Status of Vertical Farms 2018

Posted December 2018

Introduction

The agricultural revolution has been ongoing for some 10-12,000 years. Ten thousand years of history may seem like a long time to some, but in terms of human evolution (approx. 300,000 years – Jean-Jacques, 2017), the revolution spawned by the advent of agriculture represents less than four percent of the total time we have been around as a species. One major advantage of farming over hunting and gathering was apparent from the very beginning, and would become the mantra for millions of people throughout temperate regions of the world–sustainability. Settling in one place, rather than relying on the abundance of game animals, required us to reinvent how we carried out our daily lives. Farming allowed the food to come to those who opted for a new life in the built environment, and created the luxury of leisure time. So began the development of modern civilizations (Maisels,1990). Music, the visual arts, mathematics, science, formal religions, written languages, astronomy, and countless other human activities not related to the clans of hunter/gatherers of the pre-agricultural world burst upon the scene, creating an unparalleled richness of life for city dwellers. Civilizations could finally evolve towards realizing their full potential, and many blossomed. At the same time, the urban environment was rapidly expanding and changing as it grew (Mumford, 1961; Kotkin, 2005). Cities underwent extensive transformations, from haphazard collections of temporary living quarters (cloth and animal skin tents and flimsily constructed huts) and no planning for urban differentiation, to what we have now come to expect from all modern metropolises.

Many of the earliest cities arose adjacent to fields of wheat, barley, millet and rice, and in most instances accommodated farming within their boundaries. As more and more people became comfortable living in densely settled areas, the populations of city dwellers increased, inevitably encroaching on the very farmland that fostered and nurtured the birth and development of the urban landscape. This trend was to set into motion an explosion of urbanization that continues to this day. By the 1500s, the city had achieved its full breadth and depth of specialized zones (e.g., retail, manufacturing, transportation, entertainment, housing, education, to name but a few), and the choicest inner city properties skyrocketed in value. Farming inside the boundaries of the built environment was no longer financially viable. Growing food became a pastoral activity, and the farmer became agriculture’ssymbol of rural life. While being able to grow edible plants, particularly grains, jump-started and nurtured the evolution of civilizations, many of the earliest cities were abandoned due to lack of adequate levels of seasonal rain (Diamond, 2011). Settlements within the Fertile Crescent, for example, soon after being founded, felt the effects of a decidedly more arid climate regime, and the wheat farms that first enabled those early settlements to thrive failed. The same was not true for the ancient Egyptian cities that formed several hundred miles to the west along the banks of the River Nile and its extensive delta system. The success of Egypt’s urban centers was due almost exclusively to less fluctuation in patterns of weather in the Sudan region to the south, enabling a long-term sustainable farming economy to thrive and survive. In many places, the scarcity of water led to the invention of ingenious irrigation systems in an attempt to farm despite changes in natural patterns of weather– Peru, the American southwest, Southeast Asia, Central America (Scarborough, 2003). Eventually, even these cultures failed to provide enough calories to sustain their struggling populations, again due to the lack of a reliable hydrological cycle.

Today, cities are, for the large majority, clearly separated from the origins of their food sources, with many of the largest ones hundreds to thousands of miles away from the commercial mega-farms that supply them with fresh produce. To compensate for this disconnect, extensive transportation systems arose, and trade agreements between countries that could not grow significant amounts of edible crops (e.g., the Arab Emirates) and those with abundant farmland insured a steady flow of harvests into those desert societies. Globalization of the food system is now the norm, but confounding factors, the main one being rapid climate change, are still rearranging food networks almost on a monthly basis. Between 2005-2018, crop failures caused by floods, droughts, insect pests, and microbial plant pathogens resulted in significant annual fluctuations in the global food price index released each year by the Food And Agriculture Organization of the World Health Organization. Volatility in the availability of food has created a constant state of financial chaos for hundreds of millions of people who, by no choice of their own, are forced to live in poverty.

For many years, scientists were convinced that the answer to more reliable yields of grain crops lay in better tools for coping with extremes in weather patterns (Key, 2008;Jacobsen, 2013). Genetically modified plants have been engineered to be more drought-resistant (rice and corn – Gomez, 2017), while attempts to define the conditions under which drought-resistant wheat can be produced have so far been unsuccessful. Regardless, even if GMOs were somehow to allow most grain crops to overcome the current trend towards a warmer, drier climate, those countries with the greatest need for them (China and India, for example) could not afford to purchase enough GMO seed to feed their still growing populations.

As depressing as the current situation appears regarding the future of outdoor farming, irrespective of location, there are other agricultural strategies to growing our food that do not require any modification in the plants themselves, and that can be efficiently carried out literally anywhere on earth–it’s called controlled environment agriculture (CEA), aka indoor farming. CEA is not a new agricultural strategy, having been employed since the late 1700s, but greenhouses are not only what is meant by CEA. In the past century, greenhouses were typically owned by people living in single-family dwellings in the suburbs, and very few were used for food production. Within the last fifty years, a robust commercial greenhouse industry has been established that now serves as a half-way point between seed manufacturers and the plowed fields of industrial farms. Their usefulness to the outdoor farming industry is widely appreciated, but it’s unrealistic to think that greenhouses could replace the current approximately 1.87 billion hectares of farmland, or overcome the devastating effects of rapid climate change even though their annual yield can be higher due to year-round production. A new strategy is required. Enter the vertical farm (Despommier, 2010). The defining feature of a vertical farm, in contrast to a greenhouse, lies in its height. Simply think of stacking greenhouses on top of each other. The result is a dramatic increase in plant yield, without changing the architectural footprint. Large commercial vertical farms are capable of producing millions of tons of produce each year, and while no vertical farm to date has exceeded two hundred thousand square feet of production space, it is only a matter of time before one does. Like the modern skyscraper, the vertical farm has limits, but as of yet the constraint of height has not discouraged architects and builders to continue to “reach for the sky”. Since vertical farms outwardly resemble other tall buildings in the urban landscape and can operate with “zero” pollution circular reuse grow systems (see: plantchicago.org), getting approval for their construction has become straightforward, especially from city planners and citizen groups concerned about the reintroduction of traditional agriculture into the built environment. Today, vertical farms are common in Japan, China, Singapore, Taiwan, and the United States. Perhaps this approach will finally enable the world’s human population to become truly self-sufficient and free it from the whims of nature.

This essay will describe and evaluate the methods used to grow edible plants indoors and will present a survey of many of the commercial vertical farms currently operating that employ them. Judging only by the astounding growth of the vertical farm industry over the last five years, vertical farming is projected to become a common feature of the built environment on a global scale within the next ten to twenty years. For review articles covering the topic of vertical farming, see: (Despommier, 2013; Thomaier, 2015; Kalantari, 2017; Esposito, 2017; Benke, 2017).

The Vertical Farm: from inception to reality 

Background and rationale

The concept of raising food indoors can be traced back to the days of the Roman Empire, thanks to the writings of Pliny The Elder. The emperor Tiberius Julius Caesar (42 BC-37AD) was explicitly instructed by his physician to eat one Armenian cucumber a day to insure a long life. Quite a challenge, considering that Rome routinely experienced cold, snowy winters. To keep these temperature-sensitive vine vegetables from dying, the plants were grown in above-ground wooden beds on wheels filled with soil (the forerunner of today’s wheelbarrow). They could then be moved indoors into the royal palace when the frost was on the pumpkin, providing these round, snake-shaped pale green delectables with all the same creature comforts of a world-class dictator. One of the first stand-alone greenhouses was constructed out of wood in Leiden, The Netherlands, in the early 1800s by Charles Lucien Bonaparte, a renowned French botanist. He used it to culture medicinal tropical plants year-round. By then the industrial revolution, with Manchester, England at its epicenter (Kidd, 2012), was in full swing, and affected all aspects of life in Western Europe. Along with the invention of a plethora of mechanical devices designed to speed up and improve the efficiency of the manufacturing process, the second agricultural revolution began simultaneously, taking advantage of many of the inventions that arose during that era of British history. In 1888, the Chance brothers invented a mass production system for large sheets of clear glass. Transparent greenhouses would now be able to demonstrate their full value in CEA. These newly minted all-glass structures provided a year- round haven for all kinds of plants. The glass enclosed conservatory was CEA’s promise of things to come, and by popular demand, many western European countries and the United States (ibid), erected large, beautifully designed symmetrical glass edifices to show off their exquisite, diverse, colorful botanical collections, most of which were by-products of insatiable imperialism (Brockway,1979). The modern greenhouse evolved along similar lines, and became widely available to a burgeoning middle class throughout Western Europe and America. This situation continued to progress, albeit slowly, as the Western world endured the ravages of the First World War. Some thirty years later, the Second World War, a much larger set of conflicts involving the entire world, ensued, and placed enormous constraints on Allied forces ability to provide fresh produce for their troops. The lack of unprocessed vegetables and fruit was especially evident in the Pacific Theatre of Operations. At one point, well into the war, a radical solution to this dilemma was put into action on some of the islands captured by the U.S. Marines. Troops stationed on Wake Island, Okinawa and Iwo Jima initiated on-site hydroponic farming carried out in discarded 55 gallon barrels.

Crop production using this approach was carried out right up to the end of the war. After the armistice in 1945, the U.S. Army continued to produce crops hydroponically, and in 1952 harvested nearly 4,000 tons of fresh vegetables of various kinds (ibid). While hydroponic agriculture was still being practiced at a few military bases, it never rose in popularity in the civilian sector to become a major player in any nation’s domestic food production scheme. This was most likely due to the fact that climate change had not yet ramped up, and did not yet have a significant impact on most global outdoor agriculture.

The “miracle” insecticide, dichloro-diphenyl-trichloro-ethane(DDT), had saved millions of lives, both military and civilian alike, near the end of WWII, mostly by limiting the spread of epidemic typhus, malaria, and leishmaniasis by killing off the vectors (lice, mosquitoes, and sand flies) of these dreaded infectious diseases (Despommier, 2018). Now in post-war America and in Europe, as well, DDT was being touted as the salvation of modern farmers in their own war against all varieties of arthropod plant pests. Together with the introduction of modern fertilizers, soil-conserving tilling practices, and rotation of crops, the rise of the agrochemical industry catalyzed a new era in agriculture, ushering in the second green revolution, spearheaded by Norman Borlaug, who won the Nobel Peace Prize in 1970. As promising as this concerted, technology-driven approach to growing our food appeared, that green revolution was to be short-lived.

Beginning in the 1980s, traditional farming began to show the effects of exposure to Nature’s darker side (Lovelock. 2007), as droughts and floods became more prolonged and more severe. For example, as our planet warmed at an ever-increasing rate, microbes responsible for many crippling plant diseases now had a longer time each year to parasitize their crops of choice, resulting in marked decreases in yields of most grain crops. In addition, insects that fed on corn and various fruits and vegetables had become totally resistant to DDT, and to many related insecticides (Oerke, 2006), due to the indiscriminate use and over-use of these powerful invertebrate neurotoxins. Rachel Carson, in her landmark book, Silent Spring, while not severely chastising the agricultural industry for its penchant for spraying DDT at nearly everything that crawled or flew, correctly identified the linkage between the application of pesticides and the unintended loss of wildlife, mainly birds, with raptor species being particularly hard-hit (Bednarz, 1990).

In addition to the ineffectiveness of most first-generation pesticides, climate change continues to alter where and how much food we can produce. If nothing changes to slow down the rate of global warming, it is estimated that for every degree increase in the earth’s temperature, crops lost to insect pests will rise by 10-25 percent, depending upon the agricultural setting (Deutch, 2018). This “double whammy” will most surely play a significant role in limiting food production over the next century.

By the year 2000, nearly every climate scientist throughout the world was sounding the alarm, warning that if the human population did not stop putting “greenhouse” gasses into the atmosphere at an ever increasing rate, the climate might soon get completely out of control and usher in a era that would adversely affect virtually every living thing on earth (Nolan, 2018), and agriculture would become the most adversely affected human activity. As predicted, crop failures during the early 2000s were frequent, and food riots were not uncommon features in those countries most affected by them. The most convincing body of evidence-based data documenting rapid climate change came from decades of observing glaciers around the world. In only a few places, the central Andes between Chile and Argentina being one, did glaciers not show any signs of retreat. The vast remainder was melting at an alarming rate, especially as compared to the previous 100 years of observations. Data derived from the above studies clearly showed that sea level rise was also accelerating. Cutting back on the use of fossil fuels is one way to slow down the process of climate change. While many countries agree that this is a viable approach, virtually none of the largest consumers of fossil fuels (The United States, China, India, and Russia) actually practice what they espouse.

Another widely agreed upon strategy to counteract the effects of greenhouse-gas-induced climate change is to allow for more trees, one of nature’s most reliable sequesters of carbon. A collaborative study conducted in 2018 between the National Aeronautics and Space Administration and the United States Geological Survey using data collected from Landsat 8 satellite observations estimated that there are some three trillion trees on earth (Crowther, 2018). This may seem like a lot of trees, but that same study estimated that humans have cut down an equal number since the beginning of the agricultural revolution to make room for farmland, settlements, and roads. We have reduced by 50 percent earth’s most reliable way of regulating the concentration of atmospheric carbon, an ecosystem process that took more than 470 millions years of evolutionary history to perfect. More daunting is the fact that although the rate of deforestation has slowed over the past 25 years, the process still continues in order to make room for more farms that are needed to feed an ever-growing world population. If this circular set of negative human activities resembles the theme of some modern Aesop’s fable aimed at teaching us what not to do, then the reader got the message. Yet, even in the face of overwhelming agreement from a global community of climate experts warning us against such a course of action, we continue to act in this destructive fashion.

In summary, irrefutable scientific evidence corroborates the conclusion that the earth is under siege from humanity. Two anthropogenic activities explain the root causes of rapid climate change: 1. an unrelenting penchant for burning fossil fuels to generate power, 2. the disconnect between the land and the atmosphere due to the singular adverse affect on carbon sequestration of 1.87 billion hectares of soil-based outdoor farming. Regardless of whether or not policies change to bring a halt to these behaviors, we must quickly find alternative means of supplying mass quantities of food to a population that may soon reach nearly 10 billion. Failure to do so will almost certainly trigger a catastrophic reduction in our numbers caused by an accelerating rate of severe hunger and starvation, increases in vector-borne infectious diseases (e.g., malaria, Yellow fever, Dengue fever), and the precipitation of civil unrest and wars initiated by food shortages and unplanned urban sprawl. The seas around us will continue to rise and reclaim the current coastal land it relinquished during the last cool interglacial period some 20,000 years ago, confounding our efforts to adjust to an ever changing physical landscape.

Turning farming ‘outside in’: the vertical farm

If traditional outdoor soil-based agriculture is not sustainable, then shifting to an indoor setting employing soilless methods that use far fewer natural resources, particularly freshwater, may represent a viable alternative. It has the possibility of alleviating much of the suffering caused by poor distribution, shortages, or total lack of food, and offers a long-term sustainable solution to the global food crisis. The fact that this statement is no longer considered a radical agricultural approach is indicative of the progress that has occurred in just the last five years regarding the establishment of urban farming, including vertical farms (VFs). An indication as to VFs current popularity can be found simply by conducting a Google Search for vertical farm. As an example, on October 1, 2018 at 11:10 am EST, it produced 317 million hits. The eyes of the world are watching and participating in the progress of this new form of food production. What follows is a brief survey of some of the more well-established VFs throughout the world as of this writing.

Some of the first VFs were constructed in Asia. In Japan, commercial VFs were established mainly in response to a catastrophic earthquake (9.0 in magnitude) and its resulting tsunami that occurred on March 11, 2011 off the coast of the main island of Honshu. Following the meltdown of the Fukushima Daiichi nuclear reactors, fear of exposure to radiation-contaminated food spread across the entire country, resulting in a crisis at most supermarkets that promoted the sale of local produce and fish. The government rapidly mobilized and established collaborative efforts with research communities at universities that specialize in CEA (e.g., Chiba University) and industries seeking to diversify their portfolios (Toshiba, Panasonic, Fujitsu, Mitsubishi, Toyota). Within months following the disaster, several VF companies had formed and proceeded to retrofit large abandoned warehouses with indoor grow systems capable of producing large quantities of leafy green vegetables. As of 2018, the number had grown to several hundred VFs operating in many cities throughout the islands of Japan, with many more in the planning stage that will presumably open over the next five years.

In 2011, a three storey vertical farm training center opened in Suwan, Korea, adjacent to a newly constructed seed bank complex. The Rural Development Authority intended the VF center to serve as a place that would enable individuals to visit and study prior to embarking on a career in indoor urban agriculture. The project has been a success and many more training centers throughout Korea are planned for the near future. NextOn, a high tech vertical farm with 25,000 square feet of growing space opened in 2018. The most unusual feature of NextOnis its location, inside an abandoned tunnel that easily accommodates its LED lights and vertical grow systems. The advantage of situating a CEA facility in this unusual setting lies in its relatively constant temperature and humidity environment, obviating the need for energy consuming and expensive HVAC systems. Another similar VF, Growing Underground, can be found in London, England. Growing Undergroundis located in a portion of the fortified network of tunnels used during WWII as bomb shelters. Both of these VFs demonstrate the versatility of indoor farming within city limits. Another VF that opened in 2018 is Miraewon’s Fresh Farm III, located in the city of Pyeongtaek, Korea. Like many other VFs, it produces mainly leafy green vegetables (; ). The Mayor of Seoul, Park Won Soon,has enthusiastically endorsed the concept of urban agriculture and vertical farming (Hyesun, thesis), and has encouraged the establishment of VFs throughout the city. Supplying enough food for ten million city dwellers is a daunting task, but South Korea is a vibrant, modern country known for its ability to rapidly respond to difficult problems by applying cutting edge technologies. Education and innovation will undoubtedly be key should they succeed in establishing CEA as the predominant method for Seoul’s urban agriculture.

Singapore is home to six vertical farms, the largest of which is Sky Greens, a traditionally constructed multi-storey greenhouse. Crops of leafy green vegetables are grown in soil in a series of rotating trays that slowly migrate up and down in front of the transparent glass windows. Sky Greensfarm employs an ingenious mechanized support scaffolding powered by a series of pulleys driven by gravity, similar to the suspended weights tethered to chains that enable a grandfather clock to unwind. Sky Greens uses natural sunlight, as opposed to many other growers that employ grow lights. The advantages and disadvantages of each energy system will be discussed later. Upgrown Farming Company, Toshiba Vertical Farm, Fujitsu (Aizu-Wakamatsu Akisai Vegetable Factory), Sharp, and Panasonic (Agriculture Total Solutions) round out Sky Green’s VF competition.

Taiwan has over fifty-six commercial VFs scattered throughout the island country (Kozai, 2016). Yes Health iFarmis a 14-storey VF located in Luchu township in northern Taiwan and employs 130 workers (https://www.yeshealth.com.tw/). It grows 30 different kinds of vegetables and fruits and employs various spectra of LED grow lights. As of September, 2018, Yes Health iFarmstood as the tallest VF in the world. Plans are underway to build a Yes Health iFarmfacility in York, UK, with the potential of producing over 20 tons of produce per year. ARWIN, another VF, located in the city of Miaoli, also in northern Taiwan, grows leafy green vegetables and employs LED grow lights as its sole energy source.

China is seeking alternatives to traditional farming, as climate change continues to ravage its agricultural heartland with a series of Monsoon-related protracted droughts and devastating floods (Loo, 2015). Its farming communities are being decimated and people are leaving the countryside and moving to the cities. The result is hyper-urbanization. Unfortunately for those agricultural refugees, there is little in the way of job opportunities in most of China’s urban centers. Over the past three to four years, to begin to address this situation, numerous VFs have been established, but there is no convenient way of identifying most of them, since many lack a standard web site, at least as of 2018. Sanan Sino-Science is one of the exceptions. It has constructed a VF with only a 2.47-acre footprint, but with the potential to produce up to 3,000 tons of vegetables per year when operations reach full capacity. It employs LED grow lights. A number of US-based companies have been encouraged to replicate their success in China, and includes Green Sense Farmsin Portage, Indiana (https://www.greensensefarms.com/our-farms;  https://www.nwitimes.com/business/local/green-sense-farms-expands-to-china/article_0bef19fe-0c5b-5d85-8e18-b6b3ba31152b.html) and Plenty, a San Francisco-based company with an initial investment of $200 million from Soft Bank of Japan. Plentyhas announced its intention to establish some 300 VFs to be spread throughout China over the next five years. China also has a growing number of manufacturers that specialize in vertical faming equipment, as the VF industry expands into the urban environment of its iconic mega-cities. One of the newest to arrive on the scene is AEssenseGrows. This high-tech company went public in 2018, and markets a robust line of reliable aeroponic systems that are scalable from single-family dwellings up to large commercial vertical farming operations.

It is likely that as urbanization increases throughout China, a large number of vertical farms will become established to address issues directly linked to a growing rate of unemployment and increased weather-related food shortages. Sasaki Architects has been commissioned by the city of Shanghai to design a 600-acre urban agriculture training center to be located within the city limits. Its mission statement reads: “While one goal is to position Shanghai as a leader in urban food production, Sunqiao incorporates more than just the creation of vertical food factories. Providing a robust public realm that merges indoor and outdoor agricultural experiences, the Sunqiao experiment presents a new idea for urban life by celebrating food production as one of the most important functions of a city. Sunqiao not only addresses Shanghai’s increasing demand for locally-sourced food, but also educates generations of urban children about where their food comes from. As cities continue to expand, we must continue to challenge the dichotomy between what is urban and what is rural”. To date, no definite plans have been approved that would allow construction to begin.

The growth of the vertical farm industry in the Middle East was slow to develop, but during the summer of 2018, vertical farms were established in Dubai, and by Emirates Airlines, also located in Dubai. The Arabic airline is partnering with the California-based agri-tech firm One Crop Holdings. As of this writing, a 150,000 square-foot VF designed to provide enough fresh vegetables for 225,000 meals each day is under construction. Badia Farmshas established a VF in Bahrain, and Qatar, together with AeroFarms of Newark, New Jersey, has been in discussions about collaborating on establishing VFs in that country. The dual advantages of VFs, namely to provide fresh vegetables year round in even the driest of climates are the big selling points paving the way for this fledgling industry among the Arab emirates. For these reasons, it is anticipated, that over the next several years, many more VFs will become established in that region of the world.

The establishment of vertical farms in the United States had its origin in the city of Chicago, some forty years after the closing of the stockyards in 1971. Starting in 1865, following the Civil War, Chicago immediately became known as the meatpacking center of America. At any one time, during the busiest period in its history, millions of head of cattle were housed there, fattening up on corn before being shipped weeks later to the abattoirs, also located in the stockyards district. Collectively, those four-legged transients consumed a staggering 500,000 gallons of water each day. Not surprisingly, the equally staggering volume of runoff (mostly an odoriferous mix of urine and feces) adversely affected everything around it, including ecologically sensitive aquatic ecosystems (e.g., The Chicago River and Lake Michigan). People began to think twice about settling in Chicago, and many long-time residents migrated to greener pastures (no pun intended). According to the city’s Chief Environmental Officer, Sadhu Johnston (personal communication), the loss of thousands of middle class citizens from Chicago, especially between1950-1980 was solely due to their perception that the noxious air and water pollutants emanating from the stockyards were negatively impacting the health of their children. Those who could not afford to move (mostly the poor and disenfranchised minorities) had to stay and bear the brunt of those environmental insults as best they could. This kind of situation helped catalyze the advent of the modern day environmental justice movement that still continues on a global scale. Chicago was at first slow to recover from the blight left behind by an obsolete scheme to get fresh meat products to the densely populated East. But, starting in1990, the “city with big shoulders” began to quicken the pace of environmental repair, which included finding alternative uses for several intact abandoned buildings in the meatpacking district, one of which was a former meat curing facility. In 2005, Sadhu Johnston was appointed by the mayor as the Chief Environmental Officer, and with it came the power to spearhead a massive makeover of the downtown area of the city. The middle class, now comprised mostly of young millennials with no inkling of what it must have been like to suffer a hot, humid summer with all the air and water pollution associated with the stockyards, began to seek out careers in the “new” Chicago. The city had recaptured its critical missing middle class tax base. The mayor could now afford to turn his attention to a few new projects that appealed to that kind of voter. At the suggestion of a staff member, who pointed out that the Museum of Science and Industry had recently installed an exhibit featuring the new concept of the vertical farm, mayor John Daly, Jr. established the Chicago Vertical Farm Task Force on December 7, 2010. I was one of its co-directors and John Edel was a member. In 2011, Edel became the owner of the meat curing plant in Chicago’s abandoned stockyards district after presenting a working plan for its reuse to the city, explaining that, inspired by his tenure on the task force, he wanted to establish a training center for vertical farming. Once approved, over the next two years, Edel retrofitted that three-storey brick building with numerous indoor farming systems. He called his VF The Plant. Shortly thereafter, several more VFs became established in the area, including Green Sense Farms in Portage, Indiana, Green Spirit Farms in New Buffalo, Michigan, and FarmedHere (no longer in operation) in Bedford, Illinois.

Vertical Harvest is a three storey 13,500 square-foot VF in Jackson, Wyoming that generates 100,000 pounds of vegetables each year. A unique feature of Vertical Harvest is its employment practices. This VF, in collaboration with Cultivate routinely hires individuals with different abilities (e.g., Down’s Syndrome and autism). The success of this VF is evident in its profitability and robust customer list of local high-end restaurants. Together with the city of Lancaster, Pennsylvania, and the non-profit Lancaster Urban Farming Initiative, Vertical Harvest is moving ahead with plans to build a four story VF similar in design to its Jackson facility. Completion of the project is expected by 2020.

Las Vegas has partnered with Oasis Biotech, a China-based firm, to construct a 215,000 square-foot VF with the capacity to produce 9,000 servings of leafy greens each day, making it one of the largest VFs in the world, to date. The company located in Las Vegas for several reasons; lots of high-end restaurants and low energy costs. A kilowatt of electricity costs only 8.43 cents per hour there compared to the national average of 12.5 cents per hour.

Eden Green Technology, a Dallas, Texas-based company, established a 44,000 square-foot VF in Cleburne, whose customer base includes Wal-Mart. They grow over forty different kinds of edible greens. The company has plans for expansion to 1,000,000 square-feet of growing space in the near future. The energy for growing crops comes from sunlight in their two-storey plate glass enclosed facility.

80 Acres Farms locatedin Hamilton, Ohio, is a fully automated VF constructed at a cost of $15 million, that grows micro-greens, culinary herbs, leafy greens and kale. It created 40 jobs with average annual salaries of $40-50,000, plus benefits. Its customers include Whole Foods, and some local supermarket chains. The city of Hamilton attracted this VF by offering a long-term low-interest rate on property taxes. Hamilton also donated the land to the company for the construction of the VF facility. Other VFs in Ohio include Buckeye Fresh in Medina, and Mucci Farms (initial investment of $70 million USD) in Huron.

New Jersey is home to several VFs. AeroFarms, is a 70,000 square-foot facility located in Newark that employs a patented aeroponic growing technology and uses LED grow lights to produce micro-greens of a wide variety. Their customer base includes many well-known restaurants in the Iron Bound District of Newark. They were partially funded with an initial investment of $40 million from Goldman Sachs and the city of Newark. AeroFarms employs over 200 people, and has a standing open invitation employment application on their web site for anyone wishing to work for them. AeroFarms is expanding into other locations, including a 78,000 square-foot VF in Camden, New Jersey. In contrast, just down the road, in Kearney, is Bowery Farms, a completely automated VF that supplies fresh leafy greens to the restaurants of New York City. Bowery Farms also uses LED grow lights for its hydroponically grown crops that include butterhead lettuce, kale, arugula, bok choy, and romaine.

There are several VFs in Canada. TruLeaf, located in Bedford, Nova Scotia, uses LED grow lights and produces leafy green vegetables, including arugula, baby kale, pea shoots, micro-broccoli, and daikon radish. In 2016, a VF was constructed in Churchill, Manitoba for the Opaskwayak Cree First Nation. They have made good use of the facility and write: “At the moment, Opaskwayak’s vertical farm is limited to leafy vegetables and some root vegetables, but there are plans to grow fruits and grains sometime in the near future” (ibid).

The popularity of vertical farming in Europe began in France when SOA Architects put a video online of their virtual La Tour d’ Vivante, or “living tower”. SOA has been innovative in the field of urban agriculture, designing many interesting and practical buildings that could be constructed to further the idea that city farming is here to stay.

Berlin, Germany is home to infarm, an innovative VF company founded in 2013, that now has over 200 employees. infarm has ambitions to go global. They want to be able to provide as many different vegetables and herbs to consumers as the demands dictate. Currently, infarmoffers several options for CEA, including more than twenty in-store LED-powered grow modules for Berlin’s retail supermarket industry.

PlantagonInternational ABis a VF company founded in 2002 and located in Stockholm, Sweden. On their web site, they state: “In a dense city environment access to land is extremely low and the price is extremely high. A viable solution for sustainable urban food production must produce maximum volume of food on a minimum land area whilst using minimal resources and generating minimum waste”. Their strength lies in their ability to envision urban agriculture within innovative new iterations of the urban landscape. They term this hybrid construction ‘agritecture’. They have a long-term commitment to construct a VF in Linköping, and broke ground for its construction in 2012.

Evergreen Farm Oy, located in Tampers, Finland, is an impressive, modern, fully automated VF. It uses LED grow lights and an integrated grow system they term Grow360. The company claims to have constructed the world’s most highly productive indoor farm: “The Grow360 unit is a structure composed of rotating cylinders where up to 2160 plants grow vertically, thus, offering the highest yield per square and cubic meter.

The airy design surrounding the leaves enables pollination and offers a microclimate favorable for growth while keeping the leaves dry. The Grow360 unit does not create excess humidity, which is a major cause of poor production in other hydroponic systems. This allows plants to grow closer to each other.

In addition, the cylindrical shape maximizes growth area, while rotation minimizes the distance between plants and light fixtures. Therefore, offering the highest number of plants per area and volume. Due to its rotating system, the Grow360 unit radiates light evenly to all the plants”.

In The Netherlands, several VFs have been built. Staay Foods, located in Dronten, has partnered with Phillips GreenPower Lighting to construct a 900 square meter VF with 3,000 square meters of growing space employing LED grow lights for the production of lettuces of various types. The New FarmVF in The Hague (thenewfarm.nl/en), in addition to growing crops is also a newly established consulting firm for the VF industry, and a hub for disseminating information regarding the global development of VFs. The Rotterdam Food Cluster, established in 2014, invites high tech food production companies to join in this innovative urban agriculture experiment. Their mission statement reads: “The Rotterdam Food Cluster stimulates employment opportunities, entrepreneurship, innovation and collaboration in the regional food sector. The focus is on three themes: World Food Park, Food for the Future and Feeding the City”.

In the United Kingdom, Intelligent Growth Systems,in collaboration with the James Hutton Institute, has constructed an experimental VF in Invergowrie near Dundee. It will serve as an education center for those wishing to become involved in the VF industry. Intelligent Growth Systemspartnered with Omron, a high tech AI-based company, to explore innovative approaches to crop production, including AI, remote sensing, and a wide variety of experimental LED grow lighting schemes. The University of Nottingham has established the Centre for Urban Agriculture, headed by Dr. Chungui Lu. Its mission is to graduate students with advanced training in CEA, and in particular, vertical farming.  As already mentioned, GrowUp Urban Farms is located in the heart of London in tunnels that once served to protect its citizens from German air raids during WWII (). It produces mostly leafy green vegetables.

The Vertical Farm Institute located in Vienna, Austria, is headed by Daniel Podmerzig. He wrote his Ph.D. thesis on the practicality of energy use by vertical farms (Podmerzig, 2016). After graduating from Graz University, Podmerzig and several associates formed The Vertical Farm Institute. Their mission statement reads: “We specialize in the development of vertical farm operations with transparent facades to maximize utilization of the sunlight. Instead of black boxes, we rely on the power of readily available natural forces. There is another good reason for our building being transparent: We want to restore the trust in industrial food production. People are able to see for themselves how their food is grown, right in their city: Transparent, regional and with the highest of quality”.

Technologies employed by vertical farms

The remainder of this chapter will focus attention on advanced technologies that have led to the current state of progress in the vertical farming sector of urban agriculture.

 Hydroponics

Two growing strategies have become widely adopted for the indoor production of edible plants: hydroponicsand aeroponics. A third hybrid method, aquaponics, which incorporates fish production is integrated into the hydroponic growing scheme, will also be described. The application of hydroponics for growing edible plants probably had its origins in ancient times (Historia). The catalyst for this modern addition to the agricultural revolution was the emergence of the scientific method. Around the 1500s, a new way of thinking began to replace out-dated religious dogma, serving as the basis for creating an evidence-based rationale for fact finding. Those individuals driven by curiosity and a passion to know more about the natural world around them could now investigate all natural phenomena by applying observation, hypothesis, and experimentation. Two botanists, Julius von Sachs and Wilhelm Knop, working independently in Germany between 1860 and 1875, elucidated many of the basic physiological conditions for optimal growth of most green plants, ultimately enabling the invention of modern hydroponics (Douglas, 1975). Sachs (von Sachs, 1868) determined the minimal number of essential elements that green plants require in order to complete their life cycles. He grew plants suspended in a series of aqueous solutions, each enriched with a defined amount of dissolved purified chemical compound, then observed their rate of growth and production of seeds (von Sachs, 1887). Knop conducted similar experiments and obtained basically the same results. Further investigations by others confirmed that all green plants require sixteen to seventeen elements (Barker, 2015).Sachs and Knop went on to demonstrate that an inorganic source of nitrogen in the form of potassium nitrate was also required for maximum growth, and that the addition of solid animal waste, while aiding in making soil more tillable, did not contribute in a major way to plant nutrition.

It was not until 1929, when most of the basic biochemical and physiological parameters of plant growth had been described, that someone decided to take agriculture to the next level; namely growing commercial quantities of edible plants in a defined nutrient-enriched aqueous solution. Dr. William F. Gericke, working at the University of California at Berkeley, established methods now in use by many hydroponic growers. Gericke even coined the term hydroponic, after the Greek for waterworking. His book, “The Complete Guide to Soilless Gardening”, originally published in 1949 (Gericke, 2007), became the primary reference for a new generation of city farmers who appreciated the many advantages that growing vegetables without soil offered, including being able to grow them virtually anywhere within the urban landscape. Gericke’s research proved that many crops could be grown that way, including vine, tuber, and root vegetables, herbs and fruits.

Commercial-level hydroponic-based crop production is currently carried out in hundreds of thousands of greenhouses and thousands of vertical farms throughout the world (Resh, 2013; Kozai, 2016). One of its main advantages lies in its conservative use of freshwater. Compared to traditional outdoor agriculture that consumes an astounding 70 percent of the world’s liquid freshwater, hydroponic systems use 60-70 percent less to grow the same amount of crop. Several growing systems define each of the several methods employed in hydroponics. An excellent review of the general principles of hydroponics can be found at: Wikipedia.com. Nutrient film technology (NFT) and continuous-flow solution culture (CFS) are the two dominant hydroponic methods. Each system has its advantages and disadvantages.

NFT systems are typically configured in a horizontally positioned small diameter (approximately 23 cm) polyvinylchloride (PVC) pipe with regularly-spaced holes to accommodate plants (e.g., Boston bib lettuce). The pipes are angled slightly in one direction, allowing the passive flow of the nutrient solution to move from one pipe rack to another by gravity. The seedlings grow in the PVC pipe embedded in specially fitted inert fiber-filled (e.g., shredded coconut shell or finely crushed volcanic rock) containers that snug tightly into each hole. The roots barely touch the bottom of the pipe, encountering the nutrient solution, and continue to grow downstream as the plants mature. The film of nutrient solution is shallow enough to allow the roots direct exposure to the air as well as to the growth medium, achieving a high level of oxygen that maintains healthy roots. NFT systems, due to their simplicity of design, are easy to work with, and many commercial versions have built-in automated monitoring equipment for real-time tracking of nutrient concentrations, pH and Eh, temperature, etc.. While NFT is a highly efficient method with respect to energy and water consumption, the density of plants is limited by the configuration of the growing system and requires labor-intensive harvesting strategies. NFT can also exist as vertical walls covered with plants. This configuration has gained in popularity in recent years and many new vertical farm companies, including Plenty andEvergreen Farm Oy, have adopted them.

CFS uses shallow trays partially filled with a nutrient solution in which Styrofoam® rafts of densely packed plants are floated. The germinated seedlings, each nested in a fiber-filled bottomless container, send their roots into the solution below through regularly spaced holes in the plastic rafts. There may be as many as sixty holes per tray, allowing for a significant increase in plant density per square foot than can be achieved with most NFT methods. CFS requires much more water compared with NFT, and stronger pumps are required to move the solution from tray to tray, even though the trays are often configured to take advantage of gravity (e.g., Green Spirit Farms). As alluded to, one absolute requirement for plant growth is the need to supply oxygen to the roots (Letey,1962). Unlike leaves, roots lack chloroplasts, the sub-cellular organelle that contains the molecular machinery required to process sunlight into chemical energy. In soil, the roots grow underground and are unable to process sunlight in the same way that the above-ground portion of green plants does. In nature, this is not a problem, since the soil around the roots of most higher plants is porous enough to allow a sufficient amount of air to diffuse around them. The roots, as well as the leaves, generate metabolic energy by aerobic synthetic pathways using mitochondria to do so. Somehow all indoor plant growing systems must accommodate this requirement for getting oxygen to the roots. In CFS hydroponic systems, a delicate equilibrium between the pH of the nutrient solution, the solvency of metabolites, and the oxygen carrying capacity of the fluid portion of the nutrient solution must be maintained in order to realize maximum plant growth. If the temperature of the nutrient solution is too high, then the amount of dissolve oxygen is limited. If the temperature of the nutrient solution is too low, then some essential metabolites may become less soluble and could even precipitate out of solution, limiting the amount of plant life that the nutrient solution can support. Achieving a favorable balance amongst all these variables requires elaborate monitoring equipment and stringent oversight.

Aeroponics

Aeroponic grow systems (AGS) are designed expressly to expose the roots to the air, while using much less freshwater than hydroponics. Aeration of the nutrient solution is unnecessary in this technology. By eliminating one of the variables in plant growth from the equation, the system becomes easier to manage, thus avoiding “failure to thrive” situations often encountered in other more traditional hydroponic grow systems that eventually lead to lower profitability. Reviews outlining the principles and applications of aeroponics can be found at: Wikipedia.com.; Imran, 2018.

Aeroponics is a relatively new method for growing edible plants, and was first developed in 1983 by Richard J. Stoner II while working on contract from the National Aeronautics and Space Administration (Stoner and Clawson, 1999-2000). Since then, many versions of AGS have been applied to commercial CEA operations. AGS utilize a fine mist of nutrient-laden water created by its passage through a pressurized nozzle that is then directed towards the exposed root system of the plants that hang down inside of a closed container. A major advantage of AGS is that they use approximately seventy percent less water that hydroponic systems, while delivering the same amount of nutrients to the roots. Recent advances in nozzle design have improved the reliability of the system for creating the mist of nutrients by eliminating valve clogging, a major impediment to the development of this method of indoor growing (Stoner, and Clawson, 1999-2000). As the result, more vertical farms are adopting AGS for crop production. Several configurations of AGS will serve to illustrate the creative process following Stoner’s original invention.

Tower Garden , a patented vertical tubular AGS designed and manufactured by Tim Blank has evolved into a scalable technology for both home and commercial application (Future Growing). In brief, a large tub filled with a nutrient solution and a submersible pump is fitted with a PVC tube that has portals cut into it to accommodate holders of seedlings of various types (i.e., leafy greens, tomatoes, green beans, zucchini, etc.). The pump delivers a stream of nutrient solution up into the hollow body of the pipe. When it reaches the inner surface of the sealed top, a specially designed contour disperses the stream, converting it into a mist that then bringing the nutrients to the roots that are hanging inside the PVC cavity. The main disadvantage of this system is the limited number of individual plants (28 plants per tube) that can be accommodated by the tube. Tower gardens are used by many restaurants, and schools to supply fresh produce to patrons and students alike.

A second patented aeroponic growing system developed by Edward Harwood, makes use of a thick cloth-like porous inert fiber matrix onto which a lawn of germinated seeds is evenly sown. Nutrient solutions are sprayed from a reservoir below the cloth, while the plants are illuminated from above with high-efficiency LED grow lights. Their technology is ideally suited for the large-scale production of a wide variety of micro-greens.

AEssenseGrows features an in-house engineered patented aeroponic valve system for growing a wide variety of vegetables, fruits, and herbs. They manufacture units for individual home use, as well as for large-scale commercial application. Their online statement, in part, reads: “Our AEtrium System uses the latest aeroponic hydroponic technology to grow the best tasting, most beautiful, longest lasting produce. Our Guardian™ Grow Manager software optimizes grow recipes to efficiently deliver pure and naturally safe produce to worldwide populations”.

PureGrows custom designs scalable AGS for commercial applications. Their online description, in part, states: “Pure Grows Aeroponic Sytems are custom designed to every single client to perfectly fit your grow space.  Pure Grows is built on a module-based system, and each module produces 416 healthy, fast growing plants. Modules could be used independently or as part of a larger growing operation where many modules are connected together to cultivate thousands of plants maximizing the use of your available space.  Each module is complemented with a quality lighting system which together gives you a ready to grow set-up.”

Other commercial aeroponic manufacturers include True Aeroponic Systems, and Commercial Genesis Series-V Aeroponic Systems. In the near future, even more efficient next generation aeroponic growing systems will undoubtedly become available, as this version of urban agriculture becomes more popular not only with commercial growers, but with restaurants (e.g., Bidwell in Washington, D.C. , Bell, Book, and Candle in New York City and home use.

Aquaponics

Aquaponics employs an advanced, more complex form of indoor agriculture (The Plant), in which bacteria-laden water, a byproduct of freshwater fish farming, (e.g., tilapia), is circulated through an NFT system, and serves as the nutrient source for the edible plants. The removal of nutrients by the plants purifies the water, and it is then returned to the fish tanks for re-use. Ammonia, a volatile compound excreted by fish, must be passed through a bio-filter colonized with specialized bacteria that enzymatically converts ammonia into plant-friendly nitrates and nitrites. Aquaponics growers liken their method of farming to a kind of closed loop ecosystem approach to food production. To begin the circulation of nutrients, the fish are fed pellets of compressed vegetable material. The fish feces contain the essential nutrients for the plants in the form of bacteria. When the bacteria die and then lyse, they release their store of elements and organic compounds into the water, which are taken up by the plants. Since two different systems are required to complete the loop, one for fish and the other for plants, monitoring equipment for each part of the system must be incorporated into the overall design of the indoor farm (ibid). Aquaponics is by design more complex to operate and maintain than hydroponics or aeroponics, and that is why many CEA facilities have opted for the latter simpler modes of growing.

Light Emitting Diode Grow Lights

Light emitting diode (LED) grow lights have become the new standard as the source of energy supplied to edible plants grown indoors (Singh, 2016). They have essentially replaced the less efficient high-pressure sodium and fluorescent lights, and that transition occurred in just over the last four years. The reasons for the transformation in the selection of LED grow lights are several fold. First, LED lights can be customized to achieve the optimal visible light spectra for most commercial crop species of green plants. Second, the cost of LEDs has changed dramatically downward over the last five years, facilitating their current wide spread use. Third, the cost of running LEDs has been decreasing steadily as well, and is directly proportional to the steady increase in efficiency and longevity of LEDs.

The most commonly used combination of LED grow light spectra is red (600-630 nm) and blue (400-540 nm). These two LED lights cover the activation spectra for chlorophyll a and chlorophyll b (Ouzounis, C-O. O. 2015). The visible red LED light was invented by Nick Holonyak at General Electric in 1962, and while it was the first of its kind, it was soon joined by an array of other LEDs, ranging in visible light spectrum from far red (Lund, 2007) to near UV (Lin, 2010).

As of 2018, LED grow light manufacturers continue to respond to the needs of the burgeoning CEA industry by producing a steady stream of more efficient, affordable lighting systems (Nelson, 2014), at a rate similar to Moore’s Law regarding the doubling of transistor density in integrated circuits. Furthermore, the LED grow lights of 2018 come with a high degree of flexibility regarding their physical attributes for meeting the configuration requirements for most indoor crop production schemes, be they hydroponic or aeroponic.

While research on LED grow lights continues to improve the efficiency of conversion of electrons to photons, much still remains to be learned regarding the application of LEDs to the fundamental biochemical process of photosynthesis (Darko, 2014). For example, it is known that other plant pigments (e.g., phytochromes, carotenes, and xanthophylls) play important roles in regulating the overall growth patterns of plants (Zhang, 2018) and in regulating the efficiency of photosynthesis. But little is known with respect to the kinds of visible light needed to insure the activation of these accessory plant pigments. Thanks to the continued refinement of LEDs by academic and industrial researchers trained in optical physics and materials sciences, plant physiologists can now begin to explore questions regarding which precise wave-lengths of light activate which plant functions. For example, by exposing seedling plants to LEDs of varying wave-lengths not directly responsible for activating chlorophylls, new insights into the requirements for complete plant growth (e.g., flowering, seed production, stem length) can be explored that in the long-term, could dramatically improve crop production in CEA. In turn, improved efficiency of indoor plant production would undoubtedly lead to an accelerated rate in the establishment of new vertical farms.

Leaders in research and production of LED grow lights include Phillips, Illumitex, Lumigrow, and numerous lighting companies in Japan and China.

Nutrients for hydroponics and aeroponics

As important as lighting and growing system configurations are to indoor crop production, nothing is more critical than the plant diets growers employ. As mentioned, it has been determined through numerous rigorously conducted scientific studies, that all higher plants require from between sixteen and seventeen elements (Barker, 2015), in addition to an organic source of nitrogen, and of course sunlight and freshwater. Outdoor plants raised in soil also require only 16-17 elements, but will accumulate traces of nearly all ninety naturally occurring elements. This can lead to serious contamination of our food supply if, for instance, noxious elements such as lead and other heavy metals accumulate in crops grown in certain locations that used to be heavily industrialized (Kachenko, 2006). The difference between indoor and outdoor farming with regards to what is found in our food supply is one of the many reasons why CEA is becoming more and more trusted as a means of food production.

The above finding might have led to the adoption of synthetic diets composed of ACS Reagent grade chemicals for the indoor farming industry, but that has not been the case. So far this approach has only been applied to botanical research laboratories, and is probably due, in large part, to the fact that pure chemicals are expensive. In addition, since these plants are intended to serve as part of our food supply, and animals require additional elements (Pleasants,1964; Baker, 2018), plant diets must be more broadly formulated to satisfy our own needs, as well as those of our edible crops. Fortunately, there are many affordable commercially available options for supplying the required array of nutrients in hydroponic and aeroponic situations.

Challenges

The growth of the vertical farm industry has been meteoric, and as noted, not all VFs that were present five years ago are still in operation today. Many reasons why businesses fail could be listed here, and some of them undoubtedly led to the demise of what started out as optimistic beginnings for many of them. Ultimately, the economics of running an enterprise is what makes or breaks a company, be they big or small. History is full of classic examples, many of which are used today in business schools throughout the world, as “what-not-to-do” case studies. The most important thing in starting a VF is to know what is known and what is not known about how to profit from CEA. I am constantly being reminded by those who currently run these new urban food production facilities that oversight is key. To know what to look for in such a complex growing environment when things begin to go wrong, long before they become critical problems, necessitates knowledge of the overall running of a VF. This applies to all personnel, from the CEO down to the utility worker in the nursery. Failure to do so insures that things will get worse, and may lead to the shutting down of operations.

The first challenge in vertical farming is being able to hire qualified people who can trouble-shoot the systems and correct the problems. Not surprisingly, currently there is an acute shortage of those with advanced training in CEA. This needs to be corrected, and there are signs the situation is changing for the better. I recommend that every school of agriculture begin offering degrees in urban farming. This would stimulate a new generation of city dweller with strong ties to the new food system of that locale, rather than to some commodities exchange that has nothing else in mind than to make profit from growing things that have nothing to do with eating.

The second challenge relates to the energy budget of the day-to-day running of a VF. The cost of a kilowatt hour of electricity has been going down over the last few years, mostly because of a surge in the use of natural gas in power plants with the flexibility to take advantage of the cheapest fossil fuels available. In addition, the trend today is for more and more renewable energy resources to displace the use of fossil fuels. In Europe, wind power is ahead of most other renewables, while in the United States, its solar and hydropower. When the price of a kilowatt hour of electricity falls below ten cents, then it’s likely that the energy component will not be the reason the VF cannot turn a profit. As LED grow lights continue to become more efficient and cheaper to purchase, the number of startup VFs will continue to increase.

The third challenge addresses crop selection. The great majority of VFs grow highly profitable leafy green vegetables, and one cannot fault them for doing so, as everyone needs to make ends meet in order to go back to work the next day. But not providing a complete array of edible plants to its customer base is short-sighted and cannot sustain a food industry that just got its legs under it, so to speak. Once consumers discover the many advantages of having access to  ultra- fresh food, they will demand a single resource (brand) that can provide all their shopping needs in one place. This dilemma is reminiscent of the early days at most pharmaceutical houses. A single drug, usually an antibiotic, became the cash cow, but could not sustain that company, since others found profitability in similar natural products. By diversifying their list of therapeutics, a consequence of initiating expensive research and development programs, companies were then able to capture a much larger number of brand-loyal clientele. The same will undoubtedly apply to the vertical farm industry.

The last challenge relates to the politics of urban agriculture and its acceptance among city dwellers. As the industry matures and the many advantages of farming inside the city become better understood by politicians, planners and developers, vertical farms will assume their place in the skyline of the world’s urban centers.

The future of vertical farming and urban life

The exact number of vertical farms in operation throughout the world is not known, but prior to 2010 there were none. Based only on this one observation, and at the risk of being accused of waxing a bit over-optimistic, by extrapolation over the next five to ten years, the rate of establishing new VFs has the potential for increasing at a geometric rather than at an arithmetic rate. This means that eventually, cities will be producing significant quantities of food for more than sixty percent of our population. What are the global implications for climate change, the food system, and society in general if and when urban agriculture enables cities to feed all of their inhabitants?

Lets begin with the climate. There is broad consensus among a wide variety of scientists, governmental agencies, and interdisciplinary international consortia that if somehow we could restore the world’s forests to at least sixty to seventy percent of their former ground cover (approximately two trillion trees), then terrestrial biomes damaged by farming would regain a large portion of their ability to sequester carbon, enough to reverse the rate at which the world is currently warming. Typically, abandoned agricultural land returns to its original ecological function by the process of succession, and may take as long as fifty years to reach climax forest (Leopold,1949; Feldpausch, 2005). That process is much faster in tropical settings, provided that the farmland is not cleared by burning off the trees and understory, and that fragmented forest is left alone to regenerate itself (Crouzeilles, 2017). Vertical farming offers an environmentally acceptable way of replacing a significant portion of the 1.87 billion hectares devoted to crop production, paving the way for the regeneration of both temperate zone and tropical forests.

Many other positive environmental changes would soon follow if this were to occur. As ecosystems repair themselves and bio-diversity increases, the health of every living thing on the planet, us included, would benefit (Rees,1996; Maller, 2005). Global food systems would become greatly diminished, perhaps even disbanded, giving way to regional trade agreements not predicated on what can and cannot be grown in a give geographic location. Societal values would favor local solutions to address every aspect of urban life, encouraging cities to transform into places that did no harm to the surrounding now recovered landscape.

Projecting this idea even further into the future, if every new building erected within the city limits could sequester carbon, capture all rainwater, generate energy by photovoltaic cladding and clear photovoltaic windows, and grow enough food to support all those who worked or lived in it (i.e., some form of vertical farming in every building), then the city itself would become the technological equivalent of a hardwood forest. These desirable characteristics for the modern skyscraper may seem a bit Jetsonesque, but there is no need for new technologies to construct this kind of building. All of the above-proposed functions for the built environment are already incorporated into a few new buildings. By combining all of those functions into a single edifice, a sustainable future for the urban landscape would be assured, and the rest of nature could breathe a bit easier and celebrate in its return to uninterrupted wildness.

Finally, it is important to remember that the single most important advance that got us this far in our evolution was the invention of agriculture; the consequence of which was the emergence and maturation of modern civilizations. Ironically, sustainability has become our new mantra for the third green revolution now unfolding in the twenty first century. By inventing technologies enabling us to live long and prosper, we inadvertently created a set of massive health hazards; pollutions and resource abuses attendant with short-term practices linked to industrialization and traditional farming. The long feared crisis of too many mouths to feed with too little food available to do so has finally arrived. We have caused this dilemma and we must now change course to correct that inequality. It will require strong political will and total societal buy in at all levels in order to be able to apply all we have learned over the last 10,000 years to allow us and the rest of Earth’s life forms to survive unscathed into the next 10,000 years of planet Earth’s history. Learning how to grow our food without damaging the environment will go a long way to helping humanity achieve the elusive but highly desirable goal: sustainability.

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