Atop an industrial building in Greenpoint, Brooklyn, the crew at Gotham Greens can harvest the equivalent of six acres of salad greens and herbs without getting their hands dirty. Bibb lettuce, basil and other leafy plants spout from a stream of recirculated, nutrient-rich water in the company's 15,000-square-foot hydroponic greenhouse.
The process actually uses 20 times less water than a soil-based farm, according to Viraj Puri, Gotham Greens co-founder and CEO. “It's a very efficient, productive way to grow,” he said.
Gotham Greens, with 25 employees, had its first harvest in June. Two soil-based operations—Eagle Street Rooftop Farm, in Greenpoint, and Brooklyn Grange, in Long Island City, Queens—have started up within the past two years, selling their crops to restaurants and markets throughout the city.
But it remains to be seen whether these rooftop farms can compete in a system dominated by national growers.
... The cost of a hydroponic rooftop is about $2 million to $2.5 million, says Paul Lightfoot, CEO of Manhattan-based BrightFarms, a firm that finances hydroponic outfits.
... Mr. Puri would not disclose startup costs for the 0.3-acre farm....
The urban farm's strategy is to focus on growing items that are highly perishable and expensive to ship. “Food goes bad while people own it,”....
Eagle Street co-founder and head farmer Annie Novak says keeping labor costs low is essential to its success. The 6,000-square-foot farm relies on volunteers, apprentices and a partner organization, Growing Chefs, to assist its four paid employees.
The farm focuses on leafy greens and herbs, which provide the best return, says Ms. Novak. “An herb is perfect, because it has a high price and requires zero labor,” she said.
Eagle Street breaks even on crops, with annual revenues of about $1.25 to $1.50 a square foot. The business makes an additional $2,000 from sales of T-shirts and nonperishables such as honey, Ms. Novak said. Building owner Broadway Stages paid for the $60,000 roof, which was designed and installed by New York-based Goode Green. The cost—amounting to about $10 a square foot—was significantly lower than that of many similar projects.
Because Gotham Greens can achieve a denser yield and harvest year-round, Mr. Puri forecasts first-year revenues to be higher “by a factor of hundreds” than those of the average soil-based rooftop farm.
Demand for Gotham Greens items already outstrips supply. Mr. Puri is in talks to open another Brooklyn facility next year and expects to establish several more.
According to The Eagle Street Rooftop Farm Fact Sheet at http://rooftopfarms.org/wp-content/uploads/2010/01/EagleStreetRooftopFarmFactSheet2010.pdf :
• The green roof base system is comprised of 2” of built-up components: polyethelene, drainange mat, and retention and separation fabrics.
• With the approval of the building's engineer, 200,000 pounds of growing medium were lifted onto the roof by crane, in "super-sacks", over the course of a single day. The growing medium, laid directly onto the green roof base, is a mixture of compost, rock particulates and shale and is manufactured in Pennsylvania. It is a green roof component that at the same time retains water, allows for air circulation and is lightweight.
• The green roof can hold over 1.5” of rain, providing a significant reduction in storm water runoff. The captured water, in turn, can help to cool the warehouse below yielding a reduction in cooling costs.
• Installation cost was approximately $10 per square foot. This is significantly lower than most green roof installations due in part to two main factors: the three story building and open expanse of roof were very accessible and, two, that recycled materials such as used rafters were utilized for edging.
• Upon completion of Goode Green's base system installation, the growing medium was moved into by place by a team of farming volunteers over the course of three days. It was arranged into 16 north-south beds measuring thirty inches to four feet in width and divided down the middle by a single long aisle. The beds have a soil depth of 4-7”. The aisles were filled with mulched bark.
• Since overhead watering on a rooftop often evaporates or blows away, irrigation was inititally provided via black plastic drip lines, using city tap water. In 2010, the drip irrigation system was de-installed, as the root systems of the crops rotated and intercropped through the farm during the growing season were incondusive with drip watering (e.g. carrots, microgreens, radishes). Currently, the Farm relies on hand watering (via hose) for seedlings and transplants, and rainwater for established plants (kale, chard, tomatoes).
• In its first season, the Eagle Street Rooftop Farm grew over thirty types of produce, from watermelon to cabbage. Having seen what fared poorly in a greenroof growing environment, in 2010 Annie tightened the crop list to a wider range of varities within a smaller number of crops.
• In 2010, the Farm grows a narrower crop list, with a wide diversity of heirloom and rooftop-acclimated varities of produce within each crop type. In chosing her crops, Annie designed a special rooftop salad mix of seed stock designed to do well on rooftop conditions, yet provide the same colors and spice of traditional popular salad mixes. Currenly, the Farm grows cucumbers, hot peppers, tomatoes, eggplants, spinach, radishes, kale, swiss chard, carrots, peas, beans, salad greens (lettuces, mustards, arugula) herbs (sage, tarragon, oregano, parsley, chives, cilantro, dill), and flowers (cosmos, zinnias, calendula, tobacco, daisys, hops). Additionally, the Farm grows a small amount of corn and squash (winter and summer).
by Sara Eckel
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August 28, 2011