Indoor farming is a relatively new method of growing vegetables and other plants under controlled environmental conditions. These farm systems are variously referred to as indoor farms, vertical farms, vfarms, zfarms, greenhouses, controlled environment agriculture (CEA), and plant factories. Indoor farms are sometimes confused with urban farms, which typically represent small outdoor farms or gardens to grow vegetables that are located in urban areas. It also should be noted that mushrooms have been grown indoors in compost under controlled conditions without light for more than one hundred years.
The many faces of indoor farming
Greenhouses have been the workhorse for indoor growers for decades, especially in the production of flowers and ornamental plants. The modern high-tech greenhouse designs were pioneered in the Netherlands and have since been embraced all over the world. Several examples of these farms are evident throughout the United States and the largest span hundreds of acres. For example, according to Greenhouse Grower,5 Altman Plants (CA) has almost 600 acres under glass followed by Costa Farms (FL) with 345 acres. These are mainly used in the production of ornamental plants.
For vegetables, greenhouses were originally designed for tomatoes, but now are used in the production of kale, microgreens, lettuces, herbs, squash, and other types of fresh produce. These greenhouses, formerly located in rural areas, are now being positioned near urban and peri-urban areas to bring operations closer to population centers to save money and reduce the carbon footprint associated with transportation miles. For example, BrightFarms (brightfarms.com) has greenhouse operations located just outside of Philadelphia and Cincinnati to produce lettuces and other leafy greens. Gotham Greens (gothamgreens.com) situated its first greenhouse on top of a warehouse in Brooklyn, NY and has since expanded to other cities. AppHarvest (appharvest.com) is a venture located in Kentucky whose greenhouses cover more than 60 acres to produce tomatoes and other vegetables. What is common to greenhouse design is that all growing takes place on a single level, they are clothed in materials such as glass that transmit natural sunlight, and include climate control and irrigation equipment. They may also use a modest amount of supplemental artificial lighting during winter months.6
Growing leafy greens and other plants in buildings has emerged in the past 25 years whereby plants are grown vertically and hydroponically using artificial lights. Indoor vertical farms are typically located in warehouses or similar structures that have been retrofitted to provide superior heating, ventilation, and cooling (HVAC) for the benefit of plant production and racking systems to support the production systems.7-9 The PVC grow systems transport nutrient-rich water to the root zone of the plants, and the water is then returned to the main reservoir. Designed as closed re-circulating systems, indoor vertical farms only use a fraction of the amount of water as greenhouses or open-field methods. The advent of cost-effective LED lighting technologies has allowed farmers to provide the plants with just the right wavelengths of light, intensity, and photo period to optimize growth. Other advances include automation, IoT, and artificial intelligence; ie, all of the information technologies that contribute to “smart farming.”
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