The primary objective of this project was to document the air quality impact (both barn air quality and gas emissions) through a simple modification to the ventilation system of deep-pit, pig finishing buildings that are typically used in the Midwest. This simple change was the moving of the minimum ventilation fans from the pit pumpout to the building sidewall. This modification was done to one room of a “doublewide” 2800-head, deep-pitted, mechanically-ventilated grow finish barn in Western Minnesota. This barn had two identical rooms housing 1400 pigs each. For this investigation the South Room (SR) pit fans were moved into the sidewalls while the pit fans were left on the pumpouts in the North Room (NR). Monitoring of several air quality parameters was done continuously for 6 months (covering two separate batches of pigs).
Results suggest that when airflow rates in the rooms are similar, this simple change in ventilation design did not have a negative impact on barn air quality and reduced emissions of ammonia (NH3) slightly (25%) and hydrogen sulfide (H2S) considerably (75%). The differences in NH3 and H2S emissions between rooms with and without pit fans seem to be highly related to the level of manure in the under the barn pit. This was shown by the dramatic reductions in hydrogen sulfide emissions after manure pumping (from both rooms) which lowered the manure level. Ongoing monitoring and data analysis will be used to confirm these initial findings.
A secondary objective of the study was to determine the energy and nitrogen conservation impacts when this ventilation design change (elimination of pit fans in deep-pit barns) was implemented.  Tentatively, moving minimum ventilation fans from the pit to the wall should reduce electrical energy usage by fan since fewer and more energy efficient fans can be used and fans exhausting air through the barn wall typically have less pressure drop (and thus less energy use) than fans exhausting air through the pit. The use of LP Gas or other fuels to provide supplement heat in these barns with and without pit fans is still being evaluated for our second (winter) group of pigs.  Again, if similar airflow rates are maintained, it seems doubtful that additional fuel usage will be required in a barn without pit fans. Also, if NH3 emissions (N loss) can be reduced from a barn without pit fans, the manure will retain more nitrogen, which should be a benefit to producer utilizing these nutrients as crop nutrients.