Controlled-environment agriculture (CEA) is a technology-based approach toward food production. The aim of CEA is to provide protection and maintain optimal growing conditions throughout the development of the crop. Production takes place within an enclosed growing structure such as a greenhouse or building. Plants are often grown using hydroponic methods in order to supply the proper amounts of water and nutrients to the root zone. CEA optimizes the use of resources such as water, energy, space, capital and labor. CEA technologies include hydroponics, aeroponics, aquaculture, and aquaponics.Controllable variables: Temperature (air, nutrient solution, root-zone, leaf) Humidity (%RH) Carbon dioxide (CO2) Light (intensity, spectrum, duration and intervals) Nutrient concentration (PPM, EC) Nutrient pH (acidity) PestsCEA facilities can range from fully 100% environmnetally controlled enclosed closed loop systems, to fully automated glasshouses with computer controls for watering, lighting and ventilation, to low-tech solutions such as cloches or plastic film on field grown crops and plastic-covered tunnels.CEA methods can be used to grow literally any crop, though the reality is a crop has to be economically viable and this will vary considerably due to local market pricing, and resource costs. Crops can be grown for food, pharmaceutical and nutriceutical applications. It can also be used to grow algae for food or for biofuels. Using CEA methods increase food safety by removing sources of contamination, and increases the security of supply as it is unaffected by outside environment conditions, and by eliminating seasonality create stable market pricing which is good for farmer and consumer alike. CEA is used in research so that a specific aspect of production can be isolated while all other variables remain the same. Tinted glass could be compared to plain glass in this way during an investigation into photosynthesis. Another possibility would be an investigation into the use of supplementary lighting for growing lettuce under a hydroponic system.A February 2011 article in the magazine Science Illustrated states, "In commercial agriculture, CEA can increase efficiency, reduce pests and diseases, and save resources. ... Replicating a conventional farm with computers and LED lights is expensive but proves cost-efficient in the long run by producing up to 20 times as much high-end, pesticidee-free produce as a similar-size plot of soil. Fourteen thousand square feet of closely monitored plants produce 15 million seedlings annually at the solar-powered factory. Such factories will be necessary to meet urban China's rising demand for quality fruits and vegetables."
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