Urban agriculture

From Wikipedia, the free encyclopedia

An urban farm in Chicago

Urban agriculture, urban farming, or urban gardening is the practice of cultivating, processing and distributing food in or around urban areas. Urban agriculture can also involve animal husbandry, aquaculture, agroforestry, urban beekeeping, and horticulture. These activities occur in peri-urban areas as well, and peri-urban agriculture may have different characteristics.

Urban agriculture can reflect varying levels of economic and social development. It may be a social movement for sustainable communities, where organic growers, "foodies," and "locavores" form social networks founded on a shared ethos of nature and community holism. These networks can evolve when receiving formal institutional support, becoming integrated into local town planning as a "transition town" movement for sustainable urban development. For others, food security, nutrition, and income generation are key motivations for the practice. In either case, more direct access to fresh vegetables, fruits, and meat products through urban agriculture can improve food security and food safety.

History

In semi-desert towns of Persia, oases were fed through aqueducts that carried mountain water to support intensive food production, nurtured by wastes from the communities. In Machu Picchu, water was conserved and reused as part of the stepped architecture of the city, and vegetable beds were designed to gather sun in order to prolong the growing season.

A gardening demonstration in New York City, 1922

The idea of supplemental food production beyond rural farming operations and distant imports is not new. It has been used during war and depression times when food shortage issues arose, as well as during times of relative abundance. Allotment gardens came up in Germany in the early 19th century as a response to poverty and food insecurity.

In 1893, citizens of a depression-struck Detroit were asked to use any vacant lots to grow vegetables. They were nicknamed Pingree's Potato Patches after the mayor, Hazen S. Pingree, who came up with the idea. He intended for these gardens to produce income, food supply, and even boost independence during times of hardship. Victory gardens sprouted during WWI and WWII and were fruit, vegetable, and herb gardens in US, Canada, and UK. This effort was undertaken by citizens to reduce pressure on food production that was to support the war effort. 

During the first World War, President Woodrow Wilson called upon all American citizens to utilize any available open space for food growth, seeing this as a way to pull them out of a potentially damaging situation. Because most of Europe was consumed with war, they were unable to produce sufficient food supplies to be shipped to the U.S., and a new plan was implemented with the intent to feed the U.S. and even supply a surplus to other countries in need. By the year 1919, over 5 million plots were growing food and over 500 million pounds of produce was harvested. 

Peaches in Montreuil, Seine-Saint-Denis, France

A very similar practice came into use during the Great Depression that provided a purpose, a job, and food to those who would otherwise be without anything during such harsh times. In this case, these efforts helped to raise spirits socially as well as to boost economic growth. Over 2.8 million dollars worth of food was produced from the subsistence gardens during the Depression. By the time of the Second World War, the War/Food Administration set up a National Victory Garden Program that set out to systematically establish functioning agriculture within cities. With this new plan in action, as many as 5.5 million Americans took part in the victory garden movement and over 9 million pounds of fruit and vegetables were grown a year, accounting for 44% of U.S.-grown produce throughout that time.

Community gardening in most communities are open to the public and provide space for citizens to cultivate plants for food or recreation. A community gardening program that is well-established is Seattle's P-Patch. The grassroots permaculture movement has been hugely influential in the renaissance of urban agriculture throughout the world. The Severn Project in Bristol was started in 2010 for £2500 and provides 34 tons of produce per year, employing people from disadvantaged backgrounds.

City farming

A cow at Mudchute Park and Farm, Tower Hamlets, London. Note Canary Wharf in the background.

City farms are agricultural plots in urban areas, which involve people working with animals and plants to produce food. City farms are usually community-run gardens which aim to improve community relationships and offer an awareness of agriculture and farming to people who live in urbanized areas. City farms are important sources of food security for many communities around the globe. City farms vary in size from small plots in private yards to larger farms that occupy a number of acres. In 1996, a United Nations report estimated there are over 800 million people worldwide who grow food and raise livestock in cities. Although some city farms have paid employees, most rely heavily on volunteer labour, and some are run by volunteers alone. Other city farms operate as partnerships with local authorities. 

During the 1960s a number of community gardens were established in the United Kingdom, influenced by the community garden movement in the United States. The first city farm was set up in 1972 in Kentish Town, London. It combined farm animals with gardening space, an addition inspired by children's farms in the Netherlands. Other city farms followed across London and the United Kingdom. In Australia, several city farms exist in various capital cities. In Melbourne, the Collingwood Children's Farm was established in 1979 on the Abbotsford Precinct Heritage Farmlands (the APHF), the oldest continually farmed land in Victoria, farmed since 1838. 

In 2010, New York City saw the building and opening of the world's largest privately owned and operated rooftop farm, followed by an even larger location in 2012. Both were a result of municipal programs such as The Green Roof Tax Abatement Program and Green Infrastructure Grant Program.

A tidy front yard flower and vegetable garden in Aretxabaleta, Spain

Perspectives

Resource and economic

The Urban Agriculture Network has defined urban agriculture as:

[A]n industry that produces, processes, and markets food, fuel, and other outputs, largely in response to the daily demand of consumers within a town, city, or metropolis, on many types of privately and publicly held land and water bodies found throughout intra-urban and peri-urban areas. Typically urban agriculture applies intensive production methods, frequently using and reusing natural resources and urban wastes, to yield a diverse array of land-, water-, and air-based fauna and flora contributing to the food security, health, livelihood, and environment of the individual, household, and community.

Globalization has removed the need and ability of a community's agency in their food production. This results in an inability to address food injustice on a smaller, more manageable scale. This is especially true in cities. Today, most cities have lots of vacant land due to urban sprawl and home foreclosures. This land could be used to address food insecurity. One study of Cleveland shows that city could actually meet up to 100% of its fresh produce need. This would prevent up to $115 million in annual economic leakage. Using the rooftop space of New York City would also be able to provide roughly twice the amount of space necessary to supply New York City with its green vegetable yields. Space could be even better optimized through the usage of hydroponic or indoor factory production of food. Growing gardens within cities would also cut down on the amount of food waste. In order to fund these projects, it would require financial capital in the form of private enterprises or government funding. 

Environmental

The Council for Agricultural Science and Technology (CAST) defines urban agriculture to include aspects of environmental health, remediation, and recreation:

Urban agriculture is a complex system encompassing a spectrum of interests, from a traditional core of activities associated with the production, processing, marketing, distribution, and consumption, to a multiplicity of other benefits and services that are less widely acknowledged and documented. These include recreation and leisure; economic vitality and business entrepreneurship, individual health and well-being; community health and well being; landscape beautification; and environmental restoration and remediation.

Modern planning and design initiatives are often more responsive to this model of urban agriculture because it fits within the current scope of sustainable design. The definition allows for a multitude of interpretations across cultures and time. Frequently it is tied to policy decisions to build sustainable cities.

Urban farms also provide unique opportunities for individuals, especially those living in cities, to get actively involved with ecological citizenship. By reconnecting with food production and nature, urban community gardening teaches individuals the skills necessary to participate in a democratic society. Decisions must be made on a group-level basis in order to run the farm. Most effective results are achieved when residents of a community are asked to take on more active roles in the farm. 

Food security

Access to nutritious food, both economically and geographically, is another perspective in the effort to locate food and livestock production in cities. With the tremendous influx of world population to urban areas, the need for fresh and safe food is increased. The Community Food Security Coalition (CFSC) defines food security as:

All persons in a community having access to culturally acceptable, nutritionally adequate food through local, non-emergency sources at all times.

Areas faced with food security issues have limited choices, often relying on highly processed fast food or convenience store foods that are high in calories and low in nutrients, which may lead to elevated rates of diet-related illnesses such as diabetes. These problems have brought about the concept of food justice which Alkon and Norgaard (2009; 289) explain is, "places access to healthy, affordable, culturally appropriate food in the contexts of institutional racism, racial formation, and racialized geographies.... Food justice serves as a theoretical and political bridge between scholarship and activism on sustainable agriculture, food insecurity, and environmental justice." 

Some systematic reviews have already explored urban agriculture contribution to food security and other determinants of health outcomes.

Impact

A sprouting glass jar with mung beans in it

Economic

Urban and peri-urban agriculture (UPA) expands the economic base of the city through production, processing, packaging, and marketing of consumable products. This results in an increase in entrepreneurial activities and the creation of jobs, as well as reducing food costs and improving quality. UPA provides employment, income, and access to food for urban populations, which helps to relieve chronic and emergency food insecurity. Chronic food insecurity refers to less affordable food and growing urban poverty, while emergency food insecurity relates to breakdowns in the chain of food distribution. UPA plays an important role in making food more affordable and in providing emergency supplies of food. Research into market values for produce grown in urban gardens has attributed to a community garden plot a median yield value of between approximately $200 and $500 (US, adjusted for inflation).

Social

The needs of urban landscaping can be combined with those of suburban livestock farmers. (Kstovo, Russia).

Urban agriculture can have a large impact on the social and emotional well-being of individuals. UA can have an overall positive impact on community health, which directly impacts individuals social and emotional well-being.  Urban gardens are often places that facilitate positive social interaction, which also contributes to overall social and emotional well-being. Many gardens facilitate the improvement of social networks within the communities that they are located. For many neighborhoods, gardens provide a “symbolic focus,” which leads to increased neighborhood pride.

Related to the previous point, urban agriculture increases community participation through sensibilization and diagnostic workshops or different commissions in the area of vegetable gardens. Activities which involve hundreds of people.

When individuals come together around UA, physical activity levels are often increased. Many state that working in agriculture is much more interesting and fulfilling than going to the gym, and that it makes getting exercise “fun.” In addition to the exercise that individuals receive while actually working in gardens, many people say that the majority of the exercise they receive through urban agriculture is actually getting to the gardens—many people either walk or ride their bike to the sites, which provides many physical benefits.

UPA can be seen as a means of improving the livelihood of people living in and around cities. Taking part in such practices is seen mostly as informal activity, but in many cities where inadequate, unreliable, and irregular access to food is a recurring problem, urban agriculture has been a positive response to tackling food concerns. Due to the food security that comes with UA, feelings of independence and empowerment often arise. The ability to produce and grow food for oneself has also been reported to improve levels of self-esteem or of self-efficacy. Households and small communities take advantage of vacant land and contribute not only to their household food needs but also the needs of their resident city. The CFSC states that:

Community and residential gardening, as well as small-scale farming, save household food dollars. They promote nutrition and free cash for non-garden foods and other items. As an example, you can raise your own chickens on an urban farm and have fresh eggs for only $0.44 per dozen.

This allows families to generate larger incomes selling to local grocers or to local outdoor markets while supplying their household with the proper nutrition of fresh and nutritional products. 

A vegetable garden in the square in front of the train station in Ezhou, China

Some community urban farms can be quite efficient and help women find work, who in some cases are marginalized from finding employment in the formal economy. Studies have shown that participation from women have a higher production rate, therefore producing the adequate amount for household consumption while supplying more for market sale.

As most UA activities are conducted on vacant municipal land, there have been raising concerns about the allocation of land and property rights. The IDRC and the FAO have published the Guidelines for Municipal Policymaking on Urban Agriculture, and are working with municipal governments to create successful policy measures that can be incorporated in urban planning.

Over a third of U.S. households, roughly 42 million, participate in food gardening. There has also been an increase of 63% participation in farming by millennials from 2008-2013. US households participating in community gardening has also tripled from 1 to 3 million in that time frame. Urban agriculture provides unique opportunities to bridge diverse communities together. In addition, it provides opportunities for health care providers to interact with their patients. Thus, making each community garden a hub that is reflective of the community. 

Energy efficiency

Edible Oyster Mushrooms growing on used coffee grounds

The current industrial agriculture system is accountable for high energy costs for the transportation of foodstuffs. According to a study by Rich Pirog, the associate director of the Leopold Center for Sustainable Agriculture at Iowa State University, the average conventional produce item travels 1,500 miles (2,400 km), using, if shipped by tractor-trailer, 1 US gallon (3.8 l; 0.83 imp gal) of fossil fuel per 100 pounds (45 kg). The energy used to transport food is decreased when urban agriculture can provide cities with locally grown food. Pirog found that traditional, non-local, food distribution system used 4 to 17 times more fuel and emitted 5 to 17 times more CO₂ than the local and regional transport.

Similarly, in a study by Marc Xuereb and Region of Waterloo Public Health, they estimated that switching to locally grown food could save transport-related emissions equivalent to nearly 50,000 metric tons of CO₂, or the equivalent of taking 16,191 cars off the road.

A windowfarm, incorporating discarded plastic bottles into pots for hydroponic agriculture in urban windows

Carbon footprint

As mentioned above, the energy-efficient nature of urban agriculture can reduce each city's carbon footprint by reducing the amount of transport that occurs to deliver goods to the consumer.

Also, these areas can act as carbon sinks offsetting some of the carbon accumulation that is innate to urban areas, where pavement and buildings outnumber plants. Plants absorb atmospheric carbon dioxide (CO₂) and release breathable oxygen (O₂) through photosynthesis. The process of Carbon Sequestration can be further improved by combining other agriculture techniques to increase removal from the atmosphere and prevent the release of CO₂ during harvest time. However, this process relies heavily on the types of plants selected and the methodology of farming. Specifically, choosing plants that do not lose their leaves and remain green all year can increase the farm's ability to sequester carbon.

Reduction in ozone and particulate matter

The reduction in ozone and other particulate matter can benefit human health. Reducing these particulates and ozone gases could reduce mortality rates in urban areas along with increase the health of those living in cities. Just to give one example, in the article “Green roofs as a means of pollution abatement,” the author argues that a rooftop containing 2000 m² of uncut grass has the potential to remove up to 4000 kg of particulate matter. According to the article, only one square meter of green roof is needed to offset the annual particulate matter emissions of a car.

Soil decontamination

Vacant urban lots are often victim to illegal dumping of hazardous chemicals and other wastes. They are also liable to accumulate standing water and “grey water”, which can be dangerous to public health, especially left stagnant for long periods. The implementation of urban agriculture in these vacant lots can be a cost-effective method for removing these chemicals. In the process known as Phytoremediation, plants and the associated microorganisms are selected for their chemical ability to degrade, absorb, convert to an inert form, and remove toxins from the soil. Several chemicals can be targeted for removal including heavy metals (e.g. Mercury and lead) inorganic compounds (e.g. Arsenic and Uranium), and organic compounds (e.g. petroleum and chlorinated compounds like PBC's).

Phytoremeditation is both an environmentally friendly, cost-effective, and energy-efficient measure to reduce pollution. Phytoremediation only costs about $5–$40 per ton of soil being decontaminated. Implementation of this process also reduces the amount of soil that must be disposed of in a hazardous waste landfill.

Urban agriculture as a method to mediate chemical pollution can be effective in preventing the spread of these chemicals into the surrounding environment. Other methods of remediation often disturb the soil and force the chemicals contained within it into the air or water. Plants can be used as a method to remove chemicals and also to hold the soil and prevent erosion of contaminated soil decreasing the spread of pollutants and the hazard presented by these lots.

One way of identifying soil contamination is through using already well-established plants as bioindicators of soil health. Using well-studied plants is important because there has already been substantial bodies of work to test them in various conditions, so responses can be verified with certainty. Such plants are also valuable because they are genetically identical as crops as opposed to natural variants of the same species. Typically urban soil has had the topsoil stripped away and has led to soil with low aeration, porosity, and drainage. Typical measures of soil health are microbial biomass and activity, enzymes, soil organic matter (SOM), total nitrogen, available nutrients, porosity, aggregate stability, and compaction. A new measurement is active carbon (AC), which is the most usable portoin of the total organic carbon (TOC) in the soil. This contributes greatly to the functionality of the soil food web. Using common crops, which are generally well-studied, as bioindicators an be used to effectively test the quality of an urban farming plot before beginning planting. 

Noise pollution

Large amounts of noise pollution not only lead to lower property values and high frustration, they can be damaging to human hearing and health. In the study “Noise exposure and public health,” they argue that exposure to continual noise is a public health problem. They cite examples of the detriment of continual noise on humans to include: “hearing impairment, hypertension and ischemic heart disease, annoyance, sleep disturbance, and decreased school performance.” Since most roofs or vacant lots consist of hard flat surfaces that reflect sound waves instead of absorbing them, adding plants that can absorb these waves has the potential to lead to a vast reduction in noise pollution.

Nutrition and quality of food

Daily intake of a variety of fruits and vegetables is linked to a decreased risk of chronic diseases including diabetes, heart disease, and cancer. Urban agriculture is associated with increased consumption of fruits and vegetables which decreases risk for disease and can be a cost-effective way to provide citizens with quality, fresh produce in urban settings.

Produce from urban gardens can be perceived to be more flavorful and desirable than store bought produce which may also lead to a wider acceptance and higher intake. A Flint, Michigan study found that those participating in community gardens consumed fruits and vegetables 1.4 more times per day and were 3.5 times more likely to consume fruits or vegetables at least 5 times daily (p. 1). Garden-based education can also yield nutritional benefits in children. An Idaho study reported a positive association between school gardens and increased intake of fruit, vegetables, vitamin A, vitamin C and fiber among sixth graders. Harvesting fruits and vegetables initiates the enzymatic process of nutrient degradation which is especially detrimental to water soluble vitamins such as ascorbic acid and thiamin. The process of blanching produce in order to freeze or can reduce nutrient content slightly but not nearly as much as the amount of time spent in storage. Harvesting produce from one's own community garden cuts back on storage times significantly. 

Urban agriculture also provides quality nutrition for low-income households. Studies show that every $1 invested in a community garden yields $6 worth of vegetables if labor is not considered a factor in investment. Many urban gardens reduce the strain on food banks and other emergency food providers by donating shares of their harvest and provide fresh produce in areas that otherwise might be food deserts. The supplemental nutrition program Women, Infants and Children (WIC) as well as the Supplemental Nutrition Assistance Program (SNAP) have partnered with several urban gardens nationwide to improve the accessibility to produce in exchange for a few hours of volunteer gardening work.

Urban farming has been shown to increase health outcomes. Gardeners consume twice as much fruit and vegetables than non-gardeners. Levels of physical activity are also positively associated with urban farming. These results are seen indirectly and can be supported by the social involvement in an individual's community as a member of the community farm. This social involvement helped raised the aesthetic appeal of the neighborhood, boosting the motivation or efficacy of the community as a whole. This increased efficacy was shown to increase neighborhood attachment. Therefore, the positive health outcomes of urban farming can be explained in part due to the interpersonal sand social factors that boost health. Focusing on improving the aesthetics and community relationships and not only on the plant yield, is the best way to maximize the positive effect of urban farms on a neighborhood.

Economy of scale

Using high-density urban farming, as for instance with vertical farms or stacked greenhouses, many environmental benefits can be achieved on a citywide scale that would be impossible otherwise. These systems do not only provide food, but also produce potable water from waste water, and can recycle organic waste back to energy and nutrients. At the same time, they can reduce food-related transportation to a minimum while providing fresh food for large communities in almost any climate.

Health inequalities and food justice

A 2009 report by the USDA, determined that "Evidence is both abundant and robust enough for us to conclude that Americans living in low-income and minority areas tend to have poor access to healthy food", and that the "structural inequalities" in these neighborhoods "contribute to inequalities in diet and diet-related outcomes". These diet-related outcomes, including obesity and diabetes, have become epidemic in low-income urban environments in the United States. Although the definition and methods for determining "food deserts" have varied, studies indicate that, at least in the United States, there are racial disparities in the food environment. Thus using the definition of environment as the place where people live, work, play and pray, food disparities become an issue of environmental justice. This is especially true in American inner-cities where a history of racist practices have contributed to the development of food deserts in the low-income, minority areas of the urban core. The issue of inequality is so integral to the issues of food access and health that the Growing Food & Justice for All Initiative was founded with the mission of “dismantling racism” as an integral part of creating food security.

Not only can urban agriculture provide healthy, fresh food options, but also can contribute to a sense of community, aesthetic improvement, crime reduction, minority empowerment and autonomy, and even preserve culture through the use of farming methods and heirloom seeds preserved from areas of origin.

Environmental justice

Urban agriculture may advance environmental justice and food justice for communities living in food deserts. First, urban agriculture may reduce racial and class disparities in access to healthy food. When urban agriculture leads to locally grown fresh produce sold at affordable prices in food deserts, access to healthy food is not just available for those who live in wealthy areas, thereby leading to greater equity in rich and poor neighborhoods.

Improved access to food through urban agriculture can also help alleviate psychosocial stresses in poor communities. Community members engaged in urban agriculture improve local knowledge about healthy ways to fulfill dietary needs. Urban agriculture can also better the mental health of community members. Buying and selling quality products to local producers and consumers allows community members to support one another, which may reduce stress. Thus, urban agriculture can help improve conditions in poor communities, where residents experience higher levels of stress due to a perceived lack of control over the quality of their lives.

Urban agriculture may improve the livability and built environment in communities that lack supermarkets and other infrastructure due to the presence of high unemployment caused by deindustrialization. Urban farmers who follow sustainable agriculture methods can not only help to build local food system infrastructure, but can also contribute to improving local air, and water and soil quality. When agricultural products are produced locally within the community, they do not need to be transported, which reduces CO₂ emission rates and other pollutants that contribute to high rates of asthma in lower socioeconomic areas. Sustainable urban agriculture can also promote worker protection and consumer rights. For example, communities in New York City, Illinois, and Richmond, Virginia have demonstrated improvements to their local environments through urban agricultural practices.

However, urban agriculture can also present urban growers with health risks if the soil used for urban farming is contaminated. Although local produce is often believed to be clean and healthy, many urban farmers ranging from New York urban farmer Frank Meushke to Presidential First Lady Michelle Obama have found their products contained high levels of lead, due to soil contamination, which is harmful to human health when consumed. The soil contaminated with high lead levels often originates from old house paint which contained lead, vehicle exhaust, or atmospheric deposition. Without proper education on the risks of urban farming and safe practices, urban consumers of urban agricultural produce may face additional health-related issues.

Implementation

A small urban farm in Amsterdam

 

Rooftop urban farming at the Food Roof Farm in downtown St. Louis, MO

 

Creating a community-based infrastructure for urban agriculture means establishing local systems to grow and process food and transfer it from farmer (producer) to consumer.

To facilitate food production, cities have established community-based farming projects. Some projects have collectively tended community farms on common land, much like that of eighteenth-century Boston Common. One such community farm is the Collingwood Children's Farm in Melbourne, Australia. Other community garden projects use the allotment garden model, in which gardeners care for individual plots in a larger gardening area, often sharing a tool shed and other amenities. Seattle's P-Patch gardens use this model, as did the South Central Farm in Los Angeles and the Food Roof Farm in St. Louis. Independent urban gardeners also grow food in individual yards and on roofs. Garden sharing projects seek to pair producers with the land, typically, residential yard space. Roof gardens allow for urban dwellers to maintain green spaces in the city without having to set aside a tract of undeveloped land. Rooftop farms allow otherwise unused industrial roofspace to be used productively, creating work and profit. Projects around the world seek to enable cities to become 'continuous productive landscapes' by cultivating vacant urban land and temporary or permanent kitchen gardens.

Urban agriculture project in the La Romita section of Colonia Roma, Mexico City

 

Tomato plants growing in a pot farming alongside a small house in New Jersey in fifteen garbage cans filled with soil, grew over 700 tomatoes during the summer of 2013.

Food processing on a community level has been accommodated by centralizing resources in community tool sheds and processing facilities for farmers to share. The Garden Resource Program Collaborative based in Detroit has cluster tool banks. Different areas of the city have tool banks where resources like tools, compost, mulch, tomato stakes, seeds, and education can be shared and distributed with the gardeners in that cluster. Detroit's Garden Resource Program Collaborative also strengthens their gardening community by providing to their member's transplants; education on gardening, policy, and food issues; and by building connectivity between gardeners through workgroups, potlucks, tours, field trips, and cluster workdays. In Brazil, "Cities Without Hunger" has generated a public policy for the reconstruction of abandoned areas with food production and has improved the green areas of the community. 

Farmers' markets, such as the farmers' market in Los Angeles, provide a common land where farmers can sell their product to consumers. Large cities tend to open their farmer's markets on the weekends and one day in the middle of the week. For example, the farmers' market of Boulevard Richard-Lenoir in Paris, France, is open on Sundays and Thursdays. However, to create a consumer dependency on urban agriculture and to introduce local food production as a sustainable career for farmers, markets would have to be open regularly. For example, the Los Angeles Farmers' Market is open seven days a week and has linked several local grocers together to provide different food products. The market's central location in downtown Los Angeles provides the perfect interaction for a diverse group of sellers to access their consumers.

Queensland, Australia

In Queensland many people have started a trend of urban farming both utilizing Aquaponics and self-watering containers.

Cairo, Egypt

In Egypt, development of rooftop gardens began in the 1990s. In the early 1990s at Ain Shams University, a group of agriculture professors developed an initiative focused on growing organic vegetables to suit densely populated cities of Egypt. The initiative was applied on a small scale; until it was officially adopted in 2001, by the Food and Agriculture Organization (FAO).

Havana, Cuba

Farming enterprise in Havana, Cuba (2015)

After the disintegration of the Soviet Union and the Eastern Bloc, Cuba faced severe shortages of fuel and agrochemical inputs. These products had previously been imported from the Soviet Union in exchange for Cuban sugar. As a result, Cubans experienced an acute food crisis in the early 1990s, which in part was met with a popular movement of urban agriculture. Urban farmers employed – and still employ – agroecological techniques, allowing food production to take place largely without petroleum-based inputs.

In 2002, 35,000 acres (14,000 ha) of urban gardens produced 3,400,000 short tons (3,100,000 t) of food. In Havana, 90% of the city's fresh produce come from local urban farms and gardens. In 2003, more than 200,000 Cubans worked in the expanding urban agriculture sector.

Mumbai, India

Economic development in Mumbai brought a growth in population caused mainly by the migration of laborers from other regions of the country. The number of residents in the city increased more than twelve times in the last century. Greater Mumbai, formed by City Island and Salsette Island, is the largest city in India with a population of 16.4 million, according to data collected by the census of 2001. Mumbai is one of the densest cities in the world, 48,215 persons per km² and 16,082 per km² in suburban areas. In this scenario, urban agriculture seems unlikely to be put into practice since it must compete with real estate developers for the access and use of vacant lots. Alternative farming methods have emerged as a response to the scarcity of land, water, and economic resources employed in UPA. 

Dr. Doshi's city garden methods are revolutionary for being appropriate to apply in reduced spaces as terraces and balconies, even on civil construction walls, and for not requiring big investments in capital or long hours of work. His farming practice is purely organic and is mainly directed to domestic consumption. His gardening tools are composed of materials available in the local environment: sugarcane waste, polyethylene bags, tires, containers and cylinders, and soil. The containers and bags (open at both ends) are filled with the sugarcane stalks, compost, and garden soil, which make possible the use of a minimal quantity of water is compared to open fields. Dr. Doshi states that solar energy can replace soil in cities. He also recommends the idea of chain planning, or growing plants in intervals and in small quantities rather than at once and in large amounts. He has grown different types of fruit such as mangos, figs, guavas, bananas, and sugarcane stalks in his terrace of 1,200 sq ft (110 m²) in Bandra. The concept of city farming developed by Dr. Doshi consumes the entire household's organic waste. He subsequently makes the household self-sufficient in the provision of food: 5 kilograms (11 lb) of fruits and vegetables are produced daily for 300 days a year.

The main objectives of a pilot project at city farm at Rosary High School, Dockyard Road, were to promote economic support for street children, beautify the city landscape, supply locally produced organic food to urban dwellers (mainly those residing in slums), and to manage organic waste in a sustainable city. The project was conducted in the Rosary School, in Mumbai, with the participation of street children during 2004. A city farm was created in a terrace area of 400 sq ft (37 m²). The participants were trained in urban farming techniques. The farm produced vegetables, fruits, and flowers. The idea has spread the concept of city farm to other schools in the city. 

The Mumbai Port Trust (MBPT) central kitchen distributes food to approximately 3,000 employees daily, generating important amounts of organic disposal. A terrace garden created by the staff recycles ninety percent of this waste in the production of vegetables and fruits. Preeti Patil, who is the catering officer at the MBPT explains the purpose of the enterprise:

Mumbai Port Trust has developed an organic farm on the terrace of its central kitchen, which is an area of approximately 3,000 sq ft (280 m²). The activity of city farming was started initially to dispose of kitchen organic waste in an eco-friendly way. Staff members, after their daily work in the kitchen, tend the garden, which has about 150 plants.

Bangkok, Thailand

In early 2000, urban gardens were started under the direction of the NGO, Thailand Environment Institute (TEI), to help achieve the Bangkok Metropolitan Administrations (BMA) priority to "green" Thailand. With a population of 12 million and 39% of the land in the city vacant due to rapid expansion of the 1960s–80s Bangkok is a test bed for urban gardens centered on community involvement. The two urban gardens initiated by TEI are in Bangkok Noi and Bangkapi and the main tasks were stated as:

• Teach members of the communities the benefits of urban green space.
• Create the social framework to plan, implement, and maintain the urban green space.
• Create a process of a method to balance the needs of the community with the needs of the larger environmental concerns.

While the goals of the NGO are important in a global context, the community goals are being met through the work of forming the urban gardens themselves. In this sense, the creation, implementation, and maintenance of urban gardens are highly determined by the desires of the communities involved. However, the criteria by which TEI measured their success illustrates the scope of benefits to a community which practices urban agriculture. TEI's success indicators were:

• Establishing an Urban Green Plan
• Community Capacity Building
• Poverty Reduction
• Links with Government
• Developing a Model for Other Communities

China

Beijing's increase in land area from 4,822 square kilometres (1,862 sq mi) in 1956 to 16,808 square kilometres (6,490 sq mi) in 1958 led to the increased adoption of peri-urban agriculture. Such "suburban agriculture" led to more than 70% of non-staple food in Beijing, mainly consisting of vegetables and milk, to be produced by the city itself in the 1960s and 1970s. Recently, with relative food security in China, periurban agriculture has led to improvements in the quality of the food available, as opposed to quantity. One of the more recent experiments in urban agriculture is the Modern Agricultural Science Demonstration Park in Xiaotangshan.

Traditionally, Chinese cities have been known to mix agricultural activities within the urban setting. Shenzhen, once a small farming community, is now a fast-growing metropolis due to the Chinese government designation as an open economic zone. Due to large and growing population in China, the government supports urban self-sufficiency in food production. Shenzhen's village structure, sustainable methods, and new agricultural advancements initiated by the government have been strategically configured to supply food for this growing city.

The city farms are located about 10 kilometres (6.2 mi) from the city center in a two-tier system. The first tier approached from city center produces perishable items. Located just outside these farms, hardier vegetables are grown such as potatoes, carrots, and onions. This system allows producers to be sold in city markets just a few short hours after picking.

Another impressive method used in Chinese agriculture and aquaculture practice is the mulberry-dike fish-pond system, which is a response to waste recycling and soil fertility. This system can be described as:

Mulberry trees are grown to feed silkworms and the silkworm waste is fed to the fish in ponds. The fish also feed on waste from other animals, such as pigs, poultry, and buffalo. The animals, in turn, are given crops that have been fertilized by mud from the ponds. This is a sophisticated system as a continuous cycle of water, waste, and food...with a man built into the picture.

As the population grows and industry advances, the city tries to incorporate potential agricultural growth by experimenting with new agricultural methods. The Fong Lau Chee Experimental Farm in Dongguan, Guangdong has worked with new agricultural advancements in lychee production. This farm was established with aspirations of producing large quantities and high-quality lychees, by constantly monitoring sugar content, and their seeds. This research, conducted by local agricultural universities allows for new methods to be used with hopes of reaching the needs of city consumers.

However, due to increased levels of economic growth and pollution, some urban farms have become threatened. The government has been trying to step in and create new technological advancements within the agricultural field to sustain levels of urban agriculture.

"The city plans to invest 8.82 billion yuan in 39 agricultural projects, including a safe agricultural base, an agricultural high-tech park, agricultural processing and distribution, forestry, eco-agricultural tourism, which will form an urban agriculture with typical Shenzhen characteristics" in conjunction with this program the city is expected to expand the Buji Farm Produce Wholesale Market.

According to the Municipal Bureau of Agriculture, Forestry and Fishery the city will invest 600 million yuan on farms located around the city, with hopes of the farms to provide "60 percent of the meat, vegetables, and aquatic products in the Shenzhen market".

There has also been an emerging trend of going green and organic as a response to pollution and pesticides used in farming practices. Vegetable suppliers are required to pass certain inspections held by the city's Agriculture Bureau before they can be sold as "green".

Harare, Zimbabwe

Harare is particularly suited for urban agriculture, as its topography heavily features vleis, land drainage systems that become waterlogged in the rainy season. When it rains they are difficult to cross, and in the dry season they shrink and crack, which causes structural damage to infrastructure, even though the vleis are still storing water underground. Therefore, these moisture-rich areas are mostly left unbuilt, allowing for urban cultivation. 

Aside from vleis and the private residential land that Harareans cultivate, considerable public land is used for agriculture in Harare: along public roads, railway lines, undeveloped plots, road verges, and the banks of ditches. The land is mostly used for maize, groundnuts, sweet potatoes, green vegetables, fruits, paprika, and flowers. This unsanctioned cultivation has a history of necessity: in colonial times, laborers wanted towns where they could cultivate crops like at their rural homes, and with very low income, needed to supplement their food supply.

However, urban agriculture in Harare causes harm to the environment. The practice has reduced rainwater infiltration into the soil by 28.5 percent and lowered tree species diversity. In addition, most informal urban farmers use harmful chemical fertilizers. Urban agriculture has also been viewed negatively in Harare because it impedes on housing and urban development. In the eyes of Zimbabwean laws, agriculture was not an “urban” activity or a legitimate form of land use in cities. In 1983, the Greater Harare Illegal Cultivation Committee was formed, though its efforts to curb urban agriculture wholly failed. 

In the 1990s, the failure of Structural Adjustment Programs induced greater unemployment, higher prices, and lower incomes, so more people started growing their own food. Between 1990 and 1994, Harare's cultivation area increased by 92.6 percent. The boom in urban agriculture improved both the food security and the nutrition of its practitioners, as well as additional income from selling excess produce. The practice continued in the 2000s when a major recession brought about widespread poverty, unemployment, and enormous inflation. Finally, the 2002 Nyanga Declaration on Urban Agriculture in Zimbabwe explicitly acknowledged the value of urban agriculture for food security and the reduction of poverty. Accepting that many people depend on it to survive, the government allocated sixty thousand hectares of land in Harare for cultivation purposes.

United States

Nationwide Survey Findings

According to the USDA, a farm is defined as a location that produces and sells at least $1,000 worth of products. A study conducted on urban farms in 2012 surveyed over 315 farms that identified as urban. Of those, over 32% were found in the Northeast, more than 26% in the South, 22% in the West, and less than 19% in the Midwest. The survey found that most urban farms in the United States are structured as either non-profit or solely owned. Urban farms typically use techniques that allow them to produce intensively on small land. Mainly, these practices include raised beds, greenhouse, and container gardens. Of the products made, an overwhelming majority of urban farms focus on fresh vegetable, followed by herbs and flowers. If an urban farm focuses on animals, the primary animal is hens. Bees and sheep are the second most common urban farm animals.

Almost half of the urban farms that participated in the survey made a total gross sale adding to less than $10,000. The majority of these sales coming from farmers markets, Community Supported Agriculture (CSA), and restaurants. Not even 5% of the urban farms could be considered according to total gross sales statistics. Most urban farms agree on the main challenges that they face; production costs, managing pests, managing weeds, and climate. They also see profitability, financing, and farm labor as big challenges of managing an urban farm.

New York

Garden of Adam Purple, lower east-side, New York City, 1984

Many low-income residents suffer from high rates of obesity and diabetes and limited sources of fresh produce. The City and local nonprofit groups have been providing land, training and financial encouragement, but the impetus in urban farming has really come from the farmers, who often volunteer when their regular work day is done. In addition, the New York City Department of Environmental Protection offers a grant program for private property owners in combined sewer areas of New York City. The minimum requirement is to manage 1” of stormwater runoff from the contributing impervious area. Eligible projects include green roofs, rooftop farms, and rainwater harvesting on private property in combined sewer areas. Because of this grant program, New York City now has the world's largest rooftop farms.

Some urban gardeners have used empty lots to start a community or urban gardens. However, the soil must be tested for heavy contamination in city soil because of vehicle exhaust and remnants of old construction. The City also has a composting program, which is available to gardeners and farmers. One group, GreenThumb, provides free seedlings. Another program, the City Farms project operated by the nonprofit Just Food, offers courses on growing and selling food.

Two alternate means of growing are rooftop gardens and hydroponic (soil-less) growing. The New York Times wrote an article about one of Manhattan's first gardens which incorporate both these techniques. Another option urban gardeners have used is Farm-in-A-Box LLC, a company that provides hand-made, ready-to-use garden boxes to residents and schools.

California

In response to the recession of 2008, a coalition of community-based organizations, farmers, and academic institutions in California's Pomona Valley formed the Pomona Valley Urban Agriculture Initiative. 

After the passage of the North American Free Trade Agreement, cheap grain from the United States flooded Mexico, driving peasant farmers off of their land. Many immigrated to the Pomona Valley and found work in the construction industry. With the 2008 recession, the construction industry also suffered in the region. It is unlikely to regain its former strength because of severe water shortages in this desert region as well as ongoing weakness in the local economy. These immigrants were dry land organic farmers in their home country by default since they did not have access to pesticides and petroleum-based fertilizers. Now, they found themselves on the border of two counties: Los Angeles County with a population of 10 million and almost no farmland, and San Bernardino County which has the worst access to healthy food in the state. In both counties, there is a growing demand for locally grown organic produce. In response to these conditions, Uncommon Good, a community-based nonprofit organization that works with immigrant farmer families, convened a forum which became the Urban Farmers Association. The Urban Farmers Association is the first organization of its kind for poor immigrant farmers in the Pomona Valley. Its goal is to develop opportunities for its members to support themselves and their families through urban agriculture. With Uncommon Good, it is a founding member of the Pomona Valley Urban Agriculture Initiative (PVUAI). The PVUAI is working with local colleges and universities to expand upon a food assessment survey that was done in the City of Pomona.

Oakland

Urban agriculture in West Oakland has taken a radical form that can be traced back to community gardening initiatives starting in the 1970s in the cities of Berkeley and Oakland, and the city's African-American heritage. Oakland's manufacturing industry attracted new residents during WWII. To reduce racial tension, the Oakland Housing Authority established housing projects for blacks in West Oakland and whites in East Oakland. With exclusionary covenants and redlining by banks, development capital was kept out of West Oakland while the African-American population had limited opportunities to rent or buy housing outside West Oakland.

The Black Panther Party (BPP) played a role in seeding urban agricultural practices in West Oakland. One of its social programs aimed to improve the access to healthy food for the city's black population by providing breakfast in local schools, churches, and community centers. A small amount of this food came from small local gardens planted by BPP members. According to Prof. Nathan McClintock, "The Panthers used gardening as a coping mechanism and a means of supplementing their diets, as a well as a means to strengthen community members engaged in the struggle against oppression." The People of Color Greening Network (PCGN) was created in the 1990s. The group planted in empty and vacant lots in West Oakland. In addition, schools around Alameda County began teaching basic gardening skills and food education. Other groups have carried on those legacies, such as People's Grocery and Planting Justice.

In 1998, the city of Oakland's Mayor's Office of Sustainability proposed a Sustainable Community Development Initiative towards sustainable development. Due to West Oakland's lack of access to nutritious and healthy food, other organizations including the PCGN and City Slicker Farms demanded the plan include strategies for creating a sustainable impact on the local food system. City Slicker Farms was founded in 2001 in response to the lack of access to fresh produce in West Oakland. Through land donations from local residents, a network of urban farms was created through the Community Market Farms Program, and in 2005 the organization established the Backyard Garden Program to aid West Oakland residents in growing their own food at home. This program now grows upwards of 30,000  lbs. of food each year.

In 2005, Mayor Jerry Brown signed the UN World Environment Day Urban Environmental Accords, pledging Oakland to become a more sustainable city by the year 2012. This gave rise to Oakland City Council Resolutions, such as No. 76980 and No. 80332 which helped develop a Food Policy Council. It has teamed up with the Health of Oakland's People & Environment (HOPE) Collaborative, which works to improve the health and wellness of Oakland's residents. In 2009 the Oakland Food Policy Council started to plan urban agriculture in Oakland.

Canada

Montreal

Lufa Farms greenhouses are constructed on the rooftops of Greater Montreal.

 

In Montreal about 100 community gardens provide plots where citizens can grow fruits, vegetables, herbs, and flowers. The largest community garden has about 255 allotment plots, while the smallest site has about 25 plots. Out of 2 million people living in the urbanized parts of Montreal, about 10,000 residents share the garden plots. The program has been in place since 1975 and is managed by the boroughs. Some of the boroughs have a gardening instructor who visits the gardens regularly to give gardeners tips. Soil, a water supply, a space for tools, sand, fencing, and paint are provided by the city, managed by the Department of Sports, Recreation and Social Development.

Canada has a number of companies working on urban farm technology, including in Montreal. Lufa Farms built in early 2011 a 2880 sq metre (31,000 sq ft) hydroponic rooftop greenhouse atop a warehouse designated as their headquarters. They built two more large rooftop greenhouses in greater Montreal in 2013 (4,000 sq metre / 43,000 sq ft) and 2017 (5,850 sq metre / 63,000 sq ft), spending almost $10 million for the three structures. Also in 2017, an IGA supermarket in Saint-Laurent in Montreal unveiled a green roof of about 25,000 square feet of green space and products certified by Ecocert Canada. They state that they can provide over 30 different kinds of rooftop grown organic produce, along with honey produced and harvested from eight bee hives located on the roof.

Both Lufa and IGA rely on non-rooftop production for some to much of their produce. Only shallow rooted plant can grow on roofs, eliminating crops such as potatoes and corn. Some local farmers point out that the industrial systems are subsidized and are unfair competetion.

British Columbia

A Canadian urban farmer in British Columbia has published details on a crop value rating (CVR) system that urban farmers can use to determine which crops to grow, based on each crop's contribution to supporting the farm economically. This entails forgoing some crops in favor of others, but he points out that urban farmers can develop business networking with rural farmers to bring some of those other crops to the urban point of sale. For example, the urban farmer may not be able to economically justify growing sweet corn (based on long days to maturity and low yield density per linear foot of row), but a networking arrangement is mutually beneficial, as it lets a rural sweet corn grower gain an additional point of sale at retail price while also letting the urban farmer fill the gap in his product line offering.

Several community projects in Victoria, British Columbia were born to promote urban agricultural practices such as the Sharing Backyards program. This program exists to help people living in urban areas get connected with others who have extra space in their yards for the purpose of urban farming. Organizations also exist to educate people living in the urban parts of Vancouver on farming and growing food in an urban setting by running public demonstration gardens. 

Covering the roof of the west building of the Vancouver Convention Centre is the largest green roof in Canada and one of the 10 largest green roofs in the world. With around six acres of living space, it is home to more than 400,000 indigenous plants and grasses that provide insulation. It is also home to four Western honey bee beehives which pollinate the plants on the roof and provide honey. The living includes other sustainable practices such as recycling and reusing water.

The city of Kamloops, in British Columbia, are actively promoting urban agricultural practices within their community. They stress on the importance of food security and its affect on the economy as well as the ecology. They created the Food and Urban Agriculture Plan (FUAP), initiated in 2014, which lays out goals and strategies to implement a sustainable food system. The Areas which they cover include: Food Production and Land Availability, Food Processing and Preparing, Food Distribution/Retail/Access, Cooking/Eating and Celebrating Food, Food Waste and Resource Management, as well as Education/Governance and Capacity Building. The FUAP greatly emphasizes on Urban Agriculture.

Ontario

Ontario is the second biggest province and has one of the most urbanized cities in Canada, Toronto. The provincial government of Ontario has a website dedicated to providing information to those who are interested in establishing an urban farm or for those who just want to learn more about urban agriculture in Ontario. 

UrbanHensTo is a 3-year pilot program that launched in the City of Toronto on March 2, 2018. This program allows eligible resident in 4 wards across the city to keep a maximum of 4 hens (no roosters) for the purpose of enjoyment or personal consumption of only the eggs. There are other requirements included with rearing these hens under this program such as zoning and guidelines for building the enclosure, waste and disposal. The wards eligible for this program from the UrbanHensTo site include:

• Ward 13 (Parkdale-High Park)
• Ward 21 (St. Paul's)
• Ward 5 (Etobicoke-Lakeshore)
• Ward 32 (Beaches-East York)

Workshops are also available to those interested in rearing urban hens. However, failure to abide by these rules and regulations can result in fines.

Toronto has a green roof policy and bylaw which has promoted the practice of installing green roofs. According to the Green Roof Industry Survey in 2016, the city was recognized as having the most green roofs installed on buildings in all of North America. This came to be after they developed a green roof strategy in 2009 where new development buildings are required to install a green roof. 

UK

Todmorden is a town of 17,000 inhabitants in Yorkshire, United Kingdom with a successful urban agriculture model. The project, which began in 2008, has meant that food crops have been planted at forty locations throughout the town. The produce is all free, the work is done by volunteers, and passers-by and visitors are invited to pick and use the produce. Some Todmorden plots have been permission plots while others have been examples of guerilla gardening. All are "propaganda gardens" promoting locals to consider growing local, to eat seasonal, to consider the provenance of their food, and to enjoy fresh. There are food plots in the street, in the health center car park, at the rail station, in the police station, in the cemetery, and in all the town's schools.

Argentina

The city of Rosario (population: 1.3 million) has incorporated agriculture fully into its land use planning and urban development strategy. Its Land Use Plan 2007-2017 makes specific provision for the agricultural use of public land. Under its Metropolitan Strategic Plan 2008-2018, Rosario is building a “green circuit”, passing through and around the city, consisting of family and community gardens, large-scale, commercial vegetable gardens and orchards, multifunctional garden parks, and “productive barrios”, where agriculture is integrated into programmes for the construction of public housing and the upgrading of slums. In 2014, the green circuit consisted of more than 30 ha of land used to grow vegetables, fruit and medicinal and aromatic plants. The city has five garden parks – large, landscaped green areas covering a total of 72 ha of land, which are used for agriculture and for cultural, sports and educational activities.

Benefits

The benefits that UPA brings along to cities that implement this practice are numerous. The transformation of cities from only consumers of food to generators of agricultural products contributes to sustainability, improved health, and poverty alleviation.

• UPA assists to close the open loop system in urban areas characterized by the importation of food from rural zones and the exportation of waste to regions outside the city or town.
• Wastewater and organic solid waste can be transformed into resources for growing agriculture products: the former can be used for irrigation, the latter as fertilizer.
• Vacant urban areas can be used for agriculture production.
• Other natural resources can be conserved. The use of wastewater for irrigation improves water management and increases the availability of freshwater for drinking and household consumption.
• UPA can help to preserve bioregional ecologies from being transformed into cropland.
• Urban agriculture saves energy (e.g. energy consumed in transporting food from rural to urban areas).
• Local production of food also allows savings in transportation costs, storage, and in product loss, what results in food cost reduction.
• UPA improves the quality of the urban environment through greening and thus, a reduction in pollution.
• Urban agriculture also makes the city a healthier place to live by improving the quality of the environment.
• UPA is a very effective tool to fight against hunger and malnutrition since it facilitates the access to food by an impoverished sector of the urban population.

Poverty alleviation: It is known that a large part of the people involved in urban agriculture is the urban poor. In developing countries, the majority of urban agricultural production is for self-consumption, with surpluses being sold in the market. According to the FAO (Food and Agriculture Organization of the United Nations), urban poor consumers spend between 60 and 80 percent of their income on food, making them very vulnerable to higher food prices.

• UPA provides food and creates savings in household expenditure on consumables, thus increasing the amount of income allocated to other uses.
• UPA surpluses can be sold in local markets, generating more income for the urban poor.

Community centers and gardens educate the community to see agriculture as an integral part of urban life. The Florida House Institute for Sustainable Development in Sarasota, Florida, serves as a public community and education center in which innovators with sustainable, energy-saving ideas can implement and test them. Community centers like Florida House provide urban areas with a central location to learn about urban agriculture and to begin to integrate agriculture with the urban lifestyle.

Urban farms also are a proven effective educational tool to teach kids about healthy eating and meaningful physical activity.

Trade-offs

• Space is at a premium in cities and is accordingly expensive and difficult to secure.
• The utilization of untreated wastewater for urban agricultural irrigation can facilitate the spread of waterborne diseases among the human population.
• Although studies have demonstrated improved air quality in urban areas related to the proliferation of urban gardens, it has also been shown that increasing urban pollution (related specifically to a sharp rise in the number of automobiles on the road), has led to an increase in insect pests, which consume plants produced by urban agriculture. It is believed that changes to the physical structure of the plants themselves, which have been correlated to increased levels of air pollution, increase plants' palatability to insect pests. Reduced yields within urban gardens decreases the amount of food available for human consumption.
• Studies indicate that the nutritional quality of wheat suffers when urban wheat plants are exposed to high nitrogen dioxide and sulfur dioxide concentrations. This problem is particularly acute in the developing world, where outdoor concentrations of sulfur dioxide are high and large percentages of the population rely upon urban agriculture as a primary source of food. These studies have implications for the nutritional quality of other staple crops that are grown in urban settings.
• Agricultural activities on land that is contaminated (with such metals as lead) pose potential risks to human health. These risks are associated both with working directly on contaminated land and with consuming food that was grown in contaminated soil.

Municipal greening policy goals can pose conflicts. For example, policies promoting urban tree canopy are not sympathetic to vegetable gardening because of the deep shade cast by trees. However, some municipalities like Portland, Oregon, and Davenport, Iowa are encouraging the implementation of fruit-bearing trees (as street trees or as park orchards) to meet both greening and food production goals.

Aeroponics

From Wikipedia, the free encyclopedia

Lettuce and wheat grown in an aeroponic apparatus, NASA, 1998

Aeroponics is the process of growing plants in an air or mist environment without the use of soil or an aggregate medium (known as geoponics). The word "aeroponic" is derived from the Greek meanings of aer (ἀήρ, "air") and ponos (πόνος, "labour"). Aeroponic culture differs from both conventional hydroponics, aquaponics, and in-vitro (plant tissue culture) growing. Unlike hydroponics, which uses a liquid nutrient solution as a growing medium and essential minerals to sustain plant growth; or aquaponics which uses water and fish waste, aeroponics is conducted without a growing medium. It is sometimes considered a type of hydroponics, since water is used in aeroponics to transmit nutrients.

Methods

The basic principle of aeroponic growing is to grow plants suspended in a closed or semi-closed environment by spraying the plant's dangling roots and lower stem with an atomized or sprayed, nutrient-rich water solution. The leaves and crown, often called the canopy, extend above. The roots of the plant are separated by the plant support structure. Often, closed-cell foam is compressed around the lower stem and inserted into an opening in the aeroponic chamber, which decreases labor and expense; for larger plants, trellising is used to suspend the weight of vegetation and fruit. 

Ideally, the environment is kept free from pests and disease so that the plants may grow healthier and more quickly than plants grown in a medium. However, since most aeroponic environments are not perfectly closed off to the outside, pests and disease may still cause a threat. Controlled environments advance plant development, health, growth, flowering and fruiting for any given plant species and cultivars. 

Due to the sensitivity of root systems, aeroponics is often combined with conventional hydroponics, which is used as an emergency "crop saver" – backup nutrition and water supply – if the aeroponic apparatus fails. 

High-pressure aeroponics is defined as delivering nutrients to the roots via 20–50 micrometre mist heads using a high-pressure (80 pounds per square inch (550 kPa)) diaphragm pump.

Benefits and drawbacks

Many types of plants can be grown aeroponically.

Increased air exposure

Close-up of the first patented aeroponic plant support structure (1983). Its unrestricted support of the plant allows for normal growth in the air/moisture environment, and is still in use today.

Air cultures optimize access to air for successful plant growth. Materials and devices which hold and support the aeroponic grown plants must be devoid of disease or pathogens. A distinction of a true aeroponic culture and apparatus is that it provides plant support features that are minimal. Minimal contact between a plant and support structure allows for 100% of the plant to be entirely in air. Long-term aeroponic cultivation requires the root systems to be free of constraints surrounding the stem and root systems. Physical contact is minimized so that it does not hinder natural growth and root expansion or access to pure water, air exchange and disease-free conditions.

Benefits of oxygen in the root zone

Oxygen (O₂) in the rhizosphere (root zone) is necessary for healthy plant growth. As aeroponics is conducted in air combined with micro-droplets of water, almost any plant can grow to maturity in air with a plentiful supply of oxygen, water and nutrients. 

Some growers favor aeroponic systems over other methods of hydroponics because the increased aeration of nutrient solution delivers more oxygen to plant roots, stimulating growth and helping to prevent pathogen formation.

Clean air supplies oxygen which is an excellent purifier for plants and the aeroponic environment. For natural growth to occur, the plant must have unrestricted access to air. Plants must be allowed to grow in a natural manner for successful physiological development. The more confining the plant support becomes, the greater incidence of increasing disease pressure of the plant and the aeroponic system.

Some researchers have used aeroponics to study the effects of root zone gas composition on plant performance. Soffer and Burger [Soffer et al., 1988] studied the effects of dissolved oxygen concentrations on the formation of adventitious roots in what they termed “aero-hydroponics.” They utilized a 3-tier hydro and aero system, in which three separate zones were formed within the root area. The ends of the roots were submerged in the nutrient reservoir, while the middle of the root section received nutrient mist and the upper portion was above the mist. Their results showed that dissolved O₂ is essential to root formation, but went on to show that for the three O₂ concentrations tested, the number of roots and root length were always greater in the central misted section than either the submersed section or the un-misted section. Even at the lowest concentration, the misted section rooted successfully.

Other benefits of air (CO₂)

Plants in a true aeroponic apparatus have 100% access to the CO₂ concentrations ranging from 450 ppm to 780 ppm for photosynthesis. At one mile (1.6 km) above sea level, the CO₂ concentration in the air is 450 ppm during daylight. At night, the CO₂ level will rise to 780 ppm. Lower elevations will have higher levels. In any case, the air culture apparatus offers the ability for plants to have full access to all of the available CO₂ in the air for photosynthesis. 

Growing under lights during the evening allows aeroponics to benefit from the natural occurrence.

Disease-free cultivation

Aeroponics can limit disease transmission since plant-to-plant contact is reduced and each spray pulse can be sterile. In the case of soil, aggregate, or other media, disease can spread throughout the growth media, infecting many plants. In most greenhouses, these solid media require sterilization after each crop and, in many cases, they are simply discarded and replaced with fresh, sterile media.

A distinct advantage of aeroponic technology is that if a particular plant does become diseased, it can be quickly removed from the plant support structure without disrupting or infecting the other plants.

Basil grown from seed in an aeroponic system located inside a modern greenhouse was first achieved 1986.

Due to the disease-free environment that is unique to aeroponics, many plants can grow at higher density (plants per square meter) when compared to more traditional forms of cultivation (hydroponics, soil and Nutrient Film Technique [NFT]). Commercial aeroponic systems incorporate hardware features that accommodate the crop's expanding root systems. 

Researchers have described aeroponics as a "valuable, simple, and rapid method for preliminary screening of genotypes for resistance to specific seedling blight or root rot.”

The isolating nature of the aeroponic system allowed them to avoid the complications encountered when studying these infections in soil culture.

Water and nutrient hydro-atomization

Aeroponic equipment involves the use of sprayers, misters, foggers, or other devices to create a fine mist of solution to deliver nutrients to plant roots. Aeroponic systems are normally closed-looped systems providing macro and micro-environments suitable to sustain a reliable, constant air culture. Numerous inventions have been developed to facilitate aeroponic spraying and misting. The key to root development in an aeroponic environment is the size of the water droplet. In commercial applications, a hydro-atomizing spray at 360° is employed to cover large areas of roots utilizing air pressure misting. 

A variation of the mist technique employs the use of ultrasonic foggers to mist nutrient solutions in low-pressure aeroponic devices. 

Water droplet size is crucial for sustaining aeroponic growth. Too large a water droplet means less oxygen is available to the root system. Too fine a water droplet, such as those generated by the ultrasonic mister, produce excessive root hair without developing a lateral root system for sustained growth in an aeroponic system.

Mineralization of the ultrasonic transducers requires maintenance and potential for component failure. This is also a shortcoming of metal spray jets and misters. Restricted access to the water causes the plant to lose turgidity and wilt.

Advanced materials

NASA has funded research and development of new advanced materials to improve aeroponic reliability and maintenance reduction. It also has determined that high pressure hydro-atomized mist of 5-50 micrometres micro-droplets is necessary for long-term aeroponic growing. 

For long-term growing, the mist system must have significant pressure to force the mist into the dense root system(s). Repeatability is the key to aeroponics and includes the hydro-atomized droplet size. Degradation of the spray due to mineralization of mist heads inhibits the delivery of the water nutrient solution, leading to an environmental imbalance in the air culture environment. 

Special low-mass polymer materials were developed and are used to eliminate mineralization in next generation hydro-atomizing misting and spray jets.

Nutrient uptake

Close-up of roots grown from wheat seed using aeroponics, 1998

The discrete nature of interval and duration aeroponics allows the measurement of nutrient uptake over time under varying conditions. Barak et al. used an aeroponic system for non-destructive measurement of water and ion uptake rates for cranberries (Barak, Smith et al. 1996).

In their study, these researchers found that by measuring the concentrations and volumes of input and efflux solutions, they could accurately calculate the nutrient uptake rate (which was verified by comparing the results with N-isotope measurements). After verification of their analytical method, Barak et al. went on to generate additional data specific to the cranberry, such as diurnal variation in nutrient uptake, correlation between ammonium uptake and proton efflux, and the relationship between ion concentration and uptake. Work such as this not only shows the promise of aeroponics as a research tool for nutrient uptake, but also opens up possibilities for the monitoring of plant health and optimization of crops grown in closed environments.

Atomization (>65 pounds per square inch (450 kPa)), increases bioavailability of nutrients, consequently, nutrient strength must be significantly reduced or leaf and root burn will develop. Note the large water droplets in the photo to the right. This is caused by the feed cycle being too long or the pause cycle too short; either discourages both lateral root growth and root hair development. Plant growth and fruiting times are significantly shortened when feed cycles are as short as possible. Ideally, roots should never be more than slightly damp nor overly dry. A typical feed/pause cycle is < 2 seconds on, followed by ~1.5-2 minute pause- 24/7, however, when an accumulator system is incorporated, cycle times can be further reduced to < ~1 second on, ~1 minute pause.

As a research tool

Soon after its development, aeroponics took hold as a valuable research tool. Aeroponics offered researchers a noninvasive way to examine roots under development. This new technology also allowed researchers a larger number and a wider range of experimental parameters to use in their work.

The ability to precisely control the root zone moisture levels and the amount of water delivered makes aeroponics ideally suited for the study of water stress. K. Hubick evaluated aeroponics as a means to produce consistent, minimally water-stressed plants for use in drought or flood physiology experiments.

Aeroponics is the ideal tool for the study of root morphology. The absence of aggregates offers researchers easy access to the entire, intact root structure without the damage that can be caused by removal of roots from soils or aggregates. It’s been noted that aeroponics produces more normal root systems than hydroponics.

Terminology

• Aeroponic growing refers to plants grown in an air culture that can develop and grow in a normal and natural manner.
• Aeroponic growth refers to growth achieved in an air culture.
• Aeroponic system refers to hardware and system components assembled to sustain plants in an air culture.
• Aeroponic greenhouse refers to a climate controlled glass or plastic structure with equipment to grow plants in air/mist environment.
• Aeroponic conditions refers to air culture environmental parameters for sustaining plant growth for a plant species.
• Aeroponic roots refers to a root system grown in an air culture.

Types of aeroponics

Low-pressure units

In most low-pressure aeroponic gardens, the plant roots are suspended above a reservoir of nutrient solution or inside a channel connected to a reservoir. A low-pressure pump delivers nutrient solution via jets or by ultrasonic transducers, which then drips or drains back into the reservoir. As plants grow to maturity in these units they tend to suffer from dry sections of the root systems, which prevent adequate nutrient uptake. These units, because of cost, lack features to purify the nutrient solution, and adequately remove incontinuities, debris, and unwanted pathogens. Such units are usually suitable for bench top growing and demonstrating the principles of aeroponics.

High-pressure devices

High-pressure aeroponic techniques, where the mist is generated by high-pressure pump(s), are typically used in the cultivation of high value crops and plant specimens that can offset the high setup costs associated with this method of horticulture. 

High-pressure aeroponics systems include technologies for air and water purification, nutrient sterilization, low-mass polymers and pressurized nutrient delivery systems.

Commercial systems

Commercial aeroponic systems comprise high-pressure device hardware and biological systems. The biological systems matrix includes enhancements for extended plant life and crop maturation. 

Biological subsystems and hardware components include effluent controls systems, disease prevention, pathogen resistance features, precision timing and nutrient solution pressurization, heating and cooling sensors, thermal control of solutions, efficient photon-flux light arrays, spectrum filtration spanning, fail-safe sensors and protection, reduced maintenance & labor saving features, and ergonomics and long-term reliability features. 

Commercial aeroponic systems, like the high-pressure devices, are used for the cultivation of high value crops where multiple crop rotations are achieved on an ongoing commercial basis. 

Advanced commercial systems include data gathering, monitoring, analytical feedback and internet connections to various subsystems.

History

In 1911, V.M.Artsikhovski published in the journal "Experienced Agronomy" an article "On Air Plant Cultures", which talks about his method of physiological studies of root systems by spraying various substances in the surrounding air - the aeroponics method. He designed the first aeroponics and in practice showed their suitability for plant cultivation. 

It was W. Carter in 1942 who first researched air culture growing and described a method of growing plants in water vapor to facilitate examination of roots. As of 2006, aeroponics is used in agriculture around the globe.

In 1944, L.J. Klotz was the first to discover vapor misted citrus plants in a facilitated research of his studies of diseases of citrus and avocado roots. In 1952, G.F. Trowel grew apple trees in a spray culture.

It was F. W. Went in 1957 who first coined the air-growing process as “aeroponics”, growing coffee plants and tomatoes with air-suspended roots and applying a nutrient mist to the root section.

Genesis Machine, 1983

GTi’s Genesis Rooting System, 1983

The first commercially available aeroponic apparatus was manufactured and marketed by GTi in 1983. It was known then as the Genesis Machine - taken from the movie Star Trek II: The Wrath of Khan. The Genesis Machine was marketed as the "Genesis Rooting System".

GTi's device incorporated an open-loop water driven apparatus, controlled by a microchip, and delivered a high pressure, hydro-atomized nutrient spray inside an aeroponic chamber. 

At the time, the achievement was revolutionary in terms of a developing (artificial air culture) technology. The Genesis Machine simply connected to a water faucet and an electrical outlet.

Aeroponic propagation (cloning)

GTi's apparatus cut-away of vegetative cutting propagated aeroponically, achieved 1983

Aeroponic culturing revolutionized cloning (propagation from cutting) of plants. Firstly, aeroponics allowed the whole process to be carried out in a single, automated unit. Numerous plants which were previously considered difficult, or impossible, to propagate from cuttings could now be replicated simply from a single stem cutting. This was a major boon to green houses attempting to propagate delicate hardwoods or cacti – plants normally propagated by seed due to the likeliness of bacterial infection in cuttings. 

Aeroponics has now largely surpassed hydroponics and tissue culture as means for sterile propagation of plant species. With the Genesis Machine, or other comparable aeroponics setup, any grower could clone plants. Due to the automation of most parts of the process, plants could be cloned and grown by the hundreds or even thousands. In short, cloning became easier because the aeroponic apparatus initiated faster and cleaner root development through a sterile, nutrient rich, highly oxygenated, and moist environment (Hughes, 1983).

Air-rooted transplants

Cloned aeroponics transplanted directly into soil

Aeroponics significantly advanced tissue culture technology. It cloned plants in less time and reduced numerous labor steps associated with tissue culture techniques. Aeroponics could eliminate stage I and stage II plantings into soil (the bane of all tissue culture growers). Tissue culture plants must be planted in a sterile media (stage-I) and expanded out for eventual transfer into sterile soil (stage-II). After they are strong enough they are transplanted directly to field soil. Besides being labor-intensive, the entire process of tissue culture is prone to disease, infection, and failure. 

With the use of aeroponics, growers cloned and transplanted air-rooted plants directly into field soil. Aeroponic roots were not susceptible to wilting and leaf loss, or loss due to transplant shock (something hydroponics can never overcome). Because of their healthiness, air-rooted plants were less likely to be infected with pathogens. (If the RH of the root chamber gets above 70 degrees F, fungus gnats, algae, anaerobic bacteria are likely to develop.) 

The efforts by GTi ushered in a new era of artificial life support for plants capable of growing naturally without the use of soil or hydroponics. GTi received a patent for an all-plastic aeroponic method and apparatus, controlled by a microprocessor in 1985. 

Aeroponics became known as a time and cost saver. The economic factors of aeroponic’s contributions to agriculture were taking shape.

Genesis Growing System, 1985

GTi's Aeroponic Growing System greenhouse facility, 1985

By 1985, GTi introduced second generation aeroponics hardware, known as the "Genesis Growing System". This second generation aeroponic apparatus was a closed-loop system. It utilized recycled effluent precisely controlled by a microprocessor. Aeroponics graduated to the capability of supporting seed germination, thus making GTi's the world's first plant and harvest aeroponic system.

Many of these open-loop unit and closed-loop aeroponic systems are still in operation today.

Commercialization

Aeroponics eventually left the laboratories and entered into the commercial cultivation arena. In 1966, commercial aeroponic pioneer B. Briggs succeeded in inducing roots on hardwood cuttings by air-rooting. Briggs discovered that air-rooted cuttings were tougher and more hardened than those formed in soil and concluded that the basic principle of air-rooting is sound. He discovered air-rooted trees could be transplanted to soil without suffering from transplant shock or setback to normal growth. Transplant shock is normally observed in hydroponic transplants.

In Israel in 1982, L. Nir developed a patent for an aeroponic apparatus using compressed low-pressure air to deliver a nutrient solution to suspended plants, held by styrofoam, inside large metal containers.

In summer 1976, British researcher John Prewer carried out a series of aeroponic experiments near Newport, Isle of Wight, U.K., in which lettuces (variety Tom Thumb) were grown from seed to maturity in 22 days in polyethylene film tubes made rigid by pressurized air supplied by ventilating fans. The equipment used to convert the water-nutrient into fog droplets was supplied by Mee Industries of California. "In 1984 in association with John Prewer, a commercial grower on the Isle of Wight - Kings Nurseries - used a different design of aeroponics system to grow strawberry plants. The plants flourished and produced a heavy crop of strawberries which were picked by the nursery's customers. The system proved particularly popular with elderly customers who appreciated the cleanliness, quality and flavor of the strawberries, and the fact they did not have to stoop when picking the fruit." 

In 1983, R. Stoner filed a patent for the first microprocessor interface to deliver tap water and nutrients into an enclosed aeroponic chamber made of plastic. Stoner has gone on to develop numerous companies researching and advancing aeroponic hardware, interfaces, biocontrols and components for commercial aeroponic crop production.

The first commercial aeroponic greenhouse for aeroponic food production – 1986

In 1985, Stoner's company, GTi, was the first company to manufacture, market and apply large-scale closed-loop aeroponic systems into greenhouses for commercial crop production.

In the 1990s, GHE or General Hydroponics [Europe] thought to try to introduce aeroponics to the hobby hydroponics market and finally came to the Aerogarden system. However, this could not be classed as 'true' aeroponics because the Aerogarden produced tiny droplets of solution rather than a fine mist of solution; the fine mist was meant to reproduce true Amazon rain. In any case, a product was introduced to the market and the grower could broadly claim to be growing their hydroponic produce aeroponically. A demand for aeroponic growing in the hobby market had been established and moreover it was thought of as the ultimate hydroponic growing technique. The difference between true aeroponic mist growing and aeroponic droplet growing had become very blurred in the eyes of many people. At the end of the nineties, a UK firm, Nutriculture, was encouraged enough by industry talk to trial true aeroponic growing; although these trials showed positive results compared with more traditional growing techniques such as NFT and Ebb & Flood there were drawbacks, namely cost and maintenance. To accomplish true mist aeroponics a special pump had to be used which also presented scalability problems. Droplet-aeroponics was easier to manufacture, and as it produced comparable results to mist-aeroponics, Nutriculture began development of a scalable, easy to use droplet-aeroponic system. Through trials they found that aeroponics was ideal for plant propagation; plants could be propagated without medium and could even be grown-on. In the end, Nutriculture acknowledged that better results could be achieved if the plant was propagated in their branded X-stream aeroponic propagator and moved on to a specially designed droplet-aeroponic growing system - the Amazon.

Aeroponically grown food

In 1986, Stoner became the first person to market fresh aeroponically grown food to a national grocery chain. He was interviewed on NPR and discussed the importance of the water conservation features of aeroponics for both modern agriculture and space.

Aeroponics in space

Space plants

NASA life support GAP technology with untreated beans (left tube) and biocontrol treated beans (right tube) returned from the Mir space station aboard the space shuttle – September 1997

Plants were first taken into Earth's orbit in 1960 on two separate missions, Sputnik 4 and Discoverer 17. On the former mission, wheat, pea, maize, spring onion, and Nigella damascena seeds were carried into space, and on the latter mission Chlorella pyrenoidosa cells were brought into orbit.

Plant experiments were later performed on a variety of Bangladesh, China, and joint Soviet-American missions, including Biosatellite II (Biosatellite program), Skylab 3 and 4, Apollo-Soyuz, Sputnik, Vostok, and Zond. Some of the earliest research results showed the effect of low gravity on the orientation of roots and shoots (Halstead and Scott 1990).

Subsequent research went on to investigate the effect of low gravity on plants at the organismic, cellular, and subcellular levels. At the organismic level, for example, a variety of species, including pine, oat, mung bean, lettuce, cress, and Arabidopsis thaliana, showed decreased seedling, root, and shoot growth in low gravity, whereas lettuce grown on Cosmos showed the opposite effect of growth in space (Halstead and Scott 1990). Mineral uptake seems also to be affected in plants grown in space. For example, peas grown in space exhibited increased levels of phosphorus and potassium and decreased levels of the divalent cations calcium, magnesium, manganese, zinc, and iron (Halstead and Scott 1990).

Biocontrols in space

In 1996, NASA sponsored Stoner’s research for a natural liquid biocontrol, known then as ODC (organic disease control), that activates plants to grow without the need for pesticides as a means to control pathogens in a closed-loop culture system. ODC is derived from natural aquatic materials.

By 1997, Stoner’s biocontrol experiments were conducted by NASA. BioServe Space Technologies’s GAP technology (miniature growth chambers) delivered the ODC solution unto bean seeds. Triplicate ODC experiments were conducted in GAP’s flown to the MIR by the space shuttle; at the Kennedy Space Center; and at Colorado State University (J. Linden). All GAPS were housed in total darkness to eliminate light as an experiment variable. The NASA experiment was to study only the benefits of the biocontrol.

NASA's experiments aboard the MIR space station and shuttle confirmed that ODC elicited increased germination rate, better sprouting, increased growth and natural plant disease mechanisms when applied to beans in an enclosed environment. ODC is now a standard for pesticide-free aeroponic growing and organic farming. Soil and hydroponics growers can benefit by incorporating ODC into their planting techniques. ODC meets USDA NOP standards for organic farms.

Aeroponics for space and Earth

NASA aeroponic lettuce seed germination. Day 30.

In 1998, Stoner received NASA funding to develop a high performance aeroponic system for earth and space. Stoner demonstrated that a dry bio-mass of lettuce can be significantly increased with aeroponics. NASA utilized numerous aeroponic advancements developed by Stoner. Due to this advancement we can use as a reference to space aeroponics. 

Abstract: The purpose of the research conducted was to identify and demonstrate technologies for high-performance plant growth in a variety of gravitational environments. A low-gravity environment, for example, poses the problems of effectively bringing water and other nutrients to the plants and effecting recovery of effluents. Food production in the low-gravity environment of space provides further challenges, such as minimization of water use, water handling, and system weight. Food production on planetary bodies such as the Moon or Mars also requires dealing with a hypogravity environment. Because of the impacts to fluid dynamics in these various gravity environments, the nutrient delivery system has been a major focus in plant growth system optimization.

There are a number of methods currently utilized (both in low gravity and on Earth) to deliver nutrients to plants. Substrate dependent methods include traditional soil cultivation, zeoponics, agar, and nutrient-loaded ion exchange resins. In addition to substrate dependent cultivation, many methods using no soil have been developed such as nutrient film technique, ebb and flow, aeroponics, and many other variants. Many hydroponic systems can provide high plant performance but nutrient solution throughput is high, necessitating large water volumes and substantial recycling of solutions, and the control of the solution in hypogravity conditions is difficult at best. 

Aeroponics, with its use of a hydro-atomized spray to deliver nutrients, minimizes water use, increases oxygenation of roots, and offers excellent plant growth, while at the same time approaching or bettering the low nutrient solution throughput of other systems developed to operate in low gravity. Aeroponics’ elimination of substrates and the need for large nutrient stockpiles reduces the amount of waste materials to be processed by other life support systems. Furthermore, the absence of substrates simplifies planting and harvesting (providing opportunities for automation), decreases the volume and weight of expendable materials, and eliminates a pathway for pathogen transmission. These many advantages combined with the results of this research that prove the viability of aeroponics in microgravity makes aeroponics a logical choice for efficient food production in space.^]

NASA inflatable aeroponics

In 1999, Stoner, funded by NASA, developed an inflatable low-mass aeroponic system (AIS) for space and earth for high performance food production.This advancements are very useful in space aeroponics. 

Abstract: Aeroponics International’s (AI’s) innovation is a self-contained, self-supporting, inflatable aeroponic crop production unit with integral environmental systems for the control and delivery of a nutrient/mist to the roots. This inflatable aeroponic system addresses the needs of subtopic 08.03 Spacecraft Life Support Infrastructure and, in particular, water and nutrient delivery systems technologies for food production. The inflatable nature of our innovation makes it lightweight, allowing it to be deflated so it takes up less volume during transportation and storage. It improves on AI’s current aeroponic system design that uses rigid structures, which use more expensive materials, manufacture processes, and transportation. As a stationary aeroponic system, these existing high-mass units perform very well, but transporting and storing them can be problematic.

On Earth, these problems may hinder the economic feasibility of aeroponics for commercial growers. However, such problems become insurmountable obstacles for using these systems on long-duration space missions because of the high cost of payload volume and mass during launch and transit.

The NASA efforts lead to developments of numerous advanced materials for aeroponics for earth and space.

Benefits of aeroponics for earth and space

NASA aeroponic lettuce seed germination- Day 3

Aeroponics possesses many characteristics that make it an effective and efficient means of growing plants.

Less nutrient solution throughout

NASA aeroponic lettuce seed germination- Day 12

Plants grown using aeroponics spend 99.98% of their time in air and 0.02% in direct contact with hydro-atomized nutrient solution. The time spent without water allows the roots to capture oxygen more efficiently. Furthermore, the hydro-atomized mist also significantly contributes to the effective oxygenation of the roots. For example, NFT has a nutrient throughput of 1 liter per minute compared to aeroponics’ throughput of 1.5 milliliters per minute.

The reduced volume of nutrient throughput results in reduced amounts of nutrients required for plant development.

Another benefit of the reduced throughput, of major significance for space-based use, is the reduction in water volume used. This reduction in water volume throughput corresponds with a reduced buffer volume, both of which significantly lighten the weight needed to maintain plant growth. In addition, the volume of effluent from the plants is also reduced with aeroponics, reducing the amount of water that needs to be treated before reuse. 

The relatively low solution volumes used in aeroponics, coupled with the minimal amount of time that the roots are exposed to the hydro-atomized mist, minimizes root-to-root contact and spread of pathogens between plants.

Greater control of plant environment

NASA aeroponic lettuce seed germination (close-up of root zone environment)- Day 19

Aeroponics allows more control of the environment around the root zone, as, unlike other plant growth systems, the plant roots are not constantly surrounded by some medium (as, for example, with hydroponics, where the roots are constantly immersed in water).

Improved nutrient feeding

A variety of different nutrient solutions can be administered to the root zone using aeroponics without needing to flush out any solution or matrix in which the roots had previously been immersed. This elevated level of control would be useful when researching the effect of a varied regimen of nutrient application to the roots of a plant species of interest. In a similar manner, aeroponics allows a greater range of growth conditions than other nutrient delivery systems. The interval and duration of the nutrient spray, for example, can be very finely attuned to the needs of a specific plant species. The aerial tissue can be subjected to a completely different environment from that of the roots.

More user-friendly

The design of an aeroponic system allows ease of working with the plants. This results from the separation of the plants from each other, and the fact that the plants are suspended in air and the roots are not entrapped in any kind of matrix. Consequently, the harvesting of individual plants is quite simple and straightforward. Likewise, removal of any plant that may be infected with some type of pathogen is easily accomplished without risk of uprooting or contaminating nearby plants.

More cost effective

Close-up of aeroponically grown corn and roots inside an aeroponic (air-culture) apparatus, 2005

Aeroponic systems are more cost effective than other systems. Because of the reduced volume of solution throughput (discussed above), less water and fewer nutrients are needed in the system at any given time compared to other nutrient delivery systems. The need for substrates is also eliminated, as is the need for many moving parts .

Use of seed stocks

With aeroponics, the deleterious effects of seed stocks that are infected with pathogens can be minimized. As discussed above, this is due to the separation of the plants and the lack of shared growth matrix. In addition, due to the enclosed, controlled environment, aeroponics can be an ideal growth system in which to grow seed stocks that are pathogen-free. The enclosing of the growth chamber, in addition to the isolation of the plants from each other discussed above, helps to both prevent initial contamination from pathogens introduced from the external environment and minimize the spread from one plant to others of any pathogens that may exist.

21st century aeroponics

Modern aeroponics allows high density companion planting of many food and horticultural crops without the use of pesticides - due to unique discoveries aboard the space shuttle

Aeroponics is an improvement in artificial life support for non-damaging plant support, seed germination, environmental control and rapid unrestricted growth when compared with hydroponics and drip irrigation techniques that have been used for decades by traditional agriculturalists.

Contemporary aeroponics

Contemporary aeroponic techniques have been researched at NASA's research and commercialization center BioServe Space Technologies located on the campus of the University of Colorado in Boulder, Colorado. Other research includes enclosed loop system research at Ames Research Center, where scientists were studying methods of growing food crops in low gravity situations for future space colonization. 

In 2000, Stoner was granted a patent for an organic disease control biocontrol technology that allows for pesticide-free natural growing in an aeroponic systems.

In 2004, Ed Harwood, founder of AeroFarms, invented an aeroponic system that grows lettuces on micro fleece cloth. AeroFarms, utilizing Harwood's patented aeroponic technology, is now operating the largest indoor vertical farm in the world based on annual growing capacity in Newark, New Jersey. By using aeroponic technology the farm is able to produce and sell up to two million pounds of pesticide-free leafy greens per year.

Aeroponic bio-pharming

Aeroponically grown biopharma corn, 2005

Aeroponic bio-pharming is used to grow pharmaceutical medicine inside of plants. The technology allows for completed containment of allow effluents and by-products of biopharma crops to remain inside a closed-loop facility. As recently as 2005, GMO research at South Dakota State University by Dr. Neil Reese applied aeroponics to grow genetically modified corn. 

According to Reese it is a historical feat to grow corn in an aeroponic apparatus for bio-massing. The university’s past attempts to grow all types of corn using hydroponics ended in failure. 

Using advanced aeroponics techniques to grow genetically modified corn Reese harvested full ears of corn, while containing the corn pollen and spent effluent water and preventing them from entering the environment. Containment of these by-products ensures the environment remains safe from GMO contamination. 

Reese says, aeroponics offers the ability to make bio-pharming economically practical.

Large scale integration of aeroponics

Aeroponic Graduate Program: Hanoi Agricultural University, Hanoi, Vietnam

In 2006, the Institute of Biotechnology at Vietnam National University of Agriculture, in joint efforts with Stoner, established a postgraduate doctoral program in aeroponics. The university's Agrobiotech Research Center, under the direction of Professor Nguyen Quang Thach, is using aeroponic laboratories to advance Vietnam's minituber potato production for certified seed potato production. 

Aeroponic potato explants on day 3 after insertion in the aeroponic system, Hanoi

The historical significance for aeroponics is that it is the first time a nation has specifically called out for aeroponics to further an agricultural sector, stimulate farm economic goals, meet increased demands, improve food quality and increase production.

"We have shown that aeroponics, more than any other form of agricultural technology, will significantly improve Vietnam's potato production. We have very little tillable land, aeroponics makes complete economic sense to us”, attested Thach. 

Aeroponic greenhouse for potato minituber product Hanoi 2006

Vietnam joined the World Trade Organization (WTO) in January 2007. The impact of aeroponics in Vietnam will be felt at the farm level.

Aeroponic integration in Vietnamese agriculture will begin by producing a low cost certified disease-free organic minitubers, which in turn will be supplied to local farmers for their field plantings of seed potatoes and commercial potatoes. Potato farmers will benefit from aeroponics because their seed potatoes will be disease-free and grown without pesticides. Most importantly for the Vietnamese farmer, it will lower their cost of operation and increase their yields, says Thach.