Hydroponic Rooftop Gardens

Introduction:

Rooftop gardens are becoming very popular in many large city centers. Many gardens use soil in containers and plants are grown only during spring and summer months when the weather is favorable. However, now more companies are looking at business ventures of this nature using hydroponics and greenhouses to get year-round production to supply markets in close proximity to the greenhouse. Some sell to supermarkets while others sell directly to consumers under a Community Supported Agriculture (CSA) program. A number of operations exist in Montreal, Canada and New York City.

This is not a new idea. In 1986 I was involved in building a rooftop garden on an apartment building in the city of Taipei, Taiwan. The greenhouse was to be constructed on the 13th floor of the building. We had pre-assembled the structural members and hoisted them to the roof with a crane. Since the climate in Taiwan is tropical we needed a structure to protect the crop from the rain and to house a hydroponic system of growing. The structure was of light-weight galvanized steel with polyethylene covering of about 15,000 square feet.

Unknown to the company, GreenTech Developments, the apartment building had been recently sold as condominiums. The owners of the condominiums used the roof to walk their pets and exercise. In their short sightedness they felt the greenhouse operation would restrict them from these activities and they voted to stop the project. As a result, we had to remove the structure from the building.

When I think about it, this would have been an excellent opportunity for the condominium owners as they would have been able to form a CSA and get all of their fresh vegetables from the rooftop greenhouse. To emphasize their lack of support even more was that they could not purchase high quality, clean product in the market. Most of the product grown under field conditions used poor fertilizers, often very unsanitary, and involved the use of many hard pesticides that were not even approved under North American standards. I am sure now a rooftop garden in Taipei would be a welcomed project with the people having become more aware of the quality of vegetables they consume.

Lufa Farms:

Lufa Farms in Montreal, Canada, (www.lufa.com), is located at 1440 Antonio Barbeau in Ahuntsic-Cartierville. It was one of the first rooftop hydroponic greenhouses constructed and came into operation in the spring of 2011. There was one other under construction in New York City by Gotham Greens that came into production later during the year.

The concept of the Lufa Farms rooftop greenhouse was an idea by the owner, Mohamed Hage, co-founder of Cypra Media in Montreal and his consultant friend Kurt Lynn who contacted me to look at the feasibility of building a rooftop hydroponic greenhouse in the city of Montreal. That was in 2008-2009. My role was to layout possible crops that could be grown using various hydroponic systems and to assist in the design of the greenhouse structure.

Small-scale rooftop farms are found in numerous cities, but Lufa Farms was the furthest advanced in the development of a large-scale hydroponic greenhouse facility. Their first prototype operation is 31,000 square feet. It has been constructed on top of a two-story office building in Montreal’s Marche Central neighborhood (photos 1, 2).

The greenhouse is a glass covered galvanized steel structure with 14-ft sidewalls (gutter height). The structure was built by Westbrook Greenhouse Systems Ltd. of Beamsville, Ontario. The structure has a wall separating warm and cold ranges. The warm ranges have natural overhead ventilation whereas the cool ranges have a cooling pad on one wall (photo 3) with exhaust fans on the opposite end. Different heating zones allow two distinct climates, one for warm-season crops and the other for cool-season crops. Warm-season crops include cucumbers, tomatoes, eggplants, peppers and some herbs. The cool-season crops include various types of lettuce, arugula, bok choy, chard, herbs, microgreens and salad mixes. The environmental factors and growing system irrigation cycles are monitored and adjusted by an Argus Controller computer system. The greenhouse atmosphere is enriched with carbon dioxide from bottled carbon dioxide. To enable year-round production the greenhouses are equipped with high intensity discharge (HID) lights (photo 4), which also provide heat during the cold months of late fall and winter. Automatically drawn shade curtains assist in regulating heat and also serve as an insulation curtain during the night.

The vine crops of tomatoes, cucumbers, peppers and eggplants are grown in coco coir substrate slabs fed by drip irrigation in raised trays by FormFlex (photo 5), which are commonly used in most large commercial greenhouse hydroponic operations. Coco coir is a sustainable agricultural substrate. All of the solution is collected by the FormFlex raised trays and re-circulated to the basement of the building where the solution is filtered, sterilized, topped up with raw water and pH and EC adjusted by an injection system with stock tanks by the Argus controller system. After the solution is adjusted in the batch tanks it is returned to the crop on the roof by pumps.

There are three separate nutrient solutions and systems of irrigation controlled independently by the Argus controller. Two separate systems are for the warm season crops in the warm ranges. One is for the cucumbers while the second is for the other vine crops and warm herbs. The third system is for the cool-season crops grown in NFT and ebb & flood benches. Various lettuces, arugula, Swiss chard and bok choy are grown in the NFT system while the herbs, salad mixes, and microgreens are in the ebb & flood system. The nutrient formulation of the third irrigation system is different from that of the other two systems.

Lufa Farms grows all their crops free of pesticides by use of beneficial insects that control the pests.

When product is harvested it is moved to the next floor below by an elevator. There it is graded and packed for delivery to the consumer. The facility also has walk-in coolers to store product for short periods of time as freshness and quality are the main concern of the operation. Product is delivered in “baskets.” This basket program involves different drop-off/pick-up points for boxes in which the baskets are delivered. Customers are subscribed members of the CSA system of Lufa Farms. They receive weekly delivery of a basket of various vegetables grown in the greenhouse. The typical subscription is a 12-week period of small baskets for $264 or $22 per week, and $360 ($30/week) for a large basket. The company now has over 700 subscribed members.

The rooftop greenhouse is beneficial to the office building by conserving heat and insulating the roof. The greenhouse collects all the rainwater from the roof through its gutters and a series of drain pipes takes the water to a collection tank in the basement where it is used to top-up the nutrient tanks for the irrigation system. The greenhouse situated within the city reduces transportation costs by serving a market within a 3- to 4-mile radius where various drop-off/pick-up points are located for the consumer. This also has a very positive psychological impact on consumers by their understanding where the produce comes from and the safety of the conditions under which it is grown. Rooftop gardens also make use of previously unused space within a city.

Recently Lufa Farms Inc., entered into a cooperative agreement with a green industrial-park development group to construct buildings under a “Leadership in Energy & Environmental Design” (LEED) building certification program. Greenhouses will be constructed on top of these buildings under a lease by Lufa Farms. A second greenhouse of about 1 acre in size was completed in 2014. This larger greenhouse is expected to serve up to 5,000 households. The company’s vision is to see a city full of rooftop farms.

Gotham Greens:

Gotham Greens (www.gothamgreens.com) is a rooftop hydroponic greenhouse operation located in an industrial section of Brooklyn, NY. This is a 15,000 square foot facility located on the roof of a two-story former bowling alley (photo 6). It measures 75 ft by 160 ft. The greenhouse environment is controlled with a computer operated weather station that monitors wind, rain, temperature, humidity, carbon dioxide and light intensity similar to that of Lufa Farms. The data is collected to regulate irrigation pumps, greenhouse vents and exhaust fans, and shade curtains.

They have constructed an array of solar panels adjacent to the greenhouse that generates 55 kilowatts of energy (photo 7). Their mission is to operate as sustained agriculture with a minimum energy footprint making it environmentally friendly.

Their crops include various lettuce varieties, bok choy and herbs with specialization in basil (photos 8, 9). They grow with an NFT system which is a re-circulated closed hydroponic system to conserve water. They use integrated pest management (IPM), the use of beneficial insects and natural pesticides to control pests. Their market differs from Lufa Farms in that they market through high-end supermarkets such as D’Agostino’s, Whole Food Markets, Union Market and online grocer FreshDirect. These products are packaged in clear clamshell plastic containers.

Gotham Greens now has one greenhouse on the rooftop of a Whole Foods Store (photo 10).

BrightFarms:

New York Sun Works (NYSW) built a small rooftop hydroponic greenhouse for the Manhattan School for Children, in Manhattan, NY in 2010. BrightFarms is an offshoot from NYSW that developed and constructed the Science Barge project on the Hudson River in New York (photo 11). New York Sun Works, a nonprofit organization, is a sister company to BrightFarms. NYSW set up the Science Barge in 2007. The NYSW rooftop greenhouse offers classes in hydroponics and aquaponics to 6 and 7 year-old school children (photo 12). NYSW plans to build more classroom rooftop greenhouse gardens for schools.

BrightFarms is now called BrightFarm Systems (www.brightfarms.com) . Their mission is to build sustainable, commercial hydroponic farms on urban rooftops. They recently, in 2011, announced an arrangement with McCaffrey’s Markets to build and operate a rooftop greenhouse to market lettuce, tomatoes and herbs through McCaffery’s. BrightFarms will build a one-acre greenhouse for McCaffery’s Markets of Pennsylvania.

Summary:

While all of these companies have the same philosophy of growing produce close to their market as urban rooftop gardens, Gotham Greens and BrightFarms will market direct to supermarkets and restaurants, whereas, Lufa Farms markets direct to consumers through a CSA membership. In this way, Lufa Farms reduces all intermediary handling of their produce by using the basket system of drop-off/pick-up sites within close proximity of the greenhouse operation.