Vertical farming

Dickson Despommier shares his ideas about how "vertical farming" can help reduce hunger by changing the way we use land for agriculture. photography by kris krüg

Vertical farming as a component of urban agriculture is the practice of cultivating plant life within a skyscraper greenhouse or on vertically inclined surfaces. The modern idea of vertical farming uses techniques similar to glass houses, where natural sunlight can be augmented with artificial lighting.[1]

Types

The term "Vertical farming" was coined by Gilbert Ellis Bailey in 1915 in his book Vertical Farming. His use of the term differs from the current meaning - he wrote about farming with a special interest in soil origin, its nutrient content and the view of plant life as "vertical" life forms, specifically relating to root structures underground.[2] Modern usage refers to skyscrapers using some degree of natural light.

Mixed-use skyscrapers

Mixed-use skyscrapers were proposed and built by architect Ken Yeang. Yeang proposes that instead of hermetically sealed mass-produced agriculture that plant life should be cultivated within open air, mixed-use skyscrapers for climate control and consumption (i.e. a personal or communal planting space as per the needs of the individual). This version of vertical farming is based upon personal or community use rather than the wholesale production and distribution plant life that aspires to feed an entire city. It thus requires less of an initial investment than Despommier's "The Vertical Farm". However, neither Despommier nor Yeang are the conceptual "originators", nor is Yeang the inventor of vertical farming in skyscrapers.

Plantagon is building the world's first industrial-scale multifunctional vertical farm in Linköping, Sweden.[3]

Despommier's skyscrapers

Ecologist Dickson Despommier argues that vertical farming is legitimate for environmental reasons. He claims that the cultivation of plant life within skyscrapers will produce less embedded energy and toxicity than plant life produced on natural landscapes. He moreover claims that natural landscapes are too toxic for natural, agricultural production, despite the ecological and environmental costs of extracting materials to build skyscrapers for the simple purpose of agricultural production.

Vertical farming according to Despommier thus discounts the value of natural landscape in exchange for the idea of "skyscraper as spaceship". Plant life is mass-produced within hermetically sealed, artificial environments that have little to do with the outside world. In this sense, they could be built anywhere regardless of the context. This is unlikely to be advantageous with regards to energy consumption as the internal environment must be maintained to sustain life within the skyscraper. However, this is not necessarily the case, as one of the most important features of a vertical farm is that it would contain some form of renewable energy technology, be it solar panels, wind turbines, or a water capture system, and could contain all three. The vertical farm is designed to be sustainable, and to enable nearby inhabitants to work at the farm.

Despommier's concept of "The Vertical Farm" emerged in 1999 at Columbia University. It promotes the mass cultivation of plant life for commercial purposes in skyscrapers.[4]

History

A commercial high-rise farm such as 'The Vertical Farm' has never been built, yet extensive photographic documentation and several historical books on the subject suggest that research on the subject was not diligently pursued.[5] New sources indicate that a tower hydroponicum existed in Armenia prior to 1951.[6]

Proponents argue that, by allowing traditional outdoor farms to revert to a natural state and reducing the energy costs needed to transport foods to consumers, vertical farms could significantly alleviate climate change produced by excess atmospheric carbon. Critics have noted that the costs of the additional energy needed for artificial lighting, heating and other vertical farming operations would outweigh the benefit of the building’s close proximity to the areas of consumption.[7][8]

One of the earliest drawings of a tall building that cultivates food for the purposes of consumption was published as early as Life Magazine 1909.[9] The reproduced drawings feature vertically stacked homesteads set amidst a farming landscape. This proposal can be seen in Rem Koolhaas's Delirious New York. Koolhaas wrote that this 1909 theorem is

“

'The Skyscraper as Utopian device for the production of unlimited numbers of virgin sites on a metropolitan location' (1994, 82).

 ”

Other architectural proposals that provide the seeds for the Vertical Farm project include Le Corbusier’s Immeubles-Villas (1922) and SITE’s Highrise of homes (1972).[10] SITE’s Highrise of homes, is a near revival of the 1909 Life Magazine Theorem.[11] In fact, built examples of tower hydroponicums are quite well documented in the canonical text of "The Glass House" by John Hix. Images of the vertical farms at the School of Gardeners in Langenlois, Austria, and the glass tower at the Vienna International Horticulture Exhibition (1964) clearly show that vertical farms existed more than 40 years prior to contemporary discourse on the subject.[1] Although architectural precedents remain valuable, the technological precedents that make vertical farming possible can be traced back to horticultural history through the development of greenhouse and hydroponic technology. Early building types or Hydroponicums were developed, integrating hydroponic technology into building systems. These horticultural building systems evolved from greenhouse technology, and paved the way for the modern concept of the vertical farm. The British Interplanetary Society developed a hydroponicum for lunar conditions and other building prototypes were developed during the early days of space exploration. During this era of expansion and experimentation, the first Tower Hydroponic Units were developed in Armenia.[12]

The Armenian tower hydroponicums are the first built examples of a vertical farm, and is documented in Sholto Douglas' seminal text "Hydroponics: The Bengal System" first published in 1951 with data from the then-East Pakistan, today's Bangladesh, and the Indian state of West Bengal.[6] Contemporary notions of vertical farming are predated by this early technology by more than 50 years.[13] Contemporary precursors that have been published, or built, are Ken Yeang’s Bioclimatic Skyscraper (Menara Mesiniaga, built 1992); MVRDV’s PigCity, 2000; MVRDV's Meta City/ Datatown (1998–2000); Pich-Aguilera’s Garden Towers (2001).[10]

Ken Yeang is perhaps the most widely known architects that has promoted the idea of the 'mixed-use' Bioclimatic Skyscraper which combines living units and opportunities for food production.[14]

Early prototypes of vertical farms, or "Tower Hydroponicums" existed in Armenia prior to 1951[15] during an era of hydroponic and horticultural building system research fueled by space exploration and a transatlantic technology race.

The latest version of these very idea is Dickson Despommier's "The Vertical Farm".

Dickson Despommier, a professor of environmental health sciences and microbiology at Columbia University in New York City, modernized the idea of vertical farming in 1999 with graduate students in a medical ecology class. Although much of Despommier's suggestions have been challenged and strongly criticized from an environmental science and engineering point of view, the idea's popularization in recent years has been largely the result of Despommier's assertion that food production can be transformed.

Despommier had originally challenged his class to feed the population of Manhattan (About 2,000,000 people) using 13 acres (5.3 ha) of usable rooftop gardens. The class calculated that, by using rooftop gardening methods, only 2 percent would be fed. Unsatisfied with the results, Despommier made an off-the-cuff suggestion of growing plants indoors, vertically. The idea sparked the students' interests and gained major momentum. By 2001 the first outline of a vertical farm was introduced and today scientists, architects, and investors worldwide are working together to make the concept of vertical farming a reality. In an interview with Miller-McCune.com, Despommier described how vertical farms would function:

“ Each floor will have its own watering and nutrient monitoring systems. There will be sensors for every single plant that tracks how much and what kinds of nutrients the plant has absorbed. You'll even have systems to monitor plant diseases by employing DNA chip technologies that detect the presence of plant pathogens by simply sampling the air and using snippets from various viral and bacterial infections. It's very easy to do.

Moreover, a gas chromatograph will tell us when to pick the plant by analyzing which flavenoids the produce contains. These flavonoids are what gives the food the flavors you're so fond of, particularly for more aromatic produce like tomatoes and peppers. These are all right-off-the-shelf technologies. The ability to construct a vertical farm exists now. We don't have to make anything new.[16]

 ”

Architectural designs have been produced by Chris Jacobs and Andrew Kranis from Columbia University and Gordon Graff[17][18] from the University of Waterloo's School of Architecture in Cambridge, ON. Together with Graff, and after disagreeing with Despommier's technical assumptions regarding energy and water balances in 2011, Tahbit Chowdhury and a multidisciplinary team from Waterloo's Dept. of Environmental Engineering and Dept. of Systems Design Engineering augmented the concepts with a focus on low-energy economically-intensive protein-production. Along with Chowdhury, others who have disagreed with Despommier's approach include Pierre Desrochers of the University of Toronto and Dennis T. Avery of the Center for Global Food Issues, affiliated with the Hudson Institute.

Chowdhury and Graff applied advanced industrial engineering design philosophies to modernize current greenhouse technology as it pertains to hydroponics and aeroponics. The results of the Waterloo team's work showed that there is sufficient technical grounds to begin implementing Despommier's ideas for skyscrapers. However, Chowdhury and Graff showed that the designs will be dramatically different from what Despommier envisioned at Columbia.

Mass media attention began with an article written in New York magazine. Since 2007, articles have appeared in The New York Times,[19] U.S. News & World Report,[20] Popular Science,[21] Scientific American[22] and Maxim, among others, as well as radio and television features.

As of 2012, Vertical Harvest is working on raising funds for an urban, small-scale vertical farm in Jackson Hole, Wyoming.[23]

Advantages

Several potential advantages of vertical farming have been discussed by Despommier.[24] Many of these benefits are obtained from scaling up hydroponic or aeroponic growing methods.

Preparation for the future

It is estimated that by the year 2050, close to 80% of the world’s population will live in urban areas and the total population of the world will increase by 3 billion people. A very large amount of land may be required depending on the change in yield per hectare. Scientists are concerned that this large amount of required farmland will not be available and that severe damage to the earth will be caused by the added farmland. Vertical farms, if designed properly, may eliminate the need to create additional farmland and help create a cleaner environment.[25][26][27]

Increased crop production

Unlike traditional farming in non-tropical areas, indoor farming can produce crops year-round. All-season farming multiplies the productivity of the farmed surface by a factor of 4 to 6 depending on the crop. With some crops, such as strawberries, the factor may be as high as 30.[28][29]

Furthermore, as the crops would be sold in the same infrastructures in which they are grown, they will not need to be transported between production and sale, resulting in less spoilage, infestation, and energy required than conventional farming encounters. Research has shown that 30% of harvested crops are wasted due to spoilage and infestation, though this number is much lower in developed nations.[22]

Despommier suggests that, if dwarf versions of certain crops are used (e.g. dwarf wheat, which has been grown in space by NASA, is smaller in size but richer in nutrients[30]), year-round crops, and "stacker" plant holders are accounted for, a 30-story building with a base of a building block (5 acres (20,000 m2)) would yield a yearly crop analogous to that of 2,400 acres (9,700,000 m2) of traditional farming.[22]

Protection from weather-related problems

Crops grown in traditional outdoor farming suffer from the often suboptimal, and sometimes extreme, nature of geological and meteorological events such as undesirable temperatures or rainfall amounts, monsoons, hailstorms, tornadoes, flooding, wildfires, and severe droughts.[24] The protection of crops from weather is increasingly important as global climate change occurs. “Three recent floods (in 1993, 2007 and 2008) cost the United States billions of dollars in lost crops, with even more devastating losses in topsoil. Changes in rain patterns and temperature could diminish India’s agricultural output by 30 percent by the end of the century.”[31]

Because vertical plant farming provides a controlled environment, the productivity of vertical farms would be mostly independent of weather and protected from extreme weather events. Although the controlled environment of vertical farming negates most of these factors, earthquakes and tornadoes still pose threats to the proposed infrastructure, although this again depends on the location of the vertical farms.

Conservation of resources

Each unit of area in a vertical farm could allow up to 20 units of area of outdoor farmland to return to its natural state,[32][33] and recover farmlands due to development from original flat farmlands.

Vertical farming would reduce the need for new farmland due to overpopulation, thus saving many natural resources,[22] currently threatened by deforestation or pollution. Deforestation and desertification caused by agricultural encroachment on natural biomes would be avoided. Because vertical farming lets crops be grown closer to consumers, it would substantially reduce the amount of fossil fuels currently used to transport and refrigerate farm produce. Producing food indoors reduces or eliminates conventional plowing, planting, and harvesting by farm machinery, also powered by fossil fuels. Burning less fossil fuel would reduce air pollution and the carbon dioxide emissions that cause climate change, as well as create healthier environments for humans and animals alike.

Organic crops

The controlled growing environment reduces the need for pesticides, namely herbicides and fungicides. Advocates claim that producing organic crops in vertical farms is practical and the most likely production in the future.

Halting mass extinction

Withdrawing human activity from large areas of the Earth's land surface may be necessary to slow and eventually halt the current anthropogenic mass extinction of land animals.

Traditional agriculture is highly disruptive to wild animal populations that live in and around farmland and some argue it becomes unethical when there is a viable alternative. One study showed that wood mouse populations dropped from 25 per hectare to 5 per hectare after harvest, estimating 10 animals killed per hectare each year with conventional farming.[34] In comparison, vertical farming would cause very little harm to wildlife.[34]

Impact on human health

Traditional farming is a hazardous occupation with particular risks that often take their toll on the health of human laborers. Such risks include: exposure to infectious diseases such as malaria and schistosomes, exposure to toxic chemicals commonly used as pesticides and fungicides, confrontations with dangerous wildlife such as venomous snakes, and the severe injuries that can occur when using large industrial farming equipment. Whereas the traditional farming environment inevitably contains these risks (particularly in the farming practice known as “slash and burn”), vertical farming – because the environment is strictly controlled and predictable – reduces some of these dangers.[24] Currently, the American food system makes fast, unhealthy food cheap while fresh produce is less available and more expensive, encouraging poor eating habits. These poor eating habits lead to health problems such as obesity, heart disease, and diabetes.

Urban growth

Vertical farming, used in conjunction with other technologies and socioeconomic practices, could allow cities to expand while remaining largely self-sufficient food wise. This would allow for large urban centers that could grow without destroying considerably larger areas of forest to provide food for their people. Moreover, the industry of vertical farming will provide employment to these expanding urban centers. This may help displace the unemployment created by the dismantling of traditional farms, as more farm laborers move to cities in search of work.[24] It is highly unlikely that traditional farms will become obsolete, as there are many crops that are not suited for vertical farming, and the production costs are currently much lower.

Energy production

Vertical farms could exploit methane digesters to generate a small portion of its own electrical needs. Methane digesters could be built on site to transform the organic waste generated at the farm into biogas which is generally composed of 65% methane along with other gases. This biogas could then be burned to generate electricity for the greenhouse.[35]

Technologies and devices

Vertical farming relies on the use of various physical methods to become effective. Combining these technologies and devices in an integrated whole is necessary to make Vertical Farming a reality. Various methods are proposed and under research. The most common technologies suggested are:

Plans

Despommier argues that the technology to construct vertical farms currently exists. He also states that the system can be profitable and effective, a claim evidenced by some preliminary research posted on the project's website. Developers and local governments in the following cities have expressed serious interest in establishing a vertical farm: Incheon (South Korea), Abu Dhabi (United Arab Emirates), and Dongtan (China),[37] New York City, Portland, Ore., Los Angeles, Las Vegas,[38] Seattle, Surrey, B.C., Toronto, Paris, Bangalore, Dubai, Shanghai and Beijing. The Illinois Institute of Technology is now crafting a detailed plan for Chicago. It is suggested that prototype versions of vertical farms should be created first, possibly at large universities interested in the research of vertical farms, in order to prevent failures such as the Biosphere 2 project in Oracle, Arizona.[39]

In 2009, the world's first pilot production system was installed at Paignton Zoo Environmental Park in the United Kingdom. The project showcased a technological solution for vertical farming and provided a physical base to conduct research into sustainable urban food production. The produce is used to feed the zoo's animals while the project enables evaluation of the systems and provides an educational resource to advocate for change in unsustainable land use practices that impact upon global biodiversity and ecosystem services,[40]

In 2010, the Green Zionist Alliance proposed a resolution at the 36th World Zionist Congress calling on Keren Kayemet L'Yisrael (Jewish National Fund in Israel) to develop vertical farms in Israel.[41]

In 2012, the world's first commercial vertical farm was opened in Singapore, developed by Sky Greens Farms, and is three stories high.[42][43] They currently have over 100 towers that stand at nine meters tall.[44]

Problems

Economics

Opponents question the potential profitability of vertical farming.[45] A detailed cost analysis of start-up costs, operation costs, and revenue has not been done. The extra cost of lighting, heating, and powering the vertical farm may negate any of the cost benefits received by the decrease in transportation expenses.[46] The economic and environmental benefits of vertical farming rest partly on the concept of minimizing food miles, the distance that food travels from farm to consumer. However, a recent analysis suggests that transportation is only a minor contributor to the economic and environmental costs of supplying food to urban populations. The author of the report, University of Toronto professor Pierre Desrochers, concluded that "food miles are, at best, a marketing fad."[47] Thus the facility would have to produce a considerable profit to justify remaining in the city. A simpler concept rather than trying to stack farms on multiple stories would be to just cultivate crops on the roofs of existing building. Rooftop farming is a growing urban trend, requires little construction (other than fortifying the roof to hold the weight of the growing medium), still takes advantage of sunlight and doesn't require investment in machinery, growing lights or irrigation.[48]

Similarly, if the power needs of the vertical farm are met by fossil fuels, the environmental effect may be a net loss;[49] even building low-carbon capacity to power the farms may not make as much sense as simply leaving the traditional farms in place, and burning less coal.

The initial building costs will be easily over $100 million, for a 60 hectare vertical farm.[50] Office occupancy costs can be very high in major cities, with cities such as Tokyo, Moscow, Mumbai, Dubai, Milan, Zurich, and Sao Paulo ranging from $1850 to $880 per square meter, respectively.[51]

Energy use

During the growing season, the sun shines on a vertical surface at an extreme angle such that much less light is available to crops than when they are planted on flat land. Therefore, supplemental light, would be required in order to obtain economically viable yields. Bruce Bugbee, a crop physiologist at Utah State University, believes that the power demands of vertical farming will be too expensive and uncompetitive with traditional farms using only free natural light.[7][52] The environmental writer George Monbiot calculated that the cost of providing enough supplementary light to grow the grain for a single loaf would be about $15.[53] An article in the Economist argued that "even though crops growing in a glass skyscraper will get some natural sunlight during the day, it won't be enough" and "the cost of powering artificial lights will make indoor farming prohibitively expensive".[54]

As "The Vertical Farm" proposes a controlled environment, heating and cooling costs will be at least as costly as any other tower. But there also remains the issue of complicated, if not more expensive, plumbing and elevator systems to distribute food and water throughout. Even throughout the northern continental United States, while heating with relatively cheap fossil fuels, the heating cost can be over $200,000/hectare.[55]

To address this problem, The Plant in Chicago is building an anaerobic digester into the building. This will allow the farm to operate off the energy grid. Moreover, the anaerobic digester will be recycling waste from nearby businesses that would otherwise go into landfills.[56]

Pollution

Depending on the method of electricity generation used, regular greenhouse produce can create more greenhouse gases than field produce,[57] largely due to higher energy use per kilogram of produce. With vertical farms requiring much greater energy per kilogram of produce, mainly through increased lighting, than regular greenhouses, the amount of pollution created will be much higher than that from field produce. The amount of pollution produced is dependent on how the energy used in the process is generated.

As plants acquire nearly all their carbon from the atmosphere, greenhouse growers commonly supplement CO2 levels to 3–4 times the rate normally found in the atmosphere. This increase in CO2, which has been shown to increase photosynthesis rates by 50%, contributes to the higher yields expected in vertical farming.[58] It is not uncommon to find greenhouses burning fossil fuels purely for this purpose, as other CO2 sources, like from furnaces, contain pollutants such as sulphur dioxide and ethylene which significantly damage plants.[58] This means a vertical farm will require a CO2 source, most likely from combustion, even if the rest of the farm is powered by 'green' energy. Also, through necessary ventilation, much CO2 will be leaked into the city's atmosphere.

Greenhouse growers commonly exploit photoperiodism in plants to control whether the plants are in a vegetative or reproductive stage. As part of this control, growers will have the lights on past sunset and before sunrise or periodically throughout the night. Single story greenhouses are already a nuisance to neighbours because of light pollution, a 30 story vertical farm in a densely populated area will surely face problems because of its light pollution.[59]

Hydroponics greenhouses regularly change the water, meaning there is a large quantity of water containing fertilizers and pesticides that must be disposed of. While solutions are currently being worked on, the most common method of simply spreading the mixture over a sufficient area of neighbouring farmland or wetlands would be more difficult for an urban vertical farm.[60]

See also

References

  1. ↑ 1.0 1.1 Hix, John. 1974. The glass house. Cambridge, Mass: MIT Press.
  2. ↑ Vertical farming (1915). Wilmington, Del.: E. I. duPont de Nemours Powder Co. Retrieved 2011-07-23.
  3. ↑ In Linköping, Sweden February 9, 2012 the first Plantagon Greenhouse broke ground. A new type of greenhouse for vertical farming; an international Centre of Excellence for Urban Agriculture; a demo-plant for Swedish clean-tech and a climate-smart way to use excess heating and CO2 from industries. The potential is tremendous and ambitions high for the new greenhouse being built in Linköping, Sweden, near the regional energy company, Tekniska Verken. Not least, it will be a new landmark for the people in Linköping to enjoy. Once the drafting stage is complete, construction of the greenhouse will take an estimated 12-16 months.
  4. ↑ Venkataraman, Bina (2008-07-15). "Country, the City Version: Farms in the Sky Gain New Interest". The New York Times. Retrieved 2011-01-05.
  5. ↑ "The Rise of Urban Farming". Smithsonian Magazine. Retrieved 2011-01-05.
  6. ↑ 6.0 6.1 Sholto Douglas, James. 1976. Hydroponics: the Bengal system : with notes on other methods of soilless cultivation. Delhi: Oxford University Press
  7. ↑ 7.0 7.1 Nelson, Bryn (2007-12-12). "Could vertical farming be the future? Nelson, B. (2008).". MSNBC. Retrieved 2010-11-10.
  8. ↑ George Monbiot (2010-08-16). "Monbiot, G. (16 August 2010). Greens living in ivory towers now want to farm them too. 'The". London: Guardian. Retrieved 2010-11-10.
  9. ↑ https://store.ctbuh.org/PDF_Previews/Journal/CTBUHJournal_2009-2.pdf
  10. ↑ 10.0 10.1 Ruby, Andreas. Groundscapes pp. 87–93
  11. ↑ Eaton, Ruth. Ideal Cities p. 239
  12. ↑ link
  13. ↑ link
  14. ↑ http://www.impactlab.net/wp-content/uploads/2008/10/editt-tower-by-tr-hamzah-and-yeang.jpg
  15. ↑ http://ps-survival.com/PS/Hydroponics/Hydroponics_The_Bengal_System_1959.pdf
  16. ↑ Arnie Cooper (May 19, 2009). "Going up? Farming in High Rises Raises Hopes". Miller-mccune.com. Retrieved 2010-11-10.
  17. ↑ Whyte, Murray (2008-07-27). "Is high rise farming in Toronto's future?". Toronto Star. Retrieved 2008-08-12.
  18. ↑ "Sky Farm Proposed for Downtown Toronto". TreeHugger. Retrieved 2009-03-14.
  19. ↑ Venkataraman, Bina (2008-07-15). "Country, the City Version: Farms in the Sky Gain New Interest". The New York Times.
  20. ↑ Shute, Nancy (2007-05-20). "Farm of the Future? Someday food may grow in skyscrapers". U.S. News & World Report.
  21. ↑ Feldman, Amy (2007-07-11). "Skyscraper Farms". Popular Science.
  22. ↑ 22.0 22.1 22.2 22.3 Despommier, Dickson (November 2009). "The Rise of Vertical Farms". Scientific American (New york: Scientific American Inc.) 301 (5): 60–67. ISSN 0036-8733.
  23. ↑ http://inhabitat.com/vertical-harvest-of-jackson-hole-will-grow-organic-produce-even-in-the-winter/
  24. ↑ 24.0 24.1 24.2 24.3 Despommier, D. (2008). "Vertical Farm Essay I". Vertical Farm. Retrieved 2009-06-26.
  25. ↑ The Vertical Farm Project. 2009. “Agriculture for the 21st Century and Beyond”. http://www.verticalfarm.com/
  26. ↑ Frediani, K. L. 2010 Feeding time at the Zoo. The Horticulturalist. April 2010, pp.12–15 Institute of Horticulture.
  27. ↑ Frediani, K. L. (2011), “High rise food”, The Horticulturalist, October, pp.18–20.
  28. ↑ Despommier, D. (2008). "Vertical Farm Essay I". Vertical Farm. Retrieved 2009-06-26.
  29. ↑ "Vertical Farm Video". Discovery Channel. 2009-04-23. Retrieved 2009-06-26.
  30. ↑ "Dwarf Wheat grown aboard the International Space Station". NASA. 9 February 2003. Retrieved 17 November 2009.
  31. ↑ Michael Pollan (September 9, 2009). “Big Food vs. Big Insurance”. The New York Times.
  32. ↑ "A Farm on Every Floor", The New York Times, August 23, 2009
  33. ↑ Vertical take off, Fresh Produce Journal, 28 January 2011
  34. ↑ 34.0 34.1 S.L. Davis (2001). "The least harm principle suggests that humans should eat beef, lamb, dairy, not a vegan diet". Proceedings of the Third Congress of the European Society for Agricultural and Food Ethics. pp. 449–450.
  35. ↑ Case Study — Landfill Power Generation, H. Scott Matthews, Green Design Initiative, Carnegie Mellon University. http://gdi.ce.cmu.edu/gd/education/landfill-case.pdf Retrieved 07.02.09
  36. ↑ Folke Günther (2013-01-06). "The folkewall, greywater purification AND vertical growing". Holon.se. Retrieved 2013-06-12.
  37. ↑ McConnell, Kathryn (2008-07-01). "Vertical Farms Grow Food by Growing Up, Not Out". Bureau of International Information Programs. United States Department of State. Retrieved 2008-08-12.
  38. ↑ "Las Vegas to Build World’s First 30 Story Vertical Farm". Nextenergynews.com. Retrieved 2013-06-12.
  39. ↑ Despommier, Dickson (2010-06-15). "Dickson Despommier. November 2009. "Growing Skyscrapers: The Rise of Vertical Farms."". Scientificamerican.com. Retrieved 2010-11-10.
  40. ↑ "Vertical plant production as a public exhibit at Paignton Zoo" (PDF). Proceedings of the 4th World Botanic Garden Congress, Botanic Gardens Conservation International. June 2010. Retrieved 2013-01-27.
  41. ↑ "Green Zionist Alliance (GZA) – Bold Resolutions for 36th World Zionist Congress".
  42. ↑
  43. ↑ "World's first commercial vertical farm opens in Singapore". Io9.com. Retrieved 2013-06-12.
  44. ↑ "Urban farming looking up in Singapore – CNN.com". Edition.cnn.com. Retrieved 2013-06-12.
  45. ↑ Clive Clifton says: (2009-08-24). "Vertical Farming: Too Far Outside the Box? |". E4capital.com. Retrieved 2010-11-10.
  46. ↑ Michael Bomford says: (2010-12-02). "Energy and VerticalFarms". Retrieved 2011-03-08.
  47. ↑ Evans, P. (July 22, 2009). Local food no green panacea: professor. CBC News http://www.cbc.ca/consumer/story/2009/07/22/consumer-local-food.html
  48. ↑ https://www.youtube.com/watch?v=KZN3ucwePGk
  49. ↑ "Does it really stack up?". The Economist. 2010-12-09.
  50. ↑ "Starting a Commercial Greenhouse Business". Omafra.gov.on.ca. 2003-07-28. Retrieved 2010-11-10.
  51. ↑ Pocket World in Figures, The Economist, 2011 ed. pg 64
  52. ↑ Roach, J. (June 30, 2009). "High-Rise Farms: The Future of Food?". National Geographic News.
  53. ↑ "George Monbiot – Towering Lunacy". Monbiot.com. Retrieved 2013-06-12.
  54. ↑ The Economist (December 9, 2010). "Vertical farming: Does it really stack up?".
  55. ↑ "Crops | Greenhouse | Greenhouse Energy Calculations | Manitoba Agriculture, Food and Rural Initiatives | Province of Manitoba". Gov.mb.ca. Retrieved 2010-11-10.
  56. ↑ "About The Plant". The Plant.
  57. ↑ http://www.lcafood.dk/Material/How%20to%20prepare.pdf
  58. ↑ 58.0 58.1 Blom, T.J.; W.A. Straver; F.J. Ingratta; Shalin Khosla; Wayne Brown (December 2002). "Carbon Dioxide In Greenhouses". Retrieved 2010-10-10.
  59. ↑ Light pollution handbook – Google Books. Books.google.ca. 2004. ISBN 978-1-4020-2665-2. Retrieved 2010-11-10.
  60. ↑ "Treating and Recycling Irrigation Runoff". Aggie-horticulture.tamu.edu. Retrieved 2013-06-12.

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