Researchers at the National Soil Tilth Lab are coordinating with University of Iowa scientists to use lasers and wind tunnels to track how swine odors disperse.

Society's demands for answers to air quality issues have far outpaced agriculture's response, declares Jerry Hatfield, director of the National Soil Tilth Lab at Ames, IA.

Agriculture has intensified its study of livestock and poultry sites, measuring emissions and calculating their rate of dispersion in the immediate area.

But the emission, dispersion and distribution of hog odors is a very complex matrix, charges Hatfield, because it involves changes in biology of the animal, the manure pigs produce and the environment in which they are raised.

To meet these tough challenges, Hatfield and fellow scientists, who are part of the Agriculture Department's Agricultural Research Service (ARS), have teamed with researchers at the University of Iowa to conduct in-depth scientific trials “to get a closer look at all the pieces of the puzzle,” he says.

Laser Technology

Hatfield and colleagues believe the approach that's needed must encompass a broader environmental footprint — from the emissions given off by an entire building complex and the impact of wind turbulence, to how particulate matter and gases are collectively distributed into the atmosphere in and around farm operations.

In essence, the daunting project has taken on a whole new light in the form of LIDAR, or Light Detection and Ranging, — in which 1960s' radar-like technology utilizes short bursts of green laser lights to detect and differentiate airborne particles, gases or molecules.

Hatfield says his team first used LIDAR in 1998, when they were asked by the U.S. Department of the Interior to investigate the effect of salt cedar, a damaging shrub found in the southwest United States that extracts large amounts of soil moisture while leaving soil-damaging salts behind.

More recently, the technology has been used in conjunction with the space administration and other agencies to investigate the accuracy of remote sensors on land and in the air to determining ground-level moisture.

The latest project studies the dynamics of dispersion around hog facilities.

Instead of measuring emissions at set points coming out of a hog facility, Hatfield says LIDAR has the capability to scan across the entire facility, similar to “putting a bubble over this facility and being able to say, this is what is going out of this bubble.

“With LIDAR, we are viewing everything at the speed of light, so data can be gathered quickly.”

LIDAR has already shown there are “clouds” of particulate matter and low concentrations of odorous gases, such as phenols and creosols, floating around in the boundary layer of the atmosphere, which comprises the area up to two miles above the surface of the earth, explains John Prueger, ARS soil scientist at Ames, IA.

Sensitive technology like LIDAR has shown scientists that this low-level layer is an important receptacle for dust and gases from agricultural crop and livestock operations, and ranges in size from parts per billion to parts per trillion, adds Hatfield.

Wind Detection Instruments

But LIDAR is only one of the tools the ARS team is using to help pinpoint and track the substances that make up hog odors.

Part of what makes odor dispersion and distribution so unpredictable is wind turbulence, what Prueger calls one of the unsolved mysteries of physics.

ARS is also using sonic anemometers in the field to measure and profile the turbulence of the air between buildings. Sonic anemometers measure windspeed in all directions, and measure the turbulence structure of the air, explains Hatfield.

Because of the expense of conducting field experiments, National Soil Tilth Lab staff has also crafted a scale-model, low-speed wind tunnel to simulate the affects of wind currents on farms.

Wind Dynamics

In the past, air dispersion models were based on smokestack technology, which assumes that air movement is uniformly static.

However, wind patterns are actually very dynamic, says Hatfield.

“This is the first time we have really thought about how air flows in and around buildings, which a single-point test measurement won't pick up,” he stresses.

Wind dynamics suggest it may be more important for pork producers to study wind patterns and the local terrain when siting a hog barn, than it is to worry about how close the nearest neighbor is to the hog facility.