As cities have become home for 50% of the world’s population, urban systems have definitely caught
public attention. The urban metabolism can be improved by transforming their linear behavior into a more
circular one. This paper is based on a project initiated by the Division of Environmental Technology and
Management at Linköping university, financed by Vinnova: Megatech. The aim is to study the megacities of
Cairo and Mexico City in order to understand some of the problems they are facing. By improving their energy
and material flows behavior, these megacities can benefit from the reduction of their dependence on fossil fuels
and virgin materials; the protection of part of their social, economic and productive systems from external factors
(e.g. political drawbacks, shortage/distribution problems, international prices); an increased effectiveness of their
planning activities–as they would be based to a large extent on their own resources–and the reduction of their
environmental burden. An in situ study will take place with the participation of local stakeholders. Information
about environmental problems will be collected and potential solutions will be analyzed and suggested. A
tentative model is presented, showing how the reinsertion of the outflows into the urban system could benefit
these cities’ overall environmental performance.