Some 80,000 people live in the Za’atari refugee camp in Jordan, the world’s largest for people fleeing the war in Syria. As the camp has evolved from a temporary tent city to a semi-permanent settlement of prefabricated houses, a surprising challenge has emerged: what to do with thousands of discarded mattresses. Chemist Tony Ryan from the University of Sheffield knew exactly what to do — use them to grow food. Amy Scott spoke with Victoria Gill, who reported this story for BBC.