|Authors: ||J. Nelkin, T. Caplow|
|Keywords: ||urban agriculture, renewable energy, rain water catchment, recirculating hydroponics, sustainability|
Increasing urbanization and the high environmental and monetary costs of delivering power, water, and food to cities, suggest that a low impact form of controlled environment agriculture (CEA) could play a role in urban settings.
Environmental impacts of CEA can be aggressively reduced through carbon neutral energy supply, water recapture and recycling, and siting on pre-existing or underutilized structures.
As a pilot study, a 120 m2 greenhouse was constructed on the steel deck of a 460 m2 barge moored in central Manhattan in New York City.
All power demands are met on site by a 2.4 kW solar array, a 2 kW wind turbine array, and a 5 kW generator running on biofuels.
All water needs are met on site by rooftop rainwater catchment and by desalination of river water.
Greenhouse operations are maintained for 8 months per year, with supplemental heating available from a biofuel furnace.
Data were collected from a 24 m2 cucumber plot within the greenhouse during summer months.
Cucumber yields averaged 1.3 kg m-2 per week, with consumption of electricity and water averaging 1.4 kWh m-2 and 22.9 L m-2 per week, respectively.
A ratio of approximately 3:1 between greenhouse floor area and solar panel area (or 40 peak watts per m2 of greenhouse) would allow 100% solar operation, and a ratio of approximately 1:1 between greenhouse floor area and rainwater catchment area is sufficient to meet all irrigation demands.
These ratios suggest design parameters for rooftop applications in urban settings, where substantial unused area could be utilized for food production.
Potential benefits include an environmentally sustainable food supply, increased urban green space, greater control of rooftop thermal fluxes in supporting buildings, and educational opportunities.
Future research should address costs, suitability in different climates, and constraints on building integration.
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