One of the biggest challenges facing agricultural expansion, particularly in urban agriculture, is the shortage of available crop space. Yet, in cities across America there are thousands of square feet of available planting space. The space is the flat roofs that top many metropolitan buildings. This notion is not new, and across the country it seems to be taking root in the urban agriculture movement.Robin Shulman of the Washington Post reports that Ben Flanner has planted a 6,000 square foot farm on a rooftop in the Greenpoint section of Brooklyn, New York. Mr. Flanner has a diversity of crops—mainly vegetables and herbs and fruits. The farm sits three stories off the ground and gets direct sunlight, which is a rarity in densely-packed New York City. As Shulman points out, in American cities it makes more economic sense for investors to buy the expensive land for building construction rather than farms. But planting on rooftops provides would be farmers with both space and access to direct sunlight and could become profitable operations.
Green roofs are already in existence, and their value is well-documented. They capture rainwater and lower electricity use by keeping building warmer in the winter and cooler in the summer. Now, it appears that rooftop farming is ready to become the latest trend in urban agriculture. Flanner did get outside help in paying for his project which required 200,000 pounds of soil to be put on the roof at a cost of $60,000. “Flanner harvests in the mornings, barters vegetables for lunch at local eateries, and in the afternoons bikes dozens of pounds of produce to restaurants that have commissioned them.”
There are a few commercial-scale rooftop farms that have started up and developed a basic formula for making the operations profitable. As Shulman writes, this formula “involves the distance vegetables must travel from farm to table, their consequent price and quality, and a city's food culture and population density.” The formula seems to be working in New York where “hundreds of other rooftop gardens are in the works, some even large-scale.”
In Queens, Gotham Greens plans to build a 10,000 square-foot greenhouse on a roof that could potentially yield 30 tons of greens and herbs to sell. An affordable-housing developer is in the process of “designing a 10,000-square-foot rooftop greenhouse for an eight-story building to be run by a local food co-op” in South Bronx. And the list continues as projects are being developed across the city.
Of course, there are obstacles, the biggest one being costs. As Shulman reports, “[a] structural engineer must assess the roof's ability to bear weight. A base layer of heavy-duty plastic may be laid on the roof, and it may be retrofitted for drainage or even outfitted with a greenhouse [.]”
Other challenges include water access for plants under direct sunlight, dealing with winds, and simply getting materials to the roof. However, there are benefits, such as the sun access and the lack of pests.
Other cities are taking steps to embrace the urban agriculture movement. “In San Francisco, Mayor Gavin Newsom has required all departments to audit their land, seeking places suitable for urban agriculture. Chicago, where the mayor's office has a green roof, also has the country's first organic-certified rooftop farm, 2,500 square feet over a restaurant. Toronto just passed a law requiring green roofs on new buildings above a certain size, and many could include food.”
Large-scale rooftop farms could help drive down the price of fruits and vegetables by offering competition to the products raised elsewhere and shipped in. If the cost-benefits analyses of the initial operations are positive, then people may be seeing more farms when they fly into American cities.
To read Shulman’s article click here.
Posted: 09/15/09
