ISU Pit Digester Study
One of the top hog producers in the county contracted with Dr. Dwaine Bundy at Iowa State University to conduct a 12-month field test at 12 separate sites. Testing began in March. Four sites remained untreated and were used as the control group. Two sites each were chosen to test four different pit additives. All sites had four buildings. Both pull plug and deep pit buildings were tested. All measurements were taken inside the buildings.
Odor Measurement Approach:
Single gas measurements for hydrogen sulfide and ammonia were taken in the traditional fashion. In addition, “Odor Threshold Measurements” were also taken. Testing is conducted by a specially trained panel, determining how many units of fresh air need to be mixed with a unit of air from the building before the odor is no longer detectable.
The reason this odor measurement approach has gained broad support over single gas measurements is that the human nose detects over 200 gases emitted from a swine unit. Reduction of only one or two gases does not guarantee odor reduction.
The control units had Odor Threshold measurements nearly 2 X higher than units treated with Pit Digester. Likewise, the other treated units as a group had Odor Threshold measurements 73% higher than the units treated with Pit Digester. Pit Digester significantly reduced not only odor threshold, but hydrogen sulfide and ammonia, as well.