Throughout the U.S. there is a regulatory push to lower emissions of varies air pollutants from swine production facilities. The primary objective of this project was to determine if reductions in particulate matter (PM) and odor emissions would occur by installing a geothermal heating and cooling system in a grow-finish building. A secondary objective of the study was to estimate if the emissions reductions and any pig performance advantages from implementing a geothermal system could justify the economic investment of this alternative energy source.
The project was conducted over an approximate 12 month period at a full-scale swine grow-finish facility with 16 rooms of 400 pigs/room located in western Minnesota. The building had a deep well, geothermal system installed to provide the heating and cooling for four of the 16 rooms in the building. The pig flow for the facility consisted of groups (400+ head) of pigs of the same sex that weigh 55 to 60 lbs/pig entering a room every week, which alternates between barrows and gilts. During the study period, two rooms of barrows that were in the block of four rooms with the geothermal heated and cooled system were compared to two rooms of nearly similar sized barrows that were in the block of 12 rooms that had a conventional ventilation and heating system. For this study, a 24+ hour average total suspended particles or TSP (consisting of dust particules approximately smaller than 20 microns in diameter) sample was collected simultaneously in one of the geothermal rooms and one in the conventional rooms. Also duplicate odor samples were collected consecutively in 10 liter TedlarTM sample bags from two of the conventional and two of the geothermal rooms as well as two from the ambient or outside air which served as background sources.
Both odor and PM emissions were lower in the rooms that had the geothermal heating and cooling system compared to the conventional ventilated rooms. This result was probably due to the lower ventilation rates that were present in the geothermal rooms, since the air samples collected in both rooms had quite similar odor and PM concentrations. Improvement in pig performance such as ADG and FE in the geothermal rooms was expected but no difference in performance was found. A possible reason why pigs did not group faster and/or were more feed efficient was that 2014 was an unusually cool year in western Minnesota and thus the cooling benefit that the geothermal systems provided was not be captured. Also, in an effort to assess the viability of using a geothermal system, estimated annual electric energy use for the conventional and geothermal rooms were made and the geothermal rooms required approximately 20 % more in electrical energy than the conventional rooms. Based on the results that pig performance was not improved and that energy use in the rooms with the geothermal heating/cooling was actually slightly more than the conventional rooms, the return on investment is marginal at best with only slight reductions in odor and PM emissions having some positive benefit.
Further information concerning the findings from this study can be obtained by contacting Larry D. Jacobson at the University of Minnesota, [email protected] or 612-625-8288.