Rooftop transformation and its role in environmental sustainability in Peruvian cities

Urban environments have become through the past century the center of economic activities. However, this explosive economic and demographic growth has been associated with an ever-growing amount of raw materials being... [ view full abstract ]

Urban environments have become through the past century the center of economic activities. However, this explosive economic and demographic growth has been associated with an ever-growing amount of raw materials being extracted to satisfy their needs. In efforts to improve the sustainability of cities, these are starting to include a series of measures to reduce their dependence from areas beyond the city limits. Many of these measures are linked to the global challenge of mitigating greenhouse gas (GHG) emissions, since cities represent over 75% of these. In particular, Peruvian cities offer an attractive and challenging case for studying photovoltaic solar energy, rainwater harvesting and urban agriculture, given the variability of climates throughout the country and the economic growth prospects. In this context in which there are no studies, rooftops have been identified as underused structures with enormous potential for the implementation of sustainable actions. Therefore, the aim of this study is to analyze the environmental benefits and drawbacks of transforming Peruvian rooftops in urban areas in order to reduce resource dependency (energy, water and food products) from the cities outside region. For this, three medium sized Peruvian cities with different climates, Pucallpa (tropical rain forest/ jungle), Ica (dry warm coastal desert) and Ayacucho (dry tempered inter – Andean valley) were selected to conduct the analysis. This choice was based on the fact that each city represents a distinct Peruvian climate: tropical, desert and Andean, respectively.

The methodology used combines the use of Life Cycle Assessment (LCA) and geographic information systems (GIS) to understand the potential of rooftops to valorize their surface area to provide one of the three following services: renewable energy, rainfall harvesting and urban agriculture, depending on the characteristics of each city. Once the data collection phase was completed, a set of site-specific scenarios for the use of the rooftops was defined using GIS to determine the amount of surface available for the different uses. Thereafter, LCA was used to assess the environmental benefits and drawbacks of implementing these sustainable actions in each city as compared to current practices.

Results, which are still being processed, preliminary suggest that there are relevant benefits of transitioning to the use of photovoltaic panels in the rooftops of these cities, reducing dependence on fossil fuels and vulnerable hydropower installations. For this, it has been calculated that photovoltaic solar energy may satisfy (100%) and even overcome the necessity of the city including residential, street lighting and commercial uses. Similarly, rainfall harvesting appears as an appealing valorization route in cities located in the Andes or in the Amazon basis. Finally, urban agriculture appears as a more challenging scenario given the implications linked to limited access to water in areas of increasing scarcity, structural limitations of the rooftops and the use of fertilizers. Finally, the interpretation of the results aims to set a benchmark to create a roadmap for decision-making in urban sustainability in Peruvian cities

Keywords: Life Cycle Assessment; Peru; urban metabolism; urban sustainability