“Don’t quit your day job” – or so entrepreneurs are often advised when trying to build a business.

But Nzambi Matee of Kenya did quit her day job — and her social life and  invested all her savings into an experimental project in her mother’s back garden. “My friends were worried,” she admits. “Everyone thought I was crazy, and so many people told me to give up.” Matee is the founder of Gjenge Makers, a company that uses discarded plastic to produce building materials.

After noticing the volumes of plastic bags polluting the streets of Nairobi, she developed a machine that compresses a mixture of plastic and sand into bricks. Lighter and more durable than cement, they are affordable and have been used to pave walkways for homes and schools —including those in low-income areas where students would otherwise have to walk on dirt paths. Her business now produces 1,500 pavers per day, proving it is possible to move from a linear economy toward a circular one in which products and materials remain in use for as long as possible.