Where most people see a bruised banana, Saasha Celestial-One and Tessa Cook see a chance to share. Their new app, Olio, allows greengrocers, cafes, restaurants and neighbours to photograph and post food that is surplus, unappealing or close to expiry; other app users then request it and are notified where to pick it up. According to the UN’s Food and Agricultural Organisation, a third of all food is wasted, and more than half of that…