Food security is a top priority for the United States and countries around the world. The U.S. Department of Agriculture defines food security as “…access by all people at all times to enough nutritious food for an active, healthy life.”1 Low food security refers to a diet of reduced quality, variety, and desirability for some populations. To achieve food security, food must be (1) readily available at all times to all people, and (2) be of sufficient quality and nutritional value to sustain a healthy and active life.

The U.S. food system is vulnerable by both measures. Some households do not have access to enough food and many others lack access to the right kind. In addition, the nutritional value of food has declined by almost 25 percent over the past 15 years.2 One reason is that food is traveling across increasing distances. To accommodate the weeks spent in transport, produce is harvested long before it ripens and thus well below its peak nutrient density.

Populations in urban areas on the east coast of the U.S. are especially vulnerable to this phenomenon. The top food producing states are Texas (for animal products) and California (for produce). In addition to distance, local decisions related to purchasing power drive the access to nutritious food. Using Washington, D.C. as an example, there are eight census tracks in the city that qualify as outright food deserts (defined as fresh food being unavailable within a one-mile radius), partially due to distances from these top-food producing states. Of the 520 food retailers in D.C., 88 percent do not offer any fresh produce and only 12 percent offer an adequate variety of fresh food to support a healthy diet. Not surprisingly, nutrition-related health problems like diabetes, hypertension, and obesity are especially high in these food desert neighborhoods.3

As in most U.S. cities, Washington D.C.’s food deserts are not evenly distributed across the eight wards that make up its territory. The deserts are primarily located in Wards 5, 7, and 8, which are the wards with the lowest household incomes and the highest concentration of African-Americans. They are home to 32 percent of the D.C. population but less than 10 percent of its grocery stores. Ward 8 has the lowest median income with US$32,000 per year and 90 percent African-American residents. In comparison, Ward 3 has a median income of US$110,000 per year and an African-American population of 5 percent. Unemployment is 3.5 percent in Ward 3, compared to 24 percent in Ward 8.

Food security levels across the U.S. are monitored through the annual Household Food Security Survey.4 It indicates that 13 percent of D.C. households are food insecure and struggle with hunger; 19 percent experience food hardship and did not have enough money in the past year to buy food for themselves or their family; and 37 percent of households with children are unable to afford enough food. This is the highest rate of food insecurity among children across the entire U.S. Among the damaging effects of food insecurity are the following: impaired cognitive development, reduced school readiness, lower educational attainments, slower physical, mental, and social development, and overall health deficits.5

The U.S. food system is also highly centralized, which further adds food security risk. Of the two million farms in the U.S., less than half operate full time, 75 percent are considered ‘very small’—cultivating five acres or less—and approximately 140,000 farms produce over 80 percent of all sales in agricultural products. Food processing statistics show even higher concentrations, with just a handful of companies processing the bulk of U.S. grain and produce. This centralization also demands energy.6 Eleven percent of greenhouse gas emissions associated with the US food supply chain are transportation-related,7 and global estimates suggest that agriculture is responsible for 25 percent of all CO2, 65 percent of methane, and 90 percent of nitrous oxide emissions.8

To advance food security for the U.S. capital region, the College of Agriculture, Urban Sustainability and Environmental Sciences (CAUSES) of the University of the District of Columbia (UDC) developed its Urban Food Hubs concept. As one of the fastest growing cities in the U.S., and one of the most bifurcated, Washington, D.C. was an ideal location to develop and test the viability of urban solutions to food insecurity. The Urban Food Hubs consist of four components: (1) urban food production, (2) food processing, (3) food distribution, and (4) waste reduction/reuse. The aim is to increase urban food production, establish local food processing and food preparation to ‘add value’ to locally grown food, expand food-related business opportunities, improve nutritional health through access to fresh food via innovative distribution systems including farmers’ markets, food trucks, and collaborative models, and to improve productivity through composting and waste reduction and reuse.

Beyond the applicability within D.C., the Urban Food Hubs concept can serve as a model to address national and global needs for improved food security. Eighty percent of the U.S. population and over 50 percent of the world’s population now live in urban areas. Food security therefore cannot be addressed without solutions that reimagine the food system as decentralized and urban. Such a distributed urban food system can offer better nutritional value and be more energy efficient and resilient.

What are the Urban Food Hubs?

The Urban Food Hubs are anchored in the five landgrant centers of CAUSES. In the tradition of the U.S. landgrant universities, the centers offer a range of community education programs including nutrition education, food safety certifications, master gardening and urban agriculture certificates, soil and water quality testing, assistance with farmers’ markets, entrepreneurship classes, etc. The CAUSES landgrant centers partner with public schools, faith communities, nonprofits, and community volunteers to reach populations in all eight of D.C.’s wards.9

As part of their outreach, the Urban Food Hubs are designed to form a network of food security islands throughout D.C. In addition to improving food security, the network also aims to improve nutritional health and lower unemployment by supporting business development in the most underserved neighborhoods of the city. Each hub consists of four components:

  • Food production through efficient urban agriculture including hydroponics and aquaponics;
  • Food processing through commercial kitchens that serve as a business incubator;
  • Food distribution through networked farmers’ markets, grocery stores, restaurants, etc.; and
  • Closing the loop through waste reduction and reuse.

Since the food hubs form a network of urban sites, they stand in contrast to large-scale centralized urban agriculture concepts. For example, a recently launched 10-acre hydroponics facility on the outskirts of D.C. is slated to produce lettuce and create local jobs.


Hydroponics systems, such as those pictured at the Muirkirk Research Farm, grow vegetables in nutrient-rich water instead of the traditional soil medium.

The hubs create a network of skills, jobs, and business ownership that broadens local food production. Given their distributed intensive production methods, they also maximize the use of photosynthesis and minimize entropy relative to the kilocalories of food produced. In contrast, large scale multistoried facilities require substantial energy input in the form of heat, air conditioning, and lighting, and are typically net-energy negative even before the substantial energy inputs associated with transporting food over long distances are added.9

Food Production through Intensive Urban Agriculture

The heart of the Urban Food Hubs is a highly efficient food production system that utilizes bio-intensive production methods including low-till box gardens, hydroponics systems, and neighborhood-based aquaponic systems. Box gardens can be installed on top of existing surface areas and can mitigate soil contamination in areas where soil quality may be an issue. One of the food hubs, which is located in a food desert neighborhood in Ward 7, uses 10 raised-bed gardens as the core of its food production system. By utilizing bio-intensive production methods, the gardens produced close to 10,000 pounds of produce and supplied a small farmers’ market throughout the growing season.

A second food hub is in the process of installing two types of hydroponics systems in a small hoop house in addition to utilizing bio-intensive raised-bed gardens. Hydroponics refers to growing vegetables in nutrient-rich water rather than in soil. The method produces substantially higher yields by supporting a larger number of crop rotations. The necessary nutrient levels are maintained by monitoring the nutrient level in the growing medium (the nutrient rich water), adding liquid fertilizer as needed. Adding CO2 to the hydroponic greenhouses can further increase efficiency. While the range of food plants that can be grown hydroponically is substantial, lettuce, leafy greens, and herbs tend to do especially well. The types of hydroponics systems utilized at the Urban Food Hubs were first successfully operated at the CAUSES research farm where they produced head lettuce, basil, Swiss chard, kale, cherry tomatoes, and cucumbers.

Aquaponics refers to a food production system that combines growing fish (aquaculture) and growing vegetables without soil (hydroponics). By using the excrement from the fish as fertilizer for vegetable production, aquaponics systems eliminate the need to add fertilizer.9 To be usable as plant fertilizer, however, the nutrients in the fish waste must first be converted into plant-available nutrients. As the plants absorb nutrients, the water can also then be reused in the fish tanks.11 Alternatively, the plants can be grown in soil that is irrigated with the nutrient-rich water from the fish tanks, a technique known as fertigation. The coproduction of vegetables and protein creates a number of benefits:

  • Efficient water use: Aquaponics systems use only 10 percent of the water used to grow plants in soil, offering a 90 percent savings in water use.
  • High productivity levels: Aquaponics systems can produce large amounts of vegetables without the need for commercial fertilizers.
  • Reduced growing time: Consistent nutrient supply along with the greenhouse conditions enhance the growth of the vegetable plants and reduce growing time.
  • Reduction of waste: Because the fish waste is used as fertilizer for the plants, a minimal amount of waste leaves the facility.

The aquaponics system pioneered by CAUSES is installed in the hoop house, which is an easy-to-construct 20 by 40-foot lightweight greenhouse. Ideally it houses six small fish tanks that comprise one unit, powered by a highly efficient aeration device, a filter system that separates liquids from solids, and a biofilter system. The aerator emulsifies atmospheric oxygen with the water that circulates through the aquaponics system. The patented Flo-Vex device thus eliminates the need for mechanical compression and can be operated by a 3/4 horsepower pump. Given its high performance in maintaining the necessary oxygen levels in the fish tanks, the system can achieve a high fish stocking density that reduces water use per pound of fish, while maintaining the system’s health and fish quality.

The plants in the aquaponics system are typically grown hydroponically in the nutrient-enriched water released from the fish tanks. To maximize flexibility, the system used for the Urban Food Hubs is configured as two connected loops: a fish loop and a plant loop. When the two loops are connected, the system resembles a common circular flow configuration. Since the two loops are connected manually, a wider variety of plants can be grown, including those that thrive when the flow beds are flooded less frequently rather than continuously. Furthermore, since one of the goals is to provide access to healthy food choices, the increased flexibility in vegetable production is an advantage. The system can support the sole production of lettuce as well as the production of a range of vegetables that are high in nutritional value.

The flexibility of the system also reduces energy use and operating costs. Both fish and plants can be rotated from cold weather species/crops in the winter months to warm weather options in the summer. Two variations of this highly efficient system, one using flow beds for vegetable production and the other using fertigation, have been successfully operated at the CAUSES research farm. The flow bed version can produce 1500 pounds of fish in two 500-gallon tanks, and approximately 10,000 pounds of vegetables, depending on the selected varieties. It operated throughout the unusually harsh 2013 to 2014 winter with only a water heater for the fish tanks. There was no additional heat and no fertilizer was added beyond the nutrients produced by the fish.

Figure 1 illustrates the urban aquaponics system. Water from a holding tank is pumped through a UV screen to kill bacteria that could be harmful to the fish; it then flows through the aeration device to ensure sufficiently high levels of oxygen in the fish tanks, through a waste filter to separate solids from liquids, and then to a biofilter that assists in the nutrient conversion process. The nutrient-rich water is then circulated into flow beds that hold the plants; a degasser evacuates the stream of gases to a compost bin to accelerate the composting process.

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Figure 1. Urban Food Hubs Aquaponics System.

Various training events on high efficiency food production, including bio-intensive, hydroponic, and aquaponic techniques, are offered at the food hubs and at the CAUSES research farm. Training events range from short demonstrations to master gardening classes and certificate programs.

Food Preparation through Business Incubator Kitchens

The food preparation component of the Urban Food Hubs is centered on a commercial kitchen that can serve as a teaching and training facility to improve information about healthy eating, healthy food preparation, and age-appropriate diets. To maximize the capacity building benefits of the cooking classes, food demonstrations, and nutrition classes offered at the Hubs, CAUSES uses a train-the-trainer model whenever possible. This means that training is first offered to staff members of community partner organization as well as local residents. The partners then assume responsibility for providing additional training and education to local residents.

This train-the-trainer approach is especially valuable in a diverse community like D.C. Food is not only about nutrition but has social and cultural dimensions as well. It creates community and is often associated with cultural, ethnic, and class identities. By forming partnerships with neighborhood-based organizations and inviting their input and participation, the education programs and training events offered through the food hubs can address a broader range of cultural perspectives than what could otherwise be offered. To be successful, nutrition and food safety education must be culturally sensitive and aware of the social pressures and traditions associated with eating and food preparation habits. One successful approach is to modify family recipes and culturally significant dishes to meet improved nutrition standards and prepare them in a safe manner. Another is to provide self-monitoring devices that offer frequent feedback to improve awareness of eating habits. Much work remains to identify successful strategies that utilize food preparation to improve both economic and public health conditions.

In addition to serving as teaching facilities, the kitchens also serve as business incubators where those interested in launching food-based businesses can clean, process, and preserve the locally grown produce that can then be marketed to local farmers’ markets, restaurants, and grocery stores. The kitchens are designed to be functional, energy efficient, and food safety compliant. Demonstration areas also provide visible workspaces, and well-defined workstations for receiving, storage, preparation, recycling, and other functional areas to provide training for proper food handling, food safety, and food management. Activities of the kitchens include the following:

  • Nutrition counseling and nutrition education workshops
  • Cooking classes and food demonstrations
  • Certifications in food handling, food safety, and Hazard Analysis and Critical Control Point (HACCP)
  • Entrepreneurship classes to launch food preparation and processing-related business
  • Focus groups to identify determinants of safe food handling behaviors, risk perception, and beliefs that impede the adoption of safe food handling standards
  • Better eating habits and reduced food-related illnesses, including focus groups to assess behavioral changes related to eating and purchasing habits

Nutrition education can also offer viable business opportunities. For example, recent changes in legislation allow dietitians to prescribe therapeutic diets in addition to physicians. This shift is consistent with the growing focus on health prevention and community health that offers new opportunities to qualified dietitians and nutrition educators.

Food Distribution through Farmers’ Markets, Restaurants, and Food Retailers

The District of Columbia is home to 650,000 residents, with an additional 1.5 million living in the Washington Metropolitan area. Washington D.C. is also home to 30 farmers’ markets and close to 50 community gardens. Yet there are many areas in the city that do not have access to affordable fresh fruits and vegetables. To reduce the number of food deserts and provide fresh, nutritious food to underserved neighborhoods, CAUSES supports several farmers’ markets in food desert areas. However, it has proven challenging to attract a sufficient number of vendors to offer locally grown food especially in low-income neighborhoods that may lack the necessary purchasing power. This presents a viable business opportunity for small urban growers, especially where farmers’ markets and ethnic food markets accept food stamps and WIC coupons.


The Muirkirk Research Farm produces over 50 varieties of vegetables and herbs.

Neighborhood stores and restaurants also offer viable market outlets. Particularly promising are venues in D.C.’s ethnically diverse neighborhoods. Food tastings conducted through the CAUSES Centers for Sustainable Development and Nutrition, Diet and Health indicate significant market opportunities especially for African crops including kitale, garden eggs, and potato leaves. High-end restaurants are also showing growing interest in ethnic produce, as well as in locally grown fish, greens, and herbs that are extremely fresh.

A new addition to the Food Hubs and the CAUSES research farm are produce trucks that are operated by the college and by local business partners. The food trucks make fresh produce available in food desert neighborhoods that lack access to public transportation. The principle behind this food distribution model is to bring fresh food to the customer instead of expecting the customer to come to local markets.

This points to another important function of food hubs, namely to connect small growers and producers of value-added food products with prospective buyers. The market research, marketing, presentation, packaging, and customer service skills necessary to successfully link producers and consumers can be offered at a hub. The hubs also serve as support networks, focus group facilities, and research bases to determine product mix, marketing and finance strategies, business plans, and data analysis to ensure proof of concept.

Other distribution models include direct marketing efforts like farmers’ markets and CSAs (Community Supported Agriculture), collaborative efforts with local food banks such as gleaning agreements and food collections, and seasonal delivery agreements with stores and restaurants. Food hubs therefore create an urban food network that offers both higher quality food to consumers and a more resilient food supply, which improves urban food security. Key food distribution activities include the following:

  • Support services and training to launch food related business
  • Strategies to support local food retail through local and mobile markets
  • Web-based portal and networking tool to link food producers, processors, and buyers
  • Market research to assess opportunities in the food and hospitality industries

Sabine O'Hara

Dr. Sabine O'Hara is Dean and Director of Landgrant Programs for the College of Agriculture, Urban Sustainability and Environmental Sciences of the University of the District of Columbia. She is known...

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