Can Cities Feed Us?

By Sarah DeWeerdt

Sometime in mid-2007, the world’s demographic scales tipped. Only a century earlier, urbanites represented just over 14 percent of humanity. But by 2007, a majority of the world’s people lived in cities, and more are on the way. Over the coming decades, cities will absorb all predicted global population growth and then some. According to the U.N. Population Division, there will be 6.4 billion urban dwellers by 2050—as many people as lived on the entire planet in 2004.

That stark reality leads to another: feeding this new urban world with an old agricultural model could be a recipe for environmental ruin—and human misery. The cost of growing food on large plots of land far away from cities and transporting it to the teeming masses has begun to outweigh its benefits. Not only is the carbon footprint of such a system huge, but more often than not traditional farming has been a disaster for natural ecosystems and wildlife. And then there’s the problem of space. Already, over 80 percent of the world’s arable land is in use—some of it highly degraded. Add the 2.5 billion people who are likely to join us on the globe by 2050, and there’s simply not enough room to keep farming the way we have been.

In response, Dickson Despommier, a professor of public health at Columbia University, wants to turn the old system on its head. For the past decade, Despommier has been cultivating a vision of farms filling glass-and-steel towers the size of a city block and 30 stories high. Just one high-rise farm, he has calculated, could feed 50,000 people 2,000 calories a day all year round. Scale that up, and skyscrapers could produce enough food to feed everyone in Manhattan in a space roughly one-fifth the size of Central Park.

Despommier’s ideas are a far cry from the backyard chicken coops and vacant-lot community gardens that are most frequently touted by urban-agriculture advocates. But he passionately believes that if we think differently about food production, the big cities of the future might just be able to feed themselves.

His optimism, however, didn’t come automatically. In 1999, students in one of Despommier’s classes decided to explore the potential of rooftop agriculture in New York City. The results of their calculations were depressing: even if all of the city’s residential rooftops were converted to rice paddies, the resulting crop would provide only two percent of Manhattan residents’ caloric needs.

“Why don’t we just put the farms inside the buildings?” Despommier recalls saying. It was a throwaway line at the time. “But the more I thought about it, the more appealing that solution became.”

A 30-story building may not sound like much space compared to acres of rolling Kansas wheat, but the year-round indoor growing season quickly multiplies yields—two crops of tomatoes per year, three crops of wheat, even ten crops of strawberries. Plus, vertical farming is a chance to play a giant game of agricultural Tetris®: dwarf varieties of wheat and corn can be planted at twice the density of standard field crops, and trays of plants can be stacked two, three, or sometimes five layers deep per floor. The harvest adds up fast.

Despommier cites a long litany of vertical farming’s potential benefits. Farmers would no longer be vulnerable to droughts, floods, or storms—a particular advantage in a world buffeted by climate change. There would be no further need to burn fossil fuels for plowing, harvesting, or shipping food long distances to market. Streams and rivers would run clear, unbefouled by pesticide and fertilizer runoff.
“The very best reason for indoor farming is that you save outdoor land for something else,” Despommier says. Vertical farming could shrink the physical footprint of agriculture by upwards of 95 percent—for every acre of land farmed indoors, he has estimated, 10 to 20 acres of current farmland could go wild. Fields would return to forests, sequestering huge quantities of carbon as an added bonus.

The basic idea of growing food indoors is nothing new—the first greenhouses were built in the thirteenth century. And today’s greenhouses, of course, often have massive carbon footprints. But Despommier is doing more than just stacking greenhouses on top of one another. Instead, he’s orchestrating an ecosystem in which energy, water, and nutrients would be recycled from floor to floor.

On one floor of a vertical farm, you might find a kind of indoor marsh, with cattails and sawgrass to filter municipal graywater. The purified water would be piped off to other floors to provide water to small animals and to irrigate crops. Most of the crop plants would likely be grown hydroponically, with their roots submerged directly in water or embedded in a soil-less growing medium such as vermiculite, or aeroponically, suspended in the air and enveloped in a nutrient-rich mist. These technologies use up to 90 percent less water than soil-based agriculture, and to make the system even more water-efficient a network of cold-brine pipes would collect water released by the plants through evapotranspiration so that it could be recycled again.

Each floor of the tower would have specific temperature, humidity, nutrient, and light conditions tailored precisely to each crop. The heat on one floor would be cranked up to grow tomatoes and peppers and turned down on another to nurture cabbage and kale. Nutrients would come from sterilized, dried, and powdered wastewater solids; highly efficient LEDs would supplement natural sunlight. A positive-pressure system much like the ones in hospital ICUs would keep out diseases and pests.

The energy to run all these systems could come from wind, solar, or geothermal sources where feasible. Elsewhere, waste—including the inedible portions of crop plants—could be burned for energy or digested into methane.

If all this sounds a bit futuristic, Despommier points out, the technologies necessary to execute his vision already exist—though they’ve never been integrated into a single system. For example, biosolids (sterilized sewage sludge) are already used as fertilizer in all 50 U.S. states. Modern hydroponic systems were developed in the 1930s; the world’s largest hydroponic outfit produces over 100 million pounds of tomatoes in the Arizona desert each year, and the technology is also used to grow vegetables at McMurdo Research Station in Antarctica.

Despommier compares his vision of vertical farming to working with a box of Legos®—the blocks are all established technologies; he’s just putting them together in a new way.

Not all indoor farms would have to be massive. “I’m imagining [some] attached to restaurants, schools, hospitals, or on the tops of apartment buildings,” Despommier says. A one-story, one-acre rooftop structure could yield the equivalent of 16 acres of field-grown produce. He also envisions a smaller-scale, modular version of the system that could be used as a kind of “M.A.S.H. unit for agriculture” in famine-plagued or war-torn regions. Instead of merely receiving food aid, refugees could grow their own food—recycling water and processing human waste at the same time.

A major hurdle is cost. To build a small experimental farm—say, 5 or 10 stories—from scratch would cost somewhere between $20 and $50 million, Despommier believes. Yet consider this: a smaller indoor farm at Cornell University has been able to grow 68 heads of lettuce per square foot per year.  At $2.50 per head, that’s as much as $170 per cultivated square foot per year—or millions of dollars per farm floor.

Still, the potential revenues haven’t been enough to draw a flood of investors. Despite widespread interest in the concept, no high-rise farms exist yet. But they’re getting closer. One of the most promising operations is taking root in Chicago, where John Edel is pioneering the kind of for-profit/nonprofit/academic partnership that could make vertical farming feasible, at least at first. Last year, Edel began collaborating with professors and students from the Illinois Institute of Technology to establish a small test farm in the basement of his Chicago Sustainable Manufacturing Center. “We have 70 tilapia right now, and we’ve run through maybe five different [crop-] growing systems for testing purposes,” he says.

And now it’s time to scale up. In June, Edel closed on a 95,000-square-foot former meat-packing plant on the city’s South Side. The building will house a 10,000-square-foot, for-profit farm plus a 30,000-square-foot research farm that Edel plans to operate as a nonprofit organization. There, he and his collaborators plan experimental plots to further refine their indoor farming techniques, with the goal of developing a kind of “open-source system” that could be used by other vertical farm endeavors.

“The other half of the building is essentially going to be a food-business incubator,” Edel says—one that will integrate small start-up enterprises into the vertical farm ecosystem. For example, a microbrewery has leased space in the building, and Edel envisions composting the otherwise worthless spent distiller’s grain to use in the farm. Meanwhile, oxygen produced by the plants could be piped out to improve air quality in the various office and factory areas. “Our goal is to get the facility to net zero on energy and net negative on waste.”

If all goes according to plan, the first vegetables should be ready for harvest—or “start coming off the line,” as the sustainable-manufacturing entrepreneur puts it—by Thanksgiving. ❧

Sarah DeWeerdt is a Seattle-based freelance writer specializing in biology and the environment.

Further Reading: The Vertical Farm: The World Grows Up by Dickson Despommier, published by Thomas Dunne Books /St. Martin’s Press, will be available in October 2010.

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12 Comments

  • Lacy November 30, 2010 at 2:48 pm

    “Farmers would no longer be vulnerable to droughts, floods, or storms—a particular advantage in a world buffeted by climate change. There would be no further need to burn fossil fuels for plowing, harvesting, or shipping food long distances to market. Streams and rivers would run clear, unbefouled by pesticide and fertilizer runoff.
    ‘The very best reason for indoor farming is that you save outdoor land for something else,’ Despommier says.”

    This is a very nice idea in concept, but as with any innovation, it is important for developers and designers to consider critical input before making any steps toward this sort of food future. Only 8 paragraphs in, and I have already found two assumptions that sound very tantalizing and are very false. To assume that “there would be no further need to burn fossil fuels” to create skyscraping “vertical farms” or to pump water and nutrients against gravity to a height of 80 floors is preposterous. Cities are a very big user of fossil fuels, and urbanizing our food would not change this. Also, to assume that “indoor” space does not take up “outdoor” space to be made is a fallacy. These are just two very apparent false assumptions outside of the many potential philosophical and ecological problems (such as increasing the separation between humans and outdoors, or presuming that no one lives in rural communities and would not be allowed to) that can arise from this.

    On the other hand, the idea has its merits. Proceed with great caution.

    Reply

    • * January 12, 2011 at 6:14 pm

      Lucy, all the problems you point out are true, however you are not taking into account that this is a trade for what we already have. Indoors space does take up outdoor space, what they are stressing is that 1 acre for this skyscraper, which would be built in a city not by clearing more wilderness area, would be equivalent to 10-20 acres of farmland. Admittedly vermiculite doesn’t sound like a good idea but composting/reusing plant discards IS mentioned as a nutrient source several times in the article.

      All the energy use you discuss in you first comment is already happening, in food transport, irrigation, and countless other demands of modern agriculture. The point of this system would be to lower OVERALL energy demands, even though growing food would still be energy intensive.

      Your alternative, urban farming, does not produce anywhere enough food to support the energy demands of a city. It will never be able to because there is simply not enough space…unless you start stacking farms on top of each other. High rises such as these would be local and they COULD be managed organically.

      Ultimately my point is that in a real world you look for real solutions, not ideal solutions. There will always be trade-offs. Agreed problems should be carefully examined before proceeding, but we can’t let fear of change freeze our infrastructure in it’s current state.

      Reply

  • Lacy November 30, 2010 at 2:55 pm

    Forgive me for my piecemeal response, but further down I noticed that the plants might be grown in vermiculite. This mineral product is a potential carcinogen (some kinds indistinguishably carry asbestos fibers.) Also, this is a nonrenewable resource that would need to be extracted from “outside” to use inside. Has anyone heard of composting?

    Reply

  • Lacy November 30, 2010 at 3:09 pm

    Last one, promise:

    “The energy to run all these systems could come from wind, solar, or geothermal sources where feasible. Elsewhere, waste—including the inedible portions of crop plants—could be burned for energy or digested into methane”

    This sounds VERY resource intensive to me, and almost assuredly without the benefits of outdoor gardening that can increase (rather than decrease) the nutrition of vegetables.

    Also, are wind, solar, or geothermal fields “wild”? Rather than converting swaths of farmland to fields of solar panels or wind farms, why don’t we keep them heading to the right path: of organic produce produced for local markets (there are such things as urban farms) so that our food products can both benefit from the variability of the great outdoors and also benefit the micro-ecosystems that live in them.

    Finally, the only good reason I can see for this kind of agrodevelopment is a potential nationwide food shortage. Revolutions in agriculture, such as biointensive, biodynamic, and permaculture techniques, can be applied to systems to revitalize and replenish the degradation of soil and resources, by using a fraction of the input (and a fraction of the START-UP COSTS) that traditional agriculture or a farming building would require.

    I think a much more helpful move would be for universities, nonprofits, and the federal system of governments to help fund these local small-scale diverse, organic and very efficient farms than to funnel hundreds of millions of dollars in more skyscrapers.

    Some Food for Thought: http://permaculture.org.au/2009/12/11/greening-the-desert-ii-final/

    Best wishes for all of us.

    Reply

  • Bill December 27, 2010 at 9:39 am

    An interesting idea. A problem I see is the proposed use of sewage sludge for fertilizer. Municipal sewage sludge contains a wide variety of industrial toxicants, including heavy metals (which remain as themselves unless your treatment plant is also a nuclear reactor). This isn’t a central tenet of the idea, but it’s not something we should overlook. This said, as a resident of a single-family-residence neighborhood in Seattle, I can verify the huge amount of arable land devoted to lawns and other ornamental landscaping. Apparently plants grow fine in our yards, and we spend much time “harvesting” the produce. We don’t have to wait for high-rise farms to grow lots of food in the city.

    [WORDPRESS HASHCASH] The poster sent us ‘0 which is not a hashcash value.

    Reply

  • Mark January 16, 2011 at 11:37 am

    In response to:

    “For every acre of land cultivated in a high-rise urban farm, 10 to 20 acres of current cropland could go wild.”

    The best analysis I’ve seen suggests that the opposite may be true. A more likely summary might read,

    “…for every acre of land cultivated in a high-rise urban farm, 10 to 20 acres of current wild lands would need to be converted into biofuel crops and wind farms to keep the lights on for the silly thing…”

    A good breakdown of the energy requirements for this concept compared to alternatives is posted at the energy farms blog:

    http://energyfarms.wordpress.com/2010/12/02/energy-and-vertical-farms/

    Well worth a read.

    Also worth looking at for more good discussion of the topic:

    “Vertical farming: does it really stack up?” (the Economist, Dec 2010)
    http://www.economist.com/node/17647627

    “Greens living in ivory towers now want to farm them too” (the Guardian, Aug 2010)
    http://www.guardian.co.uk/commentisfree/2010/aug/16/green-ivory-towers-farm-skyscrapers

    Reply

  • Steve Erickson June 3, 2011 at 10:49 am

    The high yields per unit area result primarily form vertical stacking, not climate control. Vertical stacking simply results in more physical area, as anyone who has compared the yields of bush peas to taller varieties grown on trellises can attest. However, this will inevitably require large energy inputs for artificial lighting, as well as moving water and nutrients against gravity. Careful structural and cropping system design can reduce this, but will not be able to eliminate it. And even if the buildings are custom built to be thin enough for natural light to penetrate from the sides, unless they are widely spaced with no other tall structures shade will be a problem requiring energy to counteract.

    These downsides are not drop deads, but strongly suggest that the actual energetics and yields of these systems will be considerably less than what is currently being projected. Pinching and squeezing every bit of useful energy possible from the system may result in apparent high efficiency, but entropy and gravity are merciless task masters.

    As for the vision of modular food producing factories being deployed to war and disaster hit regions, this is truly ludicrous. The reason why the local food producing systems in these areas are not functioning is because they’ve been disrupted or there is a lack of security. Those problems won’t disappear just because a shiny food producing widget is parachuted in.

    Reply

  • Steve Erickson June 3, 2011 at 10:58 am

    One other comment:
    While reading this article, I couldn’t help but think of one of the first movies that looked at the Earth subject to global warming: Soylent Green. I’m reminded of what a county planning director I knew said when “country inns” were under discussion: “You see a Bed and Breakfast; I see a Motel 6.” I do find the possible socio-political possibilities highly problematic, if not downright frightening. Large, centralized, finely tuned food factories that are easily controlled and/or easily disrupted . . . This sounds to me like many of the worst structural problems of the current food system magnified. Call me paranoid.

    Reply

  • Kip Hansen July 12, 2011 at 3:03 pm

    All the energy needed by the plants to produce the edible parts for us would have to be input into the system, energy now supplied free by the sun, as nature intended.

    There is simply no way to feasibly supply that much energy.

    Ask the marijuana factories — their highest cost is electricity for light and heat — and this is their downfall as well, as the drug squad simply taps the electric companies records for excessive users.

    This proposal is innumerate – it fails to calculate the actual total energy needs of such a system against costs. May be feasible–if there is ever a population that would actually accept Factory Food–if we had access to free unlimited electricity from cold fusion plants–and about as likely.

    Reply

  • Kevin Hatfield July 29, 2011 at 9:29 am

    Perhaps sunlight is not essential, mushrooms? The indoor farms could serve as contained agricultural labs where one might take greater risks with genetic improvements: working towards a nutritious yet appetizing grey-goo? The urban environment is often inherently more toxic than the rural landscape. And much of food is currently imported where costly but needed regulations do not apply. Beef, milk draw tax subsidies to great advantage but much fruit and produce come from abroad. How could costly urban farming find a place in the market? The $2.50 a head of lettuce mentioned in the article is substantially higher than in some areas of America. One advantage is that for some urban areas, these high-rise farms might also utilize waste heat from urban industry, serving as adjacent cooling towers. That implies that the two environments of toxic industry and agriculture can be kept apart. The foodstuffs might have a mrked increase in flame retardant contamination, prozac from the urban water supply, etc. The whole concept does seem the most costly method. If one had unlimited energy, then it would be the way to go. But then if one had enough energy, then the costs of transport, etc. are mute.

    Reply

  • Hal Hurst August 8, 2011 at 9:39 am

    This much is true: in an urban environment the most limited resource is sunlight. A system needs to be analyzed to consider all the expected inputs and outputs to get a picture of whether such a system can work using the resources available.

    Solar requirements for raising plants limits use of solar collectors for other uses in the same space. Energy is lost in conversion; therefore it’s more efficient to use it directly without conversion, and the use of PV collectors and LEDs to grow crops in dark rooms is silly.

    Perhaps all this farming could take place on the uppermost floor of buildings, making use of transparent roofing and the heat already generated within the building to increase productivity; also the South sides of such buildings could be made to collect more energy, but only to the extent that they are not shaded by buildings still further south. But urban farming and PV systems are on a collision course.

    You can look up the Solar road project in Idaho, a possibility, and wind generators will still allow most of the sunlight to pass through; but solutions will need to be found which consider the entire system before a truly integrated and sustainable urban environment can come to pass.

    While urban farming may make a valuable contribution to fulfilling the needs of a city, it seems more likely to me that outlying areas will still supply resources to cities in the future, until cities themselves become more dispersed, perhaps occupying the non-arable areas, in contrast to the current trend of paving over the most productive farmland to create cities. Unless we are willing to use nuclear or some other problematic power sources to supply those LEDs with the energy to grow our food.

    Reply

  • Anna August 29, 2011 at 5:28 am

    Very interesting and cool!
    Thanks you very much

    Reply

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