Green roofing has many benefits: beautifying urban areas, reducing heating and cooling bills of offices etc., but what about using these new green areas to produce fresh vegetables and herbs? That is the brain child of Volkmar Keuter and his group from the Fraunhofer Institute for Environmental Safety and Energy Technology UMSICHT in Oberhausen. Their idea is to put green houses on the rooftops of existing buildings, heat them using excess heat and solar panels and water them using hydroponics perhaps even extracting nutrients from waste water.