Dangerous swine manure foaming and its relations to corn ethanol co-products

In the past few years, a sharp increase of pit-foaming is discovered in the swine and dairy production facilities. The foams on the swine manure hold significant amount of methane gas, thus creating a potential safety hazard as well as limiting the space for manure storage. Increasing cases of flash fires and explosions were reported recently in many Midwestern states, causing significant assets loss and worker injuries. This research combined with the field sampling and lab simulation to study the foaming mechanism, including biogas generation, surfactant identification, manure compositional analysis and microbial community analysis. Results show that the manure foaming was not induced by the obsessive growth of filamentous bacteria. As a matter of fact, it is indicated from the foaming lab simulations that the elevated concentration of long chain fatty acids together with increased concentration of undigested fibers could  initiate the formation of stable foam bubbles, entrapping the dangerous biogas. This study explored the possible correlation between  the high percentage (> 30%) of dried distiller grains solubles (DDGS) in pig diets and the foaming because DDGS may be the source of the surfactants, long chain fatty acids, the incomplete digestion of corn oil, as well as fibers, which are needed to stabilize foam. Also, DDGS diets results in greater solids in the manure, which also can enhance biogas production. With recent development of corn ethanol industry, the massive application of DDGS in the pig diet could be the major reason of this foaming issue.