SHIC Wean-to-Harvest Biosecurity: Tool to Mitigate Airborne Pathogen Spread on Farm

A study funded by the Swine Health Information Center Wean-to-Harvest Biosecurity Research Program, in partnership with the Foundation for Food & Agriculture Research and Pork Checkoff, investigated the development and evaluation of an electrostatic precipitator (ESP) prototype to mitigate airborne spread of pathogens under farm conditions. Led by Dr. Montserrat Torremorell at the University of Minnesota, the study evaluates the utility of an ESP to remove airborne particles from aerosols, including PRRSV. The ESP demonstrated high effectiveness, comparable to or slightly exceeding a MERV-16 filter, in removing airborne particles and over 99% removal of PRRSV. While the analysis showed potential for the ESP as a biosecurity tool, economic considerations, challenges related to scalability, adapting the design to swine farms, and maintenance protocols will require further commercial exploration. 

Find the industry summary for Swine Health Information Center project #23-009 here. 

Study objectives were to develop an ESP prototype designed with the goal of installation and use in a swine farm and evaluate its general performance, ability to resist the farm environment, identify prototype shortcomings, and measure energy use. Overall, intended outcomes were to evaluate the potential feasibility of an ESP as a biosecurity measure to minimize pathogen introduction through aerosols and/or maximize the biocontainment of airborne viruses post-outbreak.  

The study focused on assessing the detailed capabilities of the ESP system to remove airborne particles. Results demonstrated that the technology is highly effective at removing general airborne particulate matter. When compared to the MERV-16, widely considered the gold standard for high-efficiency filtration in controlled environments, the ESP prototype achieved similar or enhanced performance using its non-mechanical, electrostatic method. These results suggest potential opportunities for farms to shift to technologies that would be highly effective without  the rapid pressure drop and replacement burden associated with using mechanical air filration. 

A commercially available ESP was used and tested for its ability to collect airborne particles in the ASHRAE 52.2 wind tunnel in the UMN Department of Mechanical Engineering. The ESP was assessed in a controlled laboratory setting to assess the particle collection efficiency and to confirm particle size distribution. The size distribution measurements were conducted using a Size Mobility Particle Scanner and Optical Particle Scanner, covering a particle range from 10 nm to 10 µm. After laboratory characterization of the ESP was completed, the ESP was installed within a wean-to-finish barn. The barn was mechanically ventilated and used air filtration in the inlets, which were located in the attic. To evaluate the ESP performance, the filter bank in one of the ventilation boxes was replaced with the ESP setup. 

To evaluate the ESP’s performance in capturing viruses in the field, PRRSV was aerosolized and introduced at the ESP inlet. PRRSV strain VR2332 was grown and titrated to 106.75 TCID50/mL and the suspension was spiked with a fluorescein physical tracer dye at 0.3 g/L. Two trials were performed at a temperature of 15°C (59 °F) with 47% relative humidity. The airflow rate was maintained at 1200 cfm. After collection, samples were analyzed for viable virus by titration and for viral RNA through PCR testing.  

Results demonstrated that ESP collection efficiency was above 99% for particles greater than 1 µm. For particles less than 1 µm, collection efficiency varied by temperature, with higher efficiencies generally observed at lower temperatures.  The ESP was also highly effective at removing PRRSV with removal efficiencies higher than 99%.  

An assessment of the on-farm feasibility of using the ESP under field conditions included a cost comparison of purchasing, installing and operating the equipment compared to those of air filtration. Other considerations included operational sustainability as well as the upkeep and maintenance of the equipment. Unlike disposable mechanical filters, ESPs operate by electrically charging and collecting particles onto plates, which must be regularly cleaned to maintain efficiency.  

The economic analysis included assumptions on acquisition, installation, operation, maintenance and replacements costs for the ESP and filter systems. Investigators concluded that the ESP system had a $299,553 greater net present value over a 15-year period, resulting in approximately $0.25 additional cost per weaned pig, when compared to air filtration. This costing model is based on the assumptions around current technology. Future engineering advances may make this model more economically viable in the future. 

Scalability of the ESP for on-farm use involves moving the technology from laboratory- or pilot-scale units to systems capable of handling the significant air volumes necessary for large commercial farms. This requires robust engineering solutions that maintain high efficiency of ESP while operating continuously under real-world weather and climate variability. Farms have differing building designs and adoption of the use of this technology requires innovative retrofitting solutions that do not compromise the structural integrity or operational flow of the facility.  

Overall, the ESP tested in this study was highly effective at removing airborne particles with collection efficiencies similar and marginally superior to those of a MERV-16 filter. The path to commercialization and more broad scale use of ESP is dependent upon successfully resolving the complex logistical and engineering challenges of scalability, design integration, long-term maintenance, and cost-effectiveness for producers. Further commercial exploration is needed to fully optimize ESP designs and maintenance protocols for practical applications to improve biosecurity within commercial pig farms.   

Foundation for Food & Agriculture Research 

The Foundation for Food & Agriculture Research (FFAR) builds public-private partnerships to fund bold research addressing big food and agriculture challenges. FFAR was established in the 2014 Farm Bill to increase public agriculture research investments, fill knowledge gaps and complement US Department of Agriculture’s research agenda. FFAR’s model matches federal funding from Congress with private funding, delivering a powerful return on taxpayer investment. Through collaboration and partnerships, FFAR advances actionable science benefiting farmers, consumers and the environment. Connect: @FoundationFAR