DR. DICKSON DESPOMMIER spent thirty-eight years as a professor of microbiology and public health in environmental health sciences at Columbia, where he won the Best Teacher award six times. In 2003, he was awarded the American Medical Student Association Golden Apple Award for teaching. He has addressed audiences at leading universities including Harvard and MIT, and he has also been invited to speak at the United Nations. In addition, he has been asked by governments of China, India, Mexico, Jordan, Brazil, Canada, and Korea to work on environmental problems. Despommier lives in Fort Lee, New Jersey.
Energy, Veggies, And Profit
7/25/2011 9:00:37 AM

Outdoor farming is not at all efficient when it comes to the crops themselves, especially with respect to light. While solar radiation consists of the entire visible and invisible spectrum (100-3,000 nm), plants can only use a small portion of it – 3-6 percent at most. However, since the sun seems to shine every day, energy for growing crops turns out not to be the issue with traditional agriculture. Outdoor farmers do, however, use lots of energy (mostly in the form of diesel fuel) for plenty of other things (irrigating, plowing, planting, weeding, harvesting, shipping, etc.), thereby offsetting any advantage the Sun may have offered them in the way of energy input.

Moving agriculture indoors solves many energy problems associated with outdoor farming, but creates others that need to be addressed if this approach is to succeed. In all vertical farms erected so far (See: Rise of the Vertical Farm), LED lighting has played a key role in the design of the growing systems (for more, see here). Most of that application has been for green leafy vegetables. One exception is PlantLab in Holland. They are growing lots of different vegetables, including green peppers and tomatoes, as well as spinach and lettuce.  The issue at hand is ROI, or return on investment. Can a commercial vertical farmer using only LED lights as his energy source for growing crops, make a profit at the end of the day, when competing against outdoor crops of the same kind? The answer lies in the development of prototype vertical farms to allow the testing of new LED lighting fixtures specifically designed for indoor agriculture.

            Lighting an indoor farm with conventional incandescent or fluorescent bulbs has proven inefficient and hence expensive, due to the fact that these kinds of lights give off a wide spectrum of energy, most of which is useless for the plants. Light in the blue (420-460 nm wavelength) and red (640-660 nm wavelength) spectral ranges activates chlorophylls a,b,c, and d, and therefore is ideal for most plant crops. The efficiency of LEDs emitting light at the desired wavelengths for green plants saves enormous amounts of energy, and thus is much more economical in the long run compared to conventional lighting. Manufacturers of LEDs - Philips, General Electric, Lighting Science Group Corporation, and a host of Chinese manufacturers – Zhejiang G-Sun Optoelectronics Co.; Wenzhou Mvanva Photoelectric Technology Co. Ltd.; Shenzhen Baisheng Semiconductor Lighting Co. Ltd; Blue Sea Lighting (Hong Kong) – offer a wide variety of lighting fixtures in an astonishing assortment of blue and red spectra. Every year there are technical meetings held around the world (e.g., Strategies in Light; Let Life Green; LEDs Conference; Illuminating Engineering Society of North America), bringing together all those interested in making LED lights for all uses more efficient, and thus more economical to operate.

Like the increase in computing power and the growth of the hybrid car industry, every year ushers in a new generation of LEDs that costs less to run and that more accurately meets the requirements of our crop plants. It is likely that LED technologies specifically targeted for the indoor agronomist will one day advance to the point where anyone interested in getting in on vertical farming can do so without having to worry about the monthly electric bill eating up his/her profits. That day is right around the corner. Let there be light! LED light!

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