The merits of tyre pyrolysis

Online Editor

Krzysztof Wróblewski details nine advantages of waste tyre pyrolysis technology

Tyre pyrolysis is emerging as the safe, efficient and green option for recycling end-of-life tyres. It’s a circular solution that can solve the tyre waste problem and simultaneously provide in-demand inputs for several industries. By enabling circularity, tyre pyrolysis replaces fossil-based raw materials with sustainable alternatives and reduces the associated environmental impact.

The global tyre waste problem

Tyre waste has become a global environmental problem and keeps growing as vehicles on the road increase. Currently, over 1 billion end-of-life tyres (ELTs) are produced yearly. Predictions estimate that 2 billion cars and 790 million trucks will be on the road by 2040, double what existed in 2016.

The materials that make tyres durable and deliver a safe ride also make waste management of ELTs challenging. ELTs are non-biodegradable and considered a non-hazardous waste.

The European Union, a world leader in tyre waste management, sends only 4% of its ELTs to landfill. But other parts of the world suffer due to improper tyre waste management, and global estimates for landfilling ELTs stand at about 30 to 75%.

Thousands of tyres piled up isn’t only an unpleasant sight; it’s also a safety and health risk. They hold rainwater, providing breeding grounds for mosquitoes and rodents that can transmit diseases to people. ELTs are also flammable and have caused massive fires that release fine particulates and hazardous carcinogenic pollutants.

The environmental impact of landfilled tyres is also high. They leach heavy metals that pollute soil, groundwater, and runoff, which harms aquatic animals. Illegally dumped and free-floating ELTs in seas damage coral reefs and marsh vegetation and physically hinder large marine animals.

Tyre pyrolysis is the more sustainable of the various tyre recycling methods. Less environmentally friendly options include the policy of exporting ELTs to developing countries and incinerating ELTs as fuel, which can cause the same environmental and health impact as accidental fires. Furthermore, recycled tyre rubber crumbs used for civil engineering and artificial sports fields have become a significant source of microplastics.

Retreading tyres with recovered materials is a more sustainable option and extends the tyre’s life, but it doesn’t use all the waste produced. Tyre pyrolysis is increasingly considered the ideal tyre recycling solution, as it’s a circular solution that treats ELTs not as waste but as a valuable resource.

What is tyre pyrolysis?

Tyre pyrolysis is the thermo-chemical recycling of materials from end-of-life tyres and their transformation to valuable secondary reprocessed chemicals.

The process involves separating the steel from the tyres before pyrolysis. Next, the cleaned rubber is shredded and sent to the reactor. The waste rubber is heated in an oxygen-free atmosphere at temperatures between 400-700 °C. Due to lack of oxygen, instead of burning, the complex plastic polymers in rubber decompose into smaller component compounds, producing four main products: carbon black, oil, gas, and steel.

Most of the vaporised compounds liquify when cooled to give pyrolytic oil, which is rich in aromatic hydrocarbons. The remaining gas is used as fuel in the pyrolytic plants and makes them energy self-sufficient.

The solid portion is recovered carbon black (rCB). The rCB is a unique grade that can be used as a semi-reinforcement filler to produce new tyres and other rubber products and as a colouring agent.

The steel collected before the thermal treatment can be recycled as scrap.

The pyrolytic products – oil, gas, and rCB – are high-value raw materials in great demand in many industries.

Nine advantages of waste tyre pyrolysis technology

Tyre pyrolysis has become the preferred technology to recycle ELTs because it allows tyre industries to meet their sustainability and climate change commitments. A regional and assured source of secondary raw materials is also attractive in these days of disrupted supply chains and chaotic world events. Tyre pyrolysis is environmentally friendly and sustainable because of the nine achievements detailed below.

According to a 2020 study, pyrolysis reduces fossil resource use, global warming, and terrestrial ecotoxicity, mainly due to the circular use of pyrolytic products, gas, oil, carbon black and steel. As a result, people can avoid the extraction and production of virgin materials.

Using pyrolytic gas instead of new fossil fuels reduces the ecotoxicity of pyrolysis by 56.3%, according to the study.

The most significant benefits of pyrolysis are in improving human health. The process produces significantly less particulate matter and pollutants than the incineration of tyres, according to a 2022 review.

Since the plastic polymers are broken down into simpler compounds, the risk of microplastic pollution is avoided.

Recovered carbon black has a small carbon footprint. Its production emits nearly 2 tonnes of CO2 equivalent less per tonne than virgin carbon black (vCB) production.

Moreover, replacing vCB production with rCB can reduce particulate matter pollution by 34% and fossil fuel dependence by 49%, according to the 2020 study. The rCB is more responsible for reducing the environmental impact than the other pyrolytic products.

Pyrolysis reduces tyre wastes in landfills and the associated soil and water pollution.

It is possible to integrate other wastes such as plastics and biomass as feedstocks in pyrolysis, according to the 2022 review.

The process can reduce external reliance on fossil fuels by recovering gas and oil from local wastes.

The pyrolytic products' social and environmental sustainability record is far superior to other ELT recycled products. Pyrolysis also promotes circularity in the tyre industry. By joining the circular economy and using safe pyrolysis products, the tyre industry can improve its corporate ESG (environmental, social, and governance) goals.

Krzysztof Wróblewski is CEO at Contec

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