rCB

08/28/2025

Recovered carbon black (rCB) comes from the idea that if tyres are 20–30 per cent carbon black, you can cook them in a pyrolysis unit and be left with usable recycled carbon black filler.

But the product isn’t the same as virgin furnace carbon black. The recycled powder carries ash from zinc, silica and sulphur, and its surface chemistry has been baked and altered by years of service and by the thermal process itself.

The result is a weaker, inconsistent material that can only be blended at modest percentages into new tyres without hurting performance.

Each trip through the loop makes it worse. The first recovery yields something marginally useful, the second gives a filler fit for low-spec rubber, and by the third it is only good for road asphalt.

It is the same problem that paper pulp has: each recycling cycle shortens the fibres until they can no longer make paper. With rCB, each cycle adds ash and strips surface activity until it no longer behaves like the engineered material that was useful in tyres in the first place.

The carbon maths don’t help the story. Virgin carbon black costs about three kilograms of CO₂ per kilogram to make. Each pyrolysis recycle pass adds another 1.5–2 kilograms.

Run the material through three recoveries and you have emitted more than eight kilograms of CO₂ per kilogram of rCB, and its a valueless filler.

And that doesn’t include the frictional energy losses caused by having shitter tyres.

What is sold as a circular solution is really downcycling with a heavy energy and CO2 bill, a way of keeping waste tyres on the environmental balance sheet rather than writing them off and taking the hit.