Tuesday, April 30, 2013
Exhibit Hall
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 loass and worker injuries. The 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. The manure foaming was not induced by the obsessive growth of filamentous bacteria. As a matter of fact, it is primarily caused by elevated concentration of long chain free fatty acids on the surface of the manure, serving as surfactant, combined with the increased biogas generation as well increased fiber concentration, serving as the foam stabilizer. There is evidence that the high percentage (> 30%) of dried distiller grains solubles (DDGS) in pig diets may be the source of excess surfactants (long chain fatty acids, the incomplete digestion of corn oil) and fiber which are needed to generate and 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 seems to be the root cause of this foaming issue.