Rural grown produce can spent weeks traveling thousands of kilometers to reach the supermarkets of the cities, so we have the development of urban farms. Fresh product ,free from chemical spraying and genetic modification. Urban farming , if not certified organic, is for the most part done naturally, with water conservation and other environmental efforts driving the growth and cutting costs.
Lufa Farms of Montreal grows a wide variety of vegetables on top of two low rise commercial buildings. A commercial greenhouse can use a large amount of water and other resources. In Lufa’s 31,000 and 43,000 sq. ft. facilities they recirculate water through closed loop networks of tanks, pumps, pipes , and filters. Their hydroponic greenhouses use up to 90% less water than comparable ones that do not recirculate. Drip lines are used to irrigate the plants, with the water that is not absorbed or lost to evaporation captured, sent to the tanks, filtered and reused. To decrease the need for city water they harvest rainwater and indoor condensation from the greenhouses using a system of gutters.
Lufa also composts on site,saves energy through biomass heating systems and semi transparent energy curtains, and employs biological methods of pest control…ladybugs prey on anything competing with humans for produce.
The Lufa project is showing good results , and there are other similar facilities beginning to appear. Drip tape feeds seem to be the way to go, as well tent like fabric are used to contain moisture and prevent evaporation, and mulch. These are still early days for commercial urban agriculture. Drip tapes , closed loops in a hydroponic green house are the norm. Collecting rainwater and condensate harvesting are less common. This is because of the risk of contamination from air pollution, bird feces, and decaying organic matter. Making the water potable requires investment in storage tanks, pumps, filters, and some for of disinfectant which drive up costs.
The challenge is that urban farming to a large degree is still a marginal business.
How A Roof Top Farm Feeds A City: Mohamed Hage