San Francisco’s mandatory recycling scheme and sustainable public transport come under the spotlight. The panel also consider the town of Kamikatsu in Japan, which aims to be 100% zero-waste by 2020. Are they models other cities should follow?

Presenter Fi Glover returns with two new panellists to analyse and critique the best policies from global cities: Dr Ellie Cosgrave, director of UCL City Leadership Laboratory; and urbanist professor Greg Clark. The team scour the world looking for the most inspirational cities, from those tackling environmental issues and urban violence, to encouraging political participation and transforming slums.

(Photo: David Wicks (R) and Glendon Johnson (L) with the San Francisco Water Power and Sewer's SFGreasecycle, a program that collects used cooking oil from San Francisco restaurants to be recycled into biofuels. Credit: Getty Images)