BACKGROUND: As urban populations increase so does the amount of food transported to cities worldwide, and innovative agro-urban systems are being developed to integrate agricultural production into buildings; for example, by using roof top greenhouses (RTGs). This paper aims to quantify and compare, through a life cycle assessment, the environmental impact of the current linear supply system with a RTG system by using a case study for the production of tomatoes. RESULTS: The main results indicate that a change from the current linear system to the RTG system could result in a reduction, per kilogram of tomatoes (the functional unit), in the range of 44.4-75.5% for the different impact categories analysed, and savings of up to 73.5% in energy requirements. These savings are associated with re-utilisation of packaging systems (55.4-85.2%), minimisation of transport requirements (7.6-15.6%) and reduction of the loss of product during transportation and retail stages (7.3-37%). CONCLUSIONS: The RTG may become a strategic factor in the design of low-carbon cities in Mediterranean areas. Short-term implementation in the city of Barcelona could result in savings of 66.1 tonnes of CO2 eq. ha(-1) when considering the global warming potential, and of 71.03 t ha(-1) when considering that the transformation from woodland to agricultural land is avoided. (C) 2012 Society of Chemical Industry
