Carbon Black
Early car tyres at the start of the 20th century were made from natural rubber, which was light-coloured and wore out quickly. They were prone to cracking, abrasion, and heat damage. Around 1904, tyre makers began adding carbon black, originally soot from burning oil.
A small percentage of carbon black mixed into the rubber compound has the following benefits:
Strengthens the tyre by reinforcing the rubber matrix, greatly improving resistance to wear and abrasion, and improving traction.
Protects against UV degradation, since the black pigment absorbed and dissipated light that would otherwise break down the polymer chains.
Improves heat conduction, allowing tyres to shed heat more efficiently at high speeds, so grip stayed more consistent at higher speeds.
By the 1920s, nearly all major tyre manufacturers had adopted carbon black as a standard filler. Its use extended tyre life by a factor of five or more. Before, tyres were white or light-grey; after carbon black, black tyres became the norm.
Carbon black production grew into a large industry with purpose-built “furnace black” processes developed in the 1930s to produce consistent, high-surface-area material tailored for rubber reinforcement. Today, the majority of carbon black produced worldwide (around 70%) still goes into tyres, with the rest used in belts, hoses, plastics, inks, and coatings.
The composition of modern tyres is roughly as follows:
- Carbon black: ~22–28%
- Natural and/or synthetic rubber: ~40–50%
- Steel + textiles: ~10–15%
- Other additives (silica, zinc oxide, sulphur, oils, resins, etc.): ~10–15%
Recovered carbon black (rCB) has been around since the 1970s. It is the carbon black fraction left when the rubber in waste tyres is processed by pyrolysis or other controlled thermal treatments. Unlike open burning, pyrolysis is done in an oxygen-limited environment, so the rubber polymers crack into gases and oils without combusting. Steel is separated magnetically, oils can be refined for fuels or chemical feedstocks, and the residue is a fine, black powder that resembles, but isn’t identical to, virgin furnace carbon black.
The challenge with rCB is its quality and consistency. Virgin carbon black is manufactured with precise control of particle size, surface area, and structure, which directly determine a tyre’s wear, rolling resistance, and traction. rCB, on the other hand, carries remnants of ash (from other fillers in tyres like silica, zinc oxide, sulphur, etc.) and its surface chemistry has been altered by both the tyre’s service life and the pyrolysis process. As a result, it typically has lower value than fresh material. Most manufacturers who use rCB blend it at modest percentages (often around 10% of the carbon black used, so 2% of the total mass of a tyre) with virgin carbon black in new tyre compounds, balancing performance with sustainability goals.
On the positive side, rCB has become attractive because it closes the loop on one of the largest waste streams in the world. Over a billion tyres are scrapped annually. rCB use reduces landfill, cuts demand for fossil-derived feedstocks, but it increases CO₂ emissions compared to virgin production. Companies such as Michelin, Continental, Bridgestone and Goodyear have announced pilot or commercial use of rCB in selected product lines. At the same time, specialised recyclers (e.g. Scandinavian Enviro Systems, Pyrum Innovations, Delta-Energy) are scaling up industrial rCB production with more refined purification and activation techniques to get closer to virgin performance.
Like most things these days, it’s mostly bullshit. The energy used to recover the carbon black and the CO2 pollution created, means that tyres with rCB have a higher carbon footprint than normal tyres. It also degrades tyre performance. So they blend as little as they can in to justify the environmental marketing campaign.
Arguably it’s a good thing to keep tyres out of landfill but landfill is not that big of a problem. True, some countries allow the burning of old tyres, but they’re also the sort of countries that are never going to pay extra to use recycled materials.
In our lovely first world we can happily bury our old car tyres. Come back in few million years and the buried rubber will have converted to oil, which they can then burn to make their own carbon black. Now that’s what I call a circular economy.
offshore westerly 