National Hog Farmer is part of the Informa Markets Division of Informa PLC

This site is operated by a business or businesses owned by Informa PLC and all copyright resides with them. Informa PLC's registered office is 5 Howick Place, London SW1P 1WG. Registered in England and Wales. Number 8860726.

The Beauty of Biofilters

Nicolai Pork Producers Inc.

Nicolai Pork Producers Inc. • Dick Nicolai • Hector, MN

Better mousetraps don't come along every day, but when they do, the world will indeed beat a path to your door. On just one July day, Nicolai Pork Producers Inc. (NPPI) hosted visitors from North Carolina, Iowa, Ohio, Missouri, Indiana, Wisconsin and Nebraska. And, a fellow from Michigan stopped by at noon for a quick look around.

They had all beaten a path to Hector, MN, to get a look at NPPI's biofilter, a device used to treat exhaust air from buildings on a 1,500-sow, farrow-to-wean operation.

On a couple of occasions, Dick Nicolai, one of NPPI's owners, has even pitched a large tent and put on a pork sandwich feed for up to 100 folks at a time. He then took the opportunity, along with University of Minnesota extension agricultural engineers, to explain the concept of a biofilter to fellow pork producers, neighbors, equipment retailers, Minnesota Pollution Control officials, Extension agents, media and anyone else interested in learning about controlling odor from swine units. And he did it all while they were eating lunch with the biofilter, quite literally, operating right under their noses.

“Everyone who came to the event said they couldn't smell anything offensive,” Nicolai says. “They were able to eat their lunch despite the fact they were sitting right beside the fans.”

Living Laboratory

Nicolai owns NPPI along with the operation's manager, Sam Watkins, and neighbors Donn Cunningham and Gary Lamka. The unit was originally constructed in 1997 for 750 sows, and then expanded in late 1999 to 1,500 sows. The facility includes two 550-sow gestation barns and nine 26-crate farrowing rooms. Replacement gilts come in as 12-lb. weaners through an off-site isolation unit.

There's no question, however, that NPPI is also Nicolai's living laboratory in a quest to learn more about biofilters and odor control. Nicolai, whose first career was as an agricultural engineer for a machinery company, took over the family farm in 1975. In 1994, he agreed to fill in for University of Minnesota extension ag engineer Larry Jacobson, who went on sabbatical.

Nicolai's first call in the temporary position was from a pork producer plagued by odor problems. “I began to investigate odor control and odor technology,” he says. “I found information on biofilters in literature from Europe. Their conclusions were that a biofilter could work, but was too expensive to build.”

Nicolai figured he could use his tightfisted farming experiences to cut the costs of a biofilter. He experimented with a prototype he was using on a small hog building on the home farm. It seemed to work, so when the new NPPI operation went to the drawing board, a biofilter was part of the plan.

“We really didn't put the biofilter in there because we anticipated problems from neighbors,” Nicolai says. “I had an interest in the research aspect of it, and with Sam's willingness to help manage it, we thought we might contribute something of a science-based solution to odors.”

Odor Sponge

A biofilter is a layer of compost and wood chips, which serve as a medium to support microbes on their surface. As air-containing odor passes through the medium, it is absorbed into a “biofilm” layer on the wood chip and compost surfaces. Microbes convert the odorous air to carbon dioxide and water.

Two critical factors in determining how well a biofilter works are how long the air spends in the biofilter, and moisture content of the medium.

“The first biofilters that we built in 1997 are still operating at the same level as when they were installed,” Nicolai says. “They are removing about 90% of the odor, and 90% of the hydrogen sulfide.” Tests show ammonia is reduced by 65% to 80%.

Nicolai was able to cut costs by ducting from exhaust fans into a layer of shipping pallets, which act as an air plenum. The wood chip mixture is applied over the pallets, supported by plastic netting that prevents the chips from falling into the air plenum. A set of sprinklers adds moisture each evening during summer months, although no moisture needs to be added in winter.

“Most people who visit the site say they can smell only a woody compost smell,” he says. “People also comment on how quiet it is around the barns, because fan noise is muffled by the biofilter. Over the past five years, many neighbors have told me they can't smell a thing when they drive by the unit.”

Over the years, Nicolai has researched topics such as how to size a biofilter and what ratio of wood chips to compost makes the ideal medium. He was able to summarize the findings and develop a design procedure published by the University of Minnesota.

He has also found that a biofilter might be used effectively even on naturally ventilated buildings. “We probably don't need to treat 100% of the air going through a barn to be effective,” he says. “We probably only need to treat the pit gases.” A combination of proper setback and good air dispersion could provide the final polishing of the air as it leaves a site.

The best part is that biofilters are easy to design and build, and at a relatively low cost. Nicolai figures construction costs range between $80 and $120 per 1,000 cu. ft./minute (cfm) of air to be treated. Operation and management costs are budgeted at $5/1,000 cfm. Those costs include increased electrical power to push air through the biofilter, adding water through the sprinklers, rodent control and replacing the medium every five to 10 years. An aggressive rodent control program is important, because the biofilter media makes an attractive nesting area, Nicolai says.

Fertilizer Savings

NPPI also takes advantage of manure nutrients, applying them to the area's rich soil. In addition to corn and soybeans, sugar beets and canning crops, such as sweet corn and peas, are grown in this area.

A custom applicator removes manure from the building's deep pit system and applies most of it through an umbilical “drag hose” system. At times, tankers are used on distant fields or when the drag hose is not available.

Manure samples are taken prior to pumping and analyzed for nitrogen (N), phosphorus (P) and potassium (K). Manure nutrients are applied at agronomic rates.

A long-range nutrient management plan documents specific fields where application is based on soil fertility, nutrient content of manure, past crop history and crop production goals. The plan is updated each time manure is applied, adding the new data from manure and soil tests.

Nutrients are usually applied to land ahead of corn or sweet corn. Part-owner Donn Cunningham handles manure planning and field crop management. His figures from previous applications show total fertilizer savings of approximately $27/acre for fields receiving manure nutrients.

The farm has also planted a windbreak of maple, hybrid willow and honeysuckle trees around the west and north sides of the building site. “We're hoping that the trees not only will reduce the wind effect on the buildings, but will also add aesthetic appeal,” says manager Watkins. “It's also an ideal place for wildlife.”

Academic Achievement

Nicolai's living laboratory has paid off in another way. Since Watkins serves as manager and is responsible for daily operations, Nicolai was able to pursue an advanced degree at the University of Minnesota, using data from the biofilter project. He's now Dr. Dick Nicolai, PhD, and an odor expert who has joined the academic community.

Nicolai currently serves on the South Dakota State University ag engineering faculty. “I really didn't plan on going into academia at 60-something years of age,” he says. “But the biofilter work gave me the nudge to pursue a whole new path, and the opportunities just seemed to open up.”