Harvesting carbon for a circular economy

When one drives on a highway or even in city waste dumps, one sees old and used tyres thrown haphazardly about. A typical tyre comprises 50 percent natural rubber, 30 percent carbon black and 20 percent chemicals.

Tyres take a very long time to degrade in soil. On average, it can take anywhere from 50 to 80 years for a tyre to break down completely, and some estimates suggest it could take even longer—hundreds of years—depending on environmental conditions. This slow degradation process is due to the materials used in the tyres manufacturing process, such as synthetic rubber, steel, and  resistant to natural breakdown.

This slow decomposition can have environmental consequences, as tyres can leach harmful chemicals into the soil and groundwater, impacting ecosystems.
Used tyres can be big business for companies involved in their recycling. An article signed by the chief of Automotive Tyres Manufacturers Association suggests that between April and November 2023, around 8.8 lakh million tonnes of scrapped tyres were brought from developed countries into India. These were burnt or
retreated for selling into the aftermarket, which is unsafe for both humans and animals. In humans, exposure to carbon black it can cause lung disease as well as nose, eyes and throat irritation. Why are used tyres unsafe for the environment?

For one, when burnt, they release methane into the air which contributes to global warming. For another, they do not degrade easily and take up large areas in landfills. There are also other hazards including fire, mosquito breeding, micro plastics pollution, apart from the space that is required. Then there is carbon black that is used in tyre making, and gets lost if tyres are left to rot at landfills.

Studies suggest that the tyre sector drives 90 percent of the market demand for carbon black, with the rubber industry alone requiring over 15 million tons per year as a reinforcing filler sourced from fossil fuels. China is the world’s largest producer and user of carbon black. Driving its demand is manufacturing plastic and tyre products. The Asia-Pacific region's market is expected to expand due to increasing R&D efforts and product advances.

The need for carbon black is multi-fold, it is used to strengthen but also used as a pigment, UV stabiliser, and conductive or insulating agent in a variety of rubber, plastic, ink and coating applications.

Apart from tyres, carbon black is also used in the making of automotive component parts that used rubber. This is because the carbon black provides elasticity and durability as well as enhances rubber's ability to resist deformation and improve its mechanical properties. Within the auto sector, apart from tyres, carbon black is
used for engine mounts, hoses, anti-vibration parts, and sealing systems.

End Use of Recovered Carbon Black (rCB)
1. Reinforcement in rubber: Recovered carbon black can be used as a reinforcing agent in new tyre
production or other rubber products.
2. Pigments: It can be used in making inks, paints, and coatings.
3. Plastic manufacturing: It can be used as an additive to enhance material properties.
4. Construction materials: It can be incorporated into asphalt or other construction materials.

Challenges:
1. Cost: Pyrolysis plants require significant investments in equipment and energy.
2. Impurities: Recovered carbon black may have different properties than virgin carbon black, which can
limit its use in some high-end applications.

Carbon black is a petroleum-based product that is derived primarily produced from fossil fuels like natural gas, aromatic oil, and heavy tar through a furnace method. The process involves combusting hydrocarbons with limited oxygen to produce carbon black, which is then refined to meet specific particle size and fineness
criteria.

Given that it is a POL-derivative, its use and disposal needs to be handled with care as it can pollute the environment as we have seen in the case of disposed tyres. So what is government and industry doing about this?

India has already taken some steps to promote the rCB or recovered carbon black industry, including setting guidelines for the collection, storage, and disposal of used tyres. It is not easy to extract carbon black, which to the eyes appear as spherical granules grouped in aggregates. End of life (ELT) tyres are robust products.

Hold one or try to lift one and one will get an idea about this. However, recent advances in pyrolysis technology have allowed the development of valuable secondary raw materials from ELT that can help support
the circular economy.

Pyrolysis is a sustainable process that breaks down rubber into its components, including carbon black. Moreover, recycling carbon black is eco-friendly because it reduces the need for extracting new carbon black from fossil fuels. This, over the long run, helps lower greenhouse gas (GHG) and conserves our natural
resources. 

Hanover-based Continental AG last August concluded a long-term purchase agreement with Pyrum Innovations, a specialist in the thermolysis technology of end-of-life tyres, for high-quality carbon black
(rCB) recovered from end-of-life tyres. 

At Sujan ContiTech, a JV with Continental AG, we have kicked off a project to explore the possibility of using recycled CB in our anti-vibration product portfolio. It is time for companies that use rubber to make car parts to explore the possibility of using recycled CB in their product range. Moreover, undertaking projects like this
can be made an integral part of a company’s commitment to Environment, Safety and Governance (ESG). The JNV Ventures Group, that SCT is a part of is also exploring issues centered around ECG as it aims to lower the carbon footprint of its manufacturing processes and products.

Given uncertainties in oil prices and environmental concerns, there is a need to explore renewable and sustainable sources for carbon black production as well as recover as much carbon black from tyres, conveyorbelts, hoses, seals, gaskets, and rubber sheets. 

The rCB can be used to replace the carbon black that we currently use, with no impact on the properties that carbon black is known for: reinforcement, elasticity, hardness, and tear and abrasion resistance. Above all, recycling carbon black will be a significant contribution to supporting a circular economy, and helping us be a
responsible corporate citizen.

The author is AGM, R&D, CV division, Sujan ContiTech AVS Private Limited. Views are his own.