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Foam in manure pits is a perplexing problem

By Janet Kubat Willette

Date Modified: 04/01/2010 9:16 AM

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FARIBAULT, Minn. — University of Minnesota professor Larry Jacobson is among a team of researchers and farmers trying to solve a foaming — and possibly explosive — issue.

Foaming in deep manure pits has been reported in Iowa, the Dakotas, Michigan, Nebraska, Illinois and Minnesota, Jacobson said. The reports of foaming have increased over the past two to three years for unknown reasons and Jacobson suspects the foaming is related to recent flash fires and explosions in barns with deep pits.

Foaming is not necessary to have a fire, but it helps and the explosion is bigger, he said.

There have been five barn explosions in Iowa, four in Minnesota and one in Illinois in the past year. One facility was a calf and heifer raising facility with a deep pit; the others were hog barns with deep pits.

Farmers with deep-pit barns are asked to fill out a survey at as researchers try to determine common causes of manure foaming. It's a little like CSI, but the case won't be resolved in 48 minutes, Jacobson said. Rather, it's a multipart series.

The research team received money from the Rapid Agricultural Response Fund to study manure foaming, flash fires and explosions. They are making site visits and doing case studies, Jacobson said.

It's been a head scratcher so far, he said. Foaming will occur on one side of a barn, but not the other where the hogs are fed exactly the same diet. It occurs in one barn on a production site, but not in others. Foaming seems to become a problem over years, but once established it's fast growing and recurring.

Foaming reduces manure storage volume and if it gets above the slats it's messy and it reduces air quality.

The foam captures methane, which is always produced with the anaerobic breakdown of manure, Jacobson said. The foam has methane concentrations of 60 percent to 70 percent, which is above the explosive concentration of 5 percent to 20 percent. However, when the foam bubbles are broken through agitation, spray washing, pig activity or other means, it releases methane at potentially flammable concentrations. Add an ignition source, such as a heater or spark from the feed line, and the results could be explosive.

Explosions tend to occur when the barn is empty or there are low animal numbers in the building, Jacobson said. In these cases, the fans may be off, meaning there is less air movement.

Ventilation is important whether or not there are hogs in the building, Jacobson said. He told producers at a Current Issues Facing Feedlot Operators meeting in Faribault to be extremely cautious when foam is being broken. Further, if the pit is being pumped, keep people out of the building, Jacobson said.

He prefers sidewall fans to pit fans because pit fans may be restricted because of the height of the manure. When pumping, make sure to ventilate deep-pitted buildings properly, Jacobson said. Keep the fans on, close the curtains if the wind is not blowing and keep the ceiling inlets open. Agitation shouldn't occur until the manure is two feet below the slats. If possible, agitate intermittently, he said.

There are no current recommendations to reduce foam or prevent foam formation.

"We can only treat the symptoms, we don't know the cause," Jacobson said.

The situation is worsening, but "why, we really don't know," he said. Jacobson said it's likely that multiple factors are contributing to the increase.

The elephant in the room is dried distillers grain, Jacobson said. Many hog producers with deep-pit barns feed DDGs, but not everyone has foam, he said.