Plant factories continue to evolve

As technology improves, plant factories have the potential to operate in the U.S. and Canada to produce crops that are difficult to grow using current conventional methods.

By David Kuack

When you hear the term “plant factory” what picture comes to mind? University of Florida professor and mechanical engineer John Schueller said the traditional definition of a plant factory is a place in which there is no natural light and artificial light is used to produce plants.

“I’m more of a traditionalist in that I feel a plant factory is a place that has mainly or only artificial lights in order to grow plants,” Schueller said. “But a greenhouse with multiple levels of plants in which natural light is the dominant source and is supplemented with artificial light, I would also consider that to be a plant factory.

“People involved in protected plant agriculture, including greenhouses and indoor plant factories, are displaying a lot of creativity. There are a lot of different systems being tried out. It’s difficult to make a hard and fast definition of a plant factory. A traditional greenhouse with plants on raised benches or growing on the floor is not usually recognized as a plant factory.”

Plant factory automation

Schueller, who spoke at the Plant Factory Conference in Kyoto, Japan, in Nov. 2014, said the most important automation that occurs in a plant factory is during the growth stage.

“The application of light and fertilizer is when the main automation occurs,” he said. “There is automation during planting when a grower is trying to establish the plants. And there is also automation during harvesting.”

University of Florida mechanical engineer John

Schueller said the technology of plant factories

is improving with the main improvement

occurring with LED lighting.

Photos courtesy of John Schueller, Univ. of Fla.

Schueller said during the Plant Factory Conference there was a lot of discussion about which lights are the best for using in plant factories.

“There are questions that still need to be answered about what are the best wavelengths and what are the best cycles for different crops,” he said “Even though there are a considerable number of plant factories, we still don’t know what the optimal conditions are for growing plants. There is a lot of variation and experimentation occurring.”

Schueller said automation in the plant factories will probably occur with the planting practices before it happens with harvesting.

“In Japanese plant factories the finished plants are brought to the harvesters,” he said. “There is automation to transfer the plants. People are doing the harvesting of leafy greens, but they are brought to the workers at an appropriate height and position so that they can be very efficient and very productive. Obviously, if there are 14 layers of plants under lights the plants are moved to the harvesters. But there is still some human involvement in harvesting the plants.”

Schueller said an advantage to a plant factory is the ability to precisely control the environment. “The technology is improving,” he said. “The main improvement is with LED lighting. As LEDs become less expensive and better that will help in the development of plant factories. Also, less expensive sensors for measuring nutrient solutions are becoming available. As growers gain more experience with this technology they get better at controlling the production environment.”

Plant factory economics

Schueller said economics play a big role in what will be feasible in how these factories operate.

“The Japanese market for fresh fruits and vegetables is much different than in the U.S. and Canada,” he said. “In the U.S. and Canada, vegetables are cheaper. The market will not bear some of the costs that will be accepted in Japan. In Japan consumers are willing to pay $40 for a watermelon.

“From an agricultural economic standpoint, it seems to me the big advantage of a plant factory is that a grower can control the production situation very well. The disadvantages are the energy costs for running the artificial lights and the capital equipment costs. The best opportunity is to produce a product that has certain characteristics, that has no pesticides applied, that has no bacterial contamination, so that a grower can demand a premium price for it.”

John Schueller said one area of plant factory production
that shows great potential is being able to develop
techniques that allow high end vegetables to have
nutritional characteristics that can be easily manipulated.

Schueller said one area of plant factory production that shows great potential is being able to develop techniques that allow high end vegetables to have nutritional characteristics that can be easily manipulated more so than in other production environments.

“One of the Japanese plant factories that was built by Fujitsu is growing lettuce which has a low potassium content,” he said. “This lettuce is being produced for kidney dialysis patients and people with chronic kidney disease. This type of crop has a lot of potential for U.S. and Canadian markets. Developing vegetables that have nutritional characteristics so that the markets will be able to tolerate higher production costs that are associated with plant factories.”

Schueller said the plant factories in Japan can produce leafy green vegetables in about 15 days.

“The production cycle needs to be as short as possible,” he said. “If a plant factory is controlled properly and maintains sanitary conditions, it is possible to produce leafy green vegetables with specific nutrient characteristics without pesticides. For those types of crops a grower can demand a premium price to pay for the equipment and energy to produce them.”

Fast, precise production

Schueller said the plant factories in Asia are producing primarily leafy green vegetables.

“I expect these crops would have the greatest potential in the U.S. as well,” he said. “As more consumers move away from iceberg lettuce and romaine lettuce, they tend to look for other types of lettuce and leafy greens and microgreens. There might be real potential with these crops because they can usually be turned much more quickly.”

Japan has over 200 plant factories. One of the reasons that
the country has experienced a proliferation of these facilities
 is food security. Sixty percent of the country’s food is imported.

Schueller said some of the issues pushing plant factories in Asia are related to domestic food production and land availability.

“Japan imports almost 60 percent of its food,” he said. “For the Japanese it’s an issue of food security. Singapore has increased its vegetable consumption from 7 percent to 8 percent. In Singapore there is a limited amount of land. They are looking for ways to maximize food production and plant factories offer them a solution. With plant factories that have vertical farming they can push the production to maximize the space. In the U.S. that isn’t a big concern. The plant factories in the U.S. that will be successful are the ones that grow products that are difficult to produce using conventional methods.”

For more: John Schueller, University of Florida, Departments of Mechanical and Aerospace and Agricultural and Biological Engineering; (352) 392-0822; schuejk@ufl.edu.

David Kuack is a freelance technical writer in Fort Worth, Texas; dkuack@gmail.com.

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