Incorporating user preferences in rooftop food-energy-water production through integrated sustainability assessment

With the overall aim to design successful implementation strategies of food-energy-water production systems on urban roofs, we propose an integrated process that includes participatory processes and a multi-dimensional sustainability assessment of environmental, social and economic indicators. The proposed framework was applied to a typical housing estate in the Metropolitan Area of Barcelona made up of 201 buildings and 13,466 inhabitants and characterized by a high share of low-income families. We assess several future scenarios of joint electricity production (photovoltaic panels), vegetable production (through open-air farming and greenhouses), green roof implementation and rainwater harvesting and rank them according to non-participatory and participatory approaches. In general, there was a tendency for residents to choose strategies providing energy and water rather than the food production potential of rooftops. However, the environmental assessment indicated that the least impacting alternatives from a life cycle approach were those promoting vegetable production, meeting 42 to 56% of the residents’ fresh produce demand and reducing environmental impacts by 24 to 37 kg CO₂eq m⁻² of rooftop/year. Hence, we found that residents were mainly concerned with energy expenses and not so much with food insecurity, social cohesion or the impacts of long-distance supply chains. Our assessment supports urban sustainability and helps identify and breach the gap between scientific and user preferences in urban environmental proposals by informing and educating residents through a participatory integrated assessment.