Abstract
Urban planning has been focusing its attention on urban rooftop agriculture as an innovative way to produce local and reliable food in unused spaces in cities. However, there is a lack of quantitative data on soilless urban home gardens and their contribution to self-sufficiency. The aim of the present study is to provide quantitative agronomic and environmental data on an actual soilless urban garden to estimate its degree of self-sufficiency and sustainability. For this purpose, an 18 m2 soilless polyculture rooftop urban home garden in the city center of Barcelona was analyzed. From 2015 to 2017, 22 different crops were grown to feed 2 people in an open-air soilless system, and a life cycle assessment was performed. A total productivity of 10.6 kg/m2/year was achieved, meaning that 5.3 m2 would be needed to fulfill the yearly vegetable requirements of an average citizen (in terms of weight). Considering the vegetable market basket of Catalonia, an 8.2 m2 soilless garden would be needed to cover 62% of the market basket for one person. The top 5 most productive crops were tomato, chard, lettuce, pepper and eggplant, accounting for 85.5% of the total production. The water consumption was 3.7 L/m2/day, and 3.3 kg/year/m2 of waste was generated. A high degree of self-sufficiency was achieved, although adjustments could be made to adapt the production to the market basket. The environmental assessment showed that the fertilizers and their associated leachates accounted for the highest environmental impacts in all the studied impact categories. Overall, 0.6 kg CO2 eq. was generated per kg of vegetables produced. The quantitative data provided by the present study offer a reference from which urban planners and researchers can project future implementations of rooftop urban agriculture (UA) on a large scale.
Highlights
The continuously increasing world population is predicted to rise to almost 10 billion people by 2050 (United Nations, Department of Economic and Social Affairs, Population Division, 2017)
The general aim of this paper is to assess the feasibility of an open-air rooftop soilless polyculture home urban garden in Barcelona by providing quantitative agronomic and environmental data
Food production is assessed for the agronomic portion, while the environmental performance focuses on the life cycle impact assessment considering the data acquired in the inventory
Summary
The continuously increasing world population is predicted to rise to almost 10 billion people by 2050 (United Nations, Department of Economic and Social Affairs, Population Division, 2017). Assessment of Urban Home Garden in the European Union, 72% of the population already lives in urban areas (Eurostat, 2015) The consequence of this trend is a progressive urban expansion that widens the distances between production and consumption areas, increasing the dependence of cities on external resources (Scoones, 2009). In this context, the necessity of rethinking our food systems is rising to achieve urban sustainability and avoid intensive agricultural techniques that have critical environmental costs
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