Dandelions form part of future Continental tyre material mix

Car tyres may be mostly made of rubber but various other materials go into making them. By 2050 at the latest, all tyres should be made of sustainable materials, according to Claus Petschick, head of sustainability at Continental Tyres.

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.

Renewable or recycled materials already constitute about 15%-20% of a standard passenger car tyre from Continental, says the German automotive parts company. 

The tyre industry is the biggest consumer of global rubber production, accounting for more than 70%. However, Continental employs an integrated approach. Taraxagum is another approach to ensure less dependency on natural rubber, which is grown primarily in Southeast Asia.

The tyre manufacturer says it is also working on industrialising the extraction of natural rubber from specially cultivated dandelion plants.

Rubber fillers such as silica, which are essential to tyre assembly, will also be replaced. Silica 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 the hard protecting coverings of grains of rice. They are a waste product of rice production, and silica derived from the ash of rice husks is said to be 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 tyres.

In addition to the use of renewable materials, the company is working 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.

Depending on the application, season and environment, tyres have to fulfil specific requirements. This can be seen in the tread design, though passenger car tyres consist of as many as a hundred different raw materials.

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

Natural rubber is essential for ensuring outstanding tyre performance. This product accounts for between 10% and 40% of the entire weight of modern high-performance tyres due to its strength and durability.

In addition to pyrolysis, rubber, steel and textile cord are separated in another sophisticated process for reuse as part of new rubber compounds.

Continental is also working with partners to obtain high-quality polyester yarn for its tyres from recycled PET bottles that end up in incinerators or landfills.

With its ContiRe.Tex technology, the tyre manufacturer says it has developed a more energy-efficient and eco-friendly alternative that allows it to reuse between nine and 15 plastic bottles for each tyre, depending on its size. The recycled PET has already replaced conventional polyester in the structures of some tyre casings.