Meet the entrepreneurs using scrap rubber to fuel cars and make new tyres.

Each year, over a billion car tyres reach the end of their life.

They’re notoriously hard to recycle and present an environmental hazard if left to disintegrate out in the open.

But around the world, people are trying to clean up their cities by finding new uses for the mountains of rubber waste.

In Senegal, a young entrepreneur is turning them into artificial football pitches. In Zambia, an engineer is perfecting a way to turn these tyres into diesel. And in Canada, a company is making new tyres out of old ones using some very clever chemistry.