Environmental and Social Dynamics of Urban Rooftop Agriculture (URTA) and Their Impacts on Microclimate Change

Abstract

Urban cities are facing the challenges of microclimatic changes with substantially warmer environments and much less access to fresh vegetables for a healthier food supply than in adjacent rural areas. In this respect, urban rooftop agriculture is considered as a green technology for city dwellers and the community to attain environmental and socioeconomic benefits in a city. For this purpose, a roof top of 216 square meters was selected as an experimental plot where 70% of the area was covered with the selected crops (Tomato, Brinjal, Chili, Bottle Gourd and Leafy vegetables such as Spinach, Red Spinach and Water Spinach; they were cultivated under fencing panels of Bottle Gourd). The microclimatic parameters such as air temperature, near roof surface temperature, indoor temperature and relative humidity and carbon dioxide concentration from different locations of the agricultural roof and from nearby bare roofs were observed during the whole experimental period (November 2018–May 2019). Five existing rooftop gardens with green area coverages of 40, 50, 60, 80, and 85% were selected, and 5 bare nearby roofs were also selected through field visits and questionnaire surveys of 200 existing rooftop gardens. The air and ambient temperature, cooling degree day and energy saving trends were assessed for the selected roofs. The economic assessment was carried out through the net present value and internal rate of return approach of urban rooftop agriculutre. The results showed that the temperature was reduced from 1.2 to 5.5% in different area coverages of agricultural roofs with plants compared to the nearest bare roofs. For the time being, the cooling load was decreased from 3.62 to 23.73%, and energy saving was increased significantly from 5.87 to 55.63% for agricultural roofs compared to bare roofs. The study suggested that the value of urban rooftop agriculture was high environmentally and economically compared to the traditional bare roof, which would be an added amenity by the city dweller’s individual motivations and state interests, and it could be aligned to achieve a more sustainable city.