Providing food for seven billion people is fraught with difficulty. Fertilising vast tracts of land and flying fresh vegetables across the globe comes at a huge environmental cost. But more and more people are turning to hydroponics - growing plants in water, without any soil. The idea itself is hundreds of years old, but new twists on the old technique are now shaping the future of food. We investigate some of the most innovative hydroponics projects, from the refugees growing barley for their goats in the Algerian desert to the underground farm built in an abandoned London bomb shelter. But how efficient can the process become? Can hydroponics begin to offer a serious alternative to conventional farming?

Presenter: Harriet Noble