Dr Julia Ravey and Dr Ella Hubber both have a love of science, but it turns out there’s a lot they don’t know about some of the leading women at the front of the inventing game. In Unstoppable, Dr Julia and Dr Ella tell each other the hidden, world-shaping stories of the engineers, innovators and inventors they wish they’d known about when they were starting out as scientists. This week, the story of an engineer who turned plastic into gold, all starting from her mother’s backyard.

Every day, around 500 tonnes of plastic waste is generated in the Kenyan city of Nairobi. Hardly any of it is recycled – but engineer Nzambi Matee is on a mission to change that. Frustrated by the level of pollution, in 2017 Nzambi constructed a laboratory in her mother’s backyard. It was here that she used her self-taught engineering skills to convert plastic waste into bricks that are stronger and more eco-friendly than concrete.

Since then, Nzambi’s backyard operation has grown into a company – Gjenge Makers – and the bricks are widely used across Nairobi. And at only 31, Nzambi is just getting started. As Dr Julia and Dr Ella trace Nzambi’s journey, we hear from Nzambi herself about what it took to get to this point, as well as her ambitions for the future.

Presenters: Dr Ella Hubber and Dr Julia Ravey Producers: Ella Hubber and Julia Ravey Assistant producer: Sophie Ormiston Production Coordinator: Elisabeth Tuohy Editor: Holly Squire

(Photo: Nzambi Matee, Kenyan entrepreneur and inventor, holds plastic polymer recycled to make bricks. Credit: SIMON MAINA/AFP via Getty Images)