Nampa sugarbeet factory’s new digester to reduce odors

NAMPA, Idaho — This article originally appeared in the Idaho Press.

It is officially fall, and that means a trickle of trucks hauling sugarbeets into the Amalgamated Sugar factory facility in Nampa.

The beets are harvested in the fall and are processed into sugar through the winter; other production occurs year-round. But as Nampa has grown, the factory — once well outside city limits — has found itself rubbing elbows with residents and new development more often.

People who drive along Karcher Road or Northside Boulevard north of Interstate 84 may be familiar with a few different smells that have traditionally emanated from the factory. One of them, a roasted-peanut smell, can be pleasant. But the other smells rotten and unappealing, particularly during the summer months following the bulk of sugarbeet processing.

Recognizing that it wanted to be a better neighbor to the city moving in around it, company leaders began exploring installing an anaerobic digester facility to do some onsite processing of the wastewater generated from its sugar manufacturing.

“We wanted to be proactive and be a leader in the community,” said Skyler Munroe, a project engineer with the company, noting that the company invested $13.5 million in the new facility.

The Idaho Press visited the factory to learn about the new system, including how it could one day provide power back to the facility.

Water is a critical part of making sugarbeets into sugar. Recently harvested sugarbeets arriving to the facility are typically still muddy and are stored piled high in the yard outside the factory until processing. To get them into the facility, the company uses flumes — beets are dumped into a water system that floats them into the factory. One of the large root vegetables’ first stops is a giant washing machine of sorts that tumbles them around, loosening dirt, said Holly Luna, communications manager for the company.

The flume water system holds about 10 million gallons of water, which the plant reuses over and over again. But over time, that water gets dirty. Historically, at the end of the sugarbeet slicing season, usually in February, flume water was directed to open-air lagoons and slowly sent to the city of Nampa’s wastewater treatment plant.

That meant that often there was still plenty of used water in the lagoons come summertime, when warming outdoor temperatures heated the lagoons, amplifying the odor of decay.

In 2019, company staff began exploring an anaerobic digester system that could do expedited processing of the used water onsite, said Kyle Bair, regional environmental manager with the company. In 2021, the company broke ground on the digester and all of its components.

While the lagoons were aerated, the new anaerobic — sans oxygen — digester is an enclosed, heated system that uses microorganisms to break down sugars in the water. The digester itself holds 2.2 million gallons of water and was seeded with over 100,000 gallons of microorganisms from a facility that processes manufacturing waste from potato products, Bair said.

The new system has several benefits. The factory can continuously clean the flume water it is using to transport the beets into the factory instead of putting it into lagoons for cleaning at the end of the processing season. That means it is cleaner when it is time to send it to the city’s wastewater treatment plant.

Part of the process of cleaning the water is allowing the microbes to efficiently break down sugars into acids, while other microbes called methanogens convert those acids to methane and sulfur. Currently, those gasses are removed from the water and burned off in a flare. But instead of simply burning the gas, a future phase of the project could one day allow that gas to power parts of the factory, Bair said.

For example, natural gas could be used to generate electricity for the factory, including to power boilers that are part of the sugar-making process, Bair said. The company will be exploring that in a future development phase of the project, he said.

The digester became operational in May, but it takes time for the microbes to grow accustomed to their new home, Bair said. The digester is still ramping up use as staff test drive how to keep ecosystem in balance — ensuring temperature and pH stay at optimal levels: about 98 degrees and neutral — as well as getting the microbes accustomed to eating again after a break over the summer.

“By spring, we should have this at full capacity and have all of that water treated,” Bair said.

This article originally appeared in the Idaho Press, read more on IdahoPress.com.

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