HortiCann Day 2: Speakers build on business case for LEDs and CEA acumen

Day 2 of the HortiCann Light + Tech Conference (Sept. 28–29, 2021), held online this year, brought an optimistic outlook for the expansion of controlled environment agriculture (CEA) as an application and the technologies that will ultimately deliver on revenue potential, reduced energy consumption, and local, sustainable food production opportunities.

As we observed in our Day 1 HortiCann report, speakers laid the foundation for LED-based solid-state lighting (SSL) and controls systems with the latest updates on device-level design for horticultural applications, light recipe studies, and environmental control systems and conditions that can lead to improved crop yields.

On Wednesday, Cornell’s Greenhouse Lighting and Systems Engineering (GLASE) Consortium director Erico Mattos opened the program with the Plenary panel titled “Voices From the Farm.” In its debut at HortiCann 2020, the panel brought excellent context to the research- and technology-focused presentations by zeroing in on the perspectives of growers facing unique challenges and emerging needs in modern agriculture and horticulture operations. The 2021 panel leaned toward a more defined experience, with an assured link to the benefits LED lighting brought to yields, quality, and controllable outcomes.

Revolution Farms header grower Tammam Serage commented that, with a Michigan facility that endures harsh winters, LED lighting in the CEA operations allowed the farm to increase the daily light integral (DLI; a measure of total photosynthetically active radiation [usable light] received by plants). This in turn reduced production cycles of leafy greens from a high of around 52 days down to 36 days. “We can get 14 DLI to about 18-plus any time we want, any time of year” in the northern Lakes region, stated Serage.

Schuyler Greens CEO and farm manager John McMahon explained the undeniable value of LED lighting in his approximately 20,000-ft² operation. “As a small operation, I needed to invest in areas that would make me as efficient as possible,” he said, while working under electrical supply constraints in Virginia. The switch to red and blue LEDs from high-pressure sodium (HPS) lights was evident in the baby green cultivars resulting in “stout, strong, compact plants that are high yielding,” McMahon observed.

Some of our audience may be familiar with the work of Tessa Pocock, PhD, a plant scientist whose work has been featured at a previous Horticultural Lighting Conference from LEDs Magazine. Formerly with the Lighting Enabled Systems & Applications (LESA) Center laboratory at Rensselaer Polytechnic Institute and grower Plenty, Pocock is now applying her experience at Shenandoah Growers. Pocock said Shenandoah operates multiple facilities for research & development (R&D), farm configurations, and nurseries. Modularity in the growing setup has allowed Shenandoah personnel to experiment with various lighting spectra and intensity levels, as well as test lights from different manufacturers to continuously improve crop outcomes on the larger-scale commercial side. The crux of their work, she said, has demonstrated light uniformity’s “huge impact on yield” — and how crucial it is to test lights, number of fixtures, and spacing to determine realistic light delivery to crops. “I’m talking to lighting manufacturers about how we can increase uniformity and [improve] light mapping of these fixtures,” Pocock said. She emphasized how important it is for growers to be confident in what they are applying to their crops. She and Serage agreed that lighting manufacturers must be held accountable for their performance claims. Again, as a small grower representative, McMahon underscored the need for light testing with quantum sensors and access to SSL benchmarks for proper comparison of LED products.

In the mid-afternoon, Keynoter Ricardo Hernandez, PhD, and associate professor at North Carolina State University (NC State), revealed recent cannabis grow research. Outlining studies carried out by PhD student Cristian Collado, Hernandez explained the different outcomes that were achieved in varying the DLI of Cannabis sativa plants by changing the amount of supplemental LED lighting provided to plants alongside what they naturally received under sunlight in the experimental CEA setting.

Hernandez focused on the vegetative stage (growth of stems and branching) and then flower induction and growth stage of cannabis. The light-treatment studies took place over a 72-day growth cycle. The vegetative stage incurred an 18-hour photoperiod, while the flowering stage incurred a 12-hour photoperiod. During a portion of the study, the researchers fluctuated the supplemental light during the vegetative stage, with four samples receiving 150, 300, 500, and 700 µmol m^-2 s^-1 of light in addition to the natural sunlight. At the flowering stage, all four samples received 700 µmol m^-2 s^-1 of supplemental light.

Hernandez concluded that the different light levels showed how the vegetative state light level was critical, with increased branching, biomass, leaf area, and plant dry mass measured. Secondary branches demonstrated a greater impact from the supplemental light, which created a bushier plant with larger leaf area, more branches, and thicker leaves. Plants under the varied light quantities during the vegetative stage also showed increased flower dry mass. “If you lower your light intensity during the vegetative weeks, you will have a penalty in yield in your flowering,” Hernandez said. He proceeded to a cost analysis that applied electricity usage, light intensity variables, and potential market pricing of dry cannabis flower per growing area. Assuming even a 50% yield of commercially-viable flowers, he said the potential revenue more than offset the cost of electricity from the lights (without factoring in any other production/opex).

A motley assemblage of experts proved inspiring in the final session, with chief editor Maury Wright quipping, “You can see she never lacks for energy” after Gabel Energy consultant Gina Rodda finished speaking. First up was a novel partnership between Auburn University (AU) professor Daniel Wells and campus dining and concessions director Glenn Loughridge, bringing the AU horticultural/agricultural education program to bear on food production directly for use on campus. Loughridge said that the sense of community and pride among the AU campus, administration, and other supporters has helped to grow the program (no pun intended) beyond its traditional Ag focus to an initial aquaponics project and more recently to vertical farming, enabled by two shipping container farms supplied by Freight Farms. Wells said the operation is currently producing about 100 lb of spring-mix greens per week from just one of its greeneries. Loughridge added that the program has enabled collaboration between campus chefs and the farm faculty and participating students to deliver excellent quality, local produce unaffected by seasonal climate conditions.

Moving to energy code and regulations that impact growers, Rodda delivered the message that forward-looking California energy policies can help other regions to see what could be coming for them and meet any building and equipping challenges early on in the CEA planning process. As Wright reported in 2020, “The ongoing activity in the [California Energy Commission] for its 2022 Title 24 code cycle that would go into effect in January 2023 includes a virtual mandate that all new horticultural lighting use LED sources.” Rodda explained how complex the application of code requirements can be, since they not only impact the specification of energy-consuming lighting but also structural materials and even the classification of different types of grow spaces. Consultancies versed in the local and state energy-efficiency policies can help CEA operators reduce their environmental footprint while maximizing their success and manage costs effectively, she said.

Finally, head grower Adam Shinners of SuperiorFresh and Fluence by Osram director of horticulture services Abhay Thosar, PhD, spoke about the benefits of environmental control in a unique aquaponic and greenhouse operation based in Wisconsin. As earlier, Shinners echoed how the facility’s use of LED lighting helped to manage operational costs in a cooler region.

Both speakers addressed the question of the heat produced by HPS lights and growers that rely on that excess heat to condition the indoor grow environment for specific cultivars. Shinners said the lettuce varietals grown at SuperiorFresh are not heat tolerant, so using HPS in the greenhouse would require the excess heat to be exhausted — which is more energy-demanding than the natural gas boilers with set points that keep the crops comfortable in the greenhouse. “It’s cheaper to add the heat with a natural gas system” than it is to overlight with energy-demanding HPS and then remove the excess heat, he explained.

Wasted photons are not cost effective, commented Thosar, which requires a different way of thinking about what energy is being used for in the grower operation. “When you decouple the light and heat, you have much better environmental control” when using LEDs rather than HPS, he said. Furthermore, to those who say they need the heat from the HPS, he responded, “I have a furnace to heat my house; I don’t heat my house with an oven” because it’s not an efficient and intended use of the equipment.

Many more insights for technology development and application can be gleaned from the HortiCann Light + Tech Conference program, which is available on demand to all registrants for 60 days.

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