A new research has determined that gaseous ammonia and other odorous gases resulting from animal manure can attach to dust particles, leaving behind matter that is both unpleasant and unhealthy for humans.
The research, which evaluated the levels of dust stink, is among the first to quantify dust gas emissions.
During the study, dust from structures housing cattle, laying hens and pigs were studied, with the dust particles produced mainly from feed, manure, bedding, soil and the animals' dry skin.
According to co-author Jongmin Lee, a researcher in the Department of Agricultural and Biological Engineering at the University of Illinois at Urbana-Champaign, an attraction-producing force, known in physics as the Van der Waals force, causes gas molecules to bond with those of the dust.
Though the resulting bond is weaker than most chemical bonds, it's enough keep the gas stuck to the dust.
"The reverse of adsorption, desorption, is the transfer of gas from dust particles to the surrounding air, and the principles are the same as for adsorption," said Lee.
Because heat can permit the gases to volatize and separate from the dust, Lee and colleague Yuanhui Zhang created a closed cylinder device that both introduced heat and then allowed for the measurement of the released gas from dust that was scraped off of barns, pipelines and exhaust fans from animal structures located in Illinois.
For the experiment, they focused on ammonia, one of the smelliest gases produced by animals.
Based on their findings, it was determined that laying hens and pigs produced far more ammonia dust than cattle did. The researchers attribute this to the way in which the animals were housed.
The cattle were in a roomier building with open areas and plenty of natural ventilation. The pigs and chickens, on the other hand, were in more cramped quarters with mechanical ventilation.
Aside from the stink problem, the gassy particles may pose human health risks.
According to Lee, "Particles smaller than 10 micrometers can penetrate into the large upper branches just below the throat where they are caught and removed by coughing and spitting or by swallowing."
"Also, particles smaller than 2.5 micrometers can get down into the deepest portions of human lungs and can cause respiratory disease," he added.
To resolve the problem, the scientists have suggested that animal keepers improve ventilation, frequently clean their structures, properly treat manure and add oil or fat to feed.