New feature article posted on Progressive Engineer: BrightFarms pioneers hydroponic greenhouses on urban building rooftops for growing vegetables more sustainably

Bright Future

BrightFarms has pioneered rooftop hydroponic greenhouses for growing vegetables close to consumers in urban environments, offering myriad benefits such as reduced energy use and transportation costs.

One of BrightFarms’ signature projects, this greenhouse sits on the third-floor roof at the Manhattan School for Children. An evaporative cooling system helps maintain optimum temperature for growing plants. Credit: Tom Gibson.

By Tom Gibson, P.E.

I board the Metro North train from Beacon, NY and take it 60 miles south to Grand Central Terminal in New York City’s lower Manhattan, along the way taking in views of the scenic Hudson River. After stumbling around the massive station and asking directions, I take the Uptown No. 1 subway to 96th St. in Manhattan’s Upper West Side. Finally, I walk a few blocks to the Manhattan School for Children, arriving late morning. Hiking up to the third floor, I find a greenhouse on the roof, just what I came to see.

Why would I go to all this trouble to see a greenhouse at an elementary school? This one’s unique because it was created by BrightFarms to grow fruits and vegetables using hydroponics in an urban environment. This is part of an effort to grow produce with a reduced carbon footprint by reducing energy use, both in the growing process and the transportation required to bring it to consumers.

Soon after arriving, I meet with Zak Adams, director of engineering at BrightFarms. He tells me, “We marry greenhouses with environmental technologies like rainwater capture and renewable energy production. These controlled-environment agriculture facilities are highly productive. They can produce ten times the amount of food in a given area compared to conventional soil agriculture.”

Based in Manhattan, BrightFarms designs, finances, builds, and operates hydroponic greenhouse farms across the United States, mostly at supermarkets. There is no cost to the retailer to build the facility, only an obligation to purchase the output. BrightFarms enters into 10-year purchase agreements with grocery retailers, requiring them to purchase all the output at fixed prices.

Standing next to a rainwater catchment tank in the greenhouse, Zak Adams heads engineering activities at BrightFarms. Credit: Tom Gibson.

Their greenhouses typically produce lettuce and other salad greens; leafy greens such as chard, kale, and mustard greens; herbs; tomatoes; peppers; and cucumbers. Most fruits and vegetables can be grown hydroponically but not all are commercially viable yet. Typically, highly perishable fruits or vegetables, which do not store well or suffer from extensive transportation, yield higher prices and therefore justify the investment in the technology.

Extensive engineering goes into a typical BrightFarms greenhouse project, as Adams begins to elaborate. ”Structural considerations are always a big challenge when we start an initial design. We want to make sure the building underneath us can not only handle our load but also has the proper membrane on the roof so we don’t disturb any aspect of our host building’s operations.”

He described the existing roof structure here as “beefy,” saying how greenhouse structures are not relatively heavy, so most roofs in the Northeast, for example, are already built to a 40 psf (pounds per square foot) snow load, roughly equivalent to that of a greenhouse. The school has an aggregate roof with multiple epoxy membrane layers, so they peeled off and removed the membrane, leaving enough to overlap onto the greenhouse.

With the roof providing adequate overall structure, the concern shifts to point loading. The roof has girders, or I-beams, every 15-20 feet, but these didn’t match the spacing of the loads in the greenhouse, mainly water tanks. So they put in dunnage I-beams perpendicular to the girders for them, placing the loads over the girders as much as possible.

“We use rainwater catchment in our facilities, and we want to store as much water as possible. That can be difficult,” Adams explains. “You might need to come up with schemes for how to store the water. Store it at ground level and maybe pump up to a smaller tank at night when electricity’s cheaper and less in demand, for example. Or, as you can see with this facility, position your water tanks directly over very strong points in the roof, where girders intersect or where there’s a dunnage stage or an elevator bulkhead.”

Concerning the greenhouse itself, Adams says, “What you see here is pretty typical for greenhouse construction.” It has single-pane glass around the sides and double-layer polycarbonate on the roof, which is actually the opposite of how it would normally be done. They normally put glass in the roof to get the most sun exposure -- “you want the glass in the roof as clear as possible because that’s critical to plant growth.” However, school rules would’ve required safety glass with wire in it to provide extra protection for students, and this would’ve been extremely expensive. They used glass for the walls mainly so the students could see out better.

A sea change
In explaining the methodology for the whole concept, Adams says, “What we’re trying to do is revolutionary. We’re trying to change the food system fundamentally by eliminating fossil fuels from the equation as much as we can.” For starters, that requires a facility that can grow food year round. A BrightFarms greenhouse grows food with a fraction of the land and water use and produces no agricultural runoff compared to conventional methods. “The idea is to take all that energy used in transportation and to use less energy to grow the same food right next to where the consumer is.”

Lettuce and other greens are grown in water-filled tubes in a process known as succession planting. Credit: Tom Gibson.

Where they do use energy, they try to use renewable sources as well as waste energy from a host building, explaining why they build on rooftops. If an adjacent building generates waste heat from a process, for example, they pipe it into a greenhouse.

Much of the inspiration for BrightFarms came from founder Dr. Ted Caplow, viewed in the industry as an urban farming visionary and pioneer in rooftop sustainable greenhouse development. Born in New York City and raised in Virginia and Massachusetts, Caplow has a B.A. in sociology from Harvard, an M.S. in mechanical and aerospace engineering from Princeton, and a Ph.D. in environmental engineering from Columbia?.

Formerly a clean energy consultant for Capital-E, Caplow, 42, worked on energy efficiency and carbon offset credits for a range of clients including the California Energy Commission and the U.S. Department of Energy. His expertise lies mainly in the area of integrated system design, with specialties in renewable energy, water contaminant dynamics, and technology assessment.

As Caplow recalls, “After studying engineering and environmental science in graduate school, I faced a choice between a career as a university professor or something more entrepreneurial. I was interested in sustainable production systems -- food, water, and energy. I visited a large-scale hydroponic vegetable greenhouse in 2005, and I was immediately hooked. To me, hydroponics represented a fusion of engineering efficiency and grassroots food production, and the challenge of applying these ideas to the congested urban environment was immediately appealing.”

In 2006, Caplow founded nonprofit New York Sun Works to promote the use of hydroponic greenhouses for sustainable urban agriculture practices. Its mission was the design and promotion of ecologically responsible systems to produce energy, water, and food within the urban environment. In 2007, NYSW launched the renowned Science Barge, a prototype urban farm. Constructed on a steel deck barge and moored on the Hudson River in midtown Manhattan, the Science Barge serves as a public demonstration of renewable energy supporting sustainable food production. Its greenhouse electrical systems are powered by solar, wind, and biodiesel. The Science Barge also acts as an environmental education facility for students of all ages.

BrightFarms co-founder Dr. Ted Caplow has graduate degrees in engineering. Courtesy Ted Caplow.

In 2008, Caplow founded BrightFarm Systems, a consulting firm providing technical services in support of rooftop greenhouses and building integrated agriculture. Then, in January 2011, BrightFarms resulted from the merger of Better Food Solutions and BrightFarm Systems, with the company’s staff absorbing into the new company. Caplow co-founded BrightFarms with Paul Lightfoot, who now serves as CEO. Caplow serves as president of the board of directors, a shareholder, and an investor, all with the role of oversight and strategic guidance.

The initial mission of BrightFarms has been to establish sustainable urban agriculture and educate people on it, explaining why they started with schools. Opening in 2010, the Manhattan School for Children greenhouse was a project of NYSW created out of the school community’s desire for a more sustainable campus and environmentally focused curriculum. It serves over 700 students Kindergarten through 8th grade in addition to training educators from around the city, region, and world.

Shifting from schools to retail
The company has evolved over time to the point where BrightFarms focuses mainly on commercial retail clients that can handle the high volumes of produce that come out of their greenhouses, including grocery stores and produce distributors. As an example, BrightFarms signed the grocery industry’s first long-term produce purchase agreement (PPA) with McCaffrey’s Market, under which it will deliver year-round local produce to McCaffrey’s, an independent grocery with stores in Pennsylvania and New Jersey. Located in Yardley, PA, the 50,000-square-foot greenhouse will grow about 500,000 pounds of produce a year.

BrightFarms has also designed and installed a demonstration-scale urban greenhouse for a new Whole Foods Market store in Millburn, New Jersey. This was designed to produce herbs for use in Whole Foods prepared food services as well as for general sale and involved lines of vertical growing towers deployed along the window frontage to make best use of available light.

With input from myriad sensors, a computer controls the greenhouse. Courtesy BrightFarms.

Beyond schools and grocery stores, BrightFarms has also ventured into residences. Adams reports that they have implemented a system in a building in the Bronx called the Forest Houses, with the agreement that people who live in the building get a certain percentage of the produce. “I can envision CSA (community supported agriculture) schemes happening with those facilities.”

Headquartered in a house near Grand Central Terminal, the multidisciplinary BrightFarms team has expertise spanning horticultural sciences, engineering, ecology, energy analysis, environmental education, and produce marketing. Adams reveals, “We went from having three employees in November of 2011 to 16, so we’re definitely in a state of expansion.” The 32-year-old Adams has been with BrightFarms since it started and provides oversight and management of all design and engineering duties. He has played a role in the design and building of all the firm’s greenhouse projects to date.

What kind of training does an engineer typically have in this business? Hailing from Camden, New Jersey, Adams has a ?B.S. in human ecology and agroecology from Rutgers and an M.S. in ecological design from the University of Vermont, and he’s LEED AP certified. At the University of Vermont, he did his graduate work under John Todd, prominent in ecological technologies and well known for inventing the Living Machine, and he modeled, developed, and constructed agricultural and renewable energy systems. After that, he worked with New Jersey Community Water Watch, Edison Wetlands Association, Ocean Arks International, Intervale Foundation, the U.S. Department of Agriculture, the Vermont Alternative Energy Corporation, and Delaware Valley Eco-Fuels.

“If anyone asks me what my real profession or trade is, I always say ecological engineering because it involves taking the built environment and mixing it with the natural environment and marrying them to create a functioning system that serves a purpose for humanity. I’m definitely a student of biomimicry,” Adams relates.

While Adams does the in-house engineering, he says they also shop out much of their engineering work. On any given project, they will have a structural engineer, an MEP engineer, and depending on the project, perhaps a civil engineer. “Those are really key partners on the design project team. We have projects going on all over the country, and not everybody’s licensed in the same state and not everybody is familiar with certain regions, so it’s on a project-specific basis what teams we work with.”

HVAC a major consideration
Besides structural considerations, another important facet of a greenhouse is heating and cooling it. Adams takes me through the hierarchy of systems at the school. They have a side guillotine vent with panels that slide up and down like windows for cooling with natural ventilation -- this is the first stage of temperature control. Fans are the second stage; two big ones loom at one end of the greenhouse. An evaporative cooling system mounts in the wall at the other end of the building -- the third stage.

Vine plants such as nasturtiums grow in the greenhouse. Credit: Tom Gibson.

The final stage: curtains. These are aluminized plastic, meaning polypropylene with aluminum strips threaded through them; the aluminum reflects heat, like a space blanket. They go on the roof most commonly but can also be deployed on the walls. They open and close with a motor-and-push rail system controlled by computer. It generally extends the curtains at night when the interior air temperature falls below 60 F, then they will be drawn back just after sunrise, unless it is cloudy. In addition, an air-source heat pump sits outside for heating and air conditioning, mainly for heating.

Next, Adams shows me the greenhouse’s rainwater catchment system, which gathers most of the water they use in gutters along the lower edges of the roof, like on a house. From there it flows to two 350-gallon HDPE tanks connected to act as one tank. A small flotation tank on one of the tanks siphons off the first 40 gallons to catch dirt and debris, and they flush that out at the bottom of it. Adams describes the system overall as “similar to a home water system.” It operates at 40 psi and has a UV lamp filtration system to sterilize the water. All the growing systems have reservoirs with a float valve and pump.

Not surprisingly, with all its components, the greenhouse is controlled by a PC-based computer control system. As he points to a table with various electronic and electrical components on it in the corner, Adams states, “All greenhouses have one. The computer knows things like indoor and outdoor temperature. We try to keep it 75 degrees during the day and 65 night, as plants grow optimally then.” The computer also controls things like vents, fans, lights, pumps, nutrient levels, and water levels. He points to a sensor hanging from the roof in the center of the room. “There are sensors placed throughout the greenhouse. One of the interesting things is that you can log all the operational and environmental data, so you can see how you’re performing, see what technologies are working well.”

At the core of the plant production process, rows of small plants growing out of tubes mount on sawhorses. The tubes have a thin layer of water in them. The plants actually start life in trays, where they stay for about two weeks before moving to the tubes in a process known as succession planting. They constantly rotate the plants to get a consistent harvest. In another area, vines grow out of a tub on the floor, yielding tomatoes, cucumbers, and peppers.

Against one of the end walls, between the two fans, a form of vertical farming stretches out that they’re testing, like a collapsing ladder with plants mounted on the rungs. Known as a vertically integrated greenhouse (VIG), you can raise it several stories, but it collapses to ground level so you can work on it without ladders. Caplow and Adams designed and patented this.

While much of BrightFarms’ work has focused on New York City, Adams reveals, “We definitely have a desire to spread the model on a global scale. We are trying to build our facilities wherever it makes economic sense but also where it makes sense in the food system: in semi-urban to urban areas underserved by the conventional food system and with a need for fresh local produce. Anywhere where there’s a seasonal lack of fresh produce our model makes sense.”

In reflecting on the bright future, Caplow seconds that. “I think the potential is vast. Cities and peri-urban areas cover an increasing fraction of the landscape worldwide, and cities are in a constant search for more sustainable, pleasant, green, and people-friendly structures. Rooftop farms fit the bill.”