order to achieve the long-term Kuraray Vision 2026 of being a speciality chemical company that grows sustainably by integrating new foundational platforms into its own technologies and contributing to customers, society and the planet, the company will keep growing its range of products that improve the natural and living environments.