Test site conditions for the pit additives

Pit additives were tested in barns with "combination ventilation" systems. Barns are naturally ventilated with doubled sided curtains, which are raised or lowered to maintain barn temperature. Barns are also mechanically ventilated with inlets in the ceiling and exhaust is ventilated through pit fans. Manure is stored in a pit at least four feet in depth beneath a slatted floor. All test barns were oriented east and west with no trees around the site.

Test site type #1: Identical barns, each 41 x 200 feet. Manure pit capacity is in excess of 400,000 gallons; maximum capacity of each barn is about 1000 hogs.

Test site type #2: Identical with rooms 41 x 96 feet and 36 x 88 feet, holding in excess of 120,000 gallons per room; each barn's capacity is approximately 500 hogs.

How are odor tests conducted?

At the University of Minnesota, where the odor testing was completed, a protocol has been developed using panels of six to eight people. Evaluation rooms are pressurized and all entering air passed through a carbon filter to remove background odors. Panelists evaluate one sample at a time through a "sniffing port" and their individual sensitivity is calibrated through their sensitivity to
N-butanol gas.

Each sample is evaluated for two odor thresholds: recognition and detection. The detection threshold is the lowest concentration of an odorant in clean air when the odor of the mixture is detectable (the awareness of an added substance). The recognition threshold is the lowest concentration of an odorant in clean air at which the mixture can be recognized as having a specific odor quality.