Digester consultants address odor, traffic questions

By Sarah Nigbor
Posted 8/10/23

Nobody wants to live near something that produces atrocious odors. That’s what some Ellsworth residents are concerned about when it comes to a proposed anaerobic digester coming to town. …

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Digester consultants address odor, traffic questions


Nobody wants to live near something that produces atrocious odors. That’s what some Ellsworth residents are concerned about when it comes to a proposed anaerobic digester coming to town. According to their posts on the Ellsworth community Facebook page, they want answers to their questions. The way to get those answers is to attend public meetings on the topic and conduct research.

Bigadan consultants Ray Davy and Dean Doornink explained in an interview Wednesday, Aug. 2 that the Ellsworth Plan Commission is requiring a comprehensive odor plan to be part of the digester’s special use permit application.

Bigadan, a Danish renewable natural gas company, is proposing to build a contained anaerobic digester and nutrient recovery facility in Ellsworth near the East End Industrial Park on 25 acres owned by Ellsworth Cooperative Creamery.

The biogas company has more than 40 years of experience and offers engineering and construction services to biogas plants, along with specializing in renewable energy production, manure and organic waste treatment and nutrient recycling. It operates several in Denmark.

Davy said Mike McGinley of St. Croix Sensory is going to spearhead the odor management plan.

“The concept here is that there are some presumed odor issues (already in the village) and what we’re suggesting here is that this odor management plan would look at the present odors and would start analyzing them immediately over the next 1.5 years until the construction of the plant,” Davy said. “It would set a baseline for what the odors are. They (Bigadan) would work with this company that would train students from UWRF to come in and periodically use nasal rangers to monitor the odors that are available to maintain the baseline.”

Some days odors could be coming from farms on the east side of town. Sometimes it could be the creamery. Other days might be exceptionally windy and carry scents a long way. A nasal ranger would help St. Croix Sensory determine that.

What is a nasal ranger? Invented by Chuck McGinley (Mike’s father), the 14-inch-long device is used to measure and quantify odors in ambient air. It looks like a cross between a radar gun and bugle. St. Croix Sensory, located in the Twin Cities, would build an odor baseline before the plant would be up and running. They would work with the plant as it started up to see if any odors needed addressing. Davy said they would establish a call-in line for people to contact, which would enable St. Croix Sensory to pinpoint the cause of any potential odors.

St. Croix Sensory, according to their website, evaluates odorous air samples from industrial, agricultural, and municipal operations, including wastewater treatment plants, landfills, compost sites, cannabis grow operations, manufacturing, and more. For example, a stinky garbage burner was located near the current U.S. Bank Stadium. St. Croix Sensory was brought in to help solve the odor issues before the stadium was built.

According to Doornink, Bigadan will follow the regulations it must adhere to in Denmark, which are more stringent than the United States.

How does it work?

Bigadan doesn’t allow trucks to queue up outside of the digester when bringing in a load, Doornink said.

“No drivers are standing outside with a load of manure or dairy slurry waiting to unload,” Doornink said. “The load is coming from a barn on that day. We know how long it takes to load the truck at that barn and how long it takes to unload. There are never any trucks lining up to unload. That bay is already empty and the truck in front of him is already gone. There is no queuing.”

As the saying goes, time is money, and efficiency is key for keeping operating costs down, Doornink added.

Once a truck pulls up in drives into a bay, the door is locked. While the door is open, there is negative pressure in the building preventing any air from escaping. Ducts in the ceiling are collecting the air and taking it to a filter.

“Essentially what it means, air is getting sucked in, not pushed out,” Doornink said.

All the air collected from the storage tanks goes through a fan that generates the negative pressure, then heads into a bio filter, which can be made of many different things, Doornink said.

“They search for things that will treat the odor that’s in that air,” Doornink explained. “Usually some kind of bacteria that likes that odor and they glob onto it and they consume it. So the air that then goes throughout the exhaust is significantly less odorous.”

The system is controlling what air goes in and what air goes out, Ellsworth Cooperative Creamery CEO Paul Bauer said.

“We go through different building all the time that have different pressure as people go in and out,” Bauer said. “They do that with doors and fans and pressure. This is literally modified for the odors that are present at that site.”

Common bio filters include seashells and wood chips, among others.

The air that goes out of the building is emitted through the stack. The height of the stack is determined by the dispersion model, which is controlled by the Department of Natural Resources. The height is also determined by the area’s topography. It would be 6-to-7 feet in diameter and painted white.

“All of this data will be collected in the first one to two years that the plant is running,” Davy said. “It’s a windy day and someone calls to complain that it’s stinky. We told you so, they say. But if the system works right, there will be a process in place to rapidly identify the source of the smell on that day and what corrective measures will be taken.”

Bigadan will provide constant monitoring and is willing to fund determining an odor baseline in the village currently.

“If they identify a particular site in this town that is causing significant amount of odor, they would go to them if requested and work with them to solve their odor problem,” Doornink said.

The breakdown of manure, food waste and dairy slurry is anaerobic, meaning that it’s done without oxygen. This is a different process from the biosolid facility, Bauer said.

“Anything that decomposes has multiple things in it, volatile organic compounds,” Doornink said. “In the digester, to them that is food. That is why the digestate doesn’t smell like the manure going in. It’s one of the measures they use to monitor the digestion process.

“Raw manure on the land stinks because there is a lot of slimy stuff that coats the surface of the ground and prevents it from going in. That is why a lot of farms have gone to injecting.

People confuse the biosolids, creamery and municipal sewer plant, which are all aerobic. That’s why it stinks.”

Doornink said the company will not guarantee with 100% certainty that sending the creamery’s waste to the Bigadan plant will eliminate the creamery’s odor completely. Things such as power outages or high temperatures can affect things.

“They are going to continue to work on it to improve it,” Doornink said of St. Croix Sensory’s assistance. “If they see an issue, they will talk to Bigadan and help them solve the problem.”

Digester employees would also be required to wear a sensor, which would alert them to any leaks. As previously stated, Bigadan plans to operate under European Union regulations, which are more stringent. The Ellsworth digester would be a duplicate to a plant already operating in Denmark. Digester technology in the United States is not up to the same standards, Bauer said. Poor, cheap designs have been used that weren’t proven, resulting in systems that leaked, such as Emerald Dairy in St. Croix County.

“It’s like comparing a 1940s car to a 2020 car,” Bauer said. “They’re still cars, but when you look at the smells and safety features, they’re quite different.”

Bauer spoke of a digester that just opened up outside Wrightstown, Wis., used by 12-14 large families. It uses American design and technology and the odor was not contained, he said. He also made clear that no animal carcasses will be coming to the proposed digester.

Traffic concerns

The proposed digester’s location close to the creamery (which can provide 15% of loads that don’t have to be trucked in) is ideal, Bauer said. Other benefits to the location include its proximity to existing natural gas lines and major highways and being built an industrial area away from residences. It’s also close to cows, with Ellsworth the center of an agricultural economy.

“I don’t know how many more things you can align to make it a better fit,” Bauer said.

As for traffic, Doornink said all the farm candidates in St. Croix, Dunn, Pierce, Pepin and Goodhue counties have been evaluated. They’ve looked at the barns, storage facilities, lagoons and distance of farms to the plant.

“Knowing that, you can determine how many truckloads of manure will be coming through Ellsworth’s Main Street,” Doornink said. “If everyone west of Ellsworth participates, and not everyone will because there are many small farms, the maximum loads of manure coming through Ellsworth would be nine truckloads, then nine hauling back the digestate.”

The vast majority of participants would come from the east, north or south, he said. The Creamery’s traffic would be reduced, since waste is currently shipped out now. The estimate is an additional two tanker trucks driving on County Road C every 15 minutes.

According to Wisconsin Department of Transportation, the daily average of vehicles near the Highway 10/County Road C intersection is 6,400. The intersection at highways 65 and 10 sees 9,500 vehicles per day.

“Where else can you have manure spreaders, tillage equipment and combines slow down traffic on Main Street?” Bauer asked. “The whole east side of Ellsworth is based in ag.”

The Ellsworth Village Board will hold a special board meeting at 6 p.m. Monday, Aug. 14. The proposed digester project will be on the agenda.

Bigadan, anaerobic digester, manure digester, Ellsworth, Wisconsin