July/August 2012
Storage Evolution By Bill Schaefer

Walt Sparks. His name is synonymous with potato storage.

Potato storage systems have come a long way from the days of old A-frame, non-ventilated buildings. And Sparks is the person most often cited as the first researcher into potato storage theory.

You can’t discuss the history and evolution of potato storage systems without his name popping up. Whether speaking with research scientists or business professionals, Walt Sparks will enter the discussion at some point.

While Sparks was a research scientist at the University of Idaho’s Aberdeen Research and Extension Center from 1947 to 1981, his influence in the development of storage systems continues into the 21st century.

Walt was the grandfather of air movement within a storage,” Bob Thornton said.

End of ‘seat of pants’ management
Thornton and Willy Iritani, each a professor emeritus of horticulture at Washington State University (WSU), are cited by many for their expertise in the development of storage systems and the physiology of potatoes in storage. They worked with Sparks at Aberdeen prior to accepting their teaching positions at WSU.

Previously, Thornton said, storage systems had no ventilation and management consisted of opening and closing main access doors.

“You decided by the seat of your pants how long to open the doors,” Thornton said. “What Walt proposed and what became fairly common was an A-frame — not a pipe, but a wooden A-frame, essentially a non-pressurized ventilation system which allowed the air to move in underneath and travel up through the pile.”

Sparks may have led the development of air flow in storage systems, but the business model that forced growers to seek more sophisticated storage systems was the process market and the demand for quality French fries with consistent light fry color.

Mel Miller, who worked for potato process companies in the Columbia Basin since the mid 1960s, said that Sparks was a proponent of air flow in storage and keeping the pile at a uniform temperature to maintain sugar levels necessary for consistent French fry color.

By the early 1970s, Miller said, Willy Iritani had found that the processors in the Columbia Basin could improve the health of their potatoes by increasing airflow from 10 cubic feet per minute (cfm) per ton to 20 cfm. Miller said that 10 cfm was adequate in the cooler climate of eastern Idaho, but the Columbia Basin required more air-flow to cool the piles going in storage.

New demands for insulation systems
As the process industry grew to meet quick-service restaurant demand, storage systems became ever more sophisticated. In the late 1960s, storage systems began to be made from concrete. With these structures came the need for uniform temperatures and the capacity to control humidity to heal or suberize wounded tubers coming into storage, without allowing water to condense and promote soft rot, while monitoring carbon dioxide levels and pile temperatures.

Today’s storage systems continue to evolve and adapt. New systems have variable frequency fan drives, temperature and carbon dioxide sensors, control systems monitored by smart phones and wireless technology. Growers can monitor and instantly alter temperature, relative humidity, air flow, CO2 and ethylene levels. Systems come with under-floor concrete ducts that provide saturated air supply uniformly to the pile, aiding in the suberization process.

Nathan Oberg, Agri Stor storage specialist in Kimberly, Idaho, predicts that the next evolution in storage systems will be in energy efficiency.

“I think we’re going to have a large and continued push to further refine and maximize energy efficiency within our storages,” Oberg said. “That’s in terms of the way we operate our ventilation systems and control of the refrigeration system as well.”

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