A light in the dark

How LEDs are changing the way we grow food
01 September 2020
By Mara Johnson-Groh
Arctic Research Foundation greenhouse
Credit: Arctic Research Foundation

At the iced ends of the earth, there's a place where the sun doesn't rise for days on end. In this place the winter temperatures drop so low it can't snow, and there's nothing to stop the howling wind. Yet it is here you can find a flourishing garden full of lettuce, carrots, and tomatoes.

This place is not some magical garden. It's Uqsuqtuuq, also known as Gjoa Haven—a tiny hamlet along Arctic waters in the northern Canadian territory of Nunavut.

In a long, blue shipping container on the edge of town, the local community, along with the Arctic Research Foundation, are working to create a sustainable food source. This past winter, the people of Uqsuqtuuq harvested their first crop of lettuce. In a place where high-priced produce travels hundreds of miles and often arrives past its peak, the freshness was unrivaled.

The container in Uqsuqtuuq is part of a growing movement to increase access to fresh foods in remote and near-inhospitable places, as well as in urban centers. At the heart of this movement are LEDs—a light source that is revolutionizing horticulture around the world, and even beyond.

LEDs—light-emitting diodes—were first practically produced in the 1960s, but as with any new technology, it has taken them some time to enter the mainstream. Early on, LEDs' potential for energy efficiency was recognized, but the cost was prohibitively high even for substantial experimentation. Through the end of the century, successive breakthroughs led to improved designs and increased wavelength coverage that would lead LEDs on a path to wide commercial use and even to becoming the subject of a Nobel Prize in Physics in 2014.

While LEDs are now ubiquitous—from traffic signals, to lightbulbs, to billboards—their role in agriculture is just beginning. One of the earliest adopters of the lights was NASA, who saw the low energy, compact lights as a durable and long-lasting alternative for use on the International Space Station (ISS). In the 1990s, NASA began experimenting with LEDs as a way to regulate astronauts' sleep cycles and to grow food aboard the ISS.

Through the early 2000s, lighting companies helped reduce the production cost of LED bulbs from dollars to pennies. Additional inroads into refining bulbs and wavelengths, such as improving color mixing of LEDs, were made by entertainment industries. With these advances, and the proof-of-concept experiments conducted by NASA, the door to horticultural LED lighting was flung open.

Today, those developments made by NASA scientists and engineers have opened pathways to spinoff technology being used in horticulture. Robert Soler, a former-NASA expert who helped develop lighting systems for the ISS, went on to cofound BIOS, a biology-first company that designs lighting systems for commercial plant growth, including marijuana, an industry newly legalized in most of the United States.

marijuana

LED lighting systems are relied upon for indoor marijuana growing operations. Credit: BIOS

"I would say a mystique in the industry is that LEDs are not capable of doing the high-output job that traditional lighting has been doing for quite some time. And I think that maybe five to three years ago that was totally true," Soler said. "But the efficiencies of LEDs and the thermal systems that we've developed at BIOS, and others have done as well, are absolutely ready to replace the legacy lighting products."

From a horticultural perspective, LEDs make a lot of sense. They use less energy—by some estimates up to 80 percent less—they can last ten times longer, and they emit in a preferred direction, reducing the loss from redirected light. LEDs also don't burn like incandescent or fluorescent bulbs. Instead they emit light when an electrical current runs through a semiconductor material. As a result, LEDs generate very little heat and thus can be placed much closer to the plants, even in between leaves. This increases photosynthesis and decreases the amount of space needed for growing.

"It means that you can bring the light closer instead of being 20 feet away or even 10 feet away from the plant system," said Mark Lefsrud, a professor at McGill University who leads the Biomass Production Laboratory. "In some cases, we keep the lightbulbs or the LEDs cold enough that they can actually physically touch the plant without doing any damage."

To plants, not all light is equal

In the past decade, researchers have made a spate of discoveries that advanced horticultural lighting. In the eyes of a plant, not all light is created equally. Photosynthesis primarily uses the visible wavelength, between 360–760 nanometers, with peaks in efficiency in the blue and red regions. Grow light systems have been developed with this in mind. Some utilize only blue and red LEDs to target the peak of photosynthetic productivity, which helps reduce energy costs by eliminating light spent on less useful wavelengths. Advances that increase energy output from blue LEDs have significantly helped improve horticultural use.

"By and large, a lot of it is pretty much settled as far as the optimized spectrum for energy efficiency and biomass, to get the most photosynthetic yield per watt of energy," Soler said. "But I think there are some things that are being explored still as in, what if I add in far-red or what if I added ultraviolet light? What does that do to the plant characteristics?"

Recently, research has explored further refining these light recipes needed to optimize plant growth. In addition to optimizing photosynthesis, researchers have identified specific wavelengths that change plant morphology, such as increasing branching. Other wavelengths have been found that can increase yields, change taste, and maximize nutrition.

lettuce

Mark Lefsrud is experimenting with using different wavelengths of light to change tastes, yields, and nutrition content in plants. Credit: Mark Lefsrud

In experiments with lettuce, Lefsrud has found a few such correlations. "I find that [with a different red to blue ratio] we're increasing the anthocyanin accumulation, as well as some of the other secondary compounds, and I'm making a more bitter lettuce. If I choose other wavelengths, like more of a softer red, like a 630 wavelength, then I find that it's a sweeter flavor, higher carbohydrates, and less of the secondary compounds being produced."

Research spanning from beans to potatoes is finding each plant is unique in its preferred wavelengths. Such work may lead to systems tailored to specific crops that can produce higher, more nutritious yields than can even be produced by the sun itself—something which could never have been achieved with traditional high-pressure sodium lights. In greenhouses that only use LEDs to supplement natural sunlight, this effect is less pronounced, but in indoor contained systems—like the one in Uqsuqtuuq—it can have a noticeable effect.

New opportunities for agriculture

Now that LEDS are widely recognized for their commercial potential in agriculture, horticulturalists hope there will be more incentive for companies to create LEDs specific to their uses. Already companies have developed general spectrum lighting systems and are starting to play with customization for their customers.

"Horticultural lighting is a niche in the scheme of things," said Erik Runkle, a professor of horticulture at Michigan State University. "But lighting companies have realized that there's a need for, and that there's an opportunity to make products for horticulture."

New research into various phosphor coatings is helping narrow wavelength ranges produced by LEDs, creating more precise colors. While this research has been motivated by applications in lighting and entertainment, the results are also useful for horticulture, where growers are aiming for specific light recipes to tweak certain characteristics of their crops. Other advances under development, such as dual-wavelength LEDs and nanodot technology, hold the potential to further increase agricultural yields while simultaneously increasing energy efficiency. Recent breakthroughs in cadmium-free quantum dots offer the potential for even greater wavelength precision, color mixing, and efficiency—particularly in redder colors—while simultaneously using more environmentally friendly materials.

Runkle says that LEDs are now the only light source used in indoor farms developed in the last five years. This widespread use, built on reduced price and increased efficiency, has made shipping container greenhouses viable for the first time.

The greenhouse in Uqsuqtuuq is the Arctic Research Foundation's first experiment with the technology, but it's not one of a kind—other startups have created similar mini container farms across the Arctic. In a place where food travels over 1,000 miles to reach the dinner table, a head of cauliflower can easily cost $10 USD, so these greenhouses offer a hopeful avenue for food security. They also offer a way to connect to traditional cultures.

"Part of the plan going forward is to get involved in some native plants to the area," said Paul Waechter, the mobile lab technician for Arctic Research Foundation who was involved in the set up and build of the Uqsuqtuuq greenhouse. The Arctic tundra around Uqsuqtuuq, while devoid of trees and large bushes, supports a variety of hearty herbs, mosses, and lichen, many of which hold traditional medicinal value. "[We've] had a couple town meetings with the community and Inuit elders of what they'd like to see grown. They came up with about three or four different plants and the idea was to go on the land this summer, and harvest and transplant some of these plants and start growing them in a greenhouse."

solar panels

Solar panels provide most of the energy needed to run the greenhouse in the Arctic. Credit: Arctic Research Foundation

While the initial cost of the greenhouse is quite high—mostly due to transporting the system to the Arctic—there are hopes that increases in availability and subsidies can help make these systems affordable for Arctic communities. Thanks in part to the efficient LEDs, the system in Uqsuqtuuq is almost entirely powered by solar panels and wind turbines, helping reduce operation costs. An onsite generator is connected to the greenhouse for backup power, but is only needed for a few hours a day in the winter, and even less during the summer.

Shipping container greenhouses are starting to pop up elsewhere as well. They've been tested in urban centers to reduce the environmental costs of shipping produce from distant farms, as well as in desert areas where contained systems can dramatically reduce water usage. While these uses bring hope of a more environmentally friendly food system, they're still a long way off from being sustainable when run off nonrenewable energy grids. Critics of these systems also note they can't yet be scaled to efficiently grow staples, like wheat and rice.

"From the carbon footprint perspective, it's still quite a bit more efficient to grow crops outdoors and ship them long distances than it is to grow them indoors," Runkle says.

elders

Elders in Uqsuqtuuq receive packages of fresh lettuce grown in a nearby shipping container. Credit: Arctic Research Foundation

While indoor LED systems won't replace traditional agriculture anytime soon, they are foreshadowing one direction farming is headed, particularly in places like Uqsuqtuuq. A 2018 report estimated LED usage by growers would increase 32 percent annually through 2027.

"I do think [LEDs] are the future," Soler said. "They're just so energy efficient, so robust, and so reliable. It makes a ton of sense, even in a harsh environment."

In Uqsuqtuuq, LEDs certainly do seem to be the future. The first harvest last winter brought smiles to elders' faces and a new source of fresh food. Already there is talk of expanding the system by adding another container. From providing food for astronauts to remote underserved communities, horticultural LEDs are just starting to shine.

Mara Johnson-Groh is a freelance science writer and photographer who writes about everything under the Sun, and even things beyond it.

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