As I made my way to a local farmers market recently, I was thinking about a surprising statistic I had seen: Food travels an average of 1,500 miles to get to our tables. There’s a lot of transportation fuel, refrigeration energy, and spoilage implied in that stat. Farmers markets can help bring down that average, but in most parts of the country, nature puts strict limits on the portion of the year that those markets can operate.
With those thoughts in mind as I arrived at the market, I was delighted to find the stand of Green Line Growers—I’m betting that they, and others like them, can help to bring that average distance way down. Their lettuce, kale, and other greens are grown in “upcycled” shipping containers, known as Leafy Green Machines, that sit in an old parking garage just several blocks away. Those babies, from a company called Freight Farms, measure about 40.0 feet by 8.0 feet by 9.5 feet, hold about 4,500 hydroponically grown plants, and can be used year-round no matter how hot, cold, wet, or dry it gets. All they need is a water supply (a garden hose would do) and a 60-amp electric connection. The farmers market is only one of the outlets for the Green Line produce; it also goes to local restaurants and a nearby retail outlet.
Sensors and automated controls for air, water, nutrients, and light make the system work, and a key enabling technology is LED lighting. LEDs are great for all kinds of horticultural applications, for a number of reasons:
- Their spectral output can be tailored and the brightness adjusted for the particular crops being grown; different wavelengths can also influence taste and nutritional content, with research under way to quantify the effects. The right wavelengths can also be used to combat mildew and other pests that affect plants.
- With some LED fixtures, the output can be varied to suit different parts of the plant growth cycle and different times of day. A tomato grower in France recently announced the installation of tunable LED fixtures in a 366,000-square-foot greenhouse to enabe year-round growing.
- With the improved lighting that LEDs provide, plants require fewer chemical nutrients.
- LEDs are small in size and emit limited amounts of radiant heat so they can be used in tight quarters, such as recycled shipping containers—imagine installing 400-watt high-pressure sodium lamps in those tiny spaces. One manufacturer, Cree, offers LEDs that are about 80 percent smaller for the emerging indoor farming market.
- With reduced exposure to heat from the lights, less evaporation occurs, meaning plants require less water. HVAC needs are also reduced.
- LEDs are more controllable than the high-intensity discharge and fluorescent lighting typically used, making it easier to set on/off and dimming schedules.
- The long life of LEDs also means lighting maintenance costs may be reduced, as long as the fixtures are designed for the temperatures and moisture in the greenhouse environment.
Those benefits help to explain why a market study from Navigant predicts that in some areas more than half of new horticultural luminaire sales will be LED products by 2017. The study estimates that the ability to fine-tune the wavelengths of light emitted can increase crop yield by up to 30 percent for some plant species. Another study, from MarketsandMarkets, estimates that the global market for LED grow lights will reach $4.2 billion by 2022, driven by vertical farming, legalization of marijuana in the US, and a need to improve efficiency in horticultural applications.
Perhaps the largest example, in contrast to the one near my local farmers market, is a 25,000-square-foot indoor farm in a converted Sony factory in Miyagi Prefecture, Japan. Outfitted with 17,500 LED fixtures from GE, the farm produces 10,000 heads of lettuce per day while consuming less than 1 percent of the amount of water in a conventional operation, according to Mirai, the Japanese indoor farming company that built the operation. Mirai also claims a hundredfold increase in productivity per square foot.
And there’s no reason to keep production earthbound. A system from NASA, called Veggies, has successfully grown vegetables on the International Space Station. Next stop? Mars. (Hold on, Matt Damon!)
There’s still a lot of research to be done to quantify the right spectral content and intensity for a wide variety of plant species out there, but eventually we may see the capabilities described by Tessa Pocock, a researcher at Rensselaer Polytechnic Institute in her 2015 DOE conference presentation Tuning the Spectrum for Plant Growth (PDF), predicting that LEDs may become part of a feedback loop in which plants communicate their spectral needs and the lights respond accordingly. If that comes to pass, those average food-transportation miles could turn into a walk in the park!
And, if you’re interested in what lighting can do for humans, come to our E Source Forum 2016 lighting technology session “Harvesting the High-Hanging Fruit in Lighting: The Potential for LEDs, Networking, and Controls.” The session is scheduled to take place on Thursday, September 15, from 10:30 to noon in the Sheraton Denver Downtown hotel in Denver. For details on Forum registration and attendance, visit the Forum 2016 web page. We hope to see you there!