Over the last several years, foaming in manure pits has increased in swine barns across the Midwest becoming a serious issue for many pork producers. By reducing pit capacity, foaming poses a serious management problem.
Even more urgent, however, is the safety threat created by the foam. By trapping large amounts of explosive methane, foam creates a high potential for fires and explosions, especially when the foam is broken down during agitation and pumping.
For the past few years, researchers at University of Minnesota and the University of Illinois have led the way in pit foaming research. According to Larry Jacobson and David Schmidt, University of Minnesota researchers, pit foaming has been reported in up to 28 percent of Midwest swine operations.
Now, researchers at Iowa State University are studying the root cause of foaming. However, while study on the causes of pit foaming is gaining intensity, solutions to the complex problem are slow to emerge.
Foaming in deep pits requires three factors to be present, according to Steven Hoff, Iowa State researcher. According to Hoff, for foaming to occur, the following conditions must be present:
- A build-up of fine fibers, or clustering bacteria, provide a support structure in the pit.
- A surfactant of some type, such as detergent or oil, reduces the surface tension of the effluent allowing bubbles to form.
- Finally, the fibers or clustering bacteria trap gases that would otherwise dissipate.
According to Hoff, if any one of these three requirements is eliminated (support structure, gas, surfactant) you will have an excellent chance to reduce or eliminate foaming.
Methods of preventing the problem, however, are still eluding researchers. “Foaming in manure pits results from a combination of factors including nutrition, digestibility, chemistry, microbiology as well as environmental factors on the farm,” according to Hoff. “It’s a very complex problem.”
Current research is looking at several angles including microbial and chemical causes to determine the reason for foaming, according to Hoff. “It may be a combination of both,” he says.
Feeding of distillers’ dried grains with solubles (DDGS) is also being closely examined to see if the co-product of ethanol production may be a causative factor. “DDGS is not a conclusive requirement for foaming,” Hoff says. “Now, ethanol plants are extracting oil from DDGS in varying amounts adding another variable to the mix.”
Until more answers become available, pork producers must be extremely cautious when confronting the problem and safety is the top priority.
Foaming in deep pits presents a big risk, Hoff says. “Methane concentration in foam can reach 700,000 parts per million (ppm) and the explosion level of methane is about 50,000 ppm; so if you quickly try to dissipate the foam without proper precautions, and an ignition source is present, an explosion can occur,” Hoff warns.
Hoff recommends the following precautionary measures before agitation or pumping of foam:
- Turn off all ignition sources such as pilot lights
- Set a minimum ventilation rate of 30 cubic feet per minute/space (30,000 cfm in a thousand head finishing building)
- Make sure ceiling inlets are operational
- Vacate barn
Meanwhile, research will continue at a rapid pace to gain answers. Important funding for the research has been committed by the Iowa Pork Producers Association which has devoted $1 million over three years for pit foaming research projects, according to Hoff.
All three universities have excellent researchers devoting time to this problem, Hoff says. “We will find ways to remedy this very complicated issue, but we’re not there yet.”
Read more about understanding foaming manure pits and pump-out safety precautions here.