Time for your phone upgrade? What did you do with the old one? Stick it in a drawer, hand it back to your phone company or just throw it away.

Have you ever considered that your smartphone might be a treasure trove of precious metals, a rich vein of gold, silver and platinum? Welcome to the world of the Urban Miners.

And it's not just smartphones; almost anything with a circuit board contains precious metal of some sort. If you add up all the electronic and electrical waste across Scotland you have a small mountain of pre-loved devices and appliances. But stored within that mountain are rich seams of precious metals just waiting to be mined and potentially turned back into something else.

In this episode of Brainwaves Pennie Latin discovers how gold is being retrieved from smartphones, platinum from road sweepings in richer and more environmentally friendly ways than the original mining process.

This re-using of materials leads to the onset of the circular economy and potential for huge innovation, design and invention, which is being driven here in Scotland by the Institute of Remanufacture and Zero Waste Scotland who say that in a world of limited resources, re-using, re-furbishing and remanufacturing may be the only realistic way forward.