Cold Plasma Improves Air Filtration, Reduces Production Cost

Civil and Environmental Engineering Professor Herek Clack (left) and members of his team set up a lab-scale non-thermal plasma device that has previously been proven to achieve greater than 99% inactivation of an airborne viral surrogate, MS2 phage, a virus that infects E.coli bacteria at the Barton Farms family pig farm in Homer, Mich. ( Robert Coelius/Michigan Engineering )

New research from the University of Michigan (U-M) says that dangerous airborne viruses are rendered harmless when exposed to energetic, charged fragments of air molecules. Researchers are hoping to use this capability to someday replace a familiar device: the surgical mask.

Engineers have measured the virus-killing speed and effectiveness of nonthermal plasmas—the ionized, or charged, particles that form around electrical discharges such as sparks. A nonthermal plasma reactor was able to inactivate or remove from the airstream 99.9% of a test virus, with the vast majority due to inactivation, according to a university release.

“The most difficult disease transmission route to guard against is airborne because we have relatively little to protect us when we breathe,” says Herek Clack, U-M research associate professor of civil and environmental engineering.

To gauge nonthermal plasmas’ effectiveness, researchers pumped a model virus—harmless to humans—into flowing air as it entered a reactor. Inside the reactor, borosilicate glass beads are packed into a cylindrical shape, or bed. Clack says high voltages (up to 30 kV) are applied across the beads to fragment otherwise stable oxygen, nitrogen and water molecules into the energetic fragments responsible for inactivating the virus.

“In those void spaces, you’re initiating sparks,” Clack says. “By passing through the packed bed, pathogens in the air stream are oxidized by unstable atoms called radicals. What’s left is a virus that has diminished ability to infect cells.”

Researchers also tracked the amount of viral genome present in the air during these tests. Clack and his team determined that more than 99% of the air sterilizing effect was due to inactivating the virus that was present, with the remainder of the effect due to filtering the virus from the air stream.

Combining filtration and inactivation of airborne pathogens could provide a more efficient way of providing sterile air than technologies currently being used, such as filtration and ultraviolet light. 

With the swine industry’s vulnerability to contagious livestock diseases, this research holds hope. Clack and his team have begun testing their reactor on ventilation air streams at a livestock farm near Ann Arbor. 

“The technology was designed to protect against airborne disease transmission by attenuating both the transport of airborne pathogens in air as well as attenuating the ability of those pathogens to infect,” Clack says. “By operating on both principles simultaneously, we are able to reduce the operations and maintenance burden that otherwise is borne by technologies that operate on only one of those principles.”

For pork producers, Clack says this technology could lower filter replacement costs, have less impact on cooling capacity in the summer, and result in less costly infrastructure modifications upon installation.  

The researchers are conducting field testing to further expand the demonstrated performance of the device in inactivating airborne PRRS virus beyond what they have already done in lab tests at the University of Minnesota with the help of Montse Torremorell and Bernard Olson, Clack says. In addition, they are collecting data on how environmental conditions affect performance.

Although cost data is not available at this time, Clack says they are in the process of commercializing the technology through their startup company, Taza Aya LLC.

The next stage will be "human applications." In the future, they hope variations of this technology can be used as a (more effective) replacement for surgical masks. That will involve miniaturizing the technology currently adapted for buildings so that it becomes a device you can wear. 

This research was published in the Journal of Physics D: Applied Physics. The on-farm testing has been funded by the MTRAC AgBio program at Michigan State University and the completed work with the University of Minnesota was funded by the National Pork Board. For more information, visit the Clack Lab website or video.

More from Farm Journal's PORK:

Maschhoff Memo: A Tech Revolution is Taking Place Behind Those Doors

Pig-to-Human Heart Transplants One Step Closer

Gene Editing Promise Stalled at FDA