UC Nursery and Floriculture Alliance
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UC Nursery and Floriculture Alliance

Controlled Environment Agriculture

by James A. Bethke and Heiner Lieth

Very early in my career, a group of us took a behind the scenes tour of Disney’s Epcot Center (The Land) in Florida. We were there to visit with scientists who were experiencing difficulties with insect pests in their highly controlled agriculture environments. One such site was a tumbler with carrots and lettuce growing into the center of a cylindrical tumbler that was spinning with nutrient-filled water dripping over the roots growing on the outside of the tumbler. The illustration was how vegetables could be grown in space hydroponically and in artificial gravity. There were many other examples at the Center, but what they were demonstrating was growing plants in a highly controlled environment, potentially to be used in space and on other planets.

The term controlled environment agriculture (CEA) has many meanings. Wikipedia simply defines it as a technology-based approach toward food production. Some forms of protected cultivation use a covering over the plants, which can be anything from a fabric row cover to plastic covering a wooden or metal structure. The latter type of structure with covered plastic is often called a high tunnel or hoophouse (fig. 1) and is, by definition, unheated with no electricity (Cornell 2012). Some do deem this very minimal “control” to be enough to consider hoophouses as part of CEA. Additionally, attempts to grow plants without using direct sunlight have resulted in the development of technologies where plants are grown under lamp light and all growth variables are under some level of control. Such indoor production is also part of CEA.

Fig. 1. Lifted side and open-end hoophouses. Photo: J. Bethke.
Fig. 1. Lifted side and open-end hoophouses. Photo: J. Bethke.

Today, however, the trend is toward the development and establishment of controlled environments for all manner of horticulture, generally involving more monitoring and control, as well as considerable automation. The ornamental horticulture industry has been using controlled environments for a very long time, in its most recognizable form, the greenhouse (fig. 2–3).

Fig. 2. Fully covered greenhouses with high roofs and the ability to vent hot air from the roof through insect screening. Photo: J. Bethke.
Fig. 2. Fully covered greenhouses with high roofs and the ability to vent hot air from the roof through insect screening. Photo: J. Bethke.

Fig. 3. Semi-automated propagation of cuttings grown in a greenhouse. Photo: J. Bethke.
Fig. 3. Semi-automated propagation of cuttings grown in a greenhouse. Photo: J. Bethke.

Herein, we define CEA as the production of agricultural crops under modified, highly controlled conditions in greenhouses or indoor growing spaces using soilless culture (fig. 4), including hydroponics. This type of production can increase the capacity and economic viability of small commercial growers in California, particularly those located in urban and peri-urban (rural–urban transition zone) settings, because of the higher efficiency and lower demand for land and water resources. Clearly, CEA will likely play a critical role in addressing sustainable food systems initiatives throughout California. One key feature of this type of production is the continual recirculation of irrigation water, made possible by the crops growing with confined root zones. As such we also envision a substantial improvement in water-use efficiency.

Fig. 4. Crops produced in controlled environment agriculture (CEA), such the greenhouse hydroponic tomatoes shown in this photo, are grown under highl
Fig. 4. Crops produced in controlled environment agriculture (CEA), such the greenhouse hydroponic tomatoes shown in this photo, are grown under highly controlled conditions in soilless culture. Photo: J. Bethke.

The new food system initiatives that concern the increased need for food production in urban environments and a more efficient food system (Gunders 2012) are complicated. Increasing the efficiency of our food system (Gunders 2012) and getting food from the farm to our fork eats up 10% of the total U.S. energy budget (Gunders 2012). The expanding interest in local food systems is based, in part, on avoiding the energy to transport fresh produce across the United States, thus reducing a significant carbon footprint. This interest has created a focus on something called food-miles and the development of urban agriculture (NYSERDA 2016). The goals of advocacy groups and local governments are to feed a greater amount of people, especially those that need it the most, with healthy fresh food. Indeed, near heavily populated urban centers in California there is a trend toward greenhouse production of fresh vegetables and herbs and many ornamental plant producers have been experimenting in that arena and have become successful.

Plant factories, warehouse farming, closed production systems and vertical farms, which can be located in any urban environment, are some of the approaches taken by various groups across the country to address the food system needs. They can utilize abandoned buildings or shipping containers located within urban areas (Kozai and Toyoki 2013, NYSERDA 2016) and convert them into multilevel food production systems. This approach is designed to produce local, fresh vegetables. In a general sense, systems such as these use hydroponics. 

Challenges of CEA

The types of production systems outlined above have been studied by several institutions over the years, and researchers have numerous concerns regarding their efficiency and profitability. For instance, Cornell University (2012) has calculated that the sheer volume of energy that will be required to power the supplemental lighting and operate the other environmental controls will proportionally emit four times the carbon dioxide than the poundage of plants they produce. Research in recent years, however, has demonstrated that LED lighting technology reduces the carbon footprint dramatically.

Another factor is the space used in plant production. High land values and limited access to open spaces of sufficient size and shape are limiting factors that need to be considered in many areas, particularly large urban areas. Surrounding buildings may shade the crop in CEA systems that depend on sunlight. This reduces the types of agriculture grown in urban settings. One suggested solution is the use of vertical greenhouses, but horizontal greenhouses are likely a better alternative (Albright 2013) particularly if this means sharing sunlight among plants. As such, any vertical system will probably involve lamp lighting to provide all plants with photosynthetically active radiation. (Editor’s note: see the next feature article on lighting in this newsletter issue for more about photosynthetically active radiation.)

Some CEA growers have been highly successful, especially in San Diego County, but several growers failed in the last few years due to poor preparation and poor pest management. CEA is common in other countries (all European countries, Japan, South Korea, etc.) and much of the pest management for protected culture of fruits and vegetables has been worked out. There are still significant challenges, however. One such grower in San Diego County was highly successful early on, but failed completely due to an insect-vectored disease. The system they were using was not prepared properly and sanitation was not a priority until it was too late. Clearly, these growers need assistance. From a research and education perspective, we have the expertise in many of the facets of controlled environmental agriculture, but additional UC expertise is needed in this field of study.

One economic factor that is relevant to all growers: the price of lighting, as well has what the lighting can do, is changing. LED lamps are dropping in price. The improvements in technology are resulting in longer life and better-adapted spectra. This is also pressuring the conventional manufacturers of high intensity discharge (HID) lamps to find better coatings to customize the spectrum for plant production. (Editor’s note: see related feature articles on lighting for more about LED and HID lamps.) 


CEA production has been growing very rapidly as an industry. Today there are 650 acres of greenhouse production representing 427 farmers in California with an estimated annual production value of $165 million.  New indoor operations are starting throughout the state and growers are asking for advice. The growth in CEA is driven by increasing demand for locally produced, high quality food (within or near urban areas), a new generation of highly educated and technically savvy farmers, limited agricultural land and a friendly lending environment. Tremendous improvements in technology, primarily in the area of lighting systems, have made these types of production systems more accessible to operators of smaller-sized farms. However, small farm operators need a lot of technical and horticultural assistance from UC Cooperative Extension to succeed with these new tools.

Our goal is to develop a research and extension program that will help new and existing growers in California remain economically viable by increasing their production capacity, production efficiency and profitability through the use of CEA production systems. The creation of more local market opportunities could help increase access to healthy foods and enhance the vitality of local agriculture.

James A. Bethke is County Director and Farm Advisor for Nurseries and Floriculture, UC Cooperative Extension, San Diego and Riverside Counties, and Heiner Lieth is Professor Crop Ecologist and UC Cooperative Extension Crop Ecologist, Department of Plant Sciences, UC Davis. 


Albright L. 2013. Peri-urban horizontal greenhouses. Resource Magazine. 20(2): 6. (doi: 10.13031/2013.42546).

Cornell University. 2012. Controlled Environment Agriculture: Hot topics. http://www.cornellcea.com/controversialIssues.html.

Gunders D. 2012. Wasted: How America is losing up to 40 percent of its food from farm to fork to landfill. Natural Resources Defense Council. Issue Paper 12-06-B. http://www.indianasna.org/content/indianasna/documents/NRDC_Wasted_Food_Report.pdf.

Kozai T, Niu G, Takagaki M (Eds.). 2015. Plant Factory: An Indoor Vertical Farming System for Efficient Quality Food Production. Academic Press. 422 pp.

NYSERDA (New York State Energy Research and Development Authority). 2016. CEA Ongoing Projects: Comparing Energy Use and Carbon Footprints of Four Urban Food Production Systems. New York State Energy Research and Development Authority. http://www.nyserda.ny.gov/Business-and-Industry/Agriculture/CEA-Ongoing-Projects

Zeidler C, Schubert D, and Vrakking V (Eds). 2013. Feasibility Study: Vertical Farm EDEN. Institute of Space Systems. DLR-RY-SR-EVACO-2013. http://elib.dlr.de/87264/1/DLR_CEF_VF_Report_final%20high%20incl%20cover.pdf.

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