Researchers from North Carolina State University and West Virginia University have developed a new technology that can reduce air pollutant and odor emissions from swine barns while reducing energy use by recovering and possibly generating heat. 

Specifically, the research team designed, built, and evaluated a biofilter and a heat exchanger to reduce ammonia emissions from a research broiler barn, while also tempering the fresh air that was pumped into the barns.

The pollution removal component utilizes a biofiltration mechanism, in which polluted air is passed through an organic medium, such as compost or wood chips, that contains bacteria. Those bacteria interact with the pollutants and break them down into harmless or less harmful constituents.

Since biofiltration introduces additional costs for an operation, the system helps defray the costs by reducing an operation’s heat energy consumption.

The system works when warm air discharged from the livestock facility enters the biofilter where heat is transferred to the heat exchanger. When fresh air from outside is pumped into the building, it passes over the heat exchanger, warming it up.

The prototype not only helps recover heat from the facility, it also produces its own heat. This heat is generated within the biofilter when heat-producing biochemical reactions occur – for example, when the ammonia is converted into nitrate by bacteria. Moistening the air prior to its entry into the biofilter can reduce water evaporation from the biofilter medium and increase heat recovery. The heat from the biofilter is also routed to the heat exchanger.

Maintaining appropriately high temperature is important for swine operations, because it is essential for rearing piglets to maturity.

“The technology is best suited for use in pig nurseries with deep pits and pit ventilation fans. The odorous air from pit that is also high in ammonia can be effectively treated in the biofilter and when supplemental heating is needed, the system can be used to produce and recycle the heat back into the barn to reduce propane use.” says Dr. Sanjay Shah, an associate professor of biological and agricultural engineering at NC State and lead author of a paper describing the research.

“This system would be very appropriate in the upper Midwest where you have deep pit systems and high heating requirements,” said Shah. “At three cubic feet per minute of cold weather ventilation for nursery pigs, this 7.5 -foot by 20-foot unit can provide air treatment for 1,100 piglets.”

For this to be feasible, it would be necessary to ensure that pit fans can overcome the pressure drop imposed by the biofilter and maintain adequate ventilation rate; this may require the producer to replace older pit fans with more efficient fans of the same size but with more propellers. Shah explains that the technology is not compatible with summer ventilation using tunnel-fans. “We plan to continue working to improve the system design in order to make it even more efficient,” Shah says.

Source: North Carolina State University