4. Trash or Treasure: Food

The UN estimates that each year, we throw away almost a billion tonnes of food. That's an almost inconceivable amount, and one which has given rise to increasing innovation and activism. It's not just about not emptying our plates or clearing out our fridge before the food goes off: one estimate has it that a third of perfectly edible food is thrown away at source simply because it looks misshapen or unappealing.

In this episode of Trash or Treasure, we speak to zero-waste consumers, change-seeking chefs and 'dumpster divers' who save good food from supermarket dustbins; investigate apps which redistribute restaurant-surplus food; and visit the anaerobic digestion plant turning waste food into fuel and fertilizer.