South St. Paul is weighing the benefits of a proposed bioenergy facility against the city's ongoing fight to curb complaints about odor.

The $30 million project is a partnership between animal products processor Sanimax and Green Energy Partners of Denmark, Wis. The proposed SaniGreen Bioenergy facility would recycle organic waste into natural gas and help power Sanimax's nearby animal rendering plant.

Dan Ostrenga, director of organic solutions at Sanimax, said construction could begin late this year or early next year, with hopes of finishing the project by March 2015. According to SaniGreen, the plant is designed to process 150,000 tons of waste per year and produce enough natural gas to heat 7,000 homes. The plant will also create 20 full-time jobs, Ostrenga said.

The city planning commission heard Sanimax's proposal earlier this month, and discussions will continue at July's meeting. Peter Hellergers, South St. Paul's city planner, said the facility is well-designed and increased production of renewable energy is a good idea, but said Sanimax's efforts to mitigate the potential smell of the facility are less clear, despite assurances from the company.

"We want to have something a little more definitive," Hellergers said. "There's got to be a little more data behind that than just the company's assurance."

SaniGreen will use negative pressure and filters to control odor when producing natural gas, Ostrenga said.

He compared the SaniGreen plant to the Hennepin Energy Recovery Center in Minneapolis, which burns about three times the amount of waste SaniGreen would process. The HERC has been successful at reducing odor using many of the same strategies SaniGreen would, Ostrenga said.

The proposal comes at a time when city officials and several local animal-product processors are looking for the source of pungent odors said to have appeared in South St. Paul neighborhoods. In 2012, odor complaints spiked from typically less than 10 per year to more than 60, Hellergers said.

Tom Carstenbrock said the smell of rotting flesh drifted to his South St. Paul home several times per week last year, and he complained to City Hall. He's noticed foul odors a few times this year, he said, even though he hasn't heard of any action being taken.

There is no ordinance against offensive odors in South St. Paul, Hellergers said, and a proposed draft didn't gain traction. Trying to intercede by using a public nuisance statute would be difficult, Hellergers said.

There are many different industries in town that could be responsible, including plants that process animals, organic waste and hides. A number of facilities across the river from South St. Paul could be contributing to the stink as well, Hellergers said.

"We had a fairly rotten year," he said. "I think people might want to say it's one company, but it's a little more complicated than that."

This finger-pointing has been common among businesses, Hellergers said. Last year, four South St. Paul companies — Twin City Hide, Twin City Tanning, Dakota Premium Foods and Sanimax — formed an "odor consortium" to investigate odor complaints more definitively. The study is set to conclude later in the summer.

Paul Rogosheske, the attorney who represents the consortium, said preliminary results have shown many of the odor complaints cannot be attributed to the consortium businesses.

The offending odors do not coincide with when the four plants are operating, or their distinct smells.

Instead, Rogosheske said, many of the complaints come from a nearby sewer separation facility, the city's compost pile and other industries.

"What you're going to see is the majority of the smell isn't coming from the majority of these owners," he said.

"People misdiagnose the smell."

Tony Wagner is a Twin Cities freelance writer.