Two recent studies have examined the theory. In Rotterdam, all flows of raw materials and waste were identified for businesses in the port zone. The aim now is to optimise the way residual flows are processed, with potential for environmental, economic and social benefits. A second report focusing on European circular urban ports mapped out eleven port cities, using a standardised methodology. For each of the cities studied, which included both river and sea ports, the report identified best practices and summarised the strategies adopted.