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Exploding Hog Farms
New Bern, NC – It's not raining men at some hog farms in the Midwest. When the pits which can hold up to 8 feet of manure explode, it's a big mess and in most cases, thousands of lost livestock and millions of dollars in damage.
Scientists have determined that a methane-packed foam that expands on top of the deep manure pits that are common throughout the Midwest region is likely the cause. Professor and Extension Engineer for the University of Minnesota, Larry Jacobson, says the foam builds up to the point that hog farmers must beat it down.
"Foam can develop on the surface of the manure and this can create a loss of storage space probably most importantly the foam captures the methane gas that is released during anaerobic digestion that naturally occurs with manure that is stored that long."
When agitators, which helps breakdown solids, are turned on and the foam is broken down rapidly, all of the methane is released into a confined space in a short period of time. If methane trapped inside the building reaches high enough concentration levels, and an ignition source is introduced, it could result in an explosion.
"there have been several cases where it's totally destroyed the barn. So I would relate that as a fairly large explosion."
Of course, the size of explosion depends on the concentration level of methane in the air. Jacobson says at the very least, hog farmers may experience a flash fire, which is similar to a fireball created when gas stove ignition is delayed. Out of approximately 20 hog farm explosions that have occurred in the past three years, heaters have been the main ignition source. However, In September 2001, a spark from welder caused an explosion in Iowa that killed 1,500 hogs and injured a worker.
Exploding hog farms have been an issue in states like Iowa, Minnesota, Illinois, Nebraska and Indiana. But since North Carolina is ranked second in the nation for hog production, could an explosion occur here? To find out, we spoke to Dr. Tom Ray who is the North Carolina Agriculture and Consumer Service's Director of Livestock Health Programs.
"We contacted some of the veterinarians who work with some of the larger companies. In North Carolina, you can talk to three companies and with those three companies you're discussing 90 percent of the farms and 95 percent of the animals. In talking with the company veterinarians, we had history going back over 20 years, and none of these instances have occurred to anyone's knowledge in the state, either to their own companies or anecdotally from discussing it from other swine veterinarians and independent producers."
Eastern North Carolina's hog industry began around the 1980s and experienced record growth throughout the 90s. North Carolina is now ranked 2nd in the nation for hog production. There are approximately 1200 hog farms in North Carolina, many of those in the eastern portion of the state. According to the latest figures from the North Carolina Department of Agriculture, Lenoir and Pitt counties are ranked tenth in the nation for hog production. Jones County ranks 8th, Greene County is 7th, Pender is 5th, and Wayne County is ranked 4th. Duplin County is the top hog producing county in our state with over two million of North Carolina's 8.6 million hogs.
While hog farm explosions are very rare - even in the Midwest- it's highly unlikely one will happen here. That's because there are some major differences between the way hog farms are built in the Midwest and here in eastern North Carolina.
"A lot of the barns in the Midwest employ a manure storage vessel below the pigs called deep pit storage."
Don Butler is the Director for Government Relations and Public Affairs for Murphy-Brown LLC, located in Duplin County. Murphy-Brown is one of the largest hog producing companies in the state.
"Typically, those pits are usually six or eight feet deep. As the waste material leaves the animal, it falls thru slats in the floor into this containment area and is stored until farmers are ready to use it for fertilizer."
Hog houses in North Carolina generally do not have deep pits, and they are much more shallow about 4 feet. Similar to the Midwestern design, the waste falls through slits in the floor into a collection pit below. But the difference is that this pit is flushed on a regular basis to an open air lagoon for long term storage. Hog operations in eastern North Carolina typically have flaps that roll up to allow for natural ventilation, preventing high concentrations of methane to build up inside the building. In the Midwest most hog operations have solid walls and are ventilated using large fans.
According to the North Carolina Pork Council's Executive Director Deborah Johnson, foaming appears to be isolated to deep pit manure storage systems and there appears to be no clear cut cause for the foaming. Even though the factors that cause the hog farm explosions are still being researched, Professor and Extension Engineer for at the University of Minnesota Larry Jacobson believes the animal's diet could be to blame.
"things that have been identified or finger pointed at mostly is the feeding of distillers grain soluble, or DDGS which is the byproduct of producing ethanol. We have a lot of DDGS that are available in the Midwest that can be supplemented into the animals pig feed. I think it has lined up with the increase of feeding of DDGS."
According to National Hog Farmer Magazine, the estimated use of DDGS in swine diets has drastically increased since 2001. Some say the foam is a result of bacterial growth in the manure pits. The origins of the mysterious, grey foam may never be known. But Jacobson says they are doing their best to get the word out to farmers in the Midwest about the possibility of hog farm explosions, and how to prevent them from happening.
Jacobson says about a dozen explosions have occurred throughout the Midwest since 2009. Jared Brumbaugh, Public Radio East.