Techniques and crops for efficient rooftop gardens in Bologna, Italy

Abstract

Urban rooftop farming favours local food production. Although rooftop farming is perceived as a sustainable system, there is a lack of quantitative studies. There, we set up experiments in the community rooftop garden of a public housing building in Bologna, Italy, between 2012 and 2014. We grew lettuce, a leafy vegetable, using three techniques: nutrient film, floating hydroponic and soil cultivation. We also grew tomato, chilli pepper, eggplant, melon, watermelon on soils. Data was analysed by life cycle assessment for environmental and economic performance. Results reveal that the best techniques of lettuce cultivation to address global warming were floating in the summer, with 65-85 % less environmental impact per kilogran than nutrient film; and soil production in the winter, with 85-95 % less environmental impact. Furthermore, floating production was 25 % cheaper in summer, and soil was 65 % cheaper in winter, compared to the nutrient film technique. For soil production, eggplants and tomatoes showed the best environmental performances of about 74 g CO 2 per kg. Eggplant production in soil was cheapest at 0.13 € per kg.

Eco-Efficiency Assessment and Food Security Potential of Home Gardening: A Case Study in Padua, Italy

“…For climate change (Figure 7), tomato and lettuce environmental data were available for different UA forms and case studies. Home-grown tomatoes had a slightly higher environmental impact than soil-based urban farms in the United States [47] and a rooftop garden in Italy [48]. The impact was significantly lower when compared to an open-air rooftop farm in the USA [47] and community farming with organic practices in the United Kingdom [50].…”

“…The community rooftop garden in Bologna (Italy) employed electrical devices for automatic fertigation of the garden leading to a large consumption of electricity. Due to the current electricity mix in Italy, this resource consumption had a relevant impact on the environmental indicators [48]. Furthermore, the cost of the auxiliary equipment required for this automatization was also the main contributor to the life cycle costing [48].…”

“…Due to the current electricity mix in Italy, this resource consumption had a relevant impact on the environmental indicators [48]. Furthermore, the cost of the auxiliary equipment required for this automatization was also the main contributor to the life cycle costing [48]. In this home garden, the employment of manual techniques was enhanced, and thus offered a higher eco-efficiency.…”

“…The case study under assessment followed low-input agronomic practices, minimizing the consumption of certain resources. In particular, this home garden showed a great advantage of employing a manual management, while avoiding the use of electronic devices to automatize irrigation, which was a relevant element of the environmental burdens of community gardening in a case study in Bologna (Italy) [48]. Along the same lines, these manual practices also benefited the economic cost of the home-grown products, which resulted in economic savings for the gardener.…”

“…In this line, a study on home gardens in Australia assessed the variables affecting water consumption in gardens, underlining the role of lifestyle and garden management practices [46]. However, no study have quantified the environmental impacts of urban food production in home gardens-thereby considering all the external inputs and the resulting productivity, unlike other typologies of UA (e.g., rooftop agriculture, community gardening, aquaponics) [47][48][49][50][51][52][53][54][55].…”